A phase IIb trial of vorinostat in combination with lenalidomide and dexamethasone in patients with multiple myeloma refractory to previous lenalidomide-containing regimens

Clinical trials of vorinostat, a Class I/II histone deacetylase inhibitor, in combination with proteasome inhibitors and immunomodulatory agents have shown activity in relapsed/refractory multiple myeloma. This phase IIb, open-label, single-institution study evaluated the efficacy of vorinostat in combination with lenalidomide and dexamethasone in lenalidomide-refractory patients. Patients were considered lenalidomide-refractory if they had no clinical response (<minimal response) on a previous lenalidomide-containing regimen (lenalidomide non-responsive) or if they had progressive disease on or within 60days of discontinuing a previous lenalidomide-containing regimen (lenalidomide relapsed/refractory). Patients received oral vorinostat 400mg days 1-7 and 15-21, lenalidomide 25mg days 1-21, and dexamethasone 40mg days 1, 8, 15 and 22 in 28-day cycles. Twenty-five patients were enrolled, median age was 65years and patients had received a median of 5 prior regimens. The overall response rate was 24% (6 partial responses) and clinical benefit rate (stable disease) was 80%. Median time to a partial response was 19months and median duration of response was 33months. Median progression-free survival was 53months. Most common grade 3/4 adverse events were neutropenia (48%), thrombocytopenia (32%), anaemia (20%) and gastrointestinal toxicities (16%). In this heavily pre-treated population, vorinostat in combination with lenalidomide and dexamethasone was active in lenalidomide-refractory patients.