Gilead Sciences, Inc. announced results from a prespecified interim analysis of a Phase 3 study (Study 115) evaluating Zydelig® (idelalisib) in combination with bendamustine and rituximab (BR) for patients with previously treated Chronic Lymphocytic Leukemia. The analysis found a 67 percent reduction in the risk of disease progression or death (progression-free survival, PFS) in patients receiving Zydelig plus BR compared to BR alone (hazard ratio (HR) = 0.33; 95 percent CI: 0.24, 0.45; p<0.0001). Additionally, all secondary endpoints, including overall survival (OS), achieved statistical significance in this interim analysis.
Zydelig is approved in the United States in combination with rituximab for patients with relapsed CLL for whom rituximab alone would be considered appropriate therapy due to comorbidities. Based on the Study 115 results, Gilead plans to submit supplemental regulatory filings in the U.S. and Europe early next year. Study 115 enrolled 416 adult patients with previously treated CLL whose disease had progressed less than 36 months following completion of prior therapy, and was not refractory to bendamustine. Eligible patients were randomized (1:1) to receive six cycles of BR over 24 weeks with either Zydelig 150 mg or placebo taken orally twice daily until disease progression or unacceptable toxicity. In November, the trial was unblinded following the recommendation of an independent Data Monitoring Committee.
The study also found a statistically significant benefit in OS, with a 45 percent reduction in the risk of death among patients receiving Zydelig plus BR compared to those receiving BR alone (HR=0.55; 95 percent CI: 0.36, 0.86; p=0.008). Median OS has not been reached in either arm. The overall response rate (ORR) was 68 percent in the Zydelig arm and 45 percent for the control arm.
