Phase 1 trial of rituximab, lenalidomide, and ibrutinib in previously untreated follicular lymphoma: Alliance A051103.

Chemoimmunotherapy in follicular lymphoma is associated with significant toxicity. Targeted therapies are being investigated as potentially more efficacious and tolerable alternatives for this multiply-relapsing disease. Based on promising activity with rituximab and lenalidomide in previously untreated follicular lymphoma (overall response rate [ORR] 90%-96%) and ibrutinib in relapsed disease (ORR 30%-55%), the Alliance for Clinical Trials in Oncology conducted a phase 1 trial of rituximab, lenalidomide, and ibrutinib. Previously untreated patients with follicular lymphoma received rituximab 375 mg/m on days 1, 8, 15, and 22 of cycle 1 and day 1 of cycles 4, 6, 8, and 10; lenalidomide as per cohort dose on days 1 to 21 of 28 for 18 cycles; and ibrutinib as per cohort dose daily until progression. Dose escalation used a 3+3 design from a starting dose level (DL) of lenalidomide 15 mg and ibrutinib 420 mg (DL0) to DL2 (lenalidomide 20 mg, ibrutinib 560 mg). Twenty-two patients were enrolled; DL2 was determined to be the recommended phase II dose. Although no protocol-defined dose-limiting toxicities were reported, a high incidence of rash was observed (all grades 82%, grade 3 36%). Eleven patients (50%) required dose reduction, 7 because of rash. The ORR for the entire cohort was 95%, and the 12-month progression-free survival was 80% (95% confidence interval, 57%-92%). Five patients developed new malignancies; 3 had known risk factors before enrollment. Given the increased toxicity and required dose modifications, as well as the apparent lack of additional clinical benefit to the rituximab-lenalidomide doublet, further investigation of the regimen in this setting seems unwarranted. The study was registered with www.ClinicalTrials.gov as #NCT01829568.