Loss-of-function mutations of OATP1B1/1B3 have been discovered in humans, and many clinically used drugs have been identified as OATP1B1/1B3 inhibitors,18,28,34 which could result in hyperbilirubinemia in patients with EPP if encountered. Here, SLCO1B1 is linked to autosomal erythropoietic protoporphyria.