Poster Presentation 38th Lorne Cancer Conference 2026

Mechanistic deconvolution reveals DHODH as the key target of the KDM4 inhibitor QC6352​ (#163)

Jacinda JH Holtsmark 1 2 , Jayden JS Sterling 1 2 , George GJ Joun 1 2 , Tian TD Du 2 3 , Mani MK Kuchibhotla 4 5 , Terrance TJ Johns 1 5 , Antoine AW De Weck 6 7 , Lipin LL Loo 2 3 , Greg GN Neely 2 3 , Chloe Shard 8 , Karen Tran 1 2 , Guillermo Gomez 8 , Ashwini Patil 9 , Angus Saxton 10 , Jennifer Baker 11 , Yuchen Feng 1 2 , Andreas Kraemer 12 13 14 , Susanne Mueller-knapp 12 13 14 15 , Paul Workman 15 16 , Lenka Munoz 1 2
  1. Faculty of Medicine and Health, The University of Sydney, Camperdown, New South Wales, Australia
  2. Charles Perkins Centre at the University of Sydney, Camperdown, NSW, Australia
  3. School of Life and Environmental Science, Faculty of Science, The University of Sydney, Sydney, NSW, Australia
  4. Centre for Child Health Research, Medical School, University of Western Australia, Crawley, WA, Australia
  5. Cancer Centre, Telethon Kids Institute, Nedlands, WA, Australia
  6. Children’s Cancer Institute, Lowy Cancer Research Centre, University of New South Wales, Sydney, NSW, Australia
  7. School of Clinical Medicine, University of New South Wales, Sydney, NSW, Australia
  8. Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, SA, Australia
  9. Combinatics, 2-2-6 Sugano, Ichikawa-shi, Chiba, 272-0824, Japan
  10. Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW, Australia
  11. School of Science, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, NSW, Australia
  12. Institute of Pharmaceutical Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438, Frankfurt am Main, Germany
  13. Frankfurt Cancer Institute (FCI), Frankfurt am Main, Germany
  14. Structural Genomics Consortium, Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438, Frankfurt am Main, Germany
  15. Chemical Probes Portal, www.chemicalprobes.org, NA
  16. Centre for Cancer Drug Discovery, Division of Cancer Therapeutics, The Institute of Cancer 34 Research, London SM2 5NG,, UK

The small molecule QC6352, developed as an inhibitor of the histone demethylase KDM4, exhibits potent anti-cancer activity, and its derivative, zavondemstat, is currently being evaluated in cancer clinical trials. Here, we demonstrate that the anti-proliferative efficacy of QC6352 in glioblastoma models is independent of KDM4 inhibition. Transcriptomic analysis revealed that QC6352's gene expression signature in glioblastoma cells closely resembles that of drugs targeting dihydroorotate dehydrogenase (DHODH). Biochemical assays, protein crystallography, metabolomic analysis, and uridine rescue experiments confirmed that QC6352 inhibits DHODH and thereby disrupts the de novo pyrimidine biosynthesis pathway. This project underscores the ongoing issue of incorrect conclusions caused by the absence of orthogonal high-quality chemical and molecular tools targeting proteins of interest. The mechanism of action of QC6352 is a dual KDM4-DHODH inhibitor and therefore cannot be used to delineate KDM4 function in cells or organisms. We discovered that Zavondemstat, the clinical derivative of QC6352, antiproliferative efficacy is likely due to DHODH inhibition, and has even greater potency than other extensively studied DHODH inhibitors including brequinar and BAY2402234. Thus, this discovery has profound implications on future clinical trials using Zavondemstat