e12543 Background: Chidamide (CHI) is a novel benzamide type of subtype-selective histone deacetylase inhibitor approved in China for refractory and relapsed peripheral T-cell lymphoma with a dosage of 30 mg PO twice a week. A randomized, double blind and placebo-controlled phase 3 clinical trial of CHI plus exemestane (EXE) is currently ongoing in patients (pts) with hormone receptor-positive (HR+) advanced breast cancer (ABC). This abstract reports the results from the pilot study preceded the phase 3 trial. Methods: Eligible pts were postmenopausal women recurrent or progressed to at least one endocrine therapy. In the run-in period for pharmacokinetic (PK) analysis, pts received EXE 25 mg on day (D) 1 and CHI 30 mg on D 2. From D 5 pts started combination treatment having EXE 25 mg daily and CHI 30 mg twice a week until progression of disease (PD) or intolerable toxicities. A treatment cycle was defined as 28 days. Safety, PK parameters and preliminary efficacy were assessed. Results: 20 pts with HR+ and HER-2 negative were enrolled between Jul and Dec, 2015. Median duration of treatment was 5 cycles (range 0-16), with 4 pts still on treatment. 3 pts discontinued due to adverse events (AE). Drug-related AEs ≥ grade 3 in 2 or more pts were neutropenia (35%), thrombocytopenia (30%), and leucopenia (20%). Similar plasma exposure of EXE was observed in the absence and presence of CHI ( 73 ± 27 vs. 80 ± 29 ng·hr/mL). A potential increased plasma exposure of CHI was noted in the presence of EXE compared with CHI alone ( 2232 ± 973 vs 1787 ± 946 ng·hr/mL), apparently related to the inter-patient variations in CHI plasma concentrations. Best response in 18 pts was assessed by RECIST, including 3 pts with partial response, 12 pts with stable disease and 3 pts with PD. Median progression free survival was 7.6 months. Conclusions: The combination of CHI and EXE was generally well tolerated. Most AEs were related to the CHI single-agent treatment that are generally manageable. Encouraging antitumor activity was observed. The overall results from this pilot trial enabled the next-stage clinical development of this combination regimen in HR+ ABC pts. Clinical trial information: NCT02482753.
Why ACE—overview of the development of the subtype-selective histone deacetylase inhibitor chidamide in hormone receptor positive advanced breast cancer
