Gaucher
disease is a rare inborn error of glycosphingolipid metabolism due to
deficiency of lysosomal acid β-glucocerebrosidase; the condition has
totemic significance for the development of orphan drugs. A designer
therapy, which harnesses the mannose receptor to complement the
functional defect in macrophages, ameliorates the principal clinical
manifestations in hematopoietic bone marrow and viscera. While several
aspects of Gaucher disease (particularly those affecting the skeleton
and brain) are refractory to treatment, enzyme (replacement) therapy has
become a pharmaceutical blockbuster. Human β-glucocerebrosidase was
originally obtained from placenta and the Genzyme Corporation (Allston,
MA) subsequently developed a recombinant product. After purification,
the enzyme is modified to reveal terminal mannose residues which
facilitate selective uptake of the protein, imiglucerase (Cerezyme®),
in macrophage-rich tissues. The unprecedented success of Cerezyme has
attracted fierce competition: two biosimilar agents, velaglucerase-alfa,
VPRIV® (Shire Human Genetic Therapies, Dublin, Ireland) and
taliglucerase-alfa (Protalix, Carmiel, Israel), are now approved or in
late-phase clinical development as potential ‘niche busters’. Oral
treatments have advantages over biological agents for disorders
requiring lifelong therapy and additional stratagems which utilize
small, orally active molecules have been introduced; these include two
chemically distinct compounds which inhibit uridine diphosphate glucose:
N-acylsphingosine glucosyltransferase, the first step in the
biosynthesis of glucosylceramide – a key molecular target in Gaucher
disease and other glycosphingolipidoses. Academic and commercial
enterprises in biotechnology have combined strategically to expand the
therapeutic repertoire in Gaucher disease. The innovative potential of
orphan drug legislation has been realized – with prodigious rewards for
companies embracing its humanitarian precepts. In the era before enzyme
therapy, bone marrow transplantation was shown to correct systemic
disease in Gaucher patients by supplying a source of competent donor
macrophages. As a radical advance on cell- or protein-replacement
techniques, contemporary methods for transferring genes to autologous
hematopoietic stem cells, and to the brain, merit further exploration.
At present, the inflated pharmaceutical niche of Gaucher disease appears
to be resilient, but if the remaining unmet needs of patients are to be
convincingly addressed and commercial development sustained, courageous
scientific investment and clinical experimentation will be needed.
28 septembre 2011
Production woes weigh on Genzyme parent. Sanofi fails to put end to drug supply disruptions
Production woes weigh on Genzyme parent
Sanofi fails to put end to drug supply disruptions
September 27, 2011|By Robert Weisman, Globe Staff
French drug maker Sanofi SA had hoped Genzyme Corp.’s high-profile production problems would be quickly put to rest when it acquired the Cambridge company.
But five months after Sanofi completed its $20.1 billion takeover, supply disruptions for a pair of drugs to treat rare genetic disorders continue to dog Genzyme’s new owner.
Earlier this month, Sanofi’s Genzyme division told health care providers it would reduce shipments for the next four months of its best-selling Gaucher disease drug, Cerezyme, which had recently returned to full production. Last month, the company said it was delaying shipments of its Fabry disease drug, Fabrazyme, which already had been rationed.
Cerezyme patients in the United States whose normal biweekly doses had been restored in January, were temporarily back to once-a-month regimens. Fabrazyme patients faced a one-month delay in receiving already reduced dosages.
“Because we have low inventory, we’ve said that any disruption in our manufacturing will be felt by the [patient] community,’’ said Genzyme spokeswoman Lori Gorski.
The recent moves came after a rocky summer. Sanofi disclosed in July that it would not make a milestone payment to Genzyme investors because the company failed to meet manufacturing targets for the two drugs, made at the Allston Landing plant in Boston.
Around the same time, the French company gave Bill Aitchison, previously head of manufacturing for its Sanofi Pasteur vaccines business, oversight for all of Genzyme’s biologics manufacturing operations. Aitchison replaced Scott Canute, who left the company.
Sanofi’s ability to pull Genzyme out of the production morass it has been stuck in for the past two years will be key to the success of its buyout. The state of Genzyme’s manufacturing recovery was an issue hanging over the merger talks last year, with Sanofi leaders cautioning progress might be slower than their Genzyme counterparts were suggesting.
The potential milestone payment, designed to bridge the parties’ differences over how much Genzyme was worth, put those competing views to the test. Thus far, Sanofi’s skepticism has been borne out. But as Genzyme’s new owner, Sanofi is now saddled with the responsibility to fix the problems at what had been the largest biotechnology company in Massachusetts.
Sanofi can reap substantial benefits from Genzyme if it gets drug-making operations back on track, said Jonathan P. Gertler, senior partner at the Boston consulting firm Back Bay Life Science Advisors. He said Sanofi, with its global reach, can bring more resources to bear on ending the supply constraints than Genzyme could have as a stand-alone company.
“The manufacturing issue looms large in everyone’s mind,’’ Gertler said. “It’s an absolutely critical issue for Sanofi. It’s critical for them to get the buy-in from the former Genzyme employees. It’s critical for Wall Street. And it’s critical for the long-term success of what are now the Sanofi products.’’
Genzyme’s Gorski said the latest setbacks were aggravated by the low inventory at Allston Landing, where drugs go out to patients as soon as they are ready. The plant continues to produce Cerezyme and Fabrazyme as the company awaits approval from the Food and Drug Administration to open a new facility in Framingham next year.
Allston Landing, on the banks of the Charles River, was the site of a virus found in a bioreactor in the summer of 2009. That forced Genzyme to temporarily suspend production and ration doses of the enzyme replacement therapies to thousands of patients.
The drugs are produced by growing genetically modified Chinese hamster ovary cells in giant bioreactors. The conditions they treat, Gaucher and Fabry diseases, cause waste to build up in the body, swelling organs. The drugs, taken intravenously about every other week, cost up to $300,000 a year per patient.
While it keeps rebuilding its inventory, Genzyme recently has experienced smaller than expected Cerezyme “productivity’’ - meaning the amount of a drug in the production process that is ready to ship. “You expect variability in biologics manufacturing,’’ Gorski said. “But we didn’t have the buffer of inventory.’’
Genzyme has also had to make adjustments while implementing new procedures agreed to in a so-called consent decree with the FDA last year. The plant was placed under federal oversight for seven years as it worked to correct quality control problems.
“We understand better what the implications of the consent decree are,’’ Gorski said. “It’s a new environment for that [Allston Landing] facility.’’ At the same time, she said, “We remain on target with the new Framingham plant, which is pivotal to both products.’’
Patients, however, are growing restless. Some who suffer from Gaucher disease have switched to Vpriv, a rival drug produced by Irish drug maker Shire PLC, which has based its human genetic therapies division in Lexington. Some Fabry disease patients, who have been reduced to one dose or a half dose a month from their normal two a month for the past two years, might be open to switching to an alternative treatment - if there was one on the market.
Genzyme has “not been able to move as fast as the patient community would have liked,’’ said Jack Johnson, executive director of the Fabry Support and Information Group, based in Concordia, Mo. “It has created a loss of confidence, and we’ve told them so.’’
While many Fabry patients have been able to tolerate the reduced dosages, some have experienced pain, gastrointestinal problems, or other conditions, Johnson said.
Members of the Fabry group were in Washington, D.C., last week to discuss their predicament with FDA officials. Johnson said they are urging the agency to fast-track alternative Fabry disease treatments being developed by Shire and New Jersey-based Amicus Therapeutics Inc.
But they are also urging the agency to speed approval of Genzyme’s plant in Framingham, where Fabrazyme will be made.
“The rationing has gone on since 2009,’’ Johnson said. “Patients want this to come to a conclusion as soon as possible.’’
Robert Weisman can be reached at weisman@globe.com.
One consultant said Sanofi can reap substantial benefits from Genzyme if it gets the drug-making operations on track. Its an absolutely critical issue for Sanofi, said Jonathan P. Gertler.
http://articles.boston.com/2011-09-27/business/30209007_1_genzyme-cerezyme-sanofi-pasteur
Genzyme parts de marché s'effondre
20 septembre 2011
Ongoing supply problems for Genzyme’s Cerezyme
Article classé dans la catégorie : "NOUVELLES des LABORATOIRES".
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Ghislaine SURREL
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Ongoing supply problems for Genzyme’s Cerezyme
Article | 19 September 2011
US biotech Genzyme, now a subsidiary of French drug major Sanofi (Euronext: SAN), says it will have only limited supplies of its Gaucher disease drug Cerezyme (imiglucerase, injection) available for the next four months starting October.
In a letter to US health care providers, published by the National Gaucher Foundation, Genzyme said the shortage was caused by "a temporary decrease in Cerezyme yields," coupled with "changes to our product release processes and procedures".
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The company has had problems with supplies of Cerezyme, as well as its Fabry disease drug Fabrazyme (agalsidase beta) for patients worldwide, as a result of earlier manufacturing issues since June 2009 (The Pharma Letters passim). The Genzyme problems have benefited Ireland-headquartered Shire, as it has resulted in switching to the company’s Replagal (agalsidase alfa) from Fabrazyme and to Vpriv (velaglucerase alfa) from Cerezyme.
Adjustments to individual treatment plans
Changes to Cerezyme availability will be felt globally, the letter stated, adding that delays in shipments will likely affect patients and some adjustment to individual treatment plans may be necessary. For the USA from October through January, Genzyme expects to provide:
• one full dose (equivalent to the currently prescribed dose) per month for patients aged 19 years and older currently treated with Cerezyme; and
• two full doses per month for patients aged 18 years and younger and for Type 2/3 patients currently treated with Cerezyme.
Genzyme will confirm shipping availability each month. Given current improvements to productivity and progress with the firm’s manufacturing recovery, Genzyme currently anticipates an improving Cerezyme supply outlook from February 2012 forward.
In order to support the current level of patient demand, Cerezyme is made available as it is produced, which does not allow the build-up of inventory, the company explained. “Operating with little or no inventory means changes like these in our manufacturing plans can impact supply. Over the past four years there has been significant investment in a new manufacturing facility to produce Fabrazyme in Framingham, Massachusetts. We are in the process of plant validation and currently anticipate completing regulatory approval processes that will allow us to ship product in the first part of 2012. This is a critical step as it will allow us to improve Cerezyme production at the Allston facility which is producing both Cerezyme and Fabrazyme today,” said Genzyme’s letter.
http://www.thepharmaletter.com/file/107413/ongoing-supply-problems-for-genzymes-cerezyme.html?utm_source=2009_11_06-Pharma+Clean&utm_campaign=d261c6d402-RSS_EMAIL_CAMPAIGN&utm_medium=email
31 août 2011
Occlusion d'une branche de l'artère rétinienne chez un patient avec une maladie de Gaucher
| Occlusion d'une branche de l'artère rétinienne chez un patient avec une maladie de Gaucher |
| Plusieurs études ont déjà rapporté des manifestations oculaires au cours de la maladie de Gaucher (strabisme, ptérygion, opacités cornéennes et vitréennes, atteinte rétinienne) mais voici le premier cas d’occlusion d’une branche de l’artère rétinienne survenue à l’âge de 27 ans chez un homme dont le diagnostic de maladie de Gaucher était connu depuis l’âge de 19 ans. Il avait arrêté 2 mois plutôt son enzymothérapie substitutive par imiglucérase et se plaignait d’un flou visuel au niveau de l’œil gauche. L’angiographie à la fluorescéine a montré une obstruction de la branche temporale inférieure de l’artère rétinienne gauche et la tomographie à cohérence optique un épaississement des couches internes de la rétine gauche. Après 4 semaines de corticothérapie associée à la reprise de l’enzymothérapie substitutive, le patient a récupéré une bonne acuité visuelle de l’œil gauche (20/20) tandis que le fond d’œil montrait la persistance d’un vaisseau rétinien temporo-inférieur sclérotique mais avec une nette diminution de l’œdème rétinien, et l’OCT un amincissement important dû à l’atrophie des couches rétiniennes internes. Les perturbations hématologiques et hémorrhéologiques constatées au cours de la maladie de Gaucher sont probablement à l’origine de ses nombreuses manifestations vasculaires (nécrose, hypertension pulmonaire) avec participation étiologique de microthrombi qui pourraient aussi, selon les auteurs, être en cause dans l’occlusion de l’artère rétinienne chez ce patient; à cette hypothèse pathogénique s’ajoute celle d’une inflammation associée des parois vasculaires, déjà observée ailleurs et pouvant expliquer l’impact des corticoïdes. |
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OB
A branch retinal artery occlusion in a patient with Gaucher disease Alice Bruscolini1, Maria Pia Pirraglia1, Lucia Restivo1, Giovanni Spinucci1 and Alessandro Abbouda1 1 Ocular Immunovirology Service, Department of Ophthalmology, Sapienza University of Rome, V.le del Policlinico 155, 00161 Roma, Italy. Without Abstract Table of contentsIntroductionGaucher disease (GD) is a rare familial autosomal recessive disorder of lipid metabolism, resulting in an accumulation of abnormal glucocerebrosides in the reticulo-endothelial system. Patients with GD may present with hepatosplenomegaly, anemia, thrombocytopenia, and destructive bone disease. An enzyme replacement therapy with intravenous infusions of glycosylceramidase has been successfully proposed for treating the visceral manifestations. Gaucher disease can be divided into three subtypes: non-neuronopathic (type 1) which is the most common, acute neuronopathic (type 2), and subacute neuronopathic (type 3) [1]. Several studies have reported ocular manifestations such as strabismus, conjunctival pterygia, corneal opacities, vitreous opacities and retinal involvement [2-7]. To our knowledge, this is the first reported case of Gaucher disease complicated by branch retinal artery occlusion. Materials and methodsA 27-year-old man, with a diagnosis of Gaucher disease since he was 19 years old, presented at the Immunovirology Center of the Sapienza University of Rome, complaining of blurred vision in the left eye which had commenced 7 days before. He was treated with imiglucerase injection every 2 weeks, with good control of symptoms. He interrupted by choice the enzyme replacement therapy 2 months before our observation. We studied the course of ocular disease with fluorescein angiography using the Topcon Imagenet H1024 digital imaging system (Topcon Europe, The Netherlands), indocyanine green angiography, and Spectralis optical coherence tomography (Spectralis OCT, Heidelberg Engineering, Heidelberg, Germany) at 0, 2 and 4 weeks [8]. At follow-up time, MP-1 microperimetry (Nidek Technologies, Padova, Italy) was performed to provide a retinal visual function map. Humphrey automated threshold perimetry (program 30-2) was also performed to detect any visual field defect. ResultsOn the first examination, best-corrected visual acuity was 20/20 in the right eye and 20/25 in the left eye. Anterior segment examination, pupil responses and intraocular pressure were normal in both eyes. Fundus examination of the left eye disclosed a sclerotic infero-temporal artery with minimal perivascular exudation. Fluorescein angiography showed, in the left eye, delayed and interrupted filling of the temporal inferior branch of retinal artery. Filling of the temporal inferior venous branch appeared slightly delayed too. Ischemic hypofluorescence in the surrounding area and fluorescein staining due to retinal edema were also described. The choroidal filling on indocyanine green angiography was normal. Optical coherence tomography (OCT) revealed an increased thickness of the inner nuclear, inner plexiform and ganglion cell/nerve fiber layers. Cross-sectional image through the fovea revealed that the inner segment-outer (IS-OS) line was intact (Fig. 1). A diagnosis of left inferior branch retinal artery occlusion was made. Fundus examination, fluorescein angiography, indocyanine green angiography and OCT of the right eye were normal. The cardiological examination and routine blood testing were normal. The determination of the most common thrombophilic defects (antithrombin, protein C, protein S deficiencies, Factor V Leiden and MTHFR, prothrombin G20210A, Anticardiolipin IgG and IgM antibodies,) was negative. His substances history was negative for drugs, tobacco, and alcohol. The patient was started on a reducing course of oral prednisone and enoxaparin 40 mg once a day which was administered by subcutaneous injection. The corticosteroid therapy began at 0.7 mg/kg/day once a day for the first 7 days and then the prednisone dose was gradually tapered off 0.2 mg/kg every week. He started again the enzyme replacement therapy. After 2 weeks of therapy, visual acuity reduced 25/32 in the left eye and 20/20 in the right eye. Fundus examination disclosed an enlarged and well-demarcated area of retinal ischemic edema and a further proximal occlusion of the same vessel, surrounding the macula. OCT scan disclosed a marked thickening of the inner plexiform and nuclear layers in the corresponding retinal region (Fig. 2a). The oral dose of corticosteroid was then increased again to 0.7 mg/kg/day, with tapering as permitted by clinical response (0.2 mg/kg every week). After 4 weeks of therapy, there was a recovery of good visual acuity (20/20). Fundus examination revealed a sclerotic retinal vessel in the same region and a significant resolution of the ischemic edema. OCT disclosed a marked thinning due to atrophy of the inner retinal layers (Fig. 2b). Visual field testing and MP-1 microperimetry revealed a partial defect corresponding to the area of occlusion (Fig. 3). The patient refused to have a repeat fluorescein angiogram at this time. DiscussionSeveral authors reported a vitreo-retinal involvement in GD [2-4]. They mostly described vitreous opacities, severe vitritis and retinal/pre-retinal deposits probably consisting of clusters of swollen histiocytes (Gaucher cells). To date there are no reports about branch retinal artery occlusion in GD, while haematological and haemorheological alterations in such a disease have been widely reported. These alterations may explain the high incidence of vascular accidents in GD like avascular necrosis and pulmonary hypertension. The results of a recent study [9] hypothesize that microthrombi may be part of the etiology for avascular necrosis as well as pulmonary hypertension in patients with GD and enoxaparin might be beneficial to prevent their appearance or recurrence. We hypothize a similar pathogenesis for the retinal artery occlusion of our patient. Furthermore, it has been previously reported that GD may be accompanied by low grade subclinical inflammation on the wall of the vessels [9, 10]. Corticosteroids might have influenced and down-modulated this low-grade inflammation. This low-grade inflammation might be accompanied by enhanced concentrations of adhesive macromolecules in the peripheral blood. Enhanced synthesis of acute phase response proteins has been hyphothesized to have a damaging rheological effect. An increased ability of erythrocytes to aggregate might be induced and/or maintained by multiple inflammation sensitive proteins [11]. This pathological aggregation may reduce capillary perfusion and oxygen transfer to tissues and cause ischemia and tissue infarction that might theoretically play a role in skeletal damage, in lung involvement and also in ocular involvement like in our patient suffering from retinal artery occlusion. References (Exportez format texte tabulé) [1] Chen M, Wang J (2008) Gaucher disease: review of the literature. Arch Pathol Lab Med 132(5):851-853
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10 août 2011
Bisphosphonates and Atypical Femoral Shaft Fractures
Bisphosphonates and Atypical Femoral Shaft Fractures
N Engl J Med 2011; 365:377July 28, 2011
- Article
-
To the Editor:
Schilcher et al. (May 5 issue)1 report the findings of a cohort analysis that examined the risk of atypical femoral fractures with bisphosphonate use. They found a statistically significant increase in such fractures, with an absolute risk of 5 per 10,000 patient-years, similar to that reported in other studies.2 They conclude that their results are reassuring for patients taking bisphosphonates, since “the magnitude of the absolute risk [is] small.” This level of absolute risk appears identical to the absolute risks reported for hormone-replacement therapy (HRT) by the Women's Health Initiative investigators,3 yet those investigators described the risks of HRT as “substantial,” even though many of those increased risks appeared more likely to be due to chance rather than the intervention when subsequent analyses were undertaken or appropriate statistics were applied.4 This report from the Women's Health Initiative led to substantial reduction in the use of HRT (up to 50% worldwide), even though the results indicated neither harm nor benefit for more than 99% of participants. But Schilcher et al. say that they find the data on the risk of bisphosphonate use to be reassuring. Am I missing something?
