Patients with chronic lymphocytic leukemia (CLL) who are relapsed or refractory (R/R) to ibrutinib or idelalisib may benefit from venetoclax monotherapy, according to a study presented at the 2016 American Society of Clinical Oncology Annual Meeting (June 3-7; Chicago IL).
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After relapsing or becoming refractory to B-cell receptor pathway inhibitors, patients with CLL typically have very poor outcomes. In an ongoing clinical trial, investigators examined the effectiveness of venetoclax, a selective oral BCL-2 inhibitor, in patients R/R to ibrutinib (arm A) or idelalisib (arm B).
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For the phase 2 trial, investigators enrolled 38 patients with CLL R/R to ibrutinib and 10 patients R/R to idelalisib. More than half of participants (54%) had received more than 5 prior therapies, 84% had unmuted IGHV, 35% had del17p, and 24% had at least 1 node ≥10 cm. Patients received 20 mg of venetoclax daily followed by a 5-week increase to 400mg per day.
Overall, patients previously treated with ibrutinib had an objective response rate of 61%, which was higher than what was observed in those in the idelalisib arm, where the rate was 50%. Three patients in each arm achieved complete responses while 8 patients who had received ibrutinib prior to venetoclax monotherapy had minimal residual disease negativity by flow cytometry in blood at 24 weeks.
Additional analysis also revealed that the venetoclax safety profile was consistent with previously reported findings. The most common treatment-related adverse events were neutropenia (48%), diarrhea (37%), nausea (35%), anemia (32%), fatigue (24%), hyperphosphatemia (20%). More serious grade 3 to 4 adverse events were neutropenia (39%), thrombocytopenia (22%), anemia (20%), leukopenia (13%), pneumonia (13%).
From these results, the investigators concluded that venetoclax monotherapy showed promising activity in patients with CLL R/R to ibrutinib or idelalisib with an acceptable safety profile.
