Idelalisib Shows Response in Refractory Indolent Non-Hodgkin’s Lymphoma

Gilead Sciences announced interim results from its Phase 2 study (Study 101-09) evaluating idelalisib (formerly GS-1101), an investigational, targeted, oral inhibitor of phosphoinositide 3-kinase (PI3K) delta, for the treatment of patients with indolent non-Hodgkin’s lymphoma (iNHL) that is refractory (non-responsive) to rituximab and to alkylating-agent-containing chemotherapy.

Study 101-09 is a Phase 2, open-label, single-arm efficacy and safety study of idelalisib in patients with previously treated iNHL that is refractory both to rituximab and to alkylating-agent-containing chemotherapy (refractory defined as no response while on therapy or progression within six months of completion of therapy). The study enrolled 125 patients with a median age of 64 and had confirmed diagnoses of follicular lymphoma (n=72), small lymphocytic lymphoma (n=28), lymphoplasmacytic lymphoma / Waldenström macroglobulinemia (n=10) or marginal zone lymphoma (n=15). Patients had received a median of four prior treatment regimens before study entry, with 79% of patients refractory to two or more prior regimens and 74% refractory to their most recent regimen. All patients received idelalisib 150mg twice daily and were allowed to continue daily dosing as long as they benefited from therapy. The primary endpoint of the study was overall response rate, defined as the proportion of patients achieving a confirmed complete or partial response with idelalisib treatment. 

The overall response rate observed in the study was 53.6% (n=67; 95%CI: 44.5, 62.6) with five complete responses (4%), 60 partial responses (48%), two minor responses and 46 patients with stable disease (36.8%). The overall response rate was highly consistent across all subgroups analyzed. Among patients who responded, the median duration of response was 11.9 months and the median time to response was 1.9 months (1.8, 3.7). Median progression-free survival for all patients was 11.4 months. Most patients (89%) experienced some shrinkage in lymph node size.

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