John C. Stevenson, F.R.C.P.
Royal Brompton Hospital, London, United Kingdom
j.stevenson@imperial.ac.ukDr. Stevenson reports receiving research grants from Eli Lilly, Janssen-Cilag, Novo Nordisk, Organon-Schering-Plough, Schering, Shire, Solvay, and Wyeth; serving on the advisory boards of Novo Nordisk, Procter & Gamble, and Pfizer-Wyeth; and receiving consulting fees from AstraZeneca, Bayer-Schering, Novo Nordisk, Orion, Procter & Gamble, Servier, Solvay, Theramex, and Pfizer-Wyeth.
No other potential conflict of interest relevant to this letter was reported.
4 ReferencesAuthor/Editor Response
Any judgment about the magnitude of a risk must be seen in relation to other risks and benefits. Women with osteoporosis run a high risk of fracture, which is substantially reduced by bisphosphonate therapy.1 The numbers needed to treat with bisphosphonates for 3 years are 91 for hip fractures and 14 for radiologic vertebral fractures.1 Without consideration of duration of use, we found that the number needed to harm given 3 years of treatment was 667 — that is, the benefits with the therapy outweigh the risks. The absolute risk of stress (atypical) fracture in our study tended to be higher with a longer duration of bisphosphonate use. With more than 2 years of treatment, the difference in absolute risk as compared with no treatment was 8 per 10,000 women per year of treatment. This estimate corresponds to a number needed to harm of 417 for a 3-year treatment period. Thus, theoretically, for each stress fracture caused, at least 30 vertebral and about 5 hip fractures will be prevented. This is reassuring. However, without a proper indication, the benefit–risk ratio with bisphosphonate use may not be advantageous.
Jörg Schilcher, M.D.
Linköping University, Linköping, SwedenKarl Michaëlsson, M.D., Ph.D.
Uppsala University, Uppsala, SwedenPer Aspenberg, M.D., Ph.D.
Linköping University, Linköping, Sweden
per.aspenberg@liu.seSince publication of their article, the authors report no further potential conflict of interest.
http://www.nejm.org/doi/full/10.1056/NEJMc1106551?query=TOC&
13 mai 2011
Ichtyose congénitale dans la maladie de Gaucher de type II sévère avec mutation nulle homozygote
Vous trouverez des articles traitant du même sujet dans la catégorie "A propos de la maladie de Gaucher"
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Ghislaine SURREL
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Ichtyose congénitale dans la maladie de Gaucher de type II sévère avec mutation nulle homozygote
Voici l’observation d’un nouveau-né présentant une maladie de Gaucher de type II dont le phénotype était inhabituellement sévère avec une ichtyose congénitale, une hépatosplénomégalie , une hypotonie musculaire, des myoclonies et une insuffisance respiratoire. L’étude de la peau en microscopie électronique a montré au niveau de la couche cornée la présence de structures lamellaires considérées comme typiques de la maladie de Gaucher de type II. Le bébé est mort d’insuffisance respiratoire à 1 mois sans avoir fait de progrès neurologique. L’analyse moléculaire a permis d’identifier une mutation homozygote nulle jamais signalée auparavant du gène de la beta-glucocérébrosidase : c.1505G A. La maladie de Gaucher de type II (forme neuronopathique aiguë) est une maladie néo-natale rare de mauvais pronostic. La mutation homozygote décrite ici est responsable de la destruction du site donneur d’épissage entre les exons 10 et 11 à l’origine d’une suppression fonctionnelle de toute l’activité enzymatique : cette mutation entraîne donc la forme clinique la plus sévère de la maladie de Gaucher de type II. La microscopie électronique est utile au diagnostic précoce cat elle permet de montrer les reliquats caractéristiques du trouble métabolique de la barrière lipidique épidermique ; la beta-cérébroglucosidase est essentielle au fonctionnement de la barrière épidermique.
Congenital Ichthyosis in Severe Type II Gaucher Disease with a Homozygous Null Mutation
[27-04-2011]
Sabine Haverkaempera, Thorsten Marquardtc, Ingrid Hausserd, Katharina Timmea, Thomas Kuehna, Christoph Hertzbergb, Rainer Rossia
Departments of
aPediatrics and
bPediatric Neurology and Social Care, Klinikum Neukoelln, Berlin,
cDepartment of Pediatrics, University Hospital, Muenster, and
dDepartment of Dermatology, Electron Microscopy Laboratory, University Hospital, Heidelberg, Germany
Abstract
This paper describes a neonate with type II Gaucher disease. The phenotype was unusually severe with congenital ichthyosis, hepatosplenomegaly, muscular hypotonia, myoclonus and respiratory failure. Electron microscopy of the skin revealed lamellar body contents in the stratum corneum interstices, appearances considered to be typical of type II Gaucher disease. The baby died from respiratory failure 1 month postpartum having made no neurological progress. Molecular analysis identified a previously not reported homozygous null mutation, c.1505G→A of the β-glucocerebrosidase gene.
2109298_CongenitalIchthyosisinSev
Maladie de Gaucher de type 1 : anomalie de l’adhésion plaquettaire et risque de saignement muqueux (Platelet adhesion defect in
Article classé dans la catégorie : "Examens biologiques, IRM,...".
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Ghislaine SURREL
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| Maladie de Gaucher de type 1 : anomalie de l’adhésion plaquettaire et risque de saignement muqueux |
Les patients qui présentent une maladie de Gaucher de type 1 peuvent avoir une tendance clinique significative au saignement, sans rapport avec le niveau de leur taux de plaquettes. Pour vérifier le rôle joué par les plaquettes une étude israélienne a inclus 48 patients avec une maladie de Gaucher de type 1, 52 porteurs (parents d’enfants avec une maladie de Gaucher) et 19 témoins bien portants. Chez les patients l’adhésion des plaquettes était significativement plus faible que chez les témoins ou chez les porteurs. L’adhésion plaquettaire n’était pas modifiée par la prise d’une enzymothérapie substitutive spécifique de la maladie, mais elle était améliorée après splénectomie. Cette diminution de l’adhésion était liée à un défaut plaquettaire intrinsèque. Un saignement muqueux était signalé chez 17 patients (35,4%) et était associé à une anomalie de l’adhésion (odd ratios : 5,73). Chez 5 patients il existait une baisse de l’agrégation plaquettaire et tous présentaient une diminution de l’adhésion plaquettaire. Le défaut d’agrégation plaquettaire n’était pas associé avec des saignements muqueux. Une anomalie de l’adhésion plaquettaire constitue une thrombocytopathie majeure chez les patients qui présentent une maladie de Gaucher de type 1 et peut expliquer en partie la tendance augmentée au saignement.
Platelet adhesion defect in type I Gaucher Disease is associated with a risk of mucosal bleeding Galia Spectre 1, Batia Roth 1, Galia Ronen 3, Dror Rosengarten 4, Deborah Elstein 4, Ari Zimran 4, David Varon 1, Shoshana Revel‐Vilk 2 1 Coagulation Unit *Correspondence:G. Spectre, Coagulation Unit, Hadassah‐Hebrew University Medical Centre, Jerusalem 91120, Israel. E‐mail: galias@hadassah.org.il SummaryPatients with type I Gaucher Disease (GD) may have a clinically significant bleeding tendency that is disproportionate to their platelet count. We hypothesized that impaired platelet adhesion might contribute to bleeding tendency. Adult patients with type I GD with platelet counts ≥130 × 109/l and haematocrit ≥30% (n = 48), obligatory carriers (n = 52), and healthy controls (n = 19) were studied. Platelet adhesion, using the IMPACT‐R (Cone and Plate(let) Analyser), and platelet aggregation were determined. Type I GD patients had significantly lower platelet adhesion [surface coverage %, median (interquartile range)] 4·6 (3·2–7·5), compared to controls, 8·7 (7·6–10·3), or carriers, 8·1 (6·5–9·4; P = 0·001). Platelet adhesion was not affected by the use of disease‐specific enzyme replacement therapy but was improved in patients after splenectomy, 7·2 (5·8–9·3). Mixing tests showed that the reduced adhesion was an intrinsic platelet defect. Mucosal bleeding was reported in 17 (35·4%) patients and was associated with abnormal adhesion [P = 0·037, with an Odds Ratio (95% confidence interval) of 5·73 (1·1–29·6)]. Five patients (22%) had reduced platelet aggregation, all of whom had reduced platelet adhesion. Platelet aggregation defect was not associated with mucosal bleeding. In conclusion, platelet adhesion defect is a major thrombocytopathy in type I GD patients and can explain part of the increased tendency to bleeding. A bleeding tendency is a prominent feature of type I Gaucher disease (GD). The main bleeding symptom of these patients is mucocutaneous, which manifests as epistaxis, gingival bleeding, easy bruising, and/or heavy menstrual bleeding (Granovsky‐Grisaru , 1995; Larsen , 2003; Zimran , 2005). Increased bleeding tendency in GD is commonly attributed to thrombocytopenia secondary to hypersplenism and/or to bone marrow infiltration. Reduction in the activity of various coagulation factors, in particular low factor XI levels, and increased fibrinolysis, have also been described, mainly in unsplenectomized patients (Hollak , 1997; Katz , 1999; Deghady , 2006; Giona , 2006). A high gene frequency of both factor XI deficiency and type I GD in Ashkenazi Jews can explain the relatively common concurrence of both genetic disorders (Seligsohn , 1976; Berrebi , 1992). However, it has been considered that some GD patients have a clinically significant bleeding tendency that is not proportional to their platelet counts or coagulation abnormalities. Thus, an additional cause for bleeding may be an abnormal platelet function (Kelsey , 1994; Gillis , 1999; Giona , 2006). Abnormal platelet aggregation has been described in seven patients with type I GD in a series of 32 patients (22%) from our clinic (Gillis , 1999) and in six of 15 patients (40%) in another study (Giona , 2006). Adhesion of platelets to the injured vessel wall, the initial step of the haemostatic response, is crucial for normal platelet function. To date, this important aspect of platelet response has not been studied in GD. We hypothesized that impaired platelet adhesion might contribute to the bleeding diathesis observed in patients with GD. In the present study we tested platelet adhesion under arterial shear conditions in patients with type I GD, obligatory carriers of the disease, and healthy volunteers. We used the IMPACT‐R [Cone and Plate(let) Analyser] technique (Shenkman , 2000). In addition, mixing studies were performed in order to evaluate the differential role of platelets, plasma, and red blood cells (RBCs) in platelet adhesion in GD. Materials and methodsPatients and controls Type I GD adult patients followed at the Gaucher Clinic, Shaare Zedek Medical Centre were eligible for this study. Diagnosis of GD was made by demonstration of decreased glucocerebrosidase activity in leucocytes (Beutler & Kuhl, 1970) and by mutation analysis at the DNA level (Beutler , 1992). In a few patients bone marrow findings of Gaucher cells in bone marrow, with a combination of two mutated alleles were acceptable in the absence of an enzymatic diagnosis. Lower platelet counts and/or haematocrit levels are known to be associated with abnormal adhesion using the IMPACT‐R system (Varon , 1997; Kenet , 1998), therefore we included only patients with platelet counts ≥130 × 109/l and haematocrit ≥30%. Data were recorded from the clinic medical files of all patients, including year of birth, ethnic origin, mutation analysis, history of bleeding episodes, history of splenectomy, and history of medical treatment, i.e. enzyme replacement therapy (ERT) or substrate reduction therapy (SRT). Disease severity was calculated by the severity score index (SSI; Zimran , 1989). Obligatory carriers, parents of children with GD coming to the clinic at the time of study period, and a group of hospital personnel as healthy controls were also enrolled in the study. All study participants signed an informed consent form. The study was approved by the local ethics (Helsinki) committee. Blood counts and platelet adhesion tests Samples for complete blood count were collected in EDTA tubes. Platelet adhesion under flow conditions was studied using the IMPACT‐R (Cone and Plate (let) Analyser; DiaMed, Cressier, Switzerland; Shenkman , 2000). Blood samples for the IMPACT‐R test were collected in citrate tubes containing 0·38% sodium citrate, and were analysed within 3 h after blood draw. Citrated whole blood (130 μl) were placed on polystyrene plates (Nunc, Roskilde, Denmark) and subjected to a shear rate of (1800/s) for 2 min using a rotating teflon cone. The wells were then thoroughly washed with tap water, stained with May–Gruenwald stain (Sigma, Rehovot, Israel). The image of adhered platelets was analysed with an inverted light microscope (Olympus, Tokyo, Japan) connected to an image analysis system (Galai, Migdal Haemek, Israel). Two parameters of platelet adhesion were evaluated: percent surface coverage (SC, %) which is the percentage of total area covered by platelets (single platelets and clusters/aggregates) and the average size (AS, μm2) of the polystyrene bound platelet clusters/aggregates. The samples were analysed in duplicates, and the higher platelet adhesion result was used for statistical analysis. The normal values of the IMPACT‐R test were previously specified as SC: ≥7% and AS: ≥23 μm2, based on the 5th percentile of log transformed data from 98 adult controls (Revel‐Vilk , 2009). Preparation of platelet rich plasma, platelet poor plasma, and red blood cells Platelet rich plasma (PRP) was prepared by centrifugation of anti‐coagulated whole blood 180 g for 12 min at room temperature. Red blood cells were isolated by further centrifugation of the remaining layer of whole blood at 1200 g for 5 min. The supernatant consisted of platelet poor plasma (PPP). Mixing studies Mixing studies were performed in nine pairs of patients and healthy volunteers, matched for blood type. Normal RBC (adjusted to the haematocrit of 40%) were reconstituted with patient’s PRP, incubated for 5 min with gentle rotation (10 rpm) and then analysed by the IMPACT‐R test. In the same manner, normal PRP was reconstituted with the patients’ RBC, and patients’ PPP was added to normal whole blood. In all experiments, autologous reconstitution of the healthy volunteer’s blood served as a control. Platelet aggregometry Platelet aggregation was measured by a routine platelet aggregometer (PACKS‐4, Helena Laboratories, Beaumont, TX, USA) using the following agonists (obtained from Diamed, Switzerland): ADP (10 μmol/l), epinephrine (10 μmol/l), and collagen (5 μg/ml). Platelet aggregation was considered normal if maximal aggregation amplitude was >60%. Statistical analysis Characteristics of study subjects are presented as nominal data. The percentages are presented with Fisher’s exact 95% confidence interval (CI). Nominal variables are presented as median (interquartile range) or mean (95% CI), where applicable. Differences in age, platelet count, haematocrit, and SC/AS measurements between the different groups were assessed using the parametric and non‐parametric tests for normally and non‐normally distributed data, respectively. Adjustment of P values to correct for possible significance resulting from performance of multiple tests on the same data (Bonferroni like correction‐Hommel adjusted p; Wright, 1992) was performed with WINPEPI (PEPI‐for‐Windows, Version 2.8, March 2007). Differences for mixing tests were evaluated by a paired T‐test. To compare between GD patients with and without mucosal bleeding a logistic regression model was used. The following variables were considered: platelet count, haematocrit, SC/AS measurement, platelet aggregation test, SSI, and ERT. Statistical analysis was performed with the Statistical Package for the Social Sciences (SPSS), version 14 for Windows. A P value <0·05 was considered significant. ResultsForty‐eight adult patients with type I GD, 52 obligatory carriers, and 19 controls were enrolled to this study. The clinical characteristics of the GD patients are presented in Table I. I Characteristics of patients with type I Gaucher disease.
 Table 1 Effect of gaucher disease on platelet adhesion Patients with type I GD had a significantly lower SC as compared to controls and obligatory carriers (Table II). The platelet counts of GD patients were not significantly different from controls; however they were significantly lower as compared to obligatory carriers. No differences in AS measurements were found between patients, obligatory carries and controls.
II Laboratory characteristics of patients and obligatory carriers and healthy volunteers.
Data presented as median (interquartile range). M, male; F, female. *P value for Gaucher patients compared to control. †P value for Gaucher patients compared to obligatory carriers. ‡P value for controls compared to obligatory carriers. Table 2
Given that differences in platelet counts could potentially affect the difference observed in SC, 15 participants with platelet counts <160 × 109/l were excluded from the analysis in order to attain a median platelet count that was not significantly different between patients, obligatory carriers, and controls (P = 0·1). Also in this subgroups analysis, SC was significantly lower in patients, median (interquartile range), 5·9 (3·4–9), as compared to obligatory carriers, 8·1 (6·7–9·4) or controls, 8·8 (7·9–10·2; P = 0·001). Correlation was found between SC and platelet counts in patients with type I GD (correlation coefficient 0·34, P = 0·017, Spearman correlation test). No correlation was found with age and the SSI. No correlation was found between SC and platelet count in controls or in obligatory carriers. Representative photographs of platelet adhesion in a patient and a healthy control are shown (Fig 1).
Figure 1 Reduced platelet adhesion in Gaucher disease. A representative platelet adhesion picture (IMPACT‐R, Cone and platelet analyser) of a healthy control (right): Surface coverage (SC) 9% Average size (AS) 27 μm2, and a patient with Type I Gaucher disease (left) SC 3·3%, AS 23 μm2. Effect of ert and splenectomy on platelet adhesion ERT‐treated patients had similar platelet counts, SC, and AS of aggregates compared to untreated patients (Table III). Splenectomized patients on ERT had significantly higher platelet counts and SC as compared to patients on ERT only. Only one splenectomized patient did not receive ERT and was excluded from this analysis. III Characteristics of patients with Gaucher type I with or without enzyme replacement therapy (ERT).
