Development of a biomarker to monitor target engagement after treatment with dihydroorotate dehydrogenase inhibitors

Michael A. Pontikos, Christopher Leija, Zhiyu Zhao, Xiaoyu Wang, Jessica Kilgore, Belen Tornesi, Nicole Adenmatten, Margaret A. Phillips, Noelle S. Williams

Research output: Contribution to journalArticlepeer-review


Dihydroorotate dehydrogenase (DHODH) catalyzes a key step in pyrimidine biosynthesis and has recently been validated as a therapeutic target for malaria through clinical studies on the triazolopyrimidine-based Plasmodium DHODH inhibitor DSM265. Selective toxicity towards Plasmodium species could be achieved because malaria parasites lack pyrimidine salvage pathways, and DSM265 selectively inhibits Plasmodium DHODH over the human enzyme. However, while DSM265 does not inhibit human DHODH, it inhibits DHODH from several preclinical species, including mice, suggesting that toxicity could result from on-target DHODH inhibition in those species. We describe here the use of dihydroorotate (DHO) as a biomarker of DHODH inhibition. Treatment of mammalian cells with DSM265 or the mammalian DHODH inhibitor teriflunomide led to increases in DHO where the extent of biomarker buildup correlated with both dose and inhibitor potency on DHODH. Treatment of mice with leflunomide (teriflunomide prodrug) caused a large dose-dependent buildup of DHO in blood (up to 16-fold) and urine (up to 5,400-fold) that was not observed for mice treated with DSM265. Unbound plasma teriflunomide levels reached 20–85-fold above the mouse DHODH IC50, while free DSM265 levels were only 1.6–4.2-fold above, barely achieving ∼ IC90 concentrations, suggesting that unbound DSM265 plasma levels are not sufficient to block the pathway in vivo. Thus, any toxicity associated with DSM265 treatment in mice is likely caused by off-target mechanisms. The identification of a robust biomarker for mammalian DHODH inhibition represents an important advance to generally monitor for on-target effects in preclinical and clinical applications of DHODH inhibitors used to treat human disease.

Original languageEnglish (US)
Article number115237
JournalBiochemical Pharmacology
StatePublished - Oct 2022


  • Biomarker
  • Dihydroorotate dehydrogenase
  • Malaria
  • Pyrimidine metabolism

ASJC Scopus subject areas

  • Biochemistry
  • Pharmacology


Dive into the research topics of 'Development of a biomarker to monitor target engagement after treatment with dihydroorotate dehydrogenase inhibitors'. Together they form a unique fingerprint.

Cite this