Chemotherapy-Free Salvage Therapy with Rituximab, Lenalidomide, and Poseltinib in Relapsed or Refractory Primary...

Relapsed or refractory (R/R) primary central nervous system lymphoma (PCNSL) is an aggressive malignancy for which salvage chemotherapy has limited efficacy. We conducted an investigator-initiated, single-arm, multicenter phase II trial to evaluate the efficacy and safety of a chemotherapy-free salvage regimen comprising rituximab, lenalidomide, and poseltinib (R2P) in patients with R/R PCNSL.

The R2P regimen consisted of two phases: six cycles of induction with rituximab, lenalidomide, and poseltinib, followed by three cycles of consolidation with lenalidomide and poseltinib. The primary endpoints were complete response rate (CRR) and overall response rate (ORR). Secondary endpoints were toxicity, progression-free survival (PFS) and overall survival (OS).

A total of 10 patients were enrolled (one withdrew before cycle 1; nine were evaluable for efficacy). The median age was 70 years (range, 53-75), and all had received methotrexate-based first-line chemotherapy. The ORR was 55.6%, and the CRR was 33.3%. The median PFS was 5.6 months, and the median OS was not reached. Next-generation sequencing was performed in four patients (three responders and one non-responder). CD79B missense mutations were identified in all three responders. A total of 11 adverse events (AEs) were observed in six patients. The most common AE was neutropenia (30.0%). The only grade ≥3 AE was a single case of grade 3 neutropenia. No dose modifications were required due to toxicity.

Poseltinib in combination with lenalidomide and rituximab showed activity in patients with R/R PCNSL, warranting further investigation in larger studies.