Data presented as median (interquartile range). ERT, enzyme replacement therapy. *One splenectomized patient who did not receive ERT was excluded from the analysis. †P value for patients without therapy compared to those who received ERT. ‡P value for patients without therapy compared to those who received ERT and underwent splenectomy. §P value for patients who received ERT compared to who received ERT and underwent splenectomy. Table 3Although a trend of higher platelet count was found in splenectomized patients compared to controls (Fig 2A), the SC of those patients tended to be lower compared to controls (Fig 2B).
Figure 2 (A) Platelet counts in patients with Gaucher disease and controls. A box plot for the platelet count (×109/l) in untreated patients (no Rx, n = 11), patients receiving only ERT (ERT = 20), splenectomized patients also receiving ERT (ERT and splenectomy, n = 16), and controls (n = 19). A trend for higher platelet count in splenectomized patients on ERT compared to controls (P = 0·066). (B) Surface coverage in patients with Gaucher disease and controls. A box plot curve for the surface coverage (% IMPACT‐R) in untreated patients (no Rx, n = 11), patients receiving only ERT (ERT n = 20), splenectomized patients receiving also ERT (ERT and splenectomy, n = 16) and controls (n = 19). A trend for lower surface coverage in splenectomized patients on ERT as compared to controls (P = 0·071). No correlation was found between platelet counts and SC during analysis of the different treatment groups, i.e. untreated with intact spleen, ERT with intact spleen, and ERT with splenectomy. Bleeding history in patients with gaucher disease Twenty‐eight patients reported a previous history of bleeding episodes (58·3%, 95% CI 43·2%‐72·4%). Eleven patients (22·9%) reported only easy bruising. Mucosal bleeding was reported 17 patients (35·4%), including epistaxis, menorrhagia, gingival bleeding, rectal bleeding, and prolonged bleeding after cuts or surgery. A bleeding history was not obtained in one patient. A history of mucosal bleeding was not associated with the SSI, ERT, platelet counts, haematocrit level, and/or SC/AS measurements. To improve the diagnostic value of the IMPACT‐R test as a potential predicative test for mucosal bleeding, the results of both the SC and the AS measurements were used to define an abnormal test. An abnormal IMPACT‐R test, (defined as an abnormal SC < 7% and/or AS < 23 μm2) was found in 32 patients (66·7%, 95% CI 51·6–79·6%) and was associated with history of mucosal bleeding. An abnormal IMPACT‐R test was found in 15/17 (88·2%, 95% CI 63·6–98·5%) of patients with mucosal bleeding as compared to 17/30 (56·6%, 95% CI 37·4–74·5%) of patients without mucosal bleeding (P = 0·037). The Odds Ratio (95% CI) for mucosal bleeding in GD patients with an abnormal IMPACT‐R test was 5·73 (1·1–29·6). Mixing studies in patients and controls Platelet adhesion in the IMPACT‐R system is influenced by platelets, RBCs, and plasma components (Shenkman , 2000; Peerschke , 2007). To test the differential role of each component in the observed reduced platelet adhesion in GD, we performed mixing studies in nine pairs of patients and controls. Patient PRP mixed with control RBC resulted in a lower SC compared to control PRP mixed with control RBC, mean (95% CI), 3·5% (1·5–5·5%) and 8·5% (7·2–9·8%), respectively (P < 0·001; Fig 3).
Figure 3 Mixing studies in patients and controls. RBC, red blood cell; PRP, platelet rich plasma; PPP, platelet poor plasma; WB, whole blood; C, control; P, patient; NS, not significant. Surface coverage (%) of reconstituted samples of patients and controls (n = 9) as described in material and methods. Surface coverage was significantly reduced when RBC‐C were reconstituted with PRP‐P. No change in SC was observed when patient PPP or RBC was reconstituted with control blood. Mixing of control PPP with control whole blood diluted the sample and reduced platelet adhesion, mean SC (95% CI), 4·54% (3·34–5·74%). However, mixing of patient PPP with control whole blood did not reduce platelet adhesion further: mean SC (95% CI), 4·29% (2·85–5·72%). Mixing of patient RBC with control PRP did not change platelet adhesion (for the whole group of patients, n = 8), mean SC (95% CI), 5·98% (3·7–8·26%; Fig 3). However, a splenectomized patients’ RBC mixed with normal PRP reduced SC as compared to autologous mixing of control RBC and control PRP (n = 5, P = 0·04). This phenomenon did not occur in the patients with intact spleens (n = 3, P = 0·4). Platelet aggregation Platelet aggregation in response to epinephrine, ADP, collagen and ristocetin was tested in 22 patients. Platelet counts, SC/AS measurements, and rate of abnormal IMPACT‐R test were not different in patients who were tested or not for platelet aggregation. Isolated abnormal platelet aggregation in response to epinephrine was observed in three (13%) patients (Kambayashi , 1996). Abnormal platelet aggregation in response to ADP and/or collagen was observed in five (22%) patients, all of whom had an abnormal IMPACT‐R test [positive predictive value of 100% (95% CI 89–100%)]. Aggregation in response to ristocetin was normal in all patients. Platelet aggregation defect alone was not associated with mucosal bleeding (P = 0·32). DiscussionThis study was designed to assess the platelet adhesion in patients with type I GD. Platelet adhesion was found to be lower in patients with GD compared to obligatory carriers and controls. Platelet adhesion was not affected by the use of ERT and was improved after splenectomy. A platelet adhesion defect, measured by the IMPACT‐R system, occurred in two‐thirds of GD patients and was associated with history of mucosal bleeding.The IMPACT‐R system measures both the adhesion of platelets to the polystyrene surface (SC), as well as the aggregation of circulating platelets around adherent platelets associated with the release reaction (AS). The significantly lower SC in GD patients compared to controls suggests that a platelet adhesion defect is a major thrombocytopathy in patients with GD. This thrombocytopathy might be missed when testing platelet function only with the platelet aggregometer. Indeed, abnormal platelet aggregation was found in only one‐fifth of the patients in this study and others (Gillis , 1999; Giona , 2006). The mechanism of reduced platelet adhesion in patients with type I GD is not clear. Based on mixing tests, reduced adhesion is an intrinsic platelets defect and not affected by RBCs or plasma of these patients. The increased plasma levels of glucocerebroside in patients with GD may affect platelet activation (Nilsson , 1982; Aerts & Hollak, 1997; Gousset , 2002). However, this mechanism could possibly explain platelet abnormalities only in untreated patients. Alternatively, extracts of platelets were found to be rich in an aggregated, activated form of the glucocerebrosidase (Yatziv , 1974), thus lack of the enzyme in GD might cause increased glucocerebroside in the platelets and affect platelet function. In our study, patients receiving ERT did not have higher platelet counts or platelet adhesion compared to untreated patients. This is in contrast to previous studies where platelet counts and platelet aggregation were shown to be improved after starting ERT (Hollak , 1997; Gillis , 1999; Giona , 2006). By excluding patients with low platelet counts, we might have influenced the chance to find differences in platelet counts and platelet adhesion between ERT‐treated and untreated patients. In contrast, splenectomy was associated both with improved platelet counts and platelet adhesion as measured by the IMPACT‐R system. The improved platelet adhesion found after splenectomy might be directly related to the higher platelet counts. Alternatively, splenomegaly has been suggested to cause chronic platelet activation that might lead to platelet exhaustion with reduced function (Humphries & Hess, 1994; Hollak , 1997). The study inclusion criterion of a platelet count >130 × 109/l has resulted in a relatively high percentage of splenectomized patients (35%) in the era of disease‐specific ERT. The trend to lower SC in splenectomized GD patients compared to controls, in the presence of a tendency for higher platelet counts suggests that the platelet adhesion defect we observed in GD patients is a true pathological finding and is not only a reflection of the low platelet counts. The observation of a lower SC in a subgroup analysis of patients with platelet counts >160 × 109/l, supports a similar conclusion. Preliminary data from mixing studies indicate that RBC from GD patients with intact spleens may reduce the SC of normal platelets, as compared to RBC from splenectomized patients. These preliminary results suggest that the better platelet adhesion profile of splenectomized patients could also result from elimination of a yet unknown effect of splenomegaly on RBC physiology under high shear stress. Further research is needed to study the mechanism of the platelet adhesion defect in GD patients. Of interest is the association of abnormal platelet function measured by the IMPACT‐R system with history of mucocutaneous bleeding. No similar association was reported with the more commonly performed platelet aggregation test. Studying whole blood platelet adhesion under high shear rate may be a more relevant parameter for correlation with bleeding symptoms. In previous studies, the IMPACT‐R method was shown to be effective in the assessment of platelet function in thrombocytopenic patients (Kenet , 1998) and in patients undergoing cardiac surgery (Gerrah , 2004). Recently, the IMPACT‐R method was shown to be a useful screening tool for bleeding disorders in children evaluated for bleeding tendency (Revel‐Vilk , 2009). The diagnosis of bleeding risk is clinically important in preparing patients before surgery or delivery. The current recommendations in patients with GD include performing a complete history of bleeding tendency (including easy bruising and recurrent gum or nose bleeds, and heavy menstrual bleeds), a complete blood count, coagulation factors assays if the prothrombin time and/or partial thromboplastin time are abnormal, platelet aggregation tests, and von Willebrand factor levels and activity (Ioscovich , 2005; Zimran , 2005). Platelet adhesion studies are currently used in the Gaucher Clinic, Shaare Zedek Medical Centre, as part of the routine check of the haemostatic system before surgical procedures or delivery. In conclusion, platelet adhesion defect is commonly found in type I GD patients and can explain some of the increased bleeding tendency in these patients. Testing platelet adhesion should be considered before surgery, delivery or dental procedures in order to assess the need for platelet transfusions, antifibrinolytic agents or desmopressin (DDAVP) in the individual patient. The first two authors contributed equally to the paper. References (Exportez format texte tabulé) • Aerts, J.M. & Hollak, C.E. (1997) Plasma and metabolic abnormalities in Gaucher’s disease. Baillieres Clinical Haematology, 10, 691–709.
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D-dimères et atteintes osseuses et pulmonaires dans la maladie de Gaucher (D-dimer assay in Egyptian patients with Gaucher disea
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Ghislaine SURREL
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| D-dimères et atteintes osseuses et pulmonaires dans la maladie de Gaucher | Dans la maladie de Gaucher, les atteintes osseuses et pulmonaires constituent 2 causes majeures de morbidité. Pour évaluer le caractère prédictif potentiel du taux de D-dimères (indicateur fiable d’une thrombose microvasculaire active), une étude égyptienne a inclus 56 patients présentant une maladie de Gaucher (36 types 1 et 20 types 3) et 30 témoins bien portants. Le taux de D-dimères était significativement plus élevé chez tous les patients par rapport aux témoins et chez les patients avec une maladie de type 3 par rapport aux patients avec une maladie de type 1. Une proportion plus importante de patients avec un type 3 présentait une atteinte pulmonaire et une proportion plus importante de patients avec un type 1 présentait une atteinte osseuse. Le taux de D-dimères était significativement plus élevé en cas d’anomalies des os longs à l’IRM et en cas d’aspect en verre dépoli au scanner thoracique. Les patients splénectomisés présentaient un taux plus élevés de D-dimères que ceux qui ne l’étaient pas. Selon les auteurs ces résultats montrent que le taux de D-dimères est significativement élevé dans la maladie de Gaucher, en particulier dans le type 3, et suggèrent qu’il représente un marqueur prédictif potentiel d’atteinte des os et des poumons utilisable au cours de la surveillance de la réponse au traitement. |
D-dimer assay in Egyptian patients with Gaucher disease: correlation with bone and lung involvement
[13-05-2011]
Sherif, Eman Ma; Tantawy, Azza AGa; Adly, Amira AMa; Kader, Hossam Ab; Ismail, Eman ARc
aDepartment of Pediatrics, Egypt, bDepartment of Radiology, Egypt, cDepartment of Clinical Pathology, Faculty of Medicine, Ain Shams University, Cairo, Egypt
Received 20 August, 2010, Revised 17 October, 2010, Accepted 27 October, 2010
Correspondence to Eman A.R. Ismail, MD, 5 Nageb Mahfoz Street, Agouza, 12654 Giza, Egypt Fax: +202 3337 5435; e-mail: eman.ismail_70@yahoo.com
Abstract
Gaucher disease is the most frequent lysosomal storage disorder. Bone and lung involvement are two major causes of morbidity in this disease. D-dimer is a reliable indicator of active microvascular thrombosis, even in patients without overt hypercoagulation. This study aimed to assess D-dimer levels in Gaucher disease, correlating this marker to clinical characteristics and radiological parameters to investigate its role as a potential predictor for the occurrence and severity of skeletal and pulmonary manifestations. The study population consisted of 56 Egyptian patients with Gaucher disease, 36 had type 1 Gaucher disease (64.3%) and 20 had type 3 Gaucher disease (35.7%). Thirty healthy individuals were enrolled as a control group. D-dimer levels were significantly higher in all patients with Gaucher disease compared with controls (P < 0.001). Patients with type 3 showed significantly higher D-dimer concentrations compared with type 1 (P < 0.001). Pulmonary involvement was present in a significant proportion among type 3 Gaucher patients (P < 0.05), whereas bone changes were present in a higher percentage in type 1 compared with type 3 Gaucher patients. D-dimers were significantly higher in patients with abnormal MRI findings of the long bones and in those with ground glass appearance on high-resolution computerized tomography of the chest compared with patients with normal radiology (P < 0.001). Splenectomized patients displayed significantly higher D-dimer levels compared with nonsplenectomized patients (P < 0.001). Our results suggest that D-dimer is significantly elevated in Gaucher disease, particularly type 3, and may be considered as a potential marker of risk prediction of bone and lung involvement that could be used to monitor treatment response.
Introduction
The lysosomal storage diseases have a cumulative incidence of 1 in 5000 live births [1]. Gaucher disease predominates among this group, having a frequency of 1 in 40 000 in the United States [2,3]. Gaucher disease results from an autosomal recessive deficiency of the lysosomal enzyme acid [beta]-glucosidase [glucocerebrosidase (GBA)], which is responsible for hydrolysis of glucocerebroside [glucosylceramide (GLC)] [4]. Mutations in the GBA gene result in Gaucher disease and many of these mutations are missense alterations that may cause misfolding, decreased stability and/or mistrafficking of this lysosomal protein [5]. Absent or reduced enzymatic activity leads to accumulation of GLC in various cells of the macrophage–monocyte system (Gaucher cells) [6,7]. Classically, the pathophysiology of Gaucher disease has been attributed to the amount, location and rate of accumulation of the stored material [8,9]. The manifestations of Gaucher disease occurring due to accumulation of Gaucher cells in three main anatomical compartments, namely the osseous skeleton, the bone marrow and visceral organs [4,10].
As with most genetic diseases, the signs and symptoms of Gaucher disease present along a continuum, ranging from the lethal neonatal form to the asymptomatic form [11]. Currently, Gaucher disease is classified into three clinical forms: nonneuropathic (type 1), acute neuropathic (type 2) and chronic neuropathic (type 3) [3,10]. Patients with type 1 disease may present at any age with hepatosplenomegaly, anemia, thrombocytopenia, often skeletal involvement (such as avascular necrosis of the large joints or pathological fractures) or lung disease. Age and mode of presentation as well as the eventual clinical course are highly variable, yet phenotypic heterogeneity can be attributed only in part to specific mutations [9,12].
Bone disease usually designates the advanced stages of Gaucher disease, but susceptibility to fractures and avascular necrosis can be the first sign of Gaucher disease in otherwise asymptomatic patients [13]. The skeletal aspects of the disease have a much greater impact on patients' quality of life than the hematological and visceral aspects. Moreover, skeletal manifestations are commonly seen in patients with normal hematology [14]. Therefore, it is important for physicians not to focus only on hematological and visceral complications on the expense of skeletal involvement when assessing the response to enzyme replacement therapy (ERT) [15,16]. Nearly, all patients with Gaucher disease have radiological evidence of skeletal involvement including Erlenmeyer flask deformity, osteopenia, osteosclerosis, osteonecrosis, fractures and bone marrow infiltration. Skeletal involvement follows three basic processes: focal disease (irreversible lesions such as osteonecrosis and osteosclerosis), local disease (reversible abnormalities adjacent to heavily involved marrow such as cortical thinning and long bone deformity) and generalized osteopenia [17]. For more accurate assessment of bone disease in adults and children, it is desirable to conduct MRI studies at centers with radiologists experienced in evaluating patients with Gaucher disease [18].
Symptomatic lung involvement may be common at presentation, and may progress over the course of the disease to pulmonary hypertension in some patients, particularly in type 3 Gaucher disease [13]. Chest radiographs may demonstrate reticulonodular changes, and on high-resolution computerized tomography (HRCT), a range of abnormal patterns including widespread ground glass opacification may be present [19,20].
Many factors may trigger or aggravate symptoms and signs of the disease including environmental or acquired conditions, such as viral infections or pregnancy. In addition, other concurrent genetic defects such as partial deficiency of coagulation factors aggravate the tendency to bleeding and may contribute to the variability of clinical manifestations in Gaucher patients. These modifiers may be helpful in predicting risk of developing bone and/or lung disease [3,10,21]. A logical theory to explain the incidence of avascular bone necrosis and pulmonary hypertension in Gaucher disease was an inherited predilection for hypercoagulability [9,22]. Gaucher disease has been the playground to develop new therapeutic interventions such as ERT and substrate-reduction therapy. The availability of these costly therapies has stimulated research regarding suitable biomarkers to monitor onset and progression of disease, as well as the efficacy of therapeutic intervention [23].
D-dimer assays are ordered, along with laboratory tests that help to rule out, diagnose and monitor conditions associated with hypercoagulability [24,25]. The possibility of correlation between avascular bone necrosis and pulmonary hypertension in Gaucher patients with D-dimer levels was considered because it would implicate involvement of microthrombosis, without expecting a quantitative correlation with hypercoagulability per se [9]. However, there have been few studies that evaluated the impact of this reliable indicator of coagulation on the development and severity of skeletal and pulmonary manifestations in Gaucher disease.
Therefore, this study aimed to assess D-dimer levels in Egyptian patients with Gaucher disease as a potential predictor for the occurrence and severity of bone and lung involvement correlating this marker to clinical characteristics and radiological parameters.
