Results of a Phase I Study of Obinutuzumab, Venetoclax, and Lenalidomide in Relapsed and Refractory B-Cell Non-Hodgkin Lymphoma

Introduction: Venetoclax, a BCL2 inhibitor, has demonstrated efficacy both as a single agent and in combination with rituximabin several subtypes of B-cell non-Hodgkin lymphoma (NHL). The combination of obinutuzumab and lenalidomide has demonstrated safety and preliminary efficacy in follicular lymphoma (Fowler et al., JCO 2015; 35: 7531). We conducted a phase I study of obinutuzumab, venetoclax, and lenalidomide to determine the safety, maximum tolerated dose, and preliminary efficacy of the combination.

Methods: Patients with relapsed/refractory diffuse large B-cell (DLBCL), transformed, high grade B-cell (HGBCL), marginal zone, and follicular (FL) lymphoma who have received ≥ 1 prior therapy were eligible. Prior autologous (ASCT) but not allogeneic stem cell transplant were permitted. Prior lenalidomide or BCL2 family inhibitors, CNS involvement, and active hepatitis or HIV infection were not permitted. ANC > 1000/mm³, platelets > 75,000/mm³, creatinine clearance ≥50 ml/min, ALT/AST ≤ 3 x ULN, bilirubin ≤ 1.5 x ULN, and ECOG PS 0-2 were required. Treatment consisted of obinutuzumab 1000 mg on days 1, 8 and 15 of cycle 1 and then on day 1 of cycles 2-6 with escalating doses of lenalidomide days 1-21 and venetoclax days 1-28 of a 28 day cycle (Table 1). A 3+3 dose escalation schema was followed. The DLT period was 1 cycle and patients had to receive 80% of the doses of the oral agents and all doses of obinutuzumab to be considered evaluable for DLT. DLTs included: treatment delays > 28 days; ANC < 500 / mm³ or platelets <25, 000 / mm³ persisting > 28 days; grade 4 febrile neutropenia or infection; grade 3 infection that fails to resolve within 7 days; and grade 3 or 4 non-hematologic toxicity. Patients without significant toxicity or progression could continue treatment up to 12 cycles. Response was assessed by CT or PET/CT every 3 months for 12 months and then every 6 months until disease progression.

Results: 22 patients were treated. Median age was 61 years (range 31-78 years) with 16 males. Median prior therapies was 2 (range 1-10) and included 5 patients who had relapsed after chimeric antigen receptor T-cell therapy and 2 patients relapsed after ASCT. Median baseline lactate dehydrogenase was 259.5 U/L (range 147-5133, ULN 190 U/L). 16 patients had aggressive B-cell lymphoma including DLBCL, HGBCL, primary mediastinal and transformed FL, 5 patients had FL and 1 patient had marginal zone lymphoma. At dose level (DL) 1, one patient experienced a DLT, grade 3 neutropenic fever lasting > 7 days. DL 1 was expanded and no additional DLTs occurred. No further DLTs occurred at DL 2-4. DL 4 was expanded and was determined to be the MTD. Four patients, 1 in each dose level, were not evaluable for DLT and were replaced including 3 who did not receiving 80% of the oral agents due to required dose reductions and 1 patient for disease progression. Related grade 3-4 toxicities were primarily hematologic including neutropenia (n=20, 90.9%), thrombocytopenia (n=5, 22.7%), and anemia (n=3, 13.6%). Grade 3-4 infections (n=6, 27%) included sepsis, febrile neutropenia, pneumonia and a urinary tract infection. Other grade 3-4 AEs occurring once each included dysgeusia, dyspnea, nausea, vomiting, and hyperhidrosis. No clinically significant tumor lysis has occurred. Patients have received a median of 3 cycles (range 1-12) of treatment. Three patients remain on therapy and 5 patients are on follow up. Dose reductions of lenalidomide occurred for 17 patients (77%) and of venetoclax for 11 patients (50%). Nine patients have achieved a response (41%), including 8 complete (CR) and 1 partial responses (PR). Responses have occurred at each DL and include 4 patients with FL (2 CR, 2 PR), 4 patients with aggressive lymphoma (4 CR) and 1 patient with MZL (CR). 14 patients are off of the study, 9 with progression, 2 for alternative therapy, and 1 each for DLT, physician preference, and a diagnosis of MDS in a patient with 3 prior lines of chemotherapy.

Conclusions: Combined treatment with obinutuzumab, venetoclax, and lenalidomide administered up to 12 cycles is feasible with activity in multiple subtypes of relapsed NHL. Enrollment in expansion cohorts of FL and aggressive B-cell lymphoma is ongoing.

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