A Phase Ib Study of Obinutuzumab Combined with Lenalidomide for Relapsed/Refractory Follicular B-Cell Lymphoma

BACKGROUND:

Lenalidomide exerts anti-proliferative activity on lymphoma cells, enhances T- and NK-cell function, and improves ADCC. The combination of lenalidomide and rituximab (R2) has been shown to be synergistic in pre-clinical models and in patients with relapsed and first-line follicular lymphoma (FL). Obinutuzumab, a unique type II glycoengineered monoclonal anti-CD20 antibody with increased ADCC and increased direct cell death induction compared to rituximab, has shown promising efficacy in NHL. Combining obinutuzumab with lenalidomide might be even more efficient than R2 combination. In 2012, we started a phase Ib/II study to assess the safety and efficacy of this combination (ClinicalTrials.gov: NCT01582776, GALEN) for relapsed/refractory lymphoma patients. Here, we report the phase Ib part whose primary objective was to determine the maximum tolerated dose (MTD) of lenalidomide in combination with a fixed dose of obinutuzumab.

METHODS:

To identify the MTD of lenalidomide, four patient cohorts received escalating doses (10, 15, 20, and 25 mg) of daily oral lenalidomide on days 1-21 of a 28-day cycle for the first cycle and on days 2-22 of a 28-day cycle from cycles 2 to 6. Intravenous infusions of obinutuzumab at a flat dose of 1000mg were given on Days 8, 15, and 22 of the first cycle and at D1 of cycles 2 to 6 (total of 8 infusions). Steroid premedication was mandatory before first obinutuzumab infusion. All subjects were required to take daily aspirin (100 mg) for deep vein thrombosis (DVT) prophylaxis during study period. Subjects who were unable to tolerate aspirin and subjects with prior history of DVT or at high risk received low molecular weight heparin therapy or warfarin (coumadin) treatment. Dose was escalated in a 3+3 design based on dose limiting toxicity (DLT) assessment during cycle 1

RESULTS:

20 patients with FL ([10 mg: 7; 15 mg: 3; 20 mg: 6, 25 mg: 4] QD) were enrolled between Oct 2012 and Feb 2014 at 7 centers, 10 men/10 women, median age 64 (range, 39–80) years, 15 with Ann Arbor stage IV, median number of prior systemic therapies 2 (range, 1–5) and 8 were rituximab refractory. One patient was withdrawn before receiving any treatment due to neutropenia occurring at baseline screening. Median number of cycles was 6 (range, 1–6). We observed 163 AEs (87 grade 1; 53 grade 2; 21 grade 3; one grade 4 and one grade 5). The most common AEs (All grades, ≥20% patients) were neutropenia (10/19; 53%), constipation (10/19; 53%) asthenia (7/19; 37%), upper respiratory tract infection (7/19; 37%), rash/cutaneous eruption (5/19; 26%), cough (5/19; 26%), diarrhea (4/19 ; 26%) and fever (4/19, 21%). Grade (G) 3/4 AEs occurring in ≥2 patients only consisted in neutropenia (8/19; 42%). Infusion related reactions occurred in 3 patients and did not exceed grade 2. Four DLTs have occurred in 2 patients: one unexplained death (G5) at 10 mg in the setting of G3 worsening pleural effusion; another patient treated at 20 mg had G3 pulmonary infection with G3 hypokalemia, both deemed unrelated to study treatment. The MTD was not reached. Among 19 evaluable patients, 13 (68%) had an overall response according to Cheson 1999 criteria: 7 achieved CR, 3 CRu and 3 PR.

CONCLUSION:

Oral lenalidomide plus obinutuzumab is well tolerated and effective in patients with relapsed or refractory FL. Recommended dose of lenalidomide was established at 20mg based on the increased incidence of grade 3/4 neutropenia between cycle 2 and 6 at 25mg. The Phase II partis currently assessing theefficacy of lenalidomide (at 20 mg) in combination with obinutuzumab in 2 separate populations of patients: relapsed/refractory follicular lymphoma in one cohort and relapsed/refractory aggressive lymphoma (diffuse large B-cell lymphoma and mantle cell lymphoma) in another cohort.