Patients and methods
This cross-sectional study was conducted on 56 consecutive patients with Gaucher disease attending the Hematology/Oncology Clinic in Pediatric Hospital, Ain Shams University, from June 2009 to May 2010. They were 33 men and 23 women, with a male to female ratio of 1.4: 1. The mean age at diagnosis in the study population as a whole was 6.0 ± 3.9 years (range, 2.5–13 years). Control samples (peripheral blood) were obtained from 30 healthy children and adolescents with no history of inborn errors of metabolism in their first-degree and second-degree relatives. Twelve were men and 18 were women (male to female ratio, 1: 1.5). The mean age of the control population was 7.4 ± 4.24 years (range, 3–15 years). A written consent was obtained from the guardian of each case and control before participation in the study. The study was approved from the local ethical committee.
All patients were subjected to full medical history with special emphasis on bone manifestations (pains or fractures), hematological manifestations (pallor, bleeding and history of blood transfusion), pulmonary manifestations (cough, dyspnea and recurrent chest infections) and neurological symptoms (squint, convulsions, bulber manifestations, trismus and manifestations suggestive of cerebellar affection). Thorough clinical examination was performed laying stress on anthropometric measures, abdominal examination with assessment of hepatic and splenic size and full neurological examination including cranial nerves, motor and sensory systems. Radiological investigations included plain radiograph on long bones, chest radiograph, abdominal ultrasonography to assess the volume of liver and spleen in cubic centimeter (calculated as multiples of normal sizes predicted for body weight) [15] and MRI on pelvis and femur, as well as HRCT on both lung fields.
Laboratory investigations for Gaucher patients included complete blood count, examination of peripheral blood-stained smears, bone marrow aspiration and examination of stained smears and coagulation profile, as well as liver and renal function tests. GBA enzyme activity was assessed in peripheral blood leukocytes and plasma chitotriosidase was measured at diagnosis and for follow-up of the response of ERT as a sensitive indicator of dose effects. Molecular analysis of the acid GBA gene was performed for 18 patients.
Diagnostic criteria
Diagnosis of Gaucher disease was based on the presence of hepatosplenomegaly, bone involvement, hematological manifestations and developmental delay with or without neurological manifestations in the form of occulomotor abnormalities and/or convulsions. This was confirmed by laboratory findings of Gaucher cells in bone marrow aspirate and biopsy, low GBA activity [4] and high plasma level of chitotriosidase activity [26,27].
The clinical and laboratory characteristics of the studied Gaucher patients are summarized in Table 1. The studied patients were divided into two groups:
Table 1 Clinicopathological characteristics of the studied Gaucher patients
Group I included 36 patients with type 1 Gaucher disease (64.3%). They were 20 men and 16 women with a male to female ratio of 1.3: 1. Their ages at the time of the study ranged from 2.5 to 18 years with a mean of 6.6 ± 5.7 years. Type 1 patients presented initially with hepatosplenomegaly, bony manifestations, anemia and thrombocytopenia. At time of the study, 19 of 36 type 1 patients had anemia and 15 had thrombocytopenia as well as organomegaly. The duration of treatment ranged from 1 to 8 years with a mean of 2.9 ± 2.4 years. They were under ERT in a dose ranging from 60 to 90 U/kg per 2 weeks with a mean of 66 ± 13.4 U/kg per 2 weeks.
Group II included 20 patients with type 3 Gaucher disease (35.7%). They were 12 men and eight women (male to female ratio, 1.5: 1). Their ages at the time of the study ranged from 2.5 to 15 years with a mean of 7.8 ± 4.4 years. Type 3 patients presented with neurological manifestations in the form of ophthalmoplegia, neck stiffness, dysphagia, convulsions and trismus, in addition to visceral and hematological manifestations. The duration of treatment ranged from 1.5 to 8 years with a mean of 6.6 ± 5.7 years. They were under ERT in a dose ranging from 60 to 120 U/kg per 2 weeks with a mean of 84 ± 20.8 U/kg per 2 weeks.
None of the studied patients had advanced liver disease, active inflammatory conditions or were on anticoagulant therapy at time of study. Fourteen patients (35%) were splenectomized prior to the onset of ERT. All patients were under regular ERT [28,29] for a period of 1–8 years starting from January 1999. ERT was first given using the placenta-derived aglucerase (Ceredase; Genzyme Corporation, Cambridge, Massachusetts, USA) at low dose regimen (15 U/kg per 2 weeks). The recombinant enzyme imiglucerase (Cerezyme; Genzyme Corporation) was applied in March 1999 in a dose of 20–30 U/kg per month, divided into four equal weekly doses. In July 1999, Cerezyme was administered in a dose of 60 U/kg per 2 weeks. Six patients with type 3 received high doses of 120 U/kg per 2 weeks, one of them had progressive neurological disease and the others suffered severe pulmonary involvement.
Blood sampling and assay of d-dimer
As part for routine work-up for Gaucher disease, peripheral blood samples were collected on 3.2% buffered sodium citrate at a ratio of nine parts blood to one part anticoagulant (1: 10 ratio) and centrifuged at 1600 g for 15 min. D-dimer concentrations were determined in platelet-poor plasma using Tina-quant assay (Roche Diagnostics, Mannheim, Germany) on a Hitachi 917 analyzer (Roche Diagnostics). Tina-quant D-dimer is an immunoturbidimetric assay in which a beam of monochromatic light is passed through the suspension of latex microparticles coated by covalent bonding with monoclonal antibodies specific for D-dimer. The wavelength of the light is greater than the diameter of the latex microparticles and thus the solution of latex microparticles only slightly absorbs the light. In the presence of D-dimer, the particles aggregate and turbidity increases. The increase in scattered light is proportional to the amount of D-dimer in the test sample. The latex particles are coated with a monoclonal antibody that reacts with fibrin D-dimer or fragment D of fibrin. The antibody has no cross-reactivity with fibrinogen. This allows quantitative determination of D-dimer in human plasma. Normal limit of the assay is 500 µg/l. The test has a lower detectable limit of 40 µg/l [25,30–32].
Statistical analysis
The processing of data was computed using statistical package for social science (SPSS), version 14 IBM compatible PC (SPSS Inc., Chicago, Illinois, USA). Data were described in the form of number and percentage, and range and mean ± SD. In order to compare quantitative variables between two groups, both the Student's t-test and the nonparametric Mann–Whitney U-test were applied. A [chi]2-test was used to compare qualitative variables. A P-value of 0.05 or less and 0.01 or less was considered significant and highly significant, respectively, in all analyses.
Results
Clinical, hematological and radiological features of gaucher patients
Type 1 Gaucher disease was found in 64.3% of patients, and type 3 in 35.7%. Molecular analysis of the acid GBA gene in 18 patients revealed homozygosity for L444P in 11 patients (all were type 3), whereas six type 1 Gaucher patients showed mutation of N370S and only one patient with type 1 Gaucher disease displayed the uncommon homozygous D409H mutation.
As shown in Table 1, age and sex did not differ significantly between patients in both groups, although positive family history for Gaucher disease was significantly present in type 3 compared with type 1 Gaucher patients (P < 0.05). Underweight was frequently observed in type 3 patients, whereas short stature was frequently observed in type 1 (P < 0.001). Mean hepatic and splenic volumes reported in multiples of normal size predicted for body weight in type 1 Gaucher disease were significantly higher when compared with those of type 3 patients (P < 0.001). White blood cell count, hemoglobin levels and platelet counts did not show any significant difference between both study groups of Gaucher disease (P > 0.05). Type 3 Gaucher patients received significantly higher doses of ERT compared with type 1 (P < 0.001).
As regards radiological findings (Table 1), in type 1 Gaucher disease, 21 patients (58%) had Erlenmeyer flask-shaped deformity in radiograph of long bones, as well as bone marrow expansion with cortical thinning in MRI. Moreover, 13 patients (36.1%) had ground glass appearance on HRCT chest. In type 3 Gaucher disease, nine patients (45%) had Erlenmeyer flask-shaped deformity in radiograph and bone marrow expansion with cortical thinning in MRI (Fig. 1). Fourteen patients (70%) had ground glass appearance in HRCT chest (eight of them had interlobular thickening). Pulmonary involvement shown by HRCT results (Figs 2 and 3) was present in a significantly higher percentage among type 3 Gaucher patients compared with type 1 (P < 0.05). Although bone changes represented by MRI findings were present in a higher percentage in type 1 compared with type 3 Gaucher disease, yet the difference did not reach statistical significance (P > 0.05). It was noticed that the studied Gaucher patients under ERT in a dosage of 60 U/kg per 2 weeks suffered from clinically and radiologically evident pulmonary symptoms confirmed by HRCT findings. However, when these patients received higher doses of ERT ranging from 90 to 120 U/kg per 2 weeks, a remarkable improvement in their clinical manifestations was observed. The frequency and severity of chest infections that required hospitalization were markedly decreased. There was decreased dyspnoea, clubbing and cyanosis in some patients, although on radiology, lung pathology was not normalized. Others showed improved respiratory compliance, with a significant improvement of the radiological findings.
D-dimer levels in control population and gaucher patients
D-dimer was negative (<500 µg/l) in controls with a range of 77.8–410 µg/l and a mean value of 215.7 ± 32.5 µg/l. All patients with Gaucher disease had significantly elevated D-dimer levels, with a range of 510–4329 µg/l and a mean of 2018 ± 368 µg/l at time of the study (P < 0.001). Patients with type 1 and type 3 Gaucher disease displayed significantly high D-dimer concentrations than controls when compared separately (P < 0.001) (Fig. 4). Moreover, D-dimer levels were significantly higher in type 3 patients compared with type 1 (mean, 1863.5 ± 414 vs. 830 ± 275.2 µg/l; P < 0.001) (Table 1 and Fig. 4).
D-dimer analysis results in relation to clinical and radiological data
Analysis of D-dimer in relation to clinical and radiological data of Gaucher patients (Table 2) revealed significantly higher levels in patients with abnormal MRI findings of long bones compared with those with normal MRI study (mean, 1563.6 ± 357 vs. 810.7 ± 250 µg/l; P < 0.001). In addition, Gaucher patients with pulmonary involvement on HRCT chest had higher D-dimer concentrations compared with those with normal radiological study (mean, 1980 ± 400 vs. 990 ± 205 µg/l; P < 0.001). Splenectomized patients displayed significantly higher D-dimer levels compared with nonsplenectomized patients (mean, 1670 ± 326 vs. 746 ± 187 µg/l; P < 0.001).
Table 2 Clinical and radiological features of the studied Gaucher patients according to D-dimer levels
Discussion
Studies of genotype–phenotype correlations in Gaucher disease, the most common sphingolipidosis, revealed significant genotypic heterogeneity among clinically similar patients and vastly different phenotypes among patients with the same mutations [11]. The incidence of the subacute neuronopathic (type 3) form is less than one in 100 000 patients. The distribution of type 3 Gaucher disease is panethnic, but this form predominates in some geographic regions such as northern Sweden [33,34]. In the present study, type 3 Gaucher disease was found in 35.7% of patients. This could be explained by the higher prevalence of the genotype L444P among this ethnic group as it was reported that N370S homozygotes generally present with a less severe phenotype, whereas L444P and D409H homozygosity confers neurologic involvement [2,4,35]. This is in contrast to Ashkenazi Jewish population in which the genotype N370S is predominant, resulting in higher prevalence of type 1 Gaucher disease with mild clinical manifestations [13]. Moreover, some genetic mutations are unique to individual groups or families. For instance, D409H/D409H causes calcification of the heart valves and occulomotor apraxia, but without visceral affection occurring uniquely in Jenin Arabs, Japanese and Spanish patients [36,37].
Failure to thrive and underweight were prominent features in the studied patients, especially in type 3 Gaucher disease. In line with our results, Zimran et al. [38] noticed that poor weight gain and growth retardation in those patients occurred likely due to the excessive metabolic burden from accumulation of undegraded substrate and GLC in tissues, together with the chronic nature of the disease and anemia that accounts for the chronic fatigue reported by many patients. The low-grade, smoldering and subclinical internal inflammation in individuals with Gaucher disease is accompanied by an increased degree of erythrocyte and leukocyte adhesiveness/aggregation. These findings might have rheological consequences in terms of microcirculatory slow flow and tissue hypoxemia. An additional factor in type 3 Gaucher patients is pseudobulbar palsy resulting in dysphagia, regurgitation and recurrent aspiration pneumonia [39]. Similarly, Khalifa et al. [40] reported that patients with Gaucher disease were more susceptible to recurrent infection, which is a main cause of debilitation. The tendency toward infection in Gaucher disease patients was attributed to their postsplenectomy state. Furthermore, Orvisky et al. [8] noticed resumption of normal growth in children after receiving ERT.
As previously reported, the estimated life expectancy for patients with type 1 Gaucher disease was mildly decreased than the reference population being 9 years less [41]. Disease progression varies in type 1 Gaucher disease and survival may be normal depending on the severity of complications. On the contrary, evolution is rapid in type 2 Gaucher disease leading to death within the first 2 years of life, usually because of lung failure, whereas type 3 Gaucher disease patients often survive to the second or third decades of life [2,42]. In this study, the significantly higher doses of ERT received by patients with type 3 Gaucher disease compared with type 1 were in concordance to the report of Vellodi et al. [43], who stated that there is clear evidence that ERT improves systemic involvement in nonneuronopathic as well as neuronopathic Gaucher disease enhancing quality of life. In addition, ERT has reversed, stabilized or slowed the progression of neurological involvement in some patients and is considered the gold standard treatment for Gaucher disease type 1 and type 3 patients [27,43,44]. High dose provides a faster clinical response and should be considered for patients with more aggressive disease [45].
Despite some general genotype–phenotype correlations, disease severity and clinical outcomes cannot be predicted on the basis of genotype [13,46]. Genetic modifiers may play an important role in determining the eventual Gaucher phenotype [39]. Identification of biochemical markers characteristic of pathology may be of use in predicting the progression of the disease state [23,34,47]. There are no predictive tests to ascertain patients at risk for bone and lung involvement in Gaucher disease, which are slow to respond to ERT [4,9]. As reported by Deghady et al. [48], bleeding tendency in Gaucher disease may not always be related to absolute platelet counts, but may be influenced by coagulation factor deficiencies or abnormal platelet function. Acquired coagulation factor deficiencies have been demonstrated in Gaucher disease. The mechanism involved is unclear, but may include low-grade disseminated intravascular coagulation or sequestration of coagulation factors by substrate-loaded cells [10].
Quantitative D-dimer determination has become routine practice in patients evaluated for the presence of deep venous thrombosis or pulmonary emboli [25,49]. In this study, plasma fibrin D-dimer was assayed in Gaucher disease using a new quantitative latex test for cross-linked fibrin degradation products, involving a specific monoclonal antibody. This method has been proven to be rapid, sensitive and reproducible [30].
The relevance of the determination of D-dimer in Gaucher disease was evaluated and high plasma D-dimer levels were found among patients with Gaucher disease, especially type 3. In addition, a significant elevation was observed in those with bone changes and pulmonary involvement as reflected by radiological findings. In agreement with our results, Shitrit et al. [9] stated that the levels of elevated of D-dimers were related to the presence of pulmonary infiltration, by Gaucher cells, as well as bone marrow infiltration. They implied that microthrombi may be part of the pathogenesis for avascular necrosis as well as pulmonary hypertension in patients with Gaucher disease. The significant correlation of D-dimer levels with treatment may be an indirect marker of bone and/or lung in Gaucher disease [9]. Additionally, Boot et al. [33] and Maire et al. [34] reported that the elevation of the serum concentration of several serologic markers (e.g. D-dimer, CCL18/PARC, CD163) in persons with Gaucher disease is considered a possible surrogate indicator of disease burden that could be used in monitoring treatment response.
Moreover, it was reported that a normal MRI study in Gaucher patients with elevated D-dimer levels does not rule out subsequent development of bony changes in those patients, especially if splenectomized. Therefore, serial follow-up is required and the rising titer of D-dimer may determine or indicate the proper timing of the next MRI study [20].
Strikingly, higher D-dimer concentrations were found among splenectomized patients with Gaucher disease. These results were in line with those obtained by Ashkenazi et al. [50], who observed that patients with Gaucher disease usually start to suffer from severe bony manifestations and pulmonary hypertension after splenectomy. In a preliminary study, Tunaci et al. [51] reported that asplenia was strongly associated with life-threatening forms of pulmonary hypertension in Gaucher disease, as removal of the spleen, which is the primary reservoir of storage cells, promotes migration of the mononuclear phagocyte system toward other tissue macrophage pools (lung and bone). Recently, Mistry et al. [52] observed a higher risk of avascular necrosis was observed among patients who had previously undergone splenectomy.
Bone involvement was evident clinically and radiologically in the studied patients with type 1 Gaucher disease while pulmonary involvement reflected by HRCT findings was significantly found among type 3 Gaucher disease compared to type 1. This finding could be explained by the significantly elevated D-dimer levels encountered in type 3 Gaucher patients compared to type 1 Gaucher disease which is a less severe form. In this context, El-Beshlawy et al. [46] reported that bone manifestations were the most common presenting symptoms in Egyptian patients with type 1 Gaucher disease as evidenced by MRI long bones and ERT was effective in ameliorating radiological manifestations of skeletal disease and achieving complete remission of bone pain but it required a long period of treatment. Moreover, Jmoudiak and Futerman [13] reported that lung involvement including interstitial lung disease and pulmonary hypertension was found in a small number of patients with type 1 Gaucher disease. Additionally, Miller et al. [53] reported a higher frequency of pulmonary involvement in type 3 Gaucher disease compared to type 1. On the other hand, few patients develop pulmonary hypertension on ERT [54]. Mistry et al. [22] also revealed a remarkable predisposition for pulmonary hypertension in type 1 Gaucher disease. Progression to severe, life-threatening pulmonary hypertension occurs in the presence of additional genetic factors (non-N370S GBA mutation, positive family history and angiotensin converting enzyme I gene polymorphism) and epigenetic modifiers (i.e. asplenia, female sex) [22]. Therefore, routine echocardiographic monitoring of all treated and untreated patients with type 1 Gaucher disease was recommended and consideration of treatment withdrawal was suggested if the TI gradient progresses to more than 30 mmHg [54].
