Gilead announces interim Phase 2 data for idelalisib showing response in refractory indolent non-Hodgkin’s lymphoma

Gilead Sciences, Inc. (Nasdaq: GILD) today announced interim results from a single-arm, open-label Phase 2 study (Study 101-09) evaluating idelalisib (formerly GS-1101), an investigational, targeted, oral inhibitor of 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. Previously, this has been a largely unstudied population for which there is significant unmet medical need for effective therapy. In the study, single-agent treatment with idelalisib achieved an overall response rate of 53.6 percent, with a median duration of response at this interim analysis of 11.9 months. Detailed study results will be presented this Thursday during an oral session at the 12th International Conference on Malignant Lymphoma in Lugano, Switzerland (Abstract #064bis).

“Despite the progress achieved in recent years, most patients suffering from indolent non-Hodgkin’s lymphoma will progressively become resistant to currently available treatments. Therefore, there is a significant unmet medical need for novel therapies,” said Gilles A. Salles, MD, PhD, Professor of Medicine, Department of Hematology, Claude Bernard University, Lyon-Sud Hospital Center, Pierre-Benite, France. “These data suggest that idelalisib has the potential to provide durable disease control to this group of patients who have few if any remaining conventional treatment options.”

The overall response rate observed in the study was 53.6 percent (n=67; 95 percent CI: 44.5, 62.6) with five complete responses (four percent), 60 partial responses (48 percent), two minor responses and 46 patients with stable disease (36.8 percent). 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 percent) experienced some shrinkage in lymph node size.

The most common Grade ≥3 adverse event was diarrhea (10 percent). Grade ≥3 transaminase elevations (measure of liver function) were reported via central laboratory testing in 13 percent of patients; Grade ≥3 neutropenia occurred in 26 percent of patients. Sixteen percent of patients discontinued due to adverse events. The study is ongoing.

About Study 101-09

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 from approximately 50 study sites in the United States and Europe. Patients were 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 percent of patients refractory to two or more prior regimens and 74 percent refractory to their most recent regimen. All patients received idelalisib 150 mg twice daily and are allowed to continue daily dosing as long as they benefit from therapy. The primary endpoint of the study is overall response rate, defined as the proportion of patients achieving a confirmed complete or partial response with idelalisib treatment (response definitions based on standard criteria; responses assessed by study investigators and an independent review committee).

About Idelalisib

Idelalisib is an investigational, targeted, highly selective oral inhibitor of phosphoinositide 3-kinase (PI3K) delta, a molecular target that is critical for the activation, proliferation and survival of B lymphocytes. PI3K delta signaling is hyperactive in many B-cell leukemias and lymphomas and drives proliferation, survival and trafficking to lymphoid tissue. Idelalisib is being developed both as a single agent and in combination with approved and investigational therapies.

Gilead’s clinical development program for idelalisib includes three Phase 3 studies evaluating the drug in combination with approved therapies for patients with previously treated chronic lymphocytic leukemia (CLL) and two Phase 3 studies of idelalisib in combination with approved therapies for patients with previously treated indolent non-Hodgkin’s lymphoma (iNHL). In addition, combination therapy with idelalisib and GS-9973, Gilead’s novel spleen tyrosine kinase (Syk) inhibitor, is being studied in a Phase 2 trial of patients with relapsed or refractory CLL, iNHL and other lymphoid and hematological malignancies.

Additional information about clinical studies of idelalisib and Gilead’s other investigational cancer agents can be found at www.clinicaltrials.gov. Idelalisib and GS-9973 are investigational products and their safety and efficacy have not yet been established.

About Indolent Non-Hodgkin’s Lymphoma

Indolent non-Hodgkin’s Lymphoma (iNHL) refers to a group of slow-growing lymphomas that can lead to life-threatening complications such as serious infections and anemia and includes follicular lymphoma, small lymphocytic lymphoma, lymphoplasmacytic lymphoma / Waldenström macroglobulinemia and marginal zone lymphoma. Patients typically experience enlarged lymph nodes, and other organs such as the spleen and liver may also be involved. Patients may develop symptoms such as fever, night sweats, weight loss and fatigue. Most iNHL patients are diagnosed at an advanced stage of disease, which is usually not curable, and median survival from time of initial diagnosis for patients with the most common form of iNHL, follicular lymphoma, is 8 to 10 years. By contrast, the outlook for patients who are unresponsive to rituximab and chemotherapy, such as those included in this study, is less encouraging.