Raw research findings for this medication. Mostly single studies, not curated or confirmed robust.
Tegafur is an oral chemotherapy medicine that the liver converts into fluorouracil (5-FU), which stops cancer cells from making the DNA they need to divide. It is given in combination products, for example with uracil (UFT) or with gimeracil and oteracil (S-1, Teysuno), mainly for stomach, bowel and other gastrointestinal cancers, and is used most in Japan and East Asia.
Two genes act at different steps. CYP2A6 converts tegafur into fluorouracil, and its low-activity versions, common in East Asian populations, mean less is converted; most studies on this page concern CYP2A6. DPYD then breaks fluorouracil down, and people with low-function DPYD variants (such as *2A, rs3918290) keep far more of it, with a much higher chance of severe side effects. DPWG has published a guideline on DPYD and tegafur.
Clinical guidelines that name a gene for Tegafur. They sort people into groups by the gene copies they carry.
DPWG guideline: DPYD. DPYD activity score 0 to 2. 2020.
Every published finding on gene variants and Tegafur. Upload your DNA file to see which of these rows apply to you.
PharmGKB weighs all studies of a variant and rates how strong the evidence is, from 1A (strongest) to 4.
DPYD rs3918290: Level 1A · replicated. Toxicity: Neoplasms. 3.
DPYD rs67376798: Level 1A · replicated. Toxicity: Neoplasms. 3.
DPYD rs55886062: Level 1A · replicated. Toxicity: Neoplasms. 2.
CYP2A6 CYP2A6*1, CYP2A6*4, CYP2A6*7, CYP2A6*9, CYP2A6*10, CYP2A6*11, CYP2A6*18, CYP2A6*19, CYP2A6*46: Level 3. Metabolism/PK: Neoplasms. 8.
Studies of how quickly the body processes this medication.
CYP2A6 CYP2A6*1, CYP2A6*4: CYP2A6 *4 is associated with decreased metabolism of tegafur.
Studies of how well it worked in people carrying a variant.
Studies of side effects in people carrying a variant.
Study findings and evidence levels: PharmGKB (CC BY-SA 4.0). Guidelines: CPIC and DPWG, as bundled in PharmCAT. Most studies were done mainly in people of European ancestry.
More drugs from the same category
Not a prescribing recommendation. This page is educational information about pharmacogenomic research and clinical guidelines - it is not medical or dosing advice, and not a prediction of how any medication will work for you. Never start, stop, or change a medication or dose based on it; talk to your doctor or pharmacist, who can order clinical-grade testing if appropriate.
Content