In the present analysis, the remarkable improvement occurred in pulmonary manifestations with higher doses of ERT confirmed the previous reports by Elstein et al. [54] and Ashkenazi et al. [50], who noticed that the lung and bone are less accessible compartments to ERT, so that a low-dose regimen may not be sufficient to overcome a threshold for Gaucher cell infiltration and the dose must be increased to allow an adequate enzyme concentration at the site of the pathology, especially if there are fibrotic or necrotic regions. Moreover, Goitein et al. [55] reported that in patients with Gaucher disease and symptomatic lung involvement, there is great heterogeneity in presentation and response to ERT. Clinically, some benefited significantly from ERT, but in contrast to the dramatic reduction in organomegaly, there was no normalization in pulmonary function or lung architecture. These findings emphasized the importance of optimal dose of ERT, avoidance of splenectomy and vigorous combination therapy with vasodilators, as appropriate for the best outcomes in Gaucher patients [16,29,43].
In conclusion, elevated D-dimer levels in Gaucher patients can be used as a predictor for the development of skeletal and pulmonary complications and may suggest that the occurrence of these pathological changes is induced initially as microthrombi. Thereafter, it would be interesting to apply the fully quantitative automated D-dimer assay in a prospective manner to ‘borderline’ Gaucher patients with persistent dyspnea, bronchorrhea and recurrent pneumonopathy, to ascertain whether they have merely incipient pulmonary changes and follow-up them for the possibility of developing progressive pulmonary hypertension. Further studies are recommended to indicate whether a predictive cut-off level of D-dimer in Gaucher disease can be described.
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Imagerie de la maladie de Gaucher de t1 chez l’enfant (Imaging Findings in Pediatric T1 Gaucher Disease: What the Clinician Need
Article classé dans la catégorie : "Examens biologiques, IRM,...".
Vous trouverez des liens utiles à la suite de la rubrique "CATEGORIE".
Ghislaine SURREL
maladies-lysosomales-subscribe@yahoogroupes.fr
| Imagerie de la maladie de Gaucher de type 1 chez l’enfant |
| La surveillance radiologique systématique joue un rôle essentiel dans l’évaluation de la progression de la maladie de Gaucher et de la réponse au traitement : chez l’enfant elle requiert une attention particulière afin de minimiser l’exposition aux rayonnements et d’interpréter l’importance de l’atteinte médullaire au regard des modifications normales liées à la croissance. Le groupe de travail sur la maladie de Gaucher recommande la pratique d’une IRM des fémurs, du bassin et du rachis (soit une bonne partie du compartiment médullaire osseux) au moment du diagnostic puis tous les 2 ans. Une absorptiométrie biphotonique est recommandée tous les ans (rachis lombaire, fémur proximal et corps entier). La radiographie n’est pas hautement spécifique ni sensible mais elle peut représenter une première technique d’évaluation osseuse quand l’accès à l’IRM est limité. Elle permet de visualiser certaines atteintes osseuses de la maladie de Gaucher et s’avère particulièrement utile dans l’identification des causes de douleurs osseuses aiguës (fractures pathologiques, ostéonécrose) et dans le suivi post-arthroplastie. Plus rarement elle permet d’évoquer le diagnostic de maladie de Gaucher devant la découverte de la déformation classique en flacon d’Erlenmeyer (élargissement de la région métaphyso-diaphysaire des os longs). La splénectomie est associée à l’apparition de lésions ostéolytiques, d’ostéonécrose et de diminution de la densité minérale osseuse. Les découvertes radiographiques incidentes constituent rarement le premier indice d’une maladie de Gaucher chez un enfant. |
| OB |
Imaging Findings in Pediatric Type 1 Gaucher Disease: What the Clinician Needs to Know
[13-05-2011]
Green, Brian A. MD*; Alexander, Alan A.Z. MD†; Hill, Phillip R. MD*; Lowe, Lisa H. MD‡
*Department of Radiology, University of Missouri School of Medicine, 1 Hospital Drive, Columbia
‡Department of Radiology, University of Missouri-Kansas City and Children's Mercy Hospital and Clinics, Kansas City, MO
†Department of Radiology, University of Virginia, 1 Hospital Drive, Charlottesville, VA
The authors have no financial disclosures to report.
Reprints: Alan A.Z. Alexander, MD, Department of Radiology, University of Virginia, 1 Hospital Drive, Charlottesville, VA 22908 (e-mail: aaz.alexander@yahoo.com; e-mail: lhlowe@cmh.edu).
Abstract
This study presents visceral and skeletal imaging findings commonly observed in pediatric patients with type I Gaucher disease. Presented images show methods used for radiologic assessment of pediatric Gaucher patients, and imaging findings are discussed in the context of the underlying pathophysiology of the disease. Routine radiologic surveillance plays a central role in assessing Gaucher disease progression and response to treatment, but monitoring of pediatric patients presents specific challenges with regard to minimizing radiation exposure and interpreting extent of marrow involvement against the backdrop of normal growth-related changes in marrow composition. In addition to highlighting imaging findings in children with type I Gaucher disease, this manuscript discusses alternate modalities, which minimize radiation and may be just as accurate, if not better, than conventional methods exposing the child to radiation.
Keywords: gaucher disease; marrow; hepatosplenomegaly; imaging; enzyme replacement therapy
Table of contents
Gaucher disease is an inherited autosomal recessive metabolic disorder resulting from mutations in the gene encoding [beta]-glucocerebrosidase, an enzyme in the glycosphingolipid degradation pathway.1 Glucocerebrosidase deficiency leads to massive accumulation of the insoluble lipid glucocerebroside in lysosomes of cells of monocyte/macrophage lineage, principally macrophages. Engorgement with glucocerebroside alters macrophage morphology producing the so-called “Gaucher cells” that are a hallmark of the disease (Fig. 1). Gaucher cells may occur anywhere where macrophages are found, but they are particularly abundant in tissues of the reticuloendothelial system.
Symptoms and management
Gaucher disease is a rare disorder, but is the most commonly occurring lysosomal storage disease.1 Gaucher disease has been divided into 2 major clinical subtypes based on whether the nervous system is affected. The non-neuronopathic form, designated as type 1, accounts for 90% of all cases.2 The extremely rare neuronopathic variants have been subdivided into acute (type 2) and subacute (type 3) forms. Type 2 manifests in early infancy and is characterized by rapidly progressive nervous system and brain degeneration with patients seldom surviving past 2 years of age.3 Type 3 has a more protracted course with neurological signs appearing in late infancy or childhood. Inidividuals reaching adolescence may survive into their third or forth decade.1,3
Non-neurological manifestations of Gaucher disease are due to progressive infiltration of organs by Gaucher cells. Anemia, thrombocytopenia, and hepatosplenomegaly arise in all 3 forms of the disease. Patients with type 1 disease commonly develop skeletal complications due to bone marrow infiltration. Macrophage activation concomitant with lipid deposition can cause chronic, low-grade inflammation or acute flare-ups with severe bone pain.4 Children with type 1 Gaucher disease are frequently growth restricted and experience delayed puberty.4,5
Treatment for type 1 disease is enzyme replacement therapy (ERT) using macrophage-targeted recombinant human glucoceribrosidase (Cerezyme, Genzyme Corporation, Cambridge, MA).6 Treatment goals include alleviating symptoms, reducing hepatosplenomegaly, stabilizing or reversing skeletal disease, and for children, restoring normal growth rates.2,6 Most type 1 patients have near normal life spans, particularly if ERT is started early.1
A misconception about type 1 is that it is an “adult” form of Gaucher disease; 66% of type 1 patients are diagnosed before the age of 20 years.6 Childhood onset of type 1 disease generally predicts a more rapid, severe course.6,7 Noting an underappreciation of the prevalence and severity of pediatric type 1 disease, the International Collaborative Gaucher Group has called for increased focus on recognizing and assessing non-neuronopathic Gaucher disease in children.7
Imaging
Although imaging is not generally used for diagnosis, radiology at initial presentation is useful in assessing initial severity and extent of disease in the skeleton. Furthermore, it plays an important role in monitoring disease progression and response to ERT. Careful monitoring of skeletal disease is essential for preventing irreversible complications and crippling disability.8 The following is a review of visceral and skeletal imaging findings typically encountered in children with type 1 Gaucher disease.
Spleen and liver imaging findings
Hepatosplenomegaly is one of the most common effects of Gaucher disease (Fig. 2A). In children, splenomegaly can be marked and often is accompanied by growth failure, cachexia, and hypermetabolism.5 Significant organ enlargement increases the likelihood of focal abnormalities identified with cross-sectional imaging, including Gaucher cell aggregations, vascular infarctions, and regions of fibrosis 5 (Fig. 2B).
Reductions in spleen and liver size are early, sensitive indicators of response to ERT.6 Therefore, obtaining accurate baseline measures of organ volumes is important for assessing treatment response and adjusting ERT dosage. Magnetic resonance imaging (MRI) and computed tomoghaphy (CT ) were generally considered to be superior to ultrasound (US) for making volume determinations, especially in older children, and have greater accuracy and increased sensitivity for detecting focal lesions (Fig. 3). However, recently developed 3-dimensional techniques available on contemporary US machines may offer an alternative method to assess organ volumes in younger children without need for sedation or ionizing radiation exposure. Many Gaucher specialists consider US measures to be sufficiently accurate for clinical decision making.9
International Collaborative Gaucher Group guidelines recommend volume determination for children at baseline, when ERT is begun, at time of dosage change, and every 12 to 24 months thereafter.6 Measured volumes can be compared with age-based or weight-based estimates of normal volumes to determine extent of enlargement.10,11
Skeletal imaging findings
Skeletal complications are the most painful and disabling aspect of type 1 disease, with the long bones and vertebrae being most commonly affected.6 Skeletal effects are not because of glucocerebroside deposition per se, but rather result from marrow packing and replacement by Gaucher cells. Effects related to marrow infiltration by Gaucher cells include vascular occlusion, ischemia, and cytokine-induced alterations in bone turnover rates.2,10 More than 80% of patients have some degree of skeletal involvement.12 Skeletal disease manifestations include bone pain related to inflammation and edema, trabecular resorption with fibrosis, generalized osteopenia, cortical thinning and bone remodeling, pathologic fractures, and joint deformity or collapse due to avascular necrosis. Joint replacement surgery may be necessary; however, arthroplasty failure rates are higher for Gaucher-diseased bones.13
Skeletal response to ERT is slow and may take years. Children respond more quickly than adults, possibly because of their higher bone turnover rates.14 Treatment goals in pediatric patients are to prevent pain and osteonecrosis and to restore bone mineral density by the second year of treatment.2
As substantial marrow infiltration can occur before changes become apparent on plain radiographs, MRI is the preferred modality for monitoring skeletal disease.6,13 T1-weighted sequences are most sensitive for detecting marrow infiltration (Fig. 4A). Mature, adipose-containing marrow is normally hyperintense on T1-weighted MR images, but Gaucher cell infiltration reduces marrow signal intensity to approximately that of muscle. T2-weighted imaging with fat-suppressed sequences facilitates detection of complications such as infarcts (Fig. 4B). Coronal T1 and T2-weighted scans of the femora should be performed at the same intervals and frequency as the visceral assessments described above. Sagittal echo train inversion-recovery (STIR ) images may be used as an alternative to T2-weighted images if desired.6
In very young children, growth-related changes in marrow composition complicate interpretation of marrow T1 images.6,13,14 As children mature, hypointense, hematopoietic red marrow is replaced by hyperintense fatty marrow in a centripetal pattern.13,14 Therefore, increase in signal intensity due to marrow maturation may be misread as a positive treatment response, and red marrow signal may obscure Gaucher cell infiltration in younger children. To circumvent this problem, some clinicians have suggested monitoring the distal regions of the lower extremities, that is, the tibiae and ankles.13 As marrow matures earliest in these regions, reduced T1 signal would indicate significant skeletal involvement.
Several semiquantitative scoring methods have been developed to assist in staging skeletal involvement and treatment response.12,13 A quantitative assessment of marrow involvement can be obtained using chemical shift MRI, which can directly measure absolute marrow fat content.13,14 However, this methodology has not yet been widely adopted into clinical practice in children (though it has in adults). The use of 99mTc-sestamibi scintigraphy for assessment of skeletal involvement in Gaucher disease has also been discussed. Accumulation of sestamibi in the bone marrow reflects the degree of infiltration by Gaucher cells, and is not affected by physiologic age-related changes in bone marrow composition. Despite this, radiation exposure favors the use of MRI over sestamibi scintigraphy in children.8
With each sestamibi scan, the pediatric radiation exposure is at least 500 to 600 mrem, and upward of 10 mSv. According to the Alliance for Radiation Safety in Pediatric Imaging (Image Gently), <100 to 150 mSv is the acceptable cumulative low level dose during childhood years. Unique to children with radiation exposure, there is a longer time to manifest changes from exposure thereby increasing their cancer risk. Their tissues are also more radiosensitive, and the effective dose is higher for small cross sections in children when compared with adults (with similar CT parameters). Radiation dose is also cumulative over a lifetime and the risk estimate is based on a linear model; risks have been reported as high as 1:500 in the literature when exposed to low level radiation. For these reasons, we prefer use of US or MRI when possible. If CT is necessary, it is important to image only the area of interest, avoid multiphase scanning, and limit the radiation exposure by “child sizing” the CT technique.15
Dual-energy x-ray absorptiometry may also be used to monitor bone mineral density in children with Gaucher disease, as a persistently low bone mineral density in Gaucher patients on ERT may warrant consideration for bisphosphonate therapy.13
On the basis of The Gaucher disease Working Group recommended guidelines with regards to imaging, several of these aforementioned modalities may be used. The recommendations include imaging a substantial part of the bone marrow compartment (femur, pelvis, and spine) at baseline and at least every 2 years, ideally annually; T1-weighted and either T2-weighted or STIR sequences are recommended for routine evaluation, and STIR sequences are recommended to detect complications. Dual-energy x-ray absorptiometry is recommended to assess lumbar spine, proximal femur, and the entire body at baseline and annually thereafter.8
A number of Gaucher osseous effects are visible on conventional plain radiographs (Figs. 5, 6).16 Radiography is most useful for identifying causes of acute bone pain such as pathologic fractures or osteonecrosis. It is also the modality of choice for arthroplasty follow-up.12,13 Although not highly sensitive or specific, radiographs may be the primary method of evaluating the skeleton in locations with limited access to MRI. Infrequently, the diagnosis of Gaucher disease may be initially suspected by recognition of Erlenmeyer flask deformities of the long bone metaphyses (a classic radiography sign). Splenectomy is associated with the development of osteolytic lesions, osteonecrosis, and bone mineral density deficits. In addition, asymptomatic vertebral collapse may be noted, along with medial proximal humeral notching. Incidental radiographic findings may rarely provide the initial clues that a child has Gaucher disease, therefore it is essential to consider this in the differential when observing such findings.17
Acknowledgments
The authors thank Pamela S. Cooper, PhD, for editorial assistance in preparation of the manuscript, and Lei Shao, MD, for her assistance with the pathologic figure.
References
(Exportez format texte tabulé)[1.] Beutler E, Grabowski GA, et al.Scriver SA, Sly WS, Childs B Gaucher disease The Metabolic and Molecular Bases of Inherited Disease. 2001;38th ed Columbus OH McGraw-Hill:3635–3668
[2.] Pastores GM, Weinreb NJ, Aerts H, et al. Therapeutic goals in the treatment of Gaucher disease Semin Hematol.. 2004;41(suppl 5):4–14
[3.] Jmoudiak M, Futerman AH. Gaucher disease: pathological mechanisms and modern management Br J Haematol.. 2004;129:178–188
[4.] Mistry PK, Zimran AFuterman AH, Zimran A. Type I Gaucher disease—clinical features Gaucher Disease. 2007 Boca Raton, FL CRC Press:155–173
[5.] Grabowski GA. Recent clinical progress in Gaucher disease Curr Opin Pediatr.. 2005;17:519–524
[6.] Charrow J, Andersson HC, Kaplan P, et al. Enzyme replacement therapy and monitoring for children with type I Gaucher disease: consensus recommendations J Pediatr.. 2004;144:112–120
[7.] Grabowski GA, Andria G, Baldellou A, et al. Pediatric nonneuronopathic Gaucher disease: presentation, diagnosis and assessment: consensus statements Eur J Pediatr.. 2000;163:58–66
[8.] Mass M, Hangartner T, Mariani G, et al. Recommendations for the assessment and monitoring of skeletal manifestations in children with Gaucher disease Skeletal Radiol.. 2008;37:185–188
[9.] Noda T, Todani T, Watanabe Y, et al. Liver volume in children measured by computed tomography Pediatr Radiol.. 1999;27:250–252
[10.] Prassopoulos P, Cavouras D. CT assessment of normal splenic size in children Acta Radiol.. 1994;35:152–154
[11.] Elstein D, Abrahamov A, Hadas-Halpern I, et al. Recommendations for diagnosis, evaluations, and monitoring of patients with Gaucher disease [editor's correspondence] Arch Intern Med.. 1999;159:1254–1255
[12.] vom Dahl S, Poll L, Di Rocco M, et al. Evidence-based recommendations for monitoring bone disease and the response to enzyme replacement therapy in Gaucher patients Curr Med Res Opin.. 2006;22:1045–1064
[13.] Maas M, Poll LW, Terk MR. Imaging and quantifying skeletal involvement in Gaucher disease Br J Radiol.. 2002;75(suppl 1):A13–A24
[14.] Bembi B, Ciana G, Mengel E, et al. Bone complications in children with Gaucher disease Br J Radiol.. 2002;75(suppl. 1):A37–A43
[15.] Goske M. What can I do to increase safety in the use of CT?-Radiologists [Image Gently Web site]. Available at: http://www.pedrad.org/associations/5364/ig/index.cfm?page=389. Accessed November 30, 2010.
