Abstract 4049: Preclinical pharmacology profile of GTX-0196: A novel, potent and highly selective dihydroorotate dehydrogenase (DHODH) inhibitor for the treatment of hematologic malignancies

Abstract

Abstract Dihydroorotate dehydrogenase (DHODH) is a key enzyme in the de novo pyrimidine synthesis [Löffler et al., 1997]. Initial clinical studies with the DHODH inhibitor brequinar in solid tumors showed limited efficacy due to dose limiting adverse effects [Peters et al, 2018]. Recently, there is renewed interest in the use of more potent and selective DHODH inhibitors for the treatment of myeloid and lymphoid malignancies [Sykes et al, 2016]. Here we report the identification of the novel potent and highly selective DHODH inhibitor GTX-0196, with excellent physicochemical properties. GTX-0196 exhibited a biochemical IC50 of 3.7 nM in a DHODH biochemical assay and an antiproliferative IC50 of 1.1 nM in the MOLM-13 cell line, with brequinar showing IC50 values of 6.9 and 50 nM, respectively. The activity in the MOLM-13 proliferation assay was uridine-dependent, indicating absence of general toxicity of the compound and confirming DHODH-mediated efficacy. Profiling of GTX-0196 in the BioPrint panel (Eurofins/CEREP, at 10 µM), showed <50% inhibition for all 133 target proteins tested (GPCR’s, NR´s, kinases and other enzymes), illustrating the high selectivity for DHODH (> 2000-fold selectivity versus other targets tested). Furthermore, no inhibition was observed in a human CYP panel (1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1 and 3A4, at 30 µM) and in a panel of transporters (at 10 µM). High metabolic stability in human liver microsomes and hepatocytes was observed with t½ > 6h and 10h, respectively. Compared to an earlier lead compound, GTX-0196 demonstrated enhanced potency and metabolic stability (particularly in preclinical species). Potent and efficacious inhibition of proliferation through DHODH was confirmed in a large number of solid tumor and hematologic malignancy cell lines, illustrating the broad potential use of this chemical series. Furthermore, tumor growth inhibition was observed in the MOLM-13 xenograft mouse model. Due to its favorable properties, GTX-0196 has progressed towards IND-enabling studies. In parallel, we are exploring mono and combination therapy opportunities in hematological malignancies as well as combination therapy opportunities in solid tumors to investigate the full therapeutic potential in oncology for this optimized DHODH inhibitor. Löffler et al. Mol. Cell. Biochem. 1997Peters GJ et al, Nucleosides, Nucleotides and Nucleic Acids 2018Sykes DB et al. Cell 2016 Citation Format: Allard Kaptein, Sonia Lain, Diede Brunen, Edward van Wezel, Tjeerd Barf. Preclinical pharmacology profile of GTX-0196: A novel, potent and highly selective dihydroorotate dehydrogenase (DHODH) inhibitor for the treatment of hematologic malignancies [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 4049.