Safety and tolerability of lenalidomide maintenance in post-transplant acute myeloid leukemia and high-risk myelodysplastic syndrome.

Relapse after allogeneic stem cell transplant in unfavorable-risk acute myeloid leukemia (AML) and high-risk myelodysplastic syndrome (MDS) portends a poor prognosis. We conducted a single-center phase I dose-escalation study with lenalidomide maintenance in high-risk MDS and AML patients after allogeneic transplantation. Sixteen patients enrolled in a "3 + 3" study design starting at lenalidomide 5 mg daily, increasing in increments of 5 mg up to 15 mg. Lenalidomide was given for 21 days of a 28-day cycle for a total of six cycles. Most common dose-limiting toxicities were lymphopenia, diarrhea, nausea, and neutropenia. Two patients had acute graft-versus-host disease (GVHD), and five patients developed chronic GVHD. The maximum tolerated dose was 10 mg, after dose-limiting toxicities were seen in the 15 mg group. Two dose-limiting toxicities were seen from development of acute GVHD and grade III diarrhea. Limitations of the study include time to initiation at 6 months post transplant, as many high-risk patients will have relapsed within this time frame before starting maintenance lenalidomide. Overall, lenalidomide was well tolerated with minimal GVHD and low rates of relapse rates, warranting further study.