Safety, tolerability, pharmacokinetics and clinical activity of AST-3424, an AKR1C3-activated bis-alkylating moiety prodrug, in subjects with advanced solid tumors in China: A phase I dose-escalation study.
Authors: Qin Shukui , Li Jin , Liu Yunpeng , Luo Suxia , Jieer Ying , Pan Hongming , Cai Qichun , Guo Ye , Xue Junli , Teng Zan , Shou Jiawei , Xie Yanbin , Duan Jianxin , Wang Ning , Shan Qiuyue , Zhu Qian , Li Ye , Liu Nan , Sun Lin , Hao Jing 
Published: July 2024

3121 Background: Aldo-keto reductase family 1 member C3 (AKR1C3) modulates cellular differentiation and proliferation through indirect regulation of ligand access to hormone and nuclear receptor signaling. AKR1C3 is expressed at high levels in various human cancers, including hepatocellular carcinoma (HCC). AST-3424 is an AKR1C3-activated prodrug and releases a toxic bis-alkylating moiety (AST-2660) in the presence of AKR1C3, which forms intra- and inter-strand DNA crosslinks resulting in cell death. Here we report the results of a phase I dose escalation study of AST-3424 in patients with advanced solid tumors (NCT06239155). Methods: Patients with histologically and/or cytologically confirmed advanced solid tumors who failed standard treatment or no standard treatment, or not suitable for standard treatment were enrolled to receive AST-3424 intravenously (i.v.) at doses of 1, 2, 4, 6, 8 mg/m2 on Day 1 and Day 8 every 21 days. A parallel and accelerated titration for 1 and 2 mg/m2, and 3+3 dose escalation design for other cohorts were used to guide dose escalation and maximum tolerable dose (MTD) determination. Results: 21 subjects were enrolled and received at least one treatment (HCC=4, colorectal cancer=6, gastric cancer=4, pancreatic carcinoma=2, breast cancer=2, intrahepatic cholangiocarcinoma=1, prostate cancer=1, salivary gland cancer=1). 4 dose-limiting toxicities (DLTs) were observed (3 grade 4 platelet count decreased; 1 grade 2 gamma-glutamyltransferase increased, DLT reported due to dosing delayed more than 14 days). Safety Review Committee confirmed 6.0 mg/m2 as the MTD and recommended Phase 2 dose (RP2D). Grade≥3 adverse events (AEs) were observed in in 10 patients (47.6%). 8 patients (38.1%) had grade≥3 treatment-related AEs (TRAEs), being anemia (33.3%), platelet count decreased (19.0%), white blood cell count decreased (9.5%) and neutrophil count decreased (9.5%). Most of the grade≥3 AEs were observed in the 8.0 mg/m2 cohort. No patient had a fatal TRAE. 15 subjects with baseline target lesions had at least one post baseline assessment. 9 subjects (42.9%) had stable disease (SD); 1 subject (4.8%) had non-complete remission/non-disease progression (Non-CR/Non-PD); 5 subjects (23.8%) had progressive disease (PD). AST-3424 showed linear pharmacokinetic characteristics in the range of 1.0-8.0 mg/m2 with a half-life of 0.16-0.40 hours. AST-2660 showed linear pharmacokinetic characteristics in the range of 4.0-8.0 mg/m2 with a half-life of 1.59-2.08 hours. Conclusions: AST-3424 showed a tolerable safety profile and preliminary anti-tumor activity in advanced solid tumors. The phase II dose expansion phase of AST-3424 monotherapy is ongoing in subjects diagnosed as advanced HCC and with high AKR1C3 expression. Clinical trial information: NCT06239155 .