Vorinostat in combination with lenalidomide and dexamethasone in patients with relapsed/refractory multiple myeloma: A phase I study

8586 Background: Novel drug combinations may improve patient outcome in relapsed/refractory multiple myeloma (MM), which remains especially challenging to treat. Preclinical studies suggest that the histone deacetylase inhibitor vorinostat may have synergistic potential when combined with lenalidomide and dexamethasone. This phase I, multicenter, open-label study evaluated vorinostat plus lenalidomide and dexamethasone in patients (pts) with relapsed or refractory MM. The primary objective was to determine the maximum tolerated dose (MTD); other endpoints included overall safety and tolerability, as well as activity of the combination. Methods: Pts aged ≥18 years with relapsed or refractory MM were enrolled sequentially into 1 of 5 dosing levels ( Table ) using a standard 3+3 design for ≤8 cycles. Barring dose-limiting toxicities (DLTs) in the first cycle, dose escalation continued until the MTD was established. Response was assessed, and adverse events (AEs) were recorded. Results: Of 12 pts accrued to date, 11 (92%) have experienced ≥1 AE, with drug-related AEs reported by 6 pts (96% ≤Grade 2). The most common drug-related AEs (each in 4 pts) were fatigue and thrombocytopenia. Serious AEs in 2 pts (17%) were not considered drug-related. No pts discontinued due to AEs, and no DLT has been observed to date. Dose escalation to dose level (DL) 4 was achieved as no DLTs were observed in DLs 1–3. The MTD has not yet been reached. Of 11 pts evaluable for efficacy, best responses include: complete response in 1 pt, partial response in 2 pts, minimal response in 2 pts, and stable disease in 3 pts; 3 pts had progressive disease (PD). Currently, 9 pts remain on treatment, with 3 pts discontinuing treatment due to PD. Conclusions: These preliminary data suggest that vorinostat with lenalidomide and dexamethasone represents a well tolerated and active novel oral combination therapy for the treatment of relapsed/refractory MM. [Table: see text] [Table: see text]