[16.] Lowe LHSlovis TL. Diffuse Parenchymal Disease Caffey's Pediatric Diagnostic Imaging. 200811th ed Philadelphia Mosby-Elsivier:1881–1897
[17.] McHugh K, Olsen OE, Vellodi A. Gaucher disease in children: radiology of non-central nervous system manifestations Clin Radiol.. 2004;59:117–123
Journal of Pediatric Hematology/Oncology 2011; 33(4): 301-5
04 avril 2011
Les manifestations osseuses de la maladie de Gaucher à l'ère de l'enzymothérapie substitutive
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Ghislaine SURREL
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Les manifestations osseuses de la maladie de Gaucher à l'ère de l'enzymothérapie substitutive
L'enzymothérapie substitutive dans la maladie de Gaucher a prouvé son impact sur les troubles hématologiques, l'infiltration viscérale et la qualité de vie. Les complications osseuses incidentes sont moins fréquentes mais l'ostéonécrose déjà établie est au-delà de toute thérapeutique. Pour évaluer le fardeau de l'atteinte osseuse séquellaire, un bilan a été effectué chez 100 patients consécutifs suivis dans 3 centres spécialisés du Royaume-Uni. Les lésions osseuses étaient les suivantes: ostéonécrose 43 %, déformation d'Erlenmeyer 59 %, fracture de fragilité 28 %, ostéomyélite 6 % et lyse osseuse 4 %. La mobilité était altérée dans 32 % des cas et il existait des douleurs significatives chez 15 % des patients. La qualité de vie était diminuée, en corrélation avec l'ostéonécrose et les fractures de fragilité. Chez 8 patients une ostéonécrose est apparue après le début de l'enzymothérapie mais ses manifestations et son évolution étaient souvent atypiques. Dans 9 cas le traitement était en cours depuis l'enfance et l'évolution était excellente. L'ostéonécrose était associée à l'âge de début de la maladie et à la réalisation d'une splénectomie, avec un pic d'incidence au cours des 5 années suivant l'intervention qui est en faveur d'une relation causale. La présence des biomarqueurs PARC/CCL18 et chitotriosidase était associée à l'ostéonécrose, et en particulier à sa survenue sous traitement: cette corrélation offre des perspectives de stratégie de prise en charge basée sur une évaluation crédible du risque.
Medicine 2011; 90(1): 52-60
Osseous Manifestations of Gaucher Disease - A UK-wide project funded by The Gauchers Association
Professor Cox,who inspired the original application for this collaborative project to the Association, reports –
With the award of £168,000 from the Association for the then four Gaucher Specialist Centres in the United Kingdom, the Association made an enormous commitment. This commitment has been repaid by the work of the Group, which has conducted a truly collaborative exercise,despite all the cumbersome EU regulations and approvals required for multi-centre working of this kind.
The aim of the project was to document the extent and burden of the osseous manifestations of Gaucher disease in the mature therapeutic period, which it is now recognised by many patients as, in essence, a bone disease. Not only did we set out to document the extent of bone disease in UK patients,but to use correlates of severity of the bone
disease to identify, if possible, predictive markers that associate with the worst manifestations – fractures and vascular necrosis (or bone crises).
Over the three-year period, doctors in the Centres working with patients collected comprehensive clinical details from 100 adults and 11 children with Gaucher disease and thoroughly documented the extent of their condition. They collected blood samples from them, and reviewed their radiology and clinical histories.
I am pleased to announce that the two full manuscripts reporting original data from the UK Gaucher patient population participating in this work have been submitted for publication as collaborative ventures between Principal Investigators in all the Centres – a team effort brokered by the Association.
The original findings will be reported at length, but in essence the clinical studies documented severe clinical manifestations in Gaucher patients across the country.They also demonstrated that these were major determents of quality of life. In the primary clinical paper the first author, Dr Patrick Deegan, showed that splenectomy was a strong risk factor.While splenectomy has in the past been a focus of attention in Gaucher disease and was known to be associated with disease severity, no true cause-and-effect relationship has ever been established.
It was always said that if patients with very severe and early disease had had their spleens removed just because their disease was severe, any bone disease that occurred in this setting was simply a manifestation of the initial severity. By a careful temporal analysis between the onset of objectively defined bone necrosis events and the
timing of splenectomy, it was shown that there was a significant excess of bone necrosis (bone crises) in the first five years after splenectomy compared with other times, strongly indicating the cause and effect relationship.
“In a second manuscript, of which the first author is Dr. Elena Pavlova supported by the Gaucher Association, an extensive series of bioactive proteins have been quantified in the blood serum of patients previously categorised according to their bone disease. In this study, entitled ‘Potential Biomarkers of Osteonecrosis in Gaucher Disease’,
Dr. Pavlova investigated whether chemokines and cytokines are related to key bone manifestations of Gaucher disease. She was able to show that numerous serum cytokines are elevated in Gaucher disease, including those that were biomarkers previously discovered, such as chitotriosidase and CCL18/PARC. This CCLI8 is a biomarker identified in collaboration with the group of Professor Hans Aerts in The Netherlands and on the basis of support from the Gauchers Association for a PhD studentship for Dr Mary Teresa Moran (1997–2000).
Several cytokines were shown to be potential biomarkers associated with Osteonecrosis significantly later in patients failing to meet a key therapeutic goal (absence of bone necrosis) while taking enzyme replacement therapy. This was compared with a large group who had no evidence of Osteonecrosis who had had no further events, and
similar exposures to enzyme therapy. This ‘association’ study is very powerful and immediately suggests prospective studies to identify appropriate target values for easily measured parameters recommended for patients. These target values have the potential to significantly reduce the risk of ever developing avascular necrosis or other skeletal complications of Gaucher disease.
Together with my colleagues, I believe that these studies are very important in themselves, but also because they lay the groundwork for future studies which should improve the lives of Gaucher patients and allow for better management of their condition as a chronic disease in the long-termfuture.By identifying target biomarker values, it seemed very likely that it would be possible to further rationalize therapy for each patient in a more accurate and thus confident way. If successful, this might even allow for the development of improved nationally agreed
protocols of care.
I would like to again thank the Association for its huge investment in its own teams of national experts. I am sure that all the Directors and participants in the research felt the same gratitude for this team-building initiative. The award was an imaginative and adventurous enterprise by patients and their families, but despite all the complexities of the research and the organisation needed to see it through to completion, I am sure that genuine progress had been made, and that time would surely show just how much had been achieved.
Editor’s Note: Congratulations to Dr Patrick Deegan and his co- authors and investigators from the Gaucher centres – as well as the study participants – on the acceptance of the paper ‘Osseous Manifestations of Adult Gaucher Disease in the Era of Enzyme Replacement Therapy’ in Medicine (Baltimore).
http://www.gaucher.org.uk/enews.php?id=301
Maladie de Gaucher : actualités thérapeutiques
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Maladie de Gaucher : actualités thérapeutiques
La maladie de Gaucher est une maladie génétique rare due à une anomalie
du métabolisme des glycosphingolipides avec déficit en
glucocérébrosidase-bêta lysosomale. L’enzymothérapie de substitution
améliore les principales manifestations hématopoiétiques et viscérales
de la maladie, mais pas les atteintes osseuses et cérébrales. La
bêta-glucocérébrosidase recombinante (imiglucérase) est conçue pour
présenter des résidus terminaux contenant des mannoses qui facilitent
son passage vers les tissus
riches en macrophages. Deux agents biosimilaires sont en cours de
développement, la vélaglucérase alpha et la taliglucérase alpha. La
privation en substrat est une autre approche pharmacologique qui repose
sur l’inhibition partielle de l’enzyme qui catalyse la première étape de
la biosynthèse de glycosylcéramide : son taux est alors abaissé et il
peut être catabolisé par l’activité enzymatique résiduelle de
glucocérébrosidase-bêta présente dans les cellules. Avant l’ère de
l’enzymothérapie, la
greffe de moelle permettait de corriger les atteintes systémiques de la
maladie de Gaucher grâce à un apport de macrophages compétents ;
aujourd’hui la recherche porte sur la thérapie génique.
Biologics : targets & therapy 2010 ; 4: 299-313
Biologics. 2010; 4: 299–313. | PMCID: PMC3010821 |
Copyright © 2010 Cox, publisher and licensee Dove Medical Press Ltd.
Gaucher disease: clinical profile and therapeutic developments
Department of Medicine, University of Cambridge, Cambridge, UK
Correspondence:
Timothy M Cox, Addenbrooke’s Hospital, Department of Medicine,
University of Cambridge, Box 157, Level 5, Cambridge, CB2 0QQ, UK, Tel
+44 1223 336864, Fax +44 1223 336846, Email tmc12@medschl.cam.ac.uk
Received December 3, 2010
This is an Open Access article which permits unrestricted noncommercial use, provided the original work is properly cited.
Abstract
Clinical profile
Gaucher
disease was the first lysosomal disease for which a specific therapy
was introduced in the US orphan legislative milieu. The success of
Ceredase® and Cerezyme® (Genezyme Corporation,
Allston, MA) has driven pharmaceutical investment in other lysosomal
diseases which have disabling effects on life quality and survival. A
contemporary Western dilemma rests between the provision of high-cost
medicines requiring intensive investment for very few patients and the
corporate investment required to improve the health of the population by
a more radical attack on the causes of common illness.1
Gaucher disease
Definition
Gaucher
disease is caused by a functional deficiency of the acid hydrolase,
β-glucocerebrosidase, or glucosylceramidase (E.C.3.2.1.45).2,3
The immediate substrates for this enzyme are glucosylceramide and its
nonacylated analog, glucosylsphingosine. These glycosphingolipids arise
from the digestion of more complex glucosides and gangliosides present
in cell membranes. Rare variant forms of Gaucher disease result from
deficiency of the sphingolipid activator protein, saposin C.3
Latterly, inherited defects in a recently discovered molecule, LIMP-2,
have been associated with an usual phenotype with β-glucocerebrosidase
deficiency in the kidney, brain, and other tissues, but not white cells
or macrophages, in which it serves as a chaperone for delivery of
nascent glucocerebrosidase polypeptide to the lysosomal compartment.4–6
Gaucher
disease most obviously affects cells of mononuclear phagocyte lineage
in which prominent storage of undegraded lipids occurs (see Figure 1); mutations in the gene (GBA1)
which encodes human β-glucocerebrosidase may disable the protein
sufficiently to disturb its enzymatic function in other cell lineages,
including those of the nervous system and the skin, which may become
diseased.3
 | Figure 1 Pelvis, hips, and upper femora of adult Gaucher patient. |
Clinical manifestations
Gaucher disease may occur at any age and in any human population.3,7–9
Certain forms of the condition are over-represented in patients of
Ashkenazi Jewish ancestry and in a small inbred population in Northern
Sweden. For practical purposes, the condition has been classified into
three principal ‘types’. The most frequent form of the condition
(affecting ~90% of patients and assigned as type I) is associated with
subtotal deficiency of lysosomal acid β-glucocerebrosidase and
manifestations principally in the viscera (principally liver and spleen,
see Figure 2) as well as bone marrow, which are infiltrated by pathological macrophages (Gaucher cells, Figure 1)
engorged with glucosylceramide and other sphingolipids. Many mutations
responsible for the enzymatic deficiency have been identified in the
glucocerebrosidase gene; those with severe effects on enzymatic activity
are associated with various neurological manifestations and
coinheritance of severe defects in the gene with almost complete lack of
glucocerebrosidase, which is a rare cause of stillbirth with skeletal
deformities and/or dehydration as a result of abnormal skin integrity
(collodion babies). An acute form of neurological illness (for
convenience classified as type II Gaucher disease but effectively a
condition with neuronopathic features that are not slowly progressive,
as in type III) is a very rare disorder causing death in the first years
of life; characteristically, there is irritability, bulbar palsies,
opisthotonus, and modest enlargement of the viscera.
 | Figure 2 Gaucher spleen >3 kg with large recent infarct. |
Type
I Gaucher disease is generally associated with prominent visceral and
skeletal manifestations. Splenic pooling of formed elements of the blood
leads to cytopenias with bleeding due to low platelet count, anemia,
and risk of infection due to leukopenia. There may be massive
enlargement of the liver and spleen (Figure 2) and occasionally severe infiltration of the lungs by pathological macrophages.
It
is noteworthy that in the past, type I Gaucher disease was defined as
being free of neurological manifestations, but increasingly it has been
shown that patients develop an extrapyramidal disease resembling
Parkinsonism in middle life, the cause of which is not understood.
Moreover, it is now known that mutations in the human GBA1
gene, present in the heterozygous state in individuals of numerous
ethnic origins and not hitherto identified as suffering from Gaucher
disease, are the most prevalent genetic determinants of Parkinson’s
disease so far identified in many populations.10
Type
I Gaucher patients have enlarged viscera which are infiltrated by
alternatively activated macrophages which are typically found in the
sinusoids of the spleen and replace the Kupffer cells of the liver. The
macrophages are prominent in the bone marrow and contribute to acute
episodes of osteonecrosis, particularly during growth. Necrosis of the
marrow in proximity leads to impaired function of large joints,
including the hip, knee, and shoulder. Other effects on the skeleton
include local swellings (Gaucheromas) and destruction of bone in
osteolytic lesions, as well as generalized demineralization and
osteoporosis with an accompanying risk of fragility fractures (see Figure 3).
 | Figure 3 Pathological macrophages in bone marrow. |
Less
than 10% of patients with Gaucher disease develop a chronic so-called
neuronopathic form, formerly termed type III Gaucher disease, with
visual gaze palsies and other manifestations including myoclonic
epilepsy and nerve deafness – all of which may be complicated by
variable systemic involvement and at times prominent alveolar
infiltration of the lungs.
Although
Gaucher disease may declare itself at any age, in general, presentation
in infancy and childhood carries a worse prognosis. There is a
progressive deformity of the skeleton, enlargement of the viscera, and
impaired function of organs, often accompanied by painful complications
of skeletal disease. The condition shortens life, and even patients who
present in late middle life ultimately may succumb. A rare complication
of the condition is the development of hematological malignancies, most
characteristically B-cell lymphomas and multiple myeloma, the
pathogenesis of which is incompletely understood. Untreated Gaucher
disease leads to progressive misery associated with bleeding, pallor,
and anemia, together with visceral enlargement and bone pain; it is
associated with disability and markedly reduced life quality, as well as
survival.
Frequency
The birth frequency of Gaucher disease is ~1:60,000 live births in the general population,11 but genetic studies indicate a homozygote frequency of ~1:950 Ashkenazi Jews, many of whom appear to remain asymptomatic.12
In most countries, there is a marked discrepancy between the predicted
and the observed prevalence: with a population of more than 60 million
in the UK, only about 300 patients with Gaucher disease are known,
giving an operational prevalence figure of about 1 in 200,000 – very
much less than the predicted frequency at birth.8
It can readily be seen that the disease is much less common than the
threshold for designation as an orphan disorder in any country (eg, with
a prevalence <1 in 2000 in Europe or <200,000 individuals in the
United States); with <1 in 50,000 affected persons in the UK, the new
term, ‘ultraorphan,’ has been suggested.
Diagnosis of Gaucher disease
The condition may be suspected in any patient with unexplained splenomegaly, particularly those of Ashkenazi Jewish origin.3,8,12
Gaucher disease may also come to light as a result of investigations
for pancytopenia or visceromegaly; thus Gaucher cells may be identified
on tissue biopsy specimens, principally of bone marrow (during
investigations for splenomegaly or cytopenias) or liver (during the
course of investigations for hepatomegaly or abnormal liver-related
biochemical tests). It is worth emphasizing that the presence of
abnormal macrophages with the appearance of Gaucher cells is not
sufficient for the diagnosis since these may be observed in other
hematological conditions such as chronic myeloid leukemia, thalassemia,
and multiple myeloma – the last named itself a rare complication of
Gaucher disease. Specific diagnosis is, however, made by measuring acid
β-glucosidase activity in fresh peripheral blood leukocytes, or
occasionally by enzymatic analysis of fibroblasts cultured from skin
biopsy specimens. Confirmation and better characterization of the
condition may subsequently be afforded by molecular analysis of the
human GBA1 gene, which encodes lysosomal glucocerebrosidase.
The disorder may be suggested by a history of Perthés disease or as a
result of radiological investigations which show bone deformity in the
long bones due to a modeling defect, designated the Erlenmeyer flask
abnormality, in the distal femur or proximal tibia.
Pathogenesis
In
classical descriptions of the condition, although engorged macrophages
represent the pathognomonic focus of Gaucher disease, the simple
presence of storage material within these infiltrating cells provides an
incomplete explanation of causation. Storage material accumulating
within the macrophages accounts for a fraction of the massive bulk of
the organs, which show macrophage hyperplasia and hypertrophy. While the
pathological macrophages are accompanied by vascular changes and
fibrosis, for example within the liver and spleen, they are not
prominent in the brain in patients with neurological manifestations.
More likely, abnormal storage material and other chemical changes within
cells induce release of inflammatory factors, including chemokines and
cytokines, which lead to the cascade of pathological changes.3,13–20
Complex mechanisms, including abnormal calcium pooling within neural
cell compartments, have been invoked, particularly in the neurological
manifestations which characterize the severe Gaucher variants.18,19
Some authorities consider that the water-soluble lysolipid,
glucosylsphingosine, has far-reaching signaling effects and may be
responsible for cell death.13,16,17
Quasipathophysiological concentrations of glucosylsphingosine affect
the function of intracellular actin and induce a defect of cytokinesis
generating a Gaucher-like phenotype on exposure of cultured macrophage
cell lines to the molecule.20
Therapeutics of Gaucher disease
Until
the 1990s, no specific or curative treatments for most patients with
Gaucher disease were available. Supportive and palliative measures
include orthopedic interventions such as joint replacement surgery and
occasional hepatic transplantation. Splenectomy was widely used to
overcome the effects of hypersplenism in the blood, but carries with it
immediate and long-term risks of overwhelming microbial infection;21 splenectomy also contributes to the risk of osteonecrosis in Gaucher disease.22
Cellular complementation
Given
the visceral infiltration by pathological macrophages, which are of
hematopoietic origin, bone marrow transplantation has been attempted in
Gaucher disease.23
Successful engraftment given before the development of irreversible
skeletal and organ changes may correct the disease by replacing the
defective macrophages with those of healthy donor origin. Children with
the chronic neuronopathic form of Gaucher disease (type III),
particularly those of Norrbottnian origin, had an improvement in their
health but no apparent correction of the neurological disorder, despite a
repopulation of microglia in the brain slowly by mononuclear cells of
hematopoietic origin.24,25
Bone
marrow and contemporary hematopoietic stem-cell transplantation is not
in current general use for Gaucher disease, partly because of the
shortage of ideal donors (human leukocyte antigen matched) and
procedural risks, as well as the introduction of successful enzymatic
augmentation which has superseded this treatment in many countries. The
author treats one patient, the first male to receive allogeneic bone
marrow transplantation in 1984 at the age of 11 years; homozygous for
the L444P allele of the human glucocerebrosidase gene, the patient has
type III disease with lateral gaze palsy and severe skeletal
abnormalities following removal of a massive spleen aged 2 years. No
longer confined to a wheelchair and with complete donor chimerism, the
patient is now working independently as a farmer and drives a tractor
unaided; he has no clinical or hematologic signs of Gaucher disease,
which is inactive in the viscera and skeleton. From this case and a few
others reported, it is clear that most, if not all, key aspects of the
systemic disease are due to defective cells of mononuclear phagocytic
lineage and thus may be corrected by supplying healthy exogenous
hematopoietic stem cells or by transducing autologous stem cells with
vectors for transferring the wild-type human glucocerebrosidase gene in
order to restore the capacity of tissue macrophages to digest
glycolipids normally.
