Phase IB part of LOC-R01, a LOC network non-comparative randomized phase IB/II study testing R-MPV in combination with escalating doses of lenalidomide or ibrutinib for newly diagnosed primary central nervous system lymphoma (PCNSL) patients

Background Results of conventional induction chemotherapies in primary central nervous system lymphoma (PCNSL) need to be improved. Ibrutinib, a BTK inhibitor, and lenalidomide, an immunomodulatory drug, have shown promising results at relapse, supporting to further assess their individual use in combination with high-dose methotrexate-based chemotherapy. Methods Patients with newly diagnosed PCNSL were randomized to receive four 28-day cycles of ibrutinib or lenalidomide in combination with R-MPV (rituximab, methotrexate, procarbazine, vincristine and prednisone) in a 3 + 3 design. Responders then received a consolidation with R-Cytarabine and an intensive chemotherapy with autologous stem cell transplantation. The objective of the phase IB study was to define the recommended phase II dose (RP2D) based on the dose-limiting toxicity (DLT) occurring during the first induction cycle. Results Twenty-six patients (median age 52) were randomized. Four DLTs were observed: one grade 5 aspergillosis and pneumocystosis, one grade 4 catheter-related infection and two grade 3 increased alanine aminotransferase levels. RP2D of ibrutinib and lenalidomide were 560 mg daily (D3-14 and D17-28) and 15 mg daily (D1-21) respectively, in combination with R-MPV. In both arms, the most frequent grade ≥3 treatment-related adverse events were hepatic cytolysis, neutropenia and infections. One grade 4 Lyell’s syndrome was reported at cycle 2 in the lenalidomide arm. After 4 induction cycles, the overall response rates were 76.9% and 83.3% in the lenalidomide and ibrutinib arm, respectively. Conclusion Targeted induction therapies combining lenalidomide or ibrutinib with R-MPV are feasible for first-line PCNSL. The safety profile is consistent with the known safety profiles of R-MPV and both targeted therapies. The phase II part of the study is ongoing.