Eliglustat, an oral substrate reduction therapy, is approved for eligible adults with Gaucher disease type 1. In the Phase 3 ENGAGE trial of previously untreated adults with Gaucher disease type 1, eliglustat-treated patients had statistically significant improvements in organ volumes and hematologic parameters compared with placebo in the 9-month primary analysis. We report final outcomes by time on eliglustat among all patients who participated in the ENGAGE trial and extension. No patient deteriorated clinically or withdrew due to adverse events; 39/40 patients entered the open-label extension period and 34/40 (85%) remained in the trial until completion or switching to commercial eliglustat after its approval (2.3-6 years). Clinically meaningful improvements in Gaucher disease manifestations were seen in all patients concomitant with reductions in pathological lipid substrate levels (glucosylceramide and glucosylsphingosine). Among patients with 4.5 years of eliglustat exposure, mean spleen volume decreased by 66% (from 17.1 to 5.8 multiples of normal [MN], n = 13), mean liver volume decreased by 23% (from 1.5 to 1.1 MN, n = 13), mean hemoglobin increased 1.4 g/dl (from 11.9 to 13.4 g/dl, n = 12), mean platelet count increased by 87% (from 67.6 to 122.6 × 10⁹ /L, n = 12), median chitotriosidase decreased by 82% (from 13 394 to 2312 nmol/h/ml, n = 11), median glucosylceramide decreased by 79% (from 11.5 to 2.4 μg/ml, n = 11), median glucosylsphingosine decreased by 84% (from 518.5 to 72.1 ng/ml, n = 10), and mean spine T-score increased from -1.07 (osteopenia) to -0.53 (normal) (n = 9). The magnitude of improvement in Gaucher disease manifestations and biomarkers over time was similar among the full trial cohort. Eliglustat was well-tolerated and led to clinically significant improvements in previously untreated patients with Gaucher disease type 1 during 4.5 years of treatment.

Eliglustat, an oral substrate reduction therapy, is a first-line treatment for adults with Gaucher disease type 1 (GD1) who are poor, intermediate, or extensive CYP2D6 metabolizers (>90% of patients). In the primary analysis of the Phase 3 ENGAGE trial (NCT00891202), eliglustat treatment for 9 months resulted in significant reductions in spleen and liver volumes and increases in hemoglobin concentration and platelet count compared with placebo. We report 18-month outcomes of patients who entered the trial extension period, in which all patients received eliglustat. Of 40 trial patients, 39 entered the extension period, and 38 completed 18 months. Absolute values and percent change over time were determined for spleen and liver volume, hemoglobin concentration, platelet count, bone mineral density, bone marrow burden, and Gaucher disease biomarkers. For patients randomized to eliglustat in the double-blind period, continuing treatment with eliglustat for 9 more months resulted in incremental improvement of all disease parameters. For patients randomized to placebo in the double-blind period, eliglustat treatment during the 9-month, open-label period resulted in significant decrease of spleen and liver volumes and significant increase of hemoglobin and platelets, with a similar rate of change to patients who had received eliglustat in the double-blind period. Eliglustat treatment was also associated with improvement in bone marrow burden score, bone mineral density, and established biomarkers of Gaucher disease, including reduction of the bioactive lipid, glucosylsphingosine. These findings underscore the efficacy of eliglustat in treatment-naïve patients. Eliglustat was well-tolerated, and there were no new safety concerns with longer-term exposure.