A Phase I Study of Ibrutinib and Lenalidomide in Patients with Relapsed and Refractory B-Cell Non-Hodgkin's Lymphoma

Introduction:

Lenalidomide, an immunomodulatory agent, and ibrutinib, a selective and covalent inhibitor of Bruton’s tyrosine kinase, are orally bioavailable agents with promising single agent activity in relapsed/refractory B-cell NHL. We are conducting a phase I study of the combination of ibrutinib and lenalidomide to determine the maximum tolerated dose, dose limiting toxicities (DLT), and preliminary efficacy in patients with relapsed/refractory NHL.

Methods:

Patients with relapsed/refractory B-cell NHL including diffuse large B-cell (DLBCL), transformed, mantle cell, marginal zone, lymphoplasmacytic, and follicular lymphoma who have received at least one prior therapy were eligible. Prior autologous but not allogeneic stem cell transplant and prior lenalidomide were permitted. Prior ibrutinib, CNS involvement, and patients requiring anticoagulation were not permitted. ANC > 1000/mm³, platelets > 50,000/mm³, and creatinine < 2.0 mg/dL, ALT/AST ≤ 2.5 x ULN, bilirubin ≤ 1.5 x ULN, and ECOG PS 0-2 were required at study entry. Treatment consisted of escalating doses of lenalidomide days 1-21 and ibrutinib days 1-28 of a 28 day cycle. A standard 3+3 dose escalation schema was followed. DLTs were assessed during cycle 1 and included: treatment delays > 14 days for toxicity; grade 5 toxicity; tumor lysis syndrome requiring dialysis; tumor flare reaction nonresponsive to corticosteroids; ANC < 500 / mm³ or platelets <25, 000 / mm³ persisting > 7 days; grade 3 or 4 febrile neutropenia or infection; and any grade 3 or 4 non-hematologic toxicity with the exception of DVT, diarrhea, nausea, or vomiting amenable to medical therapy, correctable electrolyte abnormalities; grade 3 fatigue, or grade 3 maculopapular rash that resolved within 7 days. Patients without significant toxicity could continue treatment until disease progression. Response was assessed every 3 months for 12 months and then every 6 months until disease progression.

Results:

From September 2013 until July 2014, 13 patients have been treated. Median age is 68 years (range 45-85) with 9 males. Histologies include DLBCL (4), transformed (4), follicular (2), mantle cell (2), and lymphoplasmacyctic (1) lymphoma. Median number of prior therapies is 3 (range 2-9) with 4 patients having undergone prior autologous transplant. Four patients were treated at dose level (DL) 1 (lenalidomide 15 mg and ibrutinib 420 mg). One patient was replaced for rapid disease progression and 1 patient experienced DLT consisting of a grade 2 ischemic stroke while on aspirin with no history of cardiovascular disease that resulted in discontinuation of study therapy. As a result of this DLT, dose level 1 was expanded to 6 patients. A second DLT was observed, a grade 3 rash that resolved within 7 days with interruption of therapy but recurred with diffuse erythroderma within 4 hours of ibrutinib resumption on day 22 at 280 mg. A total of 6 patients were then treated at DL -1 (lenalidomide 10 mg and ibrutinib 280 mg), and no DLTs were encountered. Related grade 3-4 toxicities occurred in 4/13 patients (31%), including one patient with hypokalemia, neutropenia, thrombocytopenia, and pneumonia, two others with neutropenia and one with maculapapular rash. Patients have received a median of 3 cycles of therapy to date (range 1-5) and 5 remain on therapy. At DL 1, a patient with DLBCL achieved a complete response (CR) and patient with transformed follicular achieved a partial response (PR). At DL -1, a patient with DLBCL achieved a CR and a patient with mantle cell lymphoma achieved a PR. Four patients achieved stable disease. Reasons for study discontinuation include two patients with DLTs who were not evaluated for response, one patient with stable disease who went off study for alternative treatment, and five patients who have progressed.

Conclusions:

Combined therapy with lenalidomide and ibrutinib in patients with relapsed NHL has been well tolerated at doses of 10 mg and 280 mg respectively, although DLTs of recurrent rash and stroke were encountered with 15 mg lenalidomide and 420 mg ibrutinib. Dose escalation to an intermediate dose level with lenalidomide 10 mg and ibrutinib 420 mg is planned. If this dose level is deemed safe, intra-patient dose escalation of the lenalidomide from 10 mg in cycle 1 to 15 mg in cycle 2 with ibrutinib 420 mg continuously will be tested. Preliminary efficacy has been observed in patients with relapsed/refractory DLCL, MCL, and transformed NHL.