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Eliglustat tartrate (Genz-112638), a specific inhibitor of glucosylceramide synthase, is under development as an oral substrate reduction therapy for Gaucher disease type 1 (GD1

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Key Points Eliglustat treatment resulted in stable mean hemoglobin concentration, platelet count, and spleen and liver volumes for up to 4 years. Mean bone mineral density z scores also remained stable and were maintained in the healthy reference range for up to 4 years.

Eliglustat is a first‐line oral therapy for adults with Gaucher disease type 1 (GD1) and poor, intermediate or extensive CYP2D6‐metabolizer phenotypes (>90% of patients). We report the final results of a Phase 2 trial and extension (NCT00358150) in previously untreated adult GD1 patients who had splenomegaly with thrombocytopenia and/or anemia and received 50 or 100 mg eliglustat tartrate (equivalent to 42 or 84 mg eliglustat) twice daily for 8 years. In total, 19 of 26 patients completed the trial. After 8 years of eliglustat, mean spleen and liver volumes decreased by 69% and 34%, respectively. Mean hemoglobin concentration and platelet count increased by 2.2 g/dL and 113%, respectively. All patients met at least 3 of 4 therapeutic goals established for patients on long‐term enzyme replacement therapy. Mean final values for patients with severe splenomegaly (n = 6), moderate‐to‐severe anemia (n = 6), or severe thrombocytopenia (n = 8) were similar to patients with milder disease at baseline and within long‐term therapeutic goal thresholds. Biomarker median percent changes from baseline were ‐91% for chitotriosidase, ‐87% for CCL18, ‐92% for glucosylsphingosine, and ‐80% for plasma glucosylceramide. Mean lumbar spine T‐score increased by 0.96, moving from the osteopenic to the normal range. Mean quality‐of‐life scores, mostly below normal at baseline, moved into ranges seen in healthy adults. Eliglustat was well‐tolerated; 98% of adverse events were mild or moderate and 94% were considered unrelated to treatment. Clinically meaningful improvements in all parameters continued or were maintained over 8 years, with the largest margins of improvement seen in the most severely affected patients.

Eliglustat is an investigational, oral substrate reduction therapy for Gaucher disease type 1 (GD1). Nineteen treatment-naïve patients have now completed 4years of an open-label study (NCT00358150). Mean hemoglobin level and platelet count increased by 2.3±1.5g/dL (baseline: 11.3±1.5g/dL) and 95% (baseline: 68,700±21,200/mm(3)), respectively. Mean spleen and liver volumes (multiples of normal, MN) decreased by 63% (baseline: 17.3±9.5 MN) and 28% (baseline: 1.7±0.4 MN), respectively. Median chitotriosidase and CCL-18 each decreased by 82%; plasma glucosylceramide and GM3 normalized. Mean bone mineral density T-score for the lumbar spine increased by 0.8 (60%) (baseline: -1.6±1.1). Femur dark marrow, a reflection of Gaucher cell infiltration into bone marrow, was reduced or stable in 17/18 patients. There were no bone crises. Most adverse events were mild and unrelated to treatment. These results extend the safety and efficacy of eliglustat reported at 1 and 2 years to 4 years.

ObjectiveEliglustat is an investigational oral substrate reduction therapy for Gaucher disease type 1 (GD1). Its skeletal effects were evaluated by prospective monitoring of bone mineral density (BMD), fractures, marrow infiltration by Gaucher cells, focal bone lesions, and infarcts during an open-label, multi-site, single-arm phase 2 trial (NCT00358150).Materials and methodsInstitutional review board approval and patient informed consent were obtained. Eliglustat (50 or 100 mg) was self-administered by mouth twice daily; 19 patients completed 4 years of treatment. All were skeletally mature (age range, 18–55 years). DXA and MRI assessments were conducted at baseline and annually thereafter. X-rays were obtained annually until month 24, and then every other year.ResultsLumbar spine BMD increased significantly (p = 0.02; n = 15) by a mean (SD) of 9.9 % (14.2 %) from baseline to year 4; corresponding T-scores increased significantly (p = 0.01) from a mean (SD) of −1.6 (1.1) to −0.9 (1.3). Mean femur T-score remained normal through 4 years. Femur MRI showed that 10/18 (56 %) patients had decreased Gaucher cell infiltration compared to baseline; one patient with early improvement had transient worsening at year 4. There were no lumbar spine or femoral fractures and no reported bone crises during the study. At baseline, 8/19 (42 %) patients had focal bone lesions, which remained stable, and 7/19 (37 %) patients had bone infarctions, which improved in one patient by year 2. At year 4, one new asymptomatic, indeterminate bone lesion was discovered that subsequently resolved.ConclusionsEliglustat may be a therapeutic option for treating the skeletal manifestations of GD1.