Abstract 5492: Activity of RP7214, a novel, selective, and potent small molecule inhibitor of DHODH, in AML

Abstract

Abstract Background: Dihydroorotate dehydrogenase (DHODH), a rate limiting enzyme in pyrimidine synthesis, is overexpressed in certain cancers and impedes tumor cell proliferation via cell cycle arrest. RP7214 is a novel and potent DHODH inhibitor that inhibited DHODH activity in enzyme and PHA induced HWB/PBMC proliferation with IC50 and EC50 values of 7.8 & 2.5/0.60 nM respectively. Herein, we describe the efficacy of RP7214 as a single agent and in combination with standard of care drugs in preclinical models of AML Methods: Cell viability of AML cell lines (U937, HL-60, THP-1, and KG-1) following incubation with RP7214 as a single agent or in combination with Azacytidine or Venetolcax for 72 h was determined in an MTT-based assay. Cell surface expression of CD11b in THP-1 and human primary bone marrow AML mononuclear cells in presence of RP7214 was evaluated by flow cytometry. Apoptosis was evaluated following incubation of cell lines with compound for 48 or 72 h, subsequent staining with Annexin-V-PE and 7-AAD, and analysis by flow cytometry. Anti-tumor potential of RP7214 as single agent was tested in subcutaneous MV-4-11 human leukemia xenograft model. Results: RP7214 inhibited AML cell proliferation in all the four cell lines tested with GI50 ranging from 2.4 to 7.6 µM. Expression of the CD11b marker on THP-1 cell surface was enhanced by 40% following incubation with 5 µM compound; effect of which was reduced to 15% in the presence of 300 µM Uridine. Incubation of primary human bone marrow AML mononuclear cells with 10 µM of RP7214 increased the CD11b+ cells by > 15 %. Combination of 3 µM-RP7214 and 1 µM-Azacytidine inhibited cell proliferation by > 25% (P < 0.05) compared to single agents in MV-4-11 cells. Similarly, combination of 3 µM-RP7214 with 3 nM Venetoclax demonstrated 15% (P < 0.05) inhibition of cell growth compared to single agents in MV-4-11 cell line. RP7214 at 3, 10, and 30 mg/kg BID demonstrated significant anti-tumor activities in both tumor size and tumor weight in subcutaneous MV-4-11 human leukemia xenograft model. Conclusions: Results demonstrate the utility of RP7214 as a single agent and in combination with standard of care drugs in inducing apoptosis and promoting differentiation to fully mature cells in AML. A Phase 2a trial in AML patients is planned. Citation Format: Srikant Viswanadha, Satyanarayana Eleswarapu, Swaroop Vakkalanka. Activity of RP7214, a novel, selective, and potent small molecule inhibitor of DHODH, in AML [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5492.