Pharmacological Characterization of SDX-7320/Evexomostat: a Novel Methionine Aminopeptidase Type 2 Inhibitor with Anti-Tumor and Anti-Metastatic Activity

Abstract

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 analogs 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 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 1 clinical safety study in late-stage cancer patients and is currently being evaluated in multiple Phase 1b/2 clinical studies in patients with advanced solid tumors.