Abstract B135: Discovery of BGS2019, a highly potent and selective covalent inhibitor of GMPS using IMTACTM platform

Abstract

Guanosine monophosphate synthetase (GMPS) is a glutamine amidotransferase catalyzing amination of xanthosine monophosphate (XMP) to form GMP. It is a enzyme involved in de novo purine biosynthesis. T and B lymphocytes, and certain cancer cells, such as malignant melanoma are dependent on de novo synthesis of purine nucleotide for activation and proliferation. GMPS is an attractive target for drug discovery and development to treat autoimmune diseases, organ transplant rejection, and cancers. Mycophenolate acid (MPA), an active ingredient of Mycophenolate Mofetil (Cellcept) has been used for organ transplantation and autoimmune diseases. MPA is a natural product which inhibits inosine monophosphate dehydrogenase (IMPDH), an enzyme upstream of GMPS. Using IMTACTM (Isobaric Mass Tagged Affinity Characterization) platform to perform global proteome ligand screen in live cancer cells, a highly potent and highly selective irreversible inhibitor against GMPS was discovered. Here we report the identification, in vitro characterization and in vivo evaluation of this molecule BGS2019. Target engagement of BGS2019 was determined by In-Gel-Fluorescent assay in cell with an EC50 of 15.6nM. It inhibited GMPS enzymatic activity with an IC50 of 6nM. The mechanism of BGS2019 in cell-based assays was tested, which showed the accumulation of IMP (the substrate for GMPS) and the reduction of GMP, GDP and GTP, upon BGS2019 treatment. BGS2019 was evaluated for its cell growth inhibition activity in several cancer cell lines and it suppressed cancer cell growth with IC50 values from 30nM to 100nM. In vivo administration of BGS2019 was well tolerated in mice and exhibited tumor suppression in animal model. Citation Format: Hang Chen, Heather Ha, Robert Stanley, Cindy Huang, Qian Cai, Irene Yuan, Ping Cao. Discovery of BGS2019, a highly potent and selective covalent inhibitor of GMPS using IMTACTM platform [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B135. doi:10.1158/1535-7163.TARG-19-B135