Abstract 5123: Targeted thieno[2,3-d]pyrimidines with fluorinated phenyl side chains as antitumor agents

Abstract

Abstract The reduced folate carrier (RFC) is ubiquitously expressed in tissues and tumors and is the major tissue transporter for folate cofactors. Folate receptor (FR) α and β, as well as the proton-coupled folate transporter (PCFT), exhibit narrower patterns of tissue expression and are likely to serve more specialized physiologic roles. FRs are expressed in a subset of cancer cells (e.g., ovarian and non-small cell lung cancer for FRα, acute myelogenous leukemia for FRβ), whereas PCFT is expressed in a wide range of human solid tumors but not leukemias. Earlier generations of glycinamide ribonucleotide formyltransferase (GARFTase) and de novo purine nucleotide biosynthesis (e.g., Lometrexol) have shown promise as antitumor drugs. However, these compounds are excellent substrates for RFC and thus are non-selective for tumors, leading to dose-limiting toxicities. We previously reported a novel class of 6-substituted thieno[2,3-d] pyrimidines with a phenyl side chain and 3- and 4-carbon bridge lengths (AGF17 and AGF23, respectively) which selectively targeted FRs but not RFC or PCFT. To increase antitumor efficacy, we synthesized fluorinated analogs of AGF17 and AGF23, designated as AGF309 and AGF304, respectively. AGF309 and AGF304 potently inhibited proliferation of Chinese hamster ovary (CHO) cell lines engineered to individually express human FRα (IC50s of 1.08 and 2.27 nM, respectively) or FRβ (IC50s 0.48 and 1.14 nM, respectively). AGF304 and AGF309 showed nominal activity toward RFC- and PCFT-expressing CHO cells. Both AGF309 and AGF304 were also potently inhibitory toward FRα-expressing human KB human tumor cells (IC50s of 7.19 and 5.27nM, respectively). By analogy with previous iterations of 6-substituted thieno [2,3-d] pyrimidine compounds, growth inhibitory activity by AGF309 and AGF304 likely involves inhibition of de novo purine biosynthesis at GARFTase and potentially a secondary intracellular target. Collectively, our in vitro findings of the potent and selective antitumor activity and FR selectivity suggest that further preclinical evaluation of AGF309 and AGF304 as potential antitumor agents is warranted. Citation Format: Nian Tong, Aleem Gangjee, Adrianne Wallace Povrik, Carrie O’Connor, Aamod Aamod Dekhneb, Zhanjun Hou, Larry H. Matherly. Targeted thieno[2,3-d]pyrimidines with fluorinated phenyl side chains as antitumor agents [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5123. doi:10.1158/1538-7445.AM2017-5123