Marc Poirot studied organic chemistry and biochemistry at the university Paul Sabatier of Toulouse where he received his PhD degree on chemical biology. He did a post-doc at Sanofi-Elf-bio-recherche and was tenured at Inserm (French NIH) as a research scientist. Next, Marc was a visiting scientist at the National Institute of Health (NIH, Bethesda, MD, USA) working on steroid hormone receptors. Marc is presently leader of the INOV team with his long-time collaborator Sandrine Silvente-Poirot at the Cancer Research Center of Toulouse, France. His research interests include cholesterol metabolism deregulations in cancers. With Sandrine and their team, they identified new bioactive cholesterol metabolites highlighting the existence of a new branch on the cholesterol metabolic pathway. This branch is centered on 5,6-epoxycholesterols (5,6-EC) which they showed to be differentially metabolized in cancer cells compared to normal cells. They found that in tumors 5,6-EC are transformed into oncosterone an oncometabolite with tumor promoter properties. Alternatively, in normal tissue, they showed that 5,6α-EC is enzymatically conjugated to histamine to give dendrogenin A, which displays tumor suppressor properties. Dendrogenin A was the first steroidal alkaloid identified in mammals. Marc’s group is identifying new mammalian sterol metabolites, their biosynthesis enzymes, characterized their biological properties and their mechanism of action. Marc has published more than 130 scientific articles/reviews/patents and will be recipient in May 2023 of the Schroepfer medal awarded by the American Oil Chemists’ Society (AOCS) in recognition of his discoveries on the field of sterols.