Idelalisib and Rituximab in Relapsed Chronic Lymphocytic Leukemia

BackgroundPatients with relapsed chronic lymphocytic leukemia (CLL) who have clinically significant coexisting medical conditions are less able to undergo standard chemotherapy. Effective therapies with acceptable side-effect profiles are needed for this patient population. MethodsIn this multicenter, randomized, double-blind, placebo-controlled, phase 3 study, we assessed the efficacy and safety of idelalisib, an oral inhibitor of the delta isoform of phosphatidylinositol 3-kinase, in combination with rituximab versus rituximab plus placebo. We randomly assigned 220 patients with decreased renal function, previous therapy-induced myelosuppression, or major coexisting illnesses to receive rituximab and either idelalisib (at a dose of 150 mg) or placebo twice daily. The primary end point was progression-free survival. At the first prespecified interim analysis, the study was stopped early on the recommendation of the data and safety monitoring board owing to overwhelming efficacy. ResultsThe median progression-free survival was 5.5 months in the placebo group and was not reached in the idelalisib group (hazard ratio for progression or death in the idelalisib group, 0.15; P<0.001). Patients receiving idelalisib versus those receiving placebo had improved rates of overall response (81% vs. 13%; odds ratio, 29.92; P<0.001) and overall survival at 12 months (92% vs. 80%; hazard ratio for death, 0.28; P=0.02). Serious adverse events occurred in 40% of the patients receiving idelalisib and rituximab and in 35% of those receiving placebo and rituximab. ConclusionsThe combination of idelalisib and rituximab, as compared with placebo and rituximab, significantly improved progression-free survival, response rate, and overall survival among patients with relapsed CLL who were less able to undergo chemotherapy. (Funded by Gilead; ClinicalTrials.gov number, NCT01539512.) A placebo-controlled study of idelalisib in patients with relapsed chronic lymphocytic leukemia who were receiving rituximab was stopped early because of significant improvement in rates of response, progression-free survival, and overall survival with idelalisib. Chronic lymphocytic leukemia (CLL) is the most prevalent leukemia among adults. Standard treatments include combinations of purine analogues, alkylating agents, and monoclonal antibodies. In younger patients without major coexisting illnesses, these regimens can provide high response rates of durable length but have substantial toxic effects. As a result, these treatments often have unacceptable side effects in older patients and those with coexisting illnesses.(1) Patients with relapsed CLL often have limited options because of the development of resistance to, or persisting toxic effects of, previous therapies. This is particularly true for elderly patients and those with coexisting illnesses.(2) For these patients, ...