Phase I study of chidamide (CS055/HBI-8000), a new histone deacetylase inhibitor, in patients with advanced solid tumors and lymphomas

Chidamide (CS055/HBI-8000) is a new benzamide class of histone deacetylase inhibitor with marked anti-tumor activity. This study reports the phase I results. Patients with advanced solid tumors or lymphomas received oral doses of 5, 10, 17.5, 25, 32.5, or 50 mg chidamide either twice (BIW) or three times (TIW) per week for 4 consecutive weeks every 6 weeks. Safety, characteristics of pharmacokinetics (PK) and pharmacodynamics (PD), and preliminary efficacy were evaluated. A total of 31 patients were enrolled. No DLTs were identified in the BIW cohorts up to 50 mg. DLTs were grade 3 diarrhea and vomiting in two patients in the TIW cohort at 50 mg, respectively. PK analysis revealed t(1/2) of 16.8-18.3 h, T (max) of 1-2 h in most cases, and a dose-related increase in C (max) and AUC. Significant induction of histone H3 acetylation in peripheral white blood cells was observed after a single dose of chidamide. Four patients with T-cell lymphomas and 1 patient with submandibular adenoid cystic carcinoma achieved a partial response. Chidamide was generally well tolerated in patients with advanced solid tumors or lymphomas in the tested regimens. Favorable PK and PD profiles, as well as encouraging preliminary anti-tumor activity, were demonstrated.