On July 23, 2014 Gilead Sciences reported that the U.S. Food and Drug Administration (FDA) has approved Zydelig (idelalisib) 150 mg tablets for the treatment of three B-cell blood cancers (Press release Gilead Sciences, JUL 23, 2014, View Source [SID:1234500638]). Zydelig is indicated in combination with rituximab for patients with relapsed chronic lymphocytic leukemia (CLL) for whom rituximab alone would be considered appropriate therapy and as monotherapy for patients with relapsed follicular B-cell non-Hodgkin lymphoma (FL) and small lymphocytic lymphoma (SLL) who have received at least two prior systemic therapies. Accelerated approval was granted for FL and SLL based on overall response rate. Zydelig is a first-in-class inhibitor of PI3K delta, a protein that is over-expressed in many B-cell malignancies and plays a role in the viability, proliferation and migration of these cancer cells.

“Zydelig is a much needed new treatment option for appropriate patients with CLL and these indolent lymphomas who have experienced relapses and have limited, if any, treatment options,” said Bruce Cheson, MD, Professor of Medicine, Head of Hematology and Director of Hematology Research at Lombardi Comprehensive Cancer Center at Georgetown University, and a principal investigator on the Zydelig pivotal Phase 3 trial in CLL. “In clinical studies among patients with relapsed CLL, FL and SLL, Zydelig produced strong responses, including a significant improvement in progression-free survival in CLL. I believe it helps fill a significant unmet need for these patients.”

Over 200,000 Americans are living with CLL, FL or SLL, slow-growing incurable blood cancers that can lead to life-threatening complications such as anemia, serious infection and bone marrow failure requiring treatment. Relapse commonly occurs after initial chemoimmunotherapy and many patients with relapsed CLL, FL or SLL are unable to tolerate chemotherapy, which may limit their treatment options.

“Gilead is committed to the development of novel cancer therapies and we are proud to have this opportunity to make a difference in the lives of people living with these cancers,” said John C. Martin, PhD, Chairman and Chief Executive Officer, Gilead Sciences. “We extend our thanks to the many physicians and patients who participated in Zydelig clinical trials, and are now focused on making this medicine available to patients as expeditiously as possible.”

The product’s approval in CLL is supported primarily by data from a randomized, placebo-controlled Phase 3 trial (Study 116) of Zydelig plus rituximab in 220 patients with relapsed CLL who were not able to tolerate standard chemotherapy. Study 116 was stopped early in October 2013 by an independent Data Monitoring Committee due to a highly statistically significant benefit in progression-free survival (PFS) in the Zydelig arm as compared to those receiving rituximab alone (hazard ratio = 0.18 (95 percent CI: 0.10, 0.32), p<0.0001). Median PFS was not reached in the Zydelig plus rituximab arm (95 percent CI: 10.7 months, NR) and was 5.5 months in the placebo plus rituximab arm (95 percent CI: 3.8, 7.1). The FDA granted Zydelig a Breakthrough Therapy designation for relapsed CLL, a designation granted to drug candidates that may offer major advances in treatment over existing options. Zydelig’s accelerated approval in FL and SLL, two types of indolent non-Hodgkin lymphoma, is supported by data from a single-arm Phase 2 study (Study 101-09) of Zydelig monotherapy in patients refractory to rituximab and alkylating-agent-containing chemotherapy (FL: n=72; SLL: n=26). In the study, Zydelig achieved an overall response rate of 54 percent (range: 42-66 percent) and 58 percent (range: 37-77 percent), respectively, in FL and SLL patients. Of the responses seen in FL patients, 8 percent (n=6) were complete responses; all 15 responses in SLL patients were partial responses. The median duration of response was 11.9 months in SLL patients (range: 0.0, 14.7 months) and median duration of response was not reached in FL patients (range: 0.0, 14.8 months). Improvement in patient survival or disease related symptoms has not been established in these indications. Results of Study 116 and Study 101-09 were published in The New England Journal of Medicine in March 2014.