Enzymatic augmentation
Soon
after the enzymatic defect in Gaucher disease was identified in the
1960s, a long program of work into enzymatic replacement was initiated.
At the time, studies on the hepatic uptake of plasma glycoproteins by
Ashwell and Morell had been shown to be related to lectin-like activity
of cellular receptors.26
A further body of work showed that uptake of proteins by macrophages
occurred through a surface receptor recognizing terminal mannose
residues on protein ligands.27
Early attempts to correct the biochemical abnormalities of Gaucher
disease in patients after infusion of purified human glucocerebrosidase
prepared from human placentae met with scant success, but it was later
shown that the enzyme from human placentae contained enzyme molecules
with complex carbohydrate chains, and mostly with terminal sialic acid
residues.28 In key experiments, it was later shown that sequential removal of sialic acid, galactose, and N-acetylglucosamine
using exoglycosidases prepared from plant sources yielded a molecular
form of the enzyme that was avidly taken up by Kupffer cells and other
preparations of macrophages.29
This
finding formed the basis of further clinical trials of mannosylated
glucocerebrosidase in Gaucher patients – one of whom, a small boy,
showed a striking improvement in red-cell and platelet counts with a
substantial reduction in spleen size.30
A remarkable collaboration between a patient organization (the National
Gaucher Foundation), the National Institutes of Health, where Dr.
Roscoe Brady and his colleagues were working, and a newly formed
company, the Genzyme Corporation, led to a clinical trial involving 12
patients with type I Gaucher disease. The participants were studied for 6
months during a course of infusions of modified human placental
glucocerebrosidase given every 2 weeks. A large dose of the enzyme was
administered (60 IU/kg of body weight every 2 weeks), and in the event,
all the trial participants showed beneficial responses in terms of blood
count and visceral parameters.31 Mannose-terminated human placental glucocerebrosidase, later known as alglucerase (Ceredase®;Genzyme
Corporation, Cambridge, MA), was licensed under the special regulations
introduced through the orphan drug legislation in the United States. It
was notable that the trial, which was an open-label trial without a
control arm, showed clear benefit on spleen size in those patients
studied.31
As indicated above, since the splenic enlargement with hypersplenism is
a central determinant of the illness in Gaucher disease and splenectomy
can be avoided if the spleen size is decreased, this pivotal clinical
trial clearly addressed an unmet clinical need. At the same time, the
use of glucocerebrosidase derived from pooled human tissues (many
thousands of human placentae were required for the production of
sufficient Ceredase to treat a single Gaucher patient) posed
considerable risk at a time when biological agents derived from human
tissues were a known source of hepatitis viruses and HIV and were
implicated in the transmission of the Creutzfeldt–Jakob agent.
Nonetheless, numerous patients worldwide were treated with alglucerase
under license, with salutary effects on quality of life, as well as
improved blood counts, the regression of visceromegaly, and a decreased
frequency of osteonecrosis episodes and reported bone pain.
Genetically engineered enzymatic augmentation
Approximately
5 years after the licensing of alglucerase, the Genzyme Corporation
launched Cerezyme, imiglucerase – a recombinant human glucocerebrosidase
expressed in genetically engineered Chinese hamster ovary cells. As
with the purified placental product, this enzyme required further
modification by exoglycosidases to expose glycan residues which mediate
delivery to tissue macrophages utilizing the lectin-like properties of
membrane mannose receptors.
Imiglucerase
has now been given to more than 5000 patients worldwide and clearly
reverses many of the manifestations of Gaucher disease, particularly
those affecting the bone marrow and viscera.32
In adults and children, there is a salutary increase in hemoglobin
concentration, and white cell, and platelet counts, with a decrease in
surrogate biomarkers of disease activity – certain macrophage-related
proteins are released abundantly into the circulation in response to
cellular storage.33,34
Tissue
sampling, which is not routinely performed, demonstrates a reduction in
the number of pathological macrophages infiltrating bone marrow and
liver tissue. Although episodes of osteonecrosis become less frequent in
patients receiving enzyme therapy and salutary improvements in bone
mineralization density have been demonstrated in those with osteopenia
and osteonecrosis, it is not surprising that those manifestations
related to tissue and bone injury before treatment is instigated cannot
be corrected.35
While as a whole, the clinical evidence points strongly to
disease-modifying properties of enzyme therapy in Gaucher disease, it is
unclear as to whether it reduces the risk of B-cell malignancies and
myeloma in patients with Gaucher disease. Moreover, any relationship of
enzyme therapy to the development of the Parkinsonian complications of
Gaucher disease has yet to be explored. Despite these reservations,
enzyme replacement therapy for Gaucher disease with alglucerase and
imiglucerase has been a signal therapeutic and hence commercial success,
lifting the Genzyme Corporation to among the world’s largest
biotechnology companies and feeding blockbuster revenues into its
burgeoning fortune. In 2008, the total revenue of Genzyme was US$4.5
billion, of which sales of Cerezyme amounted to ~US$1.2 billion. In
Europe, Cerezyme was licensed under the newly introduced orphan
medicinal products legislation for the chronic neuronopathic type III
variant of Gaucher disease, where it also improves life quality, as well
as the hematologic manifestations and visceral engorgement.9,36,37
Biosimilar protein agents
The
term ‘biosimilar’–otherwise known as ‘follow-on’ biologic agents–is
used to describe approved new versions of innovative biopharmaceutical
products following patent expiry. With respect to the current position
of Cerezyme, the designation may be disputed in the industry. Although
Cerezyme remains the standard care for the treatment of Gaucher disease
and there is a burgeoning literature on its use over time in the mature
phase of enzyme therapy,35–38
two emerging biosimilar agents, also based on the principle of
macrophage targeting through the mannose lectin membrane receptor
system, have been introduced. The first of these, velaglucerase-alfa
(VPRIV®), was generated by a rival company, originally
Transkaryotic Therapies, now taken over by Shire Human Genetic Therapies
(Dublin, Ireland).39
This agent is generated by gene activation of the endogenous human
glucocerebrosidase gene in an immortalized human fibrosarcoma cell line.
The engineered cells are cultured in a medium containing the powerful
inhibitor kifunesine, which blocks the action of one of the processing
glycosidases for glycoprotein biosynthesis, and as a result, a human
glucocerebrosidase protein displaying terminal mannose sugars is
produced. The other biosimilar agent in late-phase development is
taliglucerase-alfa, an agent licensed by the Protalix company, based in
Israel. Taliglucerase is produced as a recombinant glycoprotein
expressed in genetically engineered plant cells.40
To secure secretion through the vacuolar pathway, the protein is
modified: it harbors additional amino acids, as well as xylose and other
sugars in its intermediate glycan sequence. Clinical trial data, now
fast emerging from these products, indicate therapeutic activity in type
I Gaucher patients attributed also to targeted delivery and uptake by
tissue macrophages.39–41
Disadvantages of enzyme replacement therapy
Contrary
to expectations, hypersensitivity and immune reactions directed against
the therapeutic proteins in type I Gaucher disease are very rare, and
<1% of patients with this form of the condition manifest resistance
to enzyme therapy. Not surprisingly, the neurological manifestations of
Gaucher disease are not corrected by enzyme therapy – a failure
attributed to the blood–brain barrier which is largely impermeable to
proteins. However, in rural areas and undeveloped countries, the
requirements for intravenous infusion pose difficulties for
administration and delivery of treatment – often even the supply of
sterile needles and infusion apparatus presents a challenge. In
addition, the high intrinsic costs of biological and other therapies for
Gaucher disease are discussed below. Despite its salutary effects and
reversal of the hematopoietic factors of Gaucher disease, enzyme therapy
has limitations and only a proportion of patients achieve their
therapeutic goals.38,42 Enzyme therapy has no direct therapeutic effect on the neurological manifestations of Gaucher disease.43–45
Finally,
it must be admitted that intravenous infusions are not the preferred
means of therapy for many patients who, given the choice, would prefer
an orally active agent to the perceived invasiveness, inconvenience, and
discomfort and apparent ‘medicalization’ signified by an intravenous
treatment.
Substrate depletion (inhibitor) therapy
As
with enzymatic augmentation, this approach to therapy is based on sound
biochemical principles; it moreover represents a telling example of
scientific translation into clinical practice within a fiercely
competitive orphan disease niche.
The
concept of substrate depletion therapy in the glycosphingolipid
diseases, of which Gaucher disease is an example, was introduced by
Norman Radin and colleagues in the late 1970s,46,47
but it is based on a principle also adopted by Akira Endo and
collaborators for the treatment of atherosclerosis due to
hypercholesterolemia. Endo discovered and developed the class of fungal
metabolites now known as statins used widely to inhibit cholesterol
biosynthesis.48
Since
the inability to break down complex glycosphingolipids is the proximate
cause of Gaucher disease and held to be the principal factor in its
pathogenesis, inhibitors to decrease the biosynthesis of the substrate
(glucosylceramide) should evince therapeutic benefit. Given that most
patients have residual glucocerebrosidase activity, attenuating
biosynthesis should allow this remaining enzymatic function to reduce
steady-state concentrations of undegraded macromolecular substrate
within lysosomes and, by rebalancing glycosphingolipid metabolism,
ultimately correct the disease. The biochemical target for this
stratagem in Gaucher disease is the first committed step for
glycosphingolipid biosynthesis catalyzed by uridine diphosphate (UDP)
glucosylceramide synthetase (UDP-glucose: N-acylsphingosine transferase).47–49
Two chemical classes of inhibitor are undergoing comprehensive
therapeutic exploration: these are iminosugars derived from naturally
occurring plant products and another class of compounds containing a
pyrrolidine ring that serve as ceramide analogs.
Miglustat
The
original compounds synthesized by Radin and colleagues were useful
experimental inhibitors of the UDP-glucosylceramide synthase, but
because of their appreciable cellular toxicity, they were not initially
developed for further clinical application.50 It was the iminosugars, in particular N-butyldeoxynojirimycin,
previously explored for an unrelated application in HIV infection,
which were identified for clinical development by Frances Platt and
Terry Butters at the University of Oxford.51,52 They recognized that micromolar concentrations of N-butyldeoxynojirimycin
inhibited the biosynthesis of glucosylceramide in cultures of a murine
macrophage cell line treated with an irreversible inhibitor of
acid-β-glucocerebrosidase, conduritol-β-epoxide. This agent induces
lysosomal abnormalities, accompanied by an accumulation of
glucosylceramide but coaddition of N-butyldeoxynojirimycin
abrogated the lysosomal storage. Subsequent animal studies were
conducted in knock-out mice lacking β-hexosaminidases, with accumulation
of GM2 ganglioside in the brain.53
A strain of these animals, the Sandhoff mouse, has a shortened life
expectancy with neurological manifestations, accompanied by progressive
storage of GM2 ganglioside throughout the central neuraxis. The
administration of N-butyldeoxynojirimycin reduced ganglioside
storage in peripheral organs and brain of these animals and extended
their survival by ~40%.54
These
preclinical studies, combined with earlier clinical trials in humans
with HIV infection, stimulated the design of a clinical trial of N-butyldeoxynojirimycin (now known as miglustat or Zavesca®) in patients with type I Gaucher disease.55
At a dose of 100 mg thrice daily, the agent reduced visceral
enlargement and slowly improved hematologic parameters, as well as
surrogate plasma biomarkers, in patients with type I Gaucher disease.56–58
An unwanted effect of the iminosugar treatment was diarrhea, caused by
an inhibition of intestinal disaccharidase activity. Some patients also
developed tremor and/or peripheral neuropathy, but the drug has been
licensed in the United States and Europe as a second-line treatment for
patients with mild to moderate type I Gaucher disease.59
A
recent study of its use in 28 patients with Gaucher disease who have
been previously stabilized with enzyme therapy reported long-term
findings with respect to organ size, blood counts, biomarkers, bone
marrow infiltration, and safety, as well as tolerability. Assessments
during routine clinic visits were carried out at 6, 12, 24, 36, and 48
months after initiating treatment with miglustat. Biomarkers improved up
to 48 months after initiation of miglustat, while other parameters were
reported to be stable. Miglustat was considered to have acceptable
safety and tolerability and to be effective for the long-term
maintenance of this group of patients with type I Gaucher disease who
had previously received enzyme therapy.60
While the authors of this report contend that their study represents
‘real-life’ clinical experience in the era after introduction of
Ceredase and Cerezyme, the failure to distinguish the effects of
miglustat from the course of type I Gaucher disease after long-term
treatment (stabilization) with enzyme therapy or the confounding
influence of patient selection, detracts from the scientific clarity of
this study.
Since in some strains of mice
the agent leads to a nongenotoxic sterility of males, strict
contraception is advised and the drug is not licensed for use in
children.61–63
With
the potential for the small iminosugar molecule to penetrate the
blood–brain barrier, a further trial was conducted in children with
chronic neuronopathic Gaucher disease. However, this trial failed to
meet its clinical end points and the drug currently is not recommended
for neurological manifestations in Gaucher disease;64
it is unknown as to whether or not it would be effective at higher
tolerable doses in humans. Of interest miglustat Zavesca has recently
received a license in Niemann–Pick disease type C, another lysosomal
disease affecting the brain in which disturbed cholesterol trafficking
to lysosomes causes secondary accumulation of glycosphingolipids in
neurons.65
Since there is no other effective treatment for this devastating
neurodegenerative disorder, Zavesca delivers, in part at least, an unmet
clinical need for patients and their families otherwise without hope.
Zavesca was first developed by Oxford Glycosciences (Oxon, UK) and is
now licensed for marketing under the orphan drug legislation by the
Actelion company (Allschwil, Switzerland).
Eliglustat tartrate (Genz-112638)
James
Shayman and colleagues in the University of Michigan and a former
student of Norman Radin identified high-affinity inhibitors of the
metabolic target of glycosphingolipid synthesis, UDP-glucyosylceramide
synthase.66
Homologues of the most potent inhibitors were generated as highly
selective inhibitors of the enzyme, with inhibitory concentrations in
the nanomolar range, but without appreciable cytotoxicity in culture.
Cytotoxicity appears to be related to increased ceramide concentrations
in cells, attributed to nonselective inhibitory effects of the prototype
agents on a previously unknown ceramide transacylase activity.
Intensive screening of isomers of a parent compound led to the
generation of Genz-112638, recently developed as eliglustat tartrate by
the Genzyme Corporation.67
Medicinal chemists within the company invented the means for efficient
enantioselective syntheses of the highly selective inhibitory isomers,
which are held under patent.68 The compound chosen for development is a structural analog of d-threo-ethylinedioxypheny
l-2-palmitoylamino-3-pyrrilidino-propanol formulated as a salt of
tartaric acid. The full chemical name of eliglustat tartrate is (1R, 2R)-Octanoic acid [2-(2′,3′-dihydro-benzo[1 ,4]dioxin-6′-yl)-2-hydroxy-1-pyrrolidin-1-ylmethyl-ethyl]-amide-l-tartaric acid salt.
This
agent, as a free base, is metabolized by the cytochrome P450 system and
in several cell lines has a powerful inhibitory action on UDP-glucose: N-acylsphingosine transferase with an IC50 of 24 nanomolar.67
At low micromolar concentrations, it has no appreciable inhibitory
action on intestinal sucrase and maltase activities or lysosomal acid
β-glucocerebrosidase. Preclinical studies were conducted in a murine
model of Gaucher disease (gbaD409V/nul), which develops occasional storage cells in viscera in association with lysosomal accumulation of glucosylceramide.69
Eliglustat tartrate is a substrate for the P-glycoprotein multi-drug
transporter and so does not accumulate in brain tissue of normal
rodents. It was shown to have satisfactory preclinical toxicology in
experimental animals.
Phase I studies
have been conducted in 99 human subjects, with doses of 50–200 mg given
twice daily inducing plasma concentrations of the agent within the
predicted therapeutic range.70
Although in preclinical studies the agent may have an effect on cardiac
conduction intervals, this effect does not appear to be significant at
therapeutic dosing levels. The drug is metabolized principally by the
CYP2D6 cytochrome, thus careful monitoring will be prudent in patients
taking other drugs known to interact with this metabolic pathway of
degradation. Such drugs include paroxetine, ketoconazole, and
rifampicin.
After satisfactory
Phase I clinical trials in healthy human volunteers, Phase II clinical
studies were undertaken, and information is available from patients
having completed 2 years of therapy.71,72
These trials were undertaken in adults with type I Gaucher disease, for
which the entry criteria required splenic enlargement of at least
10-fold normal, together with thrombocytopenia and/or anemia. The dose
of drug was either started at 50 mg twice daily or with monitoring for
pharmacokinetics adjusted to 100 mg twice daily to ensure that rapid
metabolizers would have concentrations of the drug of ≈10 ng/mL. A
composite primary efficacy end point, based on two of the three
parameters (spleen volume, hemoglobin concentration, and platelet
count), was used; furthermore, dual-energy X-ray absorptiometry studies
with T1-weighted MRI of femurs were undertaken. There was
extensive safety monitoring, particularly for untoward neurological
effects and cardiac events.72
Outcome measures
Of
the 22 patients who completed the trial at 1 year, 20 attained the
composite primary therapeutic end point, with improvements of at least
two of the three abnormal values initially present. No bone crises
occurred, and there were no changes in mobility, in bone pain, or on
X-ray examination. There were, however, early signs of improvement in
magnetic resonance imaging of bone marrow signal (dark marrow) at 2
years of treatment. Twenty of the original 26 patients had completed the
therapy and most remain on an extended trial. Continuing improvement in
spleen and liver volumes (the former decreased by a mean of 52%) with
improvement in hemoglobin concentration and a rise in platelet counts
have been observed. All these changes were accompanied by salutary
improvements in surrogate biomarkers, including the chemokine CCL18-PARC
and chitotriosidase activity. Of the 18 patients with abnormal dark
signal independently identified on magnetic resonance imaging, six had
improved by 1 year and an additional two patients had shown improvements
by 2 years on the trial.72 Further promising effects on bone mineralization density were seen with significant increases noted in most patients.
