Tegafur is a chemotherapeutic agent and a member of the fluoropyrimidine group of substances. It is a prodrug of 5-fluorouracil and mainly used to treat solid tumors, such as colorectal, breast and aerodigestive cancers. Dihydropyrimidine dehydrogenase (DPD, encoded by the DPYD gene) is the rate-limiting enzyme for fluoropyrimidine metabolism and is therefore responsible for the detoxification of these types of drugs. Patients who are homozygous for variants in DPYD that lead to a non-functional protein, such as *2A or *13, have a high risk of severe or fatal drug toxicities and may benefit from receiving an alternative chemotherapeutic drug. Patients heterozygous for these variants also have an increased risk for drug toxicities, and reduced dosing is recommended for these individuals. Guidelines regarding the use of pharmacogenomic tests in dosing for tegafur have been published in Clinical Pharmacology and Therapeutics by the Clinical Pharmacogenetics Implementation Consortium (CPIC) and are available on the PharmGKB website. [from
PharmGKB]