Combined Bendamustine, Prednisolone and Lenalidomide (RBP) In Refractory or Relapsed Multiple Myeloma. First Results of a Phase I Clinical Trial

While the role of lenalidomide monotherapy in the treatment of relapsed/refractory patients with multiple myeloma (MM) is established, combination therapies with Lenalinomide are still under investigation. Bendamustine is a bi-functional alkylating agent with a purine-like benzimidazole ring effective in combination with steroids, thalidomide and bortezomib for the treatment of patients with MM. In the current trial, combination therapy of bendamustine, lenalinomide and prednisolone (RBP) was tested for feasibility and safety in patients with relapsed or refractory MM.

This is a phase I trial examining dosing of lenalidomide in combination with bendamustine and prednisolone. The first cohort of patients received a starting dose of 10mg/d d1-21 lenalidomide, 60mg/m²/d d1-2 bendamustine and 100mg/d d1-4 prednisolone. Escalation steps in the next cohorts included 15, 20 and 25mg of lenalidomide followed by an escalation step of 75 mg/m² bendamustine. Three patients were enrolled at each dose level and the first two cycles were evaluated for maximum tolerable dose. Patients received RBP in 4-week cycles for a maximum of 8 cycles in order to evaluate efficacy. Patients with stable or responding disease following 8 cycles of RBP received single-agent oral lenalidomide 10 mg once daily on days 1–21 of each 28-day cycle as maintenance.

: Nine patients (3 at each dose level of 10 mg, 15 mg or 20 mg lenalidomide) have been enrolled to date and 9 patients have completed at least 2 cycles. Response was assessed using modified EBMT criteria to include near complete remission (nCR) and very good partial remission (VGPR). 8 of 9 patients responded after at least 2 cycles with 2 VGPR, 4 PR, 1 MR and 1 stable disease. One patient experienced progressive disease. None of the 9 patients developed dose-limiting hematoxicity as defined by an ANC < 1,0 × 10⁹/l with fever for > 3 days or an ANC <0,5 × 10⁹/l for > 7 days or platelet count < 25 × 10⁹/l for > 3 days. Neutropenia was reported in 4 patients (CTC grade ≥ 3) but no thrombocytopenia (CTC grade ≥ 3) was observed. No grade 3 or 4 non hematological toxicity was encountered and no dose modification was required.

RBP with a dose of 20 mg lenalidomide d 1–21 and 60 mg/m² bendamustine d 1–2 is well tolerated in patients with relapsed or refractory MM. Maximum tolerable dose was not reached. Further dose increase according to the protocol is in progress.

Niederwieser:Bristol-Myers Squibb: Speakers Bureau; Novartis: Speakers Bureau.