Gilead Offers Response Data from Phase 2 Study of Idelalisib

Gilead Sciences, Inc. GILD today announced results from a Phase 2 study (Study 101-08) evaluating idelalisib (formerly GS-1101), an investigational, targeted, oral inhibitor of PI3K delta, in combination with rituximab for older patients with treatment-naïve chronic lymphocytic leukemia (CLL). This regimen achieved a complete response (CR) rate of 19 percent and an overall response rate (ORR) of 97 percent, with estimated progression-free survival (PFS) at 24 months of 93 percent. Detailed results will be presented during an oral session at the 2013 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago (Abstract #7005). CLL is a slow-growing cancer that induces the production of too many mature white blood cells. It is the second most common type of leukemia in the United States and can lead to life-threatening complications, including serious infection. Currently, patients with CLL are usually treated first with rituximab in combination with one or more chemotherapy agents. Among the 64 patients in the study, Kaplan-Meier estimated PFS at 24 months was 93 percent. The median time on treatment was 14 months, with 33 patients remaining on treatment. The median time to response was two months. No relapses on study have been reported. The nine patients with chromosome 17p deletion (del 17p) (n=6) or mutation in the TP53 gene (n=3), which have been linked to poor prognosis, all responded to therapy including three with a complete response. Ninety-four percent of patients with thrombocytopenia at baseline responded to treatment (16/17), as did all patients with anemia at baseline (17/17). Of patients with systemic symptoms such as extreme fatigue, fever, night sweats or weight loss (known as “B symptoms”) at baseline, 77 percent (20/26) were asymptomatic by eight weeks. Patients completing 48 weeks of therapy without progression could continue to receive idelalisib in an extension study. Forty-three patients completed 48 weeks of treatment (21 discontinued – 17 due to adverse events, three due to death and one due to other reasons); 40 patients entered the extension study and 33 remain on treatment. During the primary and extension study, Grade 3 diarrhea and/or colitis was reported in 33 percent of patients, Grade ≥3 pneumonia in 17 percent and Grade ≥3 transaminase elevations (measure of liver function) in 23 percent of patients.