Final results of a phase I study of idelalisib, a selective inhibitor of phosphatidylinositol 3-kinase P110δ (PI3Kδ), in patients with relapsed or refractory mantle cell lymphoma (MCL).

8519 Background: PI3K-delta signaling is critical for activation, proliferation and survival of B cells and plays a role in homing and retention in lymphoid tissues. PI3Kδ signaling is hyperactive in many B-cell malignancies. Idelalisib is a first-in-class, selective, oral inhibitor of PI3Kδ. Initial response rate of 42% was previously reported in MCL (Kahl, ICML 2011). Long-term follow-up is now presented. Methods: This phase 1 study evaluated the activity of continuous (48 weeks) idelalisib monotherapy in pts with relapsed or refractory hematologic malignancies. Doses ranged from 50 mg BID to 350 mg BID in 8 cohorts. Response was based on investigator assessments using standard criteria (Cheson et al, 2007). Patients who continued to benefit were able to enroll in an extension study. Results: 40 patients with recurrent MCL enrolled. Patients were 88% male, median age [range] of 69 [52-83] years, 43% with refractory disease. The median [range] number of prior therapies was 4 [1E14]. The median [range] du...