Idelalisib more effective in CLL, iNHL than MCL

The researchers evaluated idelalisib in 40 patients with relapsed or refractory MCL. The median age was 69 years (range, 52-83). Patients had received a median of 4 prior therapies (range, 1-14), and 43% were refractory to their most recent treatment.

Patients received idelalisib at doses ranging from 50 mg to 350 mg once or twice daily for a median of 3.5 months (range, 0.7-30.7). Six patients (15%) continued treatment for more than 48 weeks, although only 1 patient remains on treatment at present.

The 34 patients who discontinued the primary study did so because of progressive disease (60%), AEs (20%), withdrawn consent (3%), or investigator request (3%). Of the 6 patients who entered the extension trial, 4 ultimately discontinued due to progressive disease and 1 due to AEs.

Grade 3 or higher AEs included diarrhea (18%), decreased appetite (15%), pneumonia (10%), nausea (5%), fatigue (3%), and rash (3%). Grade 3 or higher lab abnormalities included ALT/AST elevations (20%), neutropenia (10%), thrombocytopenia (5%), and anemia (3%).

The overall response rate was 40%, with 5% of patients achieving a complete response. The median duration of response was 2.7 months, and the median PFS was 3.7 months.

Despite the modest duration of survival observed in these patients, the researchers believe the strong initial response to idelalisib suggests the drug could still prove useful in patients with MCL.

“[I]delalisib is unlikely to receive designation as a single-agent therapy in mantle cell lymphoma due to the short duration of response,” said study author Brad S. Kahl, MD, of the University of Wisconsin Carbone Cancer Center in Madison.

“The path forward will likely include administering it in combination with other agents or developing second-generation PI3 kinase inhibitors.”