The combination of idelalisib and rituximab was highly active and resulted in durable disease control in treatment-naïve older patients with chronic lymphocytic leukemia (CLL), a new study published online ahead of print in the journal Blood has shown.1

Because idelalisib, a first-in-class oral PI3Kδ inhibitor, has shown substantial activity in patients with relapsed/refractory CLL, researchers sought to evaluate idelalisib as front-line therapy for older patients with CLL or small lymphocytic leukemia (SLL).

For the phase 2 study, researchers enrolled 64 previously untreated patients age 65 to 90 with CLL or SLL. All participants were treated with rituximab 375 mg/m2 intravenously weekly for 8 weeks plus idelalisib 150 mg orally twice daily continuously for 48 weeks. Individuals who completed 48 weeks of treatment without disease progression were eligible to participate in an extension study.

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Results showed that after a median treatment duration of 22.4 months, the overall response rate was 100% in patients with del(17p)/T53 mutations and 97% in those with unmutated IGHV. At 36 months, progression-free survival was 83%.

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In regard to safety, the most frequent adverse events were diarrhea, rash, pyrexia, nausea, chills, cough, and fatigue. The most common lab abnormality was elevated ALT/AST, which occurred in 67% of patients.

“These results support the further development of idelalisib as initial treatment for CLL,” the authors concluded.


  1. O’Brien SM, Lamanna N, Kipps TJ, et al. A phase 2 study of idelalisib plus rituximab in treatment-naïve older patients with chronic lymphocytic leukemia [published online ahead of print October 15, 2015]. Blood. doi: 10.1182/blood-2015-03-630947.