The
safety profile and efficacy of eliglustat in patients with moderate
Gaucher disease and the salutary effect on bone mineral density and
abnormal bone marrow signals have prompted initiation of several
multicenter Phase III studies. The first of these trials is a
randomized, open-label study for adults with type I Gaucher disease,
designed to compare the efficacy and safety of eliglustat tartrate with
that of Cerezyme. Recruited patients should have received enzyme therapy
for at least 3 years and have achieved clinical stability by reaching
key therapeutic goals in terms of blood counts, visceral volumes, and
bone status. The second trial is a randomized, blind, placebo-controlled
study for patients with a confirmed diagnosis of type I Gaucher
disease, who have not been treated for at least 12 months. A final trial
has been registered, which will seek to compare the effects of one
daily dosing of eliglustat tartrate with twice daily administration.
Pharmacological chaperone therapy
The
pharmacological chaperone concept is based on the ability of small
molecules to interact with mutant proteins that are misfolded and thus
prevented from realizing their normal intracellular activity. Abnormal
protein folding has been recognized as a common molecular mechanism in
many inherited diseases and leads to premature degradation of the newly
synthesized protein in the endoplasmic reticulum and also within the
Golgi complex. In the case of lysosomal enzymes, the chaperone concept
involves the binding of the agent to the active site of the mutant
lysosomal protein, thus stabilizing it for delivery to its normal site
of action in the acidic environment of the organelle. Chaperone
molecules are thus often weak inhibitors which bind at neutral pH during
biosynthesis of the enzyme and stabilize it for delivery to the
lysosome; in the lysosome, the dramatic increase in hydrogen ion
concentration is proposed to favor dissociation of the inhibitor, thus
allowing restitution of enzyme function.73
Another
iminosugar, isofagomine, shows pharmacological chaperone activity
directed toward glucocerebrosidase in fibroblasts cultured from type I
Gaucher patients. This agent has been developed for Phase I/II clinical
trials in Gaucher patients by the Amicus company (Cranbury, NJ).
Although the drug was moderately well tolerated, apart from inducing
conjunctivitis in some subjects, the first trial, with intermittent
dosing as required for a putative pharmacological chaperone, showed
disappointing therapeutic outcomes. The Amicus company continues with
its trials, in particular with a similar iminosugar
(1-deoxygalactonojirimycin) to investigate its possible therapeutic
action on mutant α-galactosidase A in the related lysosomal disease,
Anderson–Fabry disease.73
Gene therapy
While
in the context of enzyme therapy, which is safe and effective, the
risks of bone marrow transplantation or hematopoietic stem-cell therapy
render cellular complementation impractical for general application in
most patients with Gaucher disease, the same stringencies might not be
obtained for gene therapy using lentivirus-transduced autologous
hematopoietic stem cells. If used for Gaucher disease, as reported for
the neurodegenerative disease adrenoleukodystrophy74
and currently in clinical trials for presymptomatic metachromatic
leukodystrophy in infants and children, such an approach would have the
advantage of being a one-off procedure requiring less powerful
myelo-ablative conditioning and thus attractive for patients predicted
to be at risk of severe disease and originating from countries where the
availability, monitoring, or delivery of enzyme therapy is
unsatisfactory.
Early clinical trials of
macrophage-directed glucocerebrosidase using first-generation lentiviral
gene transfer vectors in two centers were disappointing with very low
transduction efficiencies and/or early shutoff of corrective gene
expression in circulating monocytes; no clinical benefit was reported.
These results were particularly disappointing since a bicistronic
retroviral vector expressing human glucocerebrosidase and a human small
cell surface antigen (CD24) as a selectable marker, under the control of
the Moloney murine leukemia viral promoter, were used to transform CD34+ hematopoietic progenitors.75
Latterly, there have been promising preclinical developments in the
gene therapy of type I Gaucher disease from Stefan Karlsson and
colleagues at the University of Lund, Sweden. This group was the first
to generate a convincing inducible mammalian model of the disorder in
the hematopoietic system and major viscera of genetically engineered
mice;76
they have further utilized this model as a test system to evaluate
lentiviral gene therapy directed to autologous hematopoietic stem cells
using busulfan for nonablative pretransplant conditioning without whole
body irradiation. With this stratagem, they were able to demonstrate
that stem-cell engraftment in the range of 1%–10% wild type confers
clear benefit in this authentic disease model.77
While
there may be residual safety issues surrounding the use of lentiviral
vectors directed to proliferating cellular compartments, the capacity
permanently to correct the principal manifestations of the condition
with a minor proportion of autologous stem cells corrected by gene
transfer is a signal advance.77
Recent studies on the use of third-generation self-inactivating (SIN)
lentiviral vector derivatives in patients with adrenoleukodystrophy with
random, rather than preferential, integration at sites with the
potentiality for oncogenesis in the human genome are also critically
important for issues of safety.74,75 However, in the recent clinical use of SIN lentiviral vectors to transduce autologous CD34+
hematopoietic stem cells in two boys with adrenoleukodystrophy by
Cartier and colleagues, a complete myelo-ablative regimen was employed.
A
further approach to the definitive treatment of non-neuronopathic
Gaucher disease (type I) in effect combines gene therapy with systemic
enzymatic complementation. In a stratagem using adeno-associated viral
(AAV)-mediated gene therapy, McEachern and colleagues78
administered a recombinant AAV8 serotype vector harboring the human
β-glucocerebrosidase gene under the control of a liver-selective
promoter intravenously to D409V/null mice with features of Gaucher
disease. The vector induced sustained hepatic secretion of the enzyme,
which was sufficient to prevent accumulation of glucosylceramide and
Gaucher cells in the liver, spleen, and lungs of young animals and had
marked benefit on these parameters in older mice with established
disease. The absence of antibodies on challenge indicated that the
animals had been tolerized to the therapeutic protein. Such a strategy
would also lend itself to the application of gene therapy to patients
with Gaucher disease: it has the potential advantage of not requiring
myelo-ablative therapy and ease of administration for what would be
envisaged as a one-off procedure. A key requirement, however, would be
sustained expression of the therapeutic gene in hepatocytes transduced
by the rAAV vector – an issue that has yet to be overcome in relation to
gene therapy for hemophilia.79
Given the current state of knowledge and preclinical studies, credible
clinical trials could soon be initiated; but the location of appropriate
investigative centers and selection of patients will be of critical
importance.
Discussion
Predictable and unexpected effects of orphan drug legislation
While
the orphan drug legislation was designed to provide strong incentives
for pharmaceutical development in neglected and rare diseases, the
commercial rewards realized in a very rare (ultraorphan) condition,
Gaucher disease, were unforeseen and unprecedented. The incentives have
been keenly felt by several companies seeking similar trophies; they
have sought also to position themselves in the field by acquisition.
Access and cost
There
can be no doubt that the general outlook for patients with Gaucher
disease and related lysosomal diseases for which enzymatic augmentation
has been introduced (as well as initiatives involving small molecule
inhibitors and chaperones) has improved immeasurably; these benefits
extend only to those patients for whom insurance and national health
care provision is available. Only a minority (≈10%) of patients with
Gaucher disease worldwide are fortunate enough to have access to enzyme
replacement therapy, principally because of the extreme cost of this
ultraorphan treatment for each patient. To capitalize on its leading
position and sustain a program of therapeutic development, Genzyme
charges highly for products provided to only a few thousand patients
internationally: the average cost to treat an adult Gaucher patient with
enzyme therapy is of the order of £100,000 and in the early debulking
phases of the illness, about £200,000 per annum.
Development costs
Although
it is claimed that the introduction of a new biological drug may cost
$500,000–$1,000,000,000, in the case of alglucerase (Ceredase) for
Gaucher disease, the manufacturer reported spending less than $58M for
development. However, we should remember that this was 20 years ago and
the burden of costs was shared with academia. Given the prolonged
marketing exclusivity awarded for the first introduction of an orphan
agent of 7 and 10 years in the United States and Europe, respectively,
the potential rewards for each corporate winner are high. While those
developing biosimilar drugs must bide their time or demonstrate that
their products have unequivocal therapeutic advantages, companies with
an active discovery portfolio can steal an advantage if their drug has
an innovative mode of action, as illustrated by the substrate
inhibitors. Since it was first proposed, progress on gene therapy has
been slow, even for monogenic diseases in which it clearly offers the
potential for a definitive and specific cure. It is salutary to recall
that more than two decades ago, the original scientific board of the
corporation advised the management of Genzyme not to proceed with the
development of enzyme therapy because gene therapy for the condition was
so far advanced at the time. Perceptions of advantage and the real
nature of competition in orphan diseases remain – as with all aspects of
biotechnology – fraught with the foibles of human judgment and error.
Clearly,
after a time, strong incentives also re-emerge for oncoming competitors
with biosimilar protein agents, since by following the data of the
innovator, development costs may be reduced to a scale of tens rather
than hundreds of millions of dollars.
The value and safety implications of competition
We
now also know that there is a previously unrecognized clinical
advantage provided by alternative biological agents, for example
velaglucerase-alfa and taliglucerase-alfa in Gaucher disease – a
guaranteed safety of supply. The necessity of competing alternatives has
emerged as a result of a catastrophic year-long shortage of Cerezyme,
resulting from a vesivirus infection occurring in the dedicated
bioreactor plant at the principal production facility of the Genzyme
Corporation in Allston, Massachusetts, in June 2009.80
At the time, although velaglucerase and taliglucerase were at an
emerging stage of clinical development, their ready availability for
several hundred patients in Europe and the United States has partially
mitigated the crisis both for the patients and their treating
physicians, as well as the prowess of the Genzyme Corporation. In the
face of this crisis, many physicians and regulatory agencies worked with
all the commercial partners to promote release of the new enzyme
preparations through compassionate access programs before licensing to
expedite the regulatory processes for licensing approval and to
accelerate approval for distribution in the United States, Europe, and
other regions, wherever possible.
The competitive niche
Biological
treatments, such as enzymatic augmentation in lysosomal disorders, can
be challenged by competitive small molecules, as has been convincingly
demonstrated in Gaucher disease. The innovation of substrate depletion
therapy with biosynthetic inhibitors of the principal glycolipids, which
accumulate in macrophages, provides an attractive scientific and
pharmaceutical alternative. Not only are such compounds more readily
distributed and administered, but their mode of action is distinct and a
compelling advantage in competition.
Other
powerful advantages include the generally cheaper manufacturing costs
of small molecular compounds, as compared with human enzyme
preparations, which in the case of Gaucher disease require elaborate
modification to ensure appropriate targeting to the affected tissues
(macrophages) in vivo. While the Actelion drug, miglustat (Zavesca), is
currently seen as a second-line agent for Gaucher disease,59,63
its inception clearly directed Genzyme to innovative departures, based
on a distinct chemistry. Genzyme has made a large investment through
numerous patents on the synthesis of its novel ceramide-like selective
inhibitor of a novel biochemical target; and one wonders if it would
have done so had a competing orally available agent with a novel
mechanism of action not come to light.
In
relation to pharmacological chaperone therapy, as yet in an undeveloped
phase for clinical practice, it can be seen that the innovative drive
and incentive for developing new therapies in Gaucher disease is
pervasive and strong. Without it, much pharmaceutical development for
needy patients with disorders otherwise lacking specific measures would
not have occurred. While enzyme replacement therapy undoubtedly provides
large measurable health gains for adults and may prevent disease if
given sufficiently early in children, we must recognize that some
accommodation is needed in our appreciation of pharmaceutical
‘miracles’. After all, if all rare diseases mandated such enthusiastic
pharmaceutical interest, the costs of diverting health care resources to
swell the revenues of pharmaceutical companies could not be sustained.
Pricing issues
The
prices set by pharmaceutical companies for their drugs are arrived at
by complex and obscure means, but are justified by the need to cover the
costs of production and accompanying investment in the light of
competing agents. The perception of health benefits is also an important
factor in price setting. The need to generate profit is an unqualified
but critical factor. In the case of orphan agents, the unmet need is
construed as very high and unchallenged, for there is by definition no
competition which would otherwise mitigate pricing. Although biological
agents notionally would be expected to be very costly, the economy of
scale and long-standing marketing exclusivity with, for example, the
production of a genetically engineered protein from cell cultures
quickly allows an astonishing profit margin to be achieved.
Issues of marketing exclusivity
Gaucher
disease provides here another vivid example, not only of the triumph of
Western capitalist principles of utility and progress linked to profit,
but of a market exclusivity of another kind. For such are the prices of
the drugs developed in Western democratic countries that the public
health care systems of other populations do not even aspire to meet
them. It will be recalled that Stalin commuted the salaries of doctors
and other health care personnel greatly: even after the fall of Stalin
and two decades after the collapse of the Communist system in Russia and
post-Soviet states, exiguous salaries and investment have given rise to
appalling state provision for health. At the same time, private medical
services for party members and emerging plutocrats in Russia and many
former Communist countries aspire to the best international standards of
delivery and comfort. Under these circumstances, for many patients,
access to expensive treatments such as Cerezyme for Gaucher disease is
either denied or highly restricted.
Compassionate supply
The
problem of access has been commendably addressed in the divisional
locations of Genzyme in capitalist countries by the introduction of free
compassionate use programs for severely ill Gaucher patients resident
in communities where health care systems do not reimburse the costs of
lifesaving therapy. However, this does not address the total need of
Gaucher patients worldwide, for it is estimated that of the 5000 or so
patients who have been treated with Cerezyme (until the recent shortage
caused by vesivirus infection and shutdown of Genzyme’s Allston plant80), this would represent a maximum of 10% of all symptomatic Gaucher patients.
Orphan drug pricing
While
the high cost of manufacturing biological agents has the appearance of
veracity, one should also expect the competing small molecules to be
made available at costs that are substantially less than those for
enzyme therapies. There is only one example for a direct comparison,
namely Zavesca, at a cost of ~$100,000 per year for an average adult. It
is thus clear that incentive and shareholder revenue overshadow the
costs of manufacture for nonbiological agents even in the orphan drug
field.
The concept of ‘pile them
high and sell them cheap’ has yet to emerge among the competitors of
first-to-market orphan drugs, but where access remains difficult for
many patients in less developed countries, this heretical idea arguably
merits consideration.
Conclusion
Future considerations for orphan drug development
Market-driven
economies reward value and should aspire to reward the value that
health – a basic human necessity – brings to its citizens.
Some
patients with rare diseases have now received welcome attention through
the agency of orphan drug legislation, and in many cases, they gain
real benefit as a result of pioneering humane initiatives. Nonetheless,
the current model will need reviewing if it is to deliver value across
the thousands of individually rare diseases in whole populations.81
As
illustrated by the remarkable example of Gaucher disease, orphan drug
legislation can, in effect, promote vulnerable monopolies and also has
other unintended consequences. Once licensed, beyond mandatory
pharmacovigilance monitoring and fulfilment of postlicensing
commitments, there is little incentive for the victorious company to
invest in therapeutic research into the cognate disease. For such
investment to occur, competition and the fear of loss of commercial
primacy need to be felt, for only strong survival instincts and the need
to demonstrate prowess will induce further scientific expenditure.
Orphan
drug legislation is anticompetitive, but we now know that even this
cannot guarantee the survival of any given drug, particularly a biologic
agent like a therapeutic enzyme: there can be no immunity from
unexpected manufacturing disasters. In the case of Gaucher disease, the
catastrophic vesivirus infection that has all but stopped production of
Cerezyme for most of the year from June 200980 (as well as Genzyme’s agent for Fabry disease, Fabrazyme®)
leading to a reported 34% fall of Cerezyme sales to $793 million, while
sales of Fabrazyme fell 13% to $494 million. The company is struggling
now to recover its inventory while supplying as many of its global
customers as possible: the catastrophe has brought home not simply the
desirability but the absolute necessity of competition for the safe provision of alternative biosimilar agents.
Much
has been learned from the modern miracle of Gaucher disease as an
orphan disorder, but at the time of writing, we are entering a period of
radical change. With a history of unresolved regulatory issues
involving production at their impressive manufacturing plant after FDA
inspections, the sudden appearance of a vesivirus infection at the
Allston facility has exposed the Genzyme Corporation to intense
scrutiny; the reputation of an inspirational leader in the field has
been publicly questioned. Moreover, Genzyme has had to bear hostile bids
in the ruthless commercial world of industrial takeovers – and in times
when pharmaceutical giants are cutting their own research and
development budgets in favour of acquiring successful biotech companies
with more innovative approaches to rare diseases (‘niche-busting’).
Although there can be no retreat, at a time of unparalleled opportunity
and competitive interest in rare disorders, some form of societal
reckoning to ensure sustainable innovation in the whole field – of which
Gaucher disease is emblematic – is surely warranted.1
Imaginative approaches will be needed to commute the prices of orphan
drugs in a mature market, so that hand-in-hand therapeutic discovery and
development can be maintained in the long term at the current
unprecedented level of productivity and clinical benefit.
Acknowledgments
Research
into Gaucher disease from the author’s group is supported in part by
the European Union, 7th Frame Programme ‘Euclyd – a European Consortium
for Lysosomal Storage Diseases’ health F2/2008 grant agreement 201678
and by the Cambridge Biomedical Research Centre of the UK National
Institute of Health Research of the Department of Health. The group has
been previously supported by the Gauchers Association UK.
I
sincerely thank Elizabeth Chatters for excellent secretarial assistance
and Liz Morris, Patrick Deegan, Jane Tindall, Naomi Wright, Joan
Grantham, and many other colleagues for their expert advice and loyal
service in the care of innumerable patients with Gaucher disease
attending our National center for lysosomal disorders at Addenbrooke’s
hospital, supported by the National Commissioning Group of the National
Health Service (England).
Disclosure
The
author reports no conflicts of interest in this work in so far as
neither he nor any member of his family has stocks or direct financial
interests in any company as mandated by his election to current board
membership of the European Working Group for the study of Gaucher
disease (honorary vice-chairman, 1993–2010). The author receives
lecturing and conference fees from Actelion, Genzyme, and Shire Human
Genetic Therapies. His laboratory has received unrestricted research
support from Genzyme and Shire for scientific projects unrelated to
Gaucher disease. The author has provided occasional advice to Actelion,
Genzyme, and Shire in relation to marketing authorization of their
products and the conduct of clinical trials, as well as to regulatory
agencies (EMEA and FDA) concerning cognate products of these companies
and the treatment of Gaucher disease; similarly, he has advised Amicus
and Protalix but without charge. The author is an investigator in
clinical trials of treatments for Gaucher disease supplied by Actelion,
Genzyme, Shire, and Protalix; he accepted investigator status for trials
with Amicus, but the trial was closed before enrolment. No professional
fees are paid to the author in respect of his status as clinical
investigator and institutional involvement with trials conducted at
Cambridge University NHS Foundation Hospitals Trust (based at
Addenbrooke’s hospital).
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