Preclinical Characterization of TP‐0903, a Novel Multikinase Inhibitor, in TP53 Mutant Acute Myeloid Leukemia

Abstract

Objective Acute myeloid leukemia (AML) with mutations in the tumor suppressor gene TP53 confers a dismal prognosis with 1-year overall survival of <5%. Effective treatment options are limited and current standard-of-care includes the hypomethylating agents (HMA) decitabine and azacytidine. While inhibition of kinases involved in cell cycle regulation has been shown to induce synthetic lethality in a variety of TP53 mutant cancers, this strategy has not been evaluated in mutant TP53 AML. Previously, we demonstrated that TP-0903 is a novel multikinase inhibitor with low nM activity against AURKA/B, CHEK1/2, and other cell cycle regulators (Jeon JY et al. JCI Insight 2020), thus providing scientific rationale to evaluate TP-0903 activity in TP53 mutant AML. Methods To generate an in vitro model of TP53 mutant AML, we isolated single-cell clones containing mutant (R248W) or wild-type (WT) TP53 from the established MV4-11 AML cell line; regulation of p53 targets (MDM2, p21) following gamma irradiation and inhibition of p-AURKA and p-CHEK1 by TP-0903 were assessed by immunoblot. Using these and additional TP53 mutant AML cell lines (Kasumi-1, HL-60), in vitro efficacy of TP-0903 alone and in combination with HMA was assessed in viability (MTT) and apoptosis (Annexin V) assays. In vivo efficacy studies were conducted in NSG mice following intravenous injection of HL-60 or luciferase-tagged MV4-11/TP53-R248W cells. Mice (5-10 per treatment cohort) were treated with vehicle, TP-0903 (50 mg/kg orally; 5 days on/2 days off), decitabine (0.2-0.4 mg/kg i.p.; 4 days on/10 days off) or the combination. Whole body bioluminescence imaging was performed weekly and median survival was determined. Results Compared to the clone with WT TP53, we observed a lack of MDM2 and p21 induction in MV4-11/TP53-R248W cells following gamma irradiation. In vitro, TP-0903 inhibited pAURKA and pCHEK1 at 50 nM, inhibited cell viability (IC50 values, 12-40nM), and induced apoptosis at 20-50nM. The combination of TP-0903 with HMA was additive to synergistic in all AML cell lines evaluated. In the HL-60 xenograft model, the TP-0903/decitabine combination prolonged median survival (75 days) compared to cohorts of mice treated with TP-0903 (63 days), decitabine (55 days), or vehicle (46 days) (P<0.0001). In the MV4-11/TP53-R248W xenograft model, bioluminescence imaging showed that TP-0903 alone or in combination with decitabine was more effective in suppressing the outgrowth of leukemia cells compared to mice treated with vehicle or decitabine alone (P<0.05); survival analysis is ongoing. Conclusions TP-0903 was effective in all evaluated preclinical models of TP53 mutant AML. Together, these results provide scientific premise for the initiation of a Phase 1b/2 trial of TP-0903 in combination with decitabine in TP53 mutant/complex karyotype AML under the umbrella Beat AML Master Trial.