Abstract 4943: SP-1-39 as a novel tubulin inhibitor overcomes taxane resistance in castration-resistant prostate cancer model

Colchicine binding site inhibitors have proven to have potent anti-cancer efficacy in many cancer types. Inhibition of tubulin polymerization, a popular mechanism of action for anti-cancer activities, will be activated once the inhibitor interacts with the colchicine binding site. We have previously developed and reported a potent tubulin inhibitor (SB-216). One of its derivatives, the compound SP-1-39, a pyrimidine dihydroquinoxalinone derivative, has been recently designed to further improve the potency and therapeutic properties. Here, we examined the impact of SP-1-39 on preclinical prostate cancer models in vitro and in vivo. EBI competition assay confirmed that SP-1-39 binds to colchicine-binding site and inhibits the formation of EBI:β-tubulin adduct. The anti-proliferation abilities of SP-1-39 was tested against melanoma, breast cancer, pancreatic cancer, prostate cancer, and paclitaxel-resistant prostate cancer cell lines by MTS assay, and defined IC50 values of 0.2-4 nmol/L. Other in vitro results showed SP-1-39 disrupted microtubule network, induced cell cycle arrest at G2/M phase, and caused apoptosis in paclitaxel-resistant human prostate cancer cells (PC-3/TxR). For in vivo study, 2.5mg/kg SP-1-39 significantly attenuated tumor growth in PC-3/TxR xenograft mouse model, inhibited angiogenesis, and overcame taxane resistance. Our findings demonstrate the preclinical therapeutic efficacy and safety of SP-1-39, and provide support for further exploration of novel tubulin inhibitors as anti-cancer agent for cancer therapy. Citation Format: Rui Wang, Kelli L. Hartman, Satyanarayana Pochampally, Duane D. Miller, Wei Li. SP-1-39 as a novel tubulin inhibitor overcomes taxane resistance in castration-resistant prostate cancer model. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4943.