Pharmacological Characterization of SDX-7320/Evexomostat: A Novel Methionine Aminopeptidase Type 2 Inhibitor with Anti-tumor and Anti-metastatic Activity.

Methionine aminopeptidase type 2 (METAP2) is a ubiquitous, evolutionarily conserved metalloprotease fundamental to protein biosynthesis which catalyzes removal of the N-terminal methionine residue from nascent polypeptides. METAP2 is an attractive target for cancer therapeutics based upon its over-expression in multiple human cancers, the importance of METAP2-specific substrates whose biological activity may be altered following METAP2 inhibition, and additionally, that METAP2 was identified as the target for the anti-angiogenic natural product, fumagillin. Irreversible inhibition of METAP2 using fumagillin analogues has established the anti-angiogenic and anti-tumor characteristics of these derivatives; however, their full clinical potential has not been realized due to a combination of poor drug-like properties and dose-limiting central nervous system (CNS) toxicity. This report describes the physicochemical and pharmacological characterization of SDX-7320 (evexomostat), a polymer-drug conjugate of the novel METAP2 inhibitor (METAP2i) SDX-7539. In vitro binding, enzyme, and cell-based assays demonstrated that SDX-7539 is a potent and selective METAP2 inhibitor. In utilizing a high molecular weight, water-soluble polymer to conjugate the novel fumagillol-derived, cathepsin-released, METAP2i SDX-7539, limitations observed with prior generation, small molecule fumagillol derivatives were ameliorated including reduced CNS exposure of the METAP2i, and prolonged half-life enabling convenient administration. Multiple xenograft and syngeneic cancer models were utilized to demonstrate the anti-tumor and anti-metastatic profile of SDX-7320. Unlike polymer-drug conjugates in general, reductions in small molecule-equivalent efficacious doses following polymer conjugation were observed. SDX-7320 has completed a phase I clinical safety study in patients with late-stage cancer and is currently being evaluated in multiple phase Ib/II clinical studies in patients with advanced solid tumors.

Intrinsic electrophilicity of a 4-substituted-5-cyano-6-(2-methylpyridin-3-yloxy)pyrimidine derivative: structural characterization of glutathione conjugates in vitro.

Isopropyl 9-anti-[5-cyano-6-(2-methyl-pyridin-3-yloxy)-pyrimidin-4-yloxy]-3-oxa-7-aza-bicyclo[3.3.1]nonane-7-carboxylate (1) represents a prototypic compound from a lead chemical series of G protein-coupled receptor 119 agonists, intended for treatment of type 2 diabetes. When compound 1 was incubated with NADPH-supplemented human liver microsomes in the presence of glutathione, two thioether conjugates M4-1 and M5-1 were observed. Omission of NADPH from the microsomal incubations prevented the formation of M5-1 but not M4-1. The formation of M4-1 was also discerned in incubations of 1 and glutathione with human liver cytosol, partially purified glutathione transferase, and in phosphate buffer at pH 7.4. M4-1 was isolated, and its structure ascertained from LC-MS/MS and NMR analysis. The mass spectral and NMR data suggested that M4-1 was obtained from a nucleophilic displacement of the 6-(2-methylpyridin-3-yloxy) group in 1 by glutathione. In addition, mass spectral studies revealed that M5-1 was derived from an analogous displacement reaction on a monohydroxylated metabolite of 1; the regiochemistry of hydroxylation was established to be on the isopropyl group. Of great interest were the findings that replacement of the 5-cyano group in 1 with a 5-methyl group resulted in 2, which was practically inert toward reaction with glutathione. This observation suggests that the electron-withdrawing potential of the C5 cyano group serves to increase the electrophilicity of the C6 carbon (via stabilization of the transition state) and favors reaction with the nucleophilic thiol. The mechanistic insights gained from these studies should assist medicinal chemistry efforts toward the design of analogs that retain primary pharmacology but are latent toward reaction with biological nucleophiles, thus mitigating the potential for toxicological outcome due to adduction with glutathione or proteins.