PI3K Inhibition in Hematologic Malignancies

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Treatment with the oral PI3K-delta inhibitor idelalisib produced an overall response rate of 57% with average response duration of 12.5 months in heavily pretreated patients with indolent non-Hodgkin’s lymphoma (iNHL). This promising benefit was seen in a single-agent, phase II study that involved 125 patients with various types of iNHL, including follicular lymphoma (72 patients), small lymphocytic lymphoma (28), marginal-zone lymphoma (15), and lymphoplasmacytic lymphoma with or without Waldenström’s macroglobulinemia (10), explains Brad S. Kahl, MD.

Based on these data, the FDA has accepted a new drug application for idelalisib for the treatment of patients with iNHL. A target review date under the Prescription Drug User Fee Act was set for September 11, 2014.

The PI3K-delta and gamma inhibitor IPI-145 has also shown promising activity in patients with chronic lymphocytic leukemia (CLL) and T-cell lymphomas, notes John C. Byrd, MD. It appears that lymphocytosis resolves sooner with IPI-145 than it does with ibrutinib. Although the follow-up of the phase I study exploring the drug is shorter, the toxicity in patients with CLL appears manageable, Byrd notes.