Selective Vulnerability to Pyrimidine Starvation in Hematologic Malignancies Revealed by AG-636, a Novel Clinical-Stage Inhibitor of Dihydroorotate Dehydrogenase

Abstract

◥Agents targeting metabolic pathways form the backbone of standard oncology treatments, though a better understanding of differential metabolic dependencies could instruct more rationale-based therapeutic approaches. We performed a chemical biology screen that revealed a strong enrichment in sensitivity to a novel dihydroorotate dehydrogenase (DHODH) inhibitor, AG-636, in cancer cell lines of hematologic versus solid tumor origin. Differential AG-636 activity translated to the in vivo setting, with complete tumor regression observed in a lymphoma model. Dissection of the relationship between uridine avail-ability and response to AG-636 revealed a divergent ability of lymphoma and solid tumor cell lines to survive and grow in the setting of depleted extracellular uridine and DHODH inhibition. Metabolic characterization paired with unbiased functional genomic and proteomic screens pointed to adaptive mechanisms to cope with nucleotide stress as contributing to response to AG-636. These findings support targeting of DHODH in lymphoma and other hematologic malignancies and suggest combination strategies aimed at interfering with DNAdamage response pathways.

Targeting cancer metabolism in the era of precision oncology

“…On the basis of these results, more potent inhibitors of DHODH are being developed for treatment of rheumatoid arthritis and SARS-CoV-2 (ReF. 205 ) as well as cancer [206][207][208] . Another DHODH inhib itor, AG-636 (ReF.…”

“…Another DHODH inhib itor, AG-636 (ReF. 208 ), with a 17 nM IC 50 , has activity against tumour growth in xenograft models of diffuse large B cell lymphoma (OCILY19), and mantlecell lymphoma (Z138), but limited activity in models of lung (A549) and colon (HCT-116) cancer 208 . Notably, DHODH function is intimately coupled to the mitochondrial ETC for ubiquinone-mediated oxidation of dihydroorotate to orotate 209 .…”

Inhibition of pyrimidine biosynthesis targets protein translation in AML

“…The discovery linking pyrimidine starvation to cell fate in AML has reinvigorated interest in DHODH as an anti-cancer target and has spurred extensive efforts to develop more potent and selective next-generation inhibitors [7][8][9][10][11] . In agreement with previous studies, we found that DHODH inhibition has excellent potency in different AML sub-types in vivo.…”

“…Leflunomide and another DHODHi, brequinar, have been trialed in various cancers and although occasional durable responses were observed, the initial data was insufficient to support further clinical development [3][4][5] . Notably however, recent findings suggesting selective efficacy of DHODHi in hematological malignancies have prompted renewed interest in DHODH as an anti-cancer target and have spurred extensive efforts to develop more potent and selective next-generation inhibitors [7][8][9][10][11] . Intriguingly, AML cells have been reported to undergo myeloid maturation in response to pyrimidine starvation [7][8][9][10] , suggesting a link between nutrient availability and cell fate that can be exploited as a form of "differentiation therapy".…”

“…To facilitate further development and clinical deployment of DHODHi, there remains a need for a comprehensive analysis of molecular and cellular responses, especially in rare leukemia stem cells (LSCs) that underpin disease progression and therapy resistance 12 . Herein we used AG636, a novel potent DHODHi that has been extensively validated by biophysical studies and metabolic profiling 11 , to characterize the link between nucleotide metabolism and therapeutic efficacy. Our findings demonstrate that DHODH inhibition has anti-proliferative and pro-differentiation activity in vivo and potent activity against multiple AML sub-types.…”