Fragment-Based Design of a Potent MAT2a Inhibitor and in Vivo Evaluation in an MTAP Null Xenograft Model

Abstract

MAT2a is a methionine adenosyltransferase that synthesizes the essential metabolite S-adenosylmethionine (SAM) from methionine and ATP. Tumors bearing the co-deletion of p16 and MTAP genes have been shown to be sensitive to MAT2a inhibition, making it an attractive target for treatment of MTAP-deleted cancers. A fragment-based lead generation campaign identified weak but efficient hits binding in a known allosteric site. By use of structure-guided design and systematic SAR exploration, the hits were elaborated through a merging and growing strategy into an arylquinazolinone series of potent MAT2a inhibitors. The selected in vivo tool compound 28 reduced SAM-dependent methylation events in cells and inhibited proliferation of MTAP-null cells in vitro. In vivo studies showed that 28 was able to induce antitumor response in an MTAP knockout HCT116 xenograft model.

Human Mat2A Uses an Ordered Kinetic Mechanism and Is Stabilized but Not Regulated by Mat2B

“…No inhibition or activation of Mat2A activity by Mat2B was observed in either the phosphate detection coupled assay or the LC–MS SAM detection assay (Figures S5 and S6). When the same types of experiments were performed using a published Mat2A inhibitor (compound 28) that binds at the same allosteric site and with an affinity similar to Mat2B (Mat2B K d = 6 ± 1 nM, compound 28 K d = 12 ± 2 nM), inhibition was observed (Figure S7), consistent with the recent literature …”

“…When the same types of experiments were performed using a published Mat2A inhibitor (compound 28) that binds at the same allosteric site and with an affinity similar to Mat2B (Mat2B K d = 6 ± 1 nM, compound 28 K d = 12 ± 2 nM), inhibition was observed (Figure S7), consistent with the recent literature. 26 We next varied the ATP concentration at several fixed levels of L-Met using the Mat2A/Mat2B complex (250 nM Mat2A and 600 nM Mat2B) and fitted the data to eq 1 to determine the steady-state kinetic constants (Figure 7A and Table 1). The magnitude of the kinetic constants obtained with the Mat2A/Mat2B complex was very similar to the values obtained with Mat2A alone.…”

“…24,25 Several potent inhibitors of Mat2A have recently been described (PF-9366, AG-270, compound 28). 10,24,26 Interestingly, these inhibitors bind to the same site as Mat2B. 10,26,27 AG-270 and compound 28 have been shown to inhibit cancer cell growth and proliferation of MTAP-deficient cancer cells and tumors.…”

“…10,24,26 Interestingly, these inhibitors bind to the same site as Mat2B. 10,26,27 AG-270 and compound 28 have been shown to inhibit cancer cell growth and proliferation of MTAP-deficient cancer cells and tumors. AG-270 has entered human clinical trials.…”

“…Mat2A has been identified as a promising target for novel cancer therapies with the discovery that it is synthetically lethal with the enzyme methylthioadenosine phosphorylase (MTAP). MTAP is deleted in around 15% of cancers, and therefore, Mat2A inhibitors are attractive candidates for targeting cancers with MTAP deletion. , Several potent inhibitors of Mat2A have recently been described (PF-9366, AG-270, compound 28). ,, Interestingly, these inhibitors bind to the same site as Mat2B. ,, AG-270 and compound 28 have been shown to inhibit cancer cell growth and proliferation of MTAP-deficient cancer cells and tumors. AG-270 has entered human clinical trials. , …”