Abstract 6244: Design, synthesis, and structure-activity relationships of substituted pyrido[3,2-d]pyrimidines as microtubule targeting agents and anti-cancer agents

Abstract

Abstract Microtubules (MTs) are composed of αβ-tubulin heterodimers and are essential components of the cellular cytoskeleton involved in critical cellular functions, including mitosis, cell migration and signaling, intracellular trafficking, and angiogenesis. Microtubule targeting agents (MTAs) are highly successful chemotherapeutic agents because they target MT dynamics and interfere with MT-dependent cellular processes. The clinical efficacy of MTAs is limited by multidrug resistance due to expression of the P-glycoprotein (Pgp) drug efflux pump or increased expression of βIII-tubulin. This necessitates the development of novel MTAs effective against cell lines expressing these forms of drug resistance, which could offer potential advantages in patients who fail to respond to current MTAs, such as paclitaxel. Previously, we reported colchicine site (CS) binding compound 1 with a pyrido[3,2-d]pyrimidine scaffold and a 2-H substitution and N4-4’-methoxyaniline substitution inhibited colchicine binding and tubulin assembly (87% inhibition at 5 µM and IC50 = 1.3 µM, respectively). Compounds 2-9 were designed with a 2-CH3 substitution to evaluate the structure-activity relationships at the 4-position by using conformational restriction and isosteric replacements. Compounds 2-9 were synthesized, and the biological evaluation showed that compounds 2-9 inhibited tubulin assembly (7, IC50 = 0.72 μM) and binding of colchicine to tubulin (7, 97% inhibition at 5 µM, 81% at 0.5 µM). Compound 7 was found to be highly potent in the MCF-7 breast cancer cell line with an IC50 of 2.5 nM which was ~3.5-fold better than combretastatin-A4 (CA4). Compound 7 inhibited the growth of the human ovarian cancer cell line OVCAR-8 with an IC50 = 3.0 nM. For the Pgp overexpressing cell line NCI/ADR-RES, 7 was equally potent (IC50 = 3.0 nM), whereas paclitaxel was almost inactive (IC50 = 1,500 nM). Thus, we have identified 2-CH3 substituted pyrido[3,2-d]pyrimidines as a novel structural scaffold for inhibition of tubulin assembly and colchicine binding that have potent cytotoxic activity against the breast cancer cell line MCF-7 and against both the parental ovarian cancer cell line OVCAR-8 and its derivative Pgp overexpressing cell line NCI/ADR-RES. These compounds thus merit further study as potential cancer chemotherapeutic agents. Citation Format: Yesha Vijaykumar Shah, Ruoli Bai, Ernest Hamel, Aleem Gangjee. Design, synthesis, and structure-activity relationships of substituted pyrido[3,2-d]pyrimidines as microtubule targeting agents and anti-cancer agents. [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 6244.