The European Commission has granted marketing authorization for the PI3K delta inhibitor idelalisib (Zydelig) to treat chronic lymphocytic leukemia (CLL) and follicular lymphoma (FL) in the European Union.
The drug is now approved for use in combination with rituximab for CLL patients who have received at least 1 prior therapy or as first-line treatment in CLL patients who have 17p deletion or TP53 mutation and are not eligible for chemo-immunotherapy.
Idelalisib is also approved as monotherapy for FL patients who were refractory to 2 prior lines of treatment.
These approvals are based on data from 2 clinical trials—Study 116 and Study 101-09.
Study 116: Idelalisib in CLL
This phase 3 trial was stopped early because idelalisib had a significant impact on progression-free survival.
The study included 220 CLL patients who could not receive chemotherapy. Half were randomized to receive idelalisib plus rituximab, and the other half were randomized to rituximab plus placebo.
Patients in the rituximab-idelalisib arm had a much higher overall response rate than patients in the rituximab-placebo arm—81% and 13%, respectively (P<0.001). There were no complete responses.
At 24 weeks, the rate of progression-free survival was 93% in the rituximab-idelalisib arm and 46% in the rituximab-placebo arm (P<0.001). The median progression-free survival was 5.5 months in the rituximab-placebo arm and not reached in the rituximab-idelalisib arm (P<0.001).
At 12 months, the overall survival rate was 92% in the rituximab-idelalisib arm and 80% in the rituximab-placebo arm (P=0.02).
Most adverse events, in either treatment arm, were grade 2 or lower. The most common events in the rituximab-idelalisib arm were pyrexia, fatigue, nausea, chills, and diarrhea. In the rituximab-placebo arm, the most common events were infusion-related reactions, fatigue, cough, nausea, and dyspnea.
There were more serious adverse events in the rituximab-idelalisib arm than in the rituximab-placebo arm—40% and 35%, respectively. The most frequent serious events were pneumonia, pyrexia, and febrile neutropenia (in both treatment arms).
Study 101-09: Idelalisib in FL
This phase 2 trial enrolled 125 patients with indolent non-Hodgkin lymphoma who were refractory to rituximab and chemotherapy containing an alkylating agent. Patients received idelalisib monotherapy.
Of the 72 subjects with FL, 54% achieved a response, and 8% had a complete response. The median duration of response was not reached (range, 0-14.8 months).
Improvements in survival or disease-related symptoms have not been established.
In all patients, the most common grade 3 or higher adverse events were neutropenia (27%), elevations in aminotransferase levels (13%), diarrhea (13%), and pneumonia (7%).
Idelalisib is under development by Gilead Sciences. The drug is already approved in the US for the aforementioned indications, as well as to treat small lymphocytic lymphoma.
