Idelalisib- a PI3Kδ targeting agent for B-cell malignancies.

Idelalisib, the first in-class phosphotidlyinositol 3-kinase delta (PI3Kδ) inhibitor, was approved by the US Food and Drug Administration in July 2014. It simultaneously received breakthrough therapy designation in combination with rituximab for the treatment of relapsed chronic lymphocytic leukemia (CLL) as well as accelerated approval as monotherapy for the treatment of relapsed follicular lymphoma and relapsed small lymphocytic lymphoma. In a pivotal phase III study of 220 patients with relapsed CLL, the overall response rate of patients who received rituximab plus idelalisib was 81%. The median progression-free survival (PFS) was 5 months with rituximab plus placebo group, but was not reached in the idelalisib arm. At 24 weeks, the PFS in patients receiving idelalisib was 93%. In a phase II trial of 125 patients with relapsed or refractory indolent non-Hodgkin lymphoma who received idelalisib 150 mg twice daily, the response rate was 57%. Complete response was seen in 6% of patients. The median duration of response was 12.5 months, and median PFS was 11 months. Idelalisib is a promising new therapy for relapsed indolent B-cell malignancies.