Ibrutinib inhibits antibody dependent cellular cytotoxicity induced by rituximab or obinutuzumab in MCL cell lines, not overcome by addition of lenalidomide

Background: The Bruton's Tyrosine Kinase (BTK)-inhibitor ibrutinib is highly active in mantle cell lymphoma (MCL) but may inhibit response to anti-CD20 antibody as previously shown in CLL models. We investigated how antibody-dependent cellular cytotoxicity (ADCC) induced by type I/II anti-CD20 antibodies was affected by treatment with ibrutinib in MCL. Furthermore, we investigated if lenalidomide, a potential sensitizer to anti-CD20 treatment, could prevent an inhibitory effect of ibrutinib. Methods: Anti-CD20 (rituximab/obinutuzumab) opsonized MCL cell lines were co-cultured with ibrutinib (± lenalidomide) - exposed effector cells, and analyzed for evaluation of cell death. Results: Cell death induced by rituximab was reduced with 75% at 0.5 μM ibrutinib and with 52% at 0.1 μM ibrutinib when induced by obinutuzumab, even by addition of lenalidomide. Moreover, obinutuzumab was associated with higher rate of cell death compared to rituximab. Conclusion: Ibrutinib negatively affects anti-CD20 induced cell death in MCL, not reversed by lenalidomide. Explorations of sequential administration and selective BTK-inhibitors may reveal the optimal combination of novel agents in MCL.