Efficacy and toxicity of histone deacetylase inhibitors in relapsed/refractory multiple myeloma: Systematic review and meta-analysis of clinical trials.

Multiple myeloma (MM) remains incurable primarily due to relapse. Histone deacetylase inhibitors (HDACis) have shown potential application for the treatment of relapsed/refractory multiple myeloma (RRMM). To assess the efficacy and safety of HDACis in RRMM treatment, a systematic review and meta-analysis were conducted based on clinical trial data. A literature search was performed using PubMed, EMBASE, Web of Science and the Cochrane Library databases. Subsequently, 19 trials with 2193 patients treated with one of the three HDACis, panobinostat, ricolinostat and vorinostat, were identified and included in the present study. The efficacy and toxicity of each agent were assessed. The data were pooled using a random effects model in STATA 13.0. The results showed that the overall response rate (ORR) was 0.64 with a 95% confidence interval (CI) of 0.61-0.68 for panobinostat, 0.51 (95% CI, 0.46-0.55) for vorinostat and 0.38 (95% CI, 0.29-0.48) for ricolinostat. Additionally, subgroup analysis revealed an ORR of 0.36 (95% CI, 0.27-0.46) for HDACis-treated bortezomib-refractory MM patients and 0.43 (95% CI, 0.30-0.55) for lenalidomide-refractory patients. The most common grade 3 and 4 hematological adverse events were thrombocytopenia, neutropenia and anemia. Non-hematological adverse events included fatigue/asthenia, diarrhea and nausea. In conclusion, analysis of the pooled data revealed that panobinostat-containing regimens were effective and tolerable for patients with RRMM. Furthermore, lenalidomide-refractory patients may derive greater benefits from these regimens. More clinical and real-world studies are required to validate these results.