Abstract 511: Targeted one-carbon (1C) metabolism inhibitors: Design, synthesis and biological evaluation of novel 5-substituted pyrrolo[3,2-d]pyrimidines with pyridyl- and ortho-fluoropyridyl glutamate side chains as selective folate receptors substrates
Authors: Doshi Arpit , Wallace-Povirk Adrianne , O'Connor Carrie , Hou Zhanjun , Matherly Larry , Gangjee Aleem 
Published: September 2020

Abstract
One-carbon (1C) metabolism, in tumor cells, provides basic metabolites needed for proliferation and is compartmentalized into the cytosol and mitochondria. The key enzymes in 1C metabolism are de novo purine biosynthesis catalyzing enzymes, glycinamide ribonucleotide formyl transferase (GARFTase) and 5-​aminoimidazole-​4-​carboxamide ribonucleotide formyltransferase (AICARFTase) and mitochondrial serine hydroxymethyltransferase 2 (SHMT2) involved in glycine synthesis and maintaining 1C pools. We have previously designed and evaluated a series of multitargeted 5-substituted pyrrolo[3,2-d]pyrimidine antifolates with a phenyl glutamate side-chain (AGF291, AGF300 and AGF299), which inhibited KB tumor cell growth. AGF291 inhibited the enzymes crucial for both cytosolic and mitochondrial 1C metabolism. However, these compounds also were transported via the ubiquitously expressed reduced folate carrier (RFC) which can lead to dose-limiting toxicities as seen for classical antifolates such as pemetrexed (PMX). In this study, we designed conformationally restricted 5-substituted pyrrolo[3,2-d]pyrimidine antifolates with pyridyl glutamate side-chains (AGF363, AGF369 and AGF370) and ortho-fluoropyridyl glutamate side-chains (AGF377 and AGF379) to decrease normal cell uptake by the ubiquitously present RFC and maintain or increase transport via tumor-selective folate receptor α (FRα) and folate receptor β (FRβ). Replacing the phenyl with the pyridyl side-chain abrogated the transport via RFC, thereby improved (AGF363 vs AGF291) or maintained (AGF369 vs AGF300 and AGF370 vs AGF299) selective uptake by FRα and FRβ over RFC and showed potent KB tumor cell inhibition (AGF363, IC50 = 10.78 nM and AGF369, IC50 = 6.97 nM). The ortho-fluorinated pyridyl analogs were also selective for FRα and FRβ over RFC but showed moderate potency towards KB tumor cells. Overall, this study identified two key pharmacophores, i.e. the pyridyl and the o-fluoropyridyl side-chains, to obtain absolute selectivity for FRα and FRβ over RFC in the 5-substituted pyrrolo[3,2-d]pyrimidine series of 1Cmetabolism inhibitors. Further preclinical studies are underway to afford viable candidates for future clinical application of selective compounds without toxicities as an improvement of currently used agents.
Citation Format: Arpit Doshi, Adrianne Wallace-Povirk, Carrie O'Connor, Zhanjun Hou, Larry Matherly, Aleem Gangjee. Targeted one-carbon (1C) metabolism inhibitors: Design, synthesis and biological evaluation of novel 5-substituted pyrrolo[3,2-d]pyrimidines with pyridyl- and ortho-fluoropyridyl glutamate side chains as selective folate receptors substrates [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 511.