Encore - a Randomized, Controlled, Open-Label Non-Inferiority Study Comparing Eliglustat to Imiglucerase in Gaucher Disease Type 1 Patients Stabilized on Enzyme Replacement Therapy: 24-Month Results

Introduction: Eliglustat is a novel oral substrate-reduction therapy in development for adults with Gaucher disease type 1 (GD1). This open-label Phase-3 trial (ENCORE, NCT00943111, Genzyme, a Sanofi company, Cambridge, MA), the largest randomized, controlled trial in GD1 to date, evaluated eliglustat and imiglucerase treatment in patients who had previously reached pre-specified therapeutic goals after ≥3 years of enzyme replacement therapy. We report efficacy data from the 12-month primary analysis period (PAP) and the first 12 months of the extension period in which all patients received eliglustat.

Methods: Patients were randomized 2 to 1 eliglustat to imiglucerase. The primary efficacy endpoint was percent of patients remaining stable on a pre-specified composite of spleen, liver, hemoglobin, and platelet parameters. As this was a non-inferiority trial, efficacy analyses were performed on the per-protocol population (99 eliglustat and 47 imiglucerase patients).

Results: Eliglustat was non-inferior to imiglucerase: after 12 months of treatment, 85% of eliglustat and 94% of imiglucerase patients maintained all 4 goals (lower bound of 95% CI of difference [-17.6%] within the pre-specified [-25%] non-inferiority margin). Of the 159 patients treated in this study, 145 (91%) completed 24 months of treatment. During the 12-month extension period, continued stability was seen in most patients in both groups. Among 99 of 106 patients who continued on eliglustat, stability was seen in spleen volume (96% of patients), hemoglobin (97%), platelet count (94%), and liver volume (96%). In 47 of 53 patients who received imiglucerase in the PAP and then eliglustat in the trial extension, continued stability was seen also in spleen volume (97% of patients), hemoglobin (100%), platelet count (90%), and liver volume (95%). Most adverse events were mild or moderate in severity. No new safety concerns have arisen after 24 months.

Conclusions: Eliglustat was non-inferior to imiglucerase in maintaining stability after 12 months of treatment in patients previously stabilized on enzyme replacement therapy. In the 12-month trial extension, clinical stability was maintained in most patients who remained on eliglustat for 24 months and in most patients who switched from imiglucerase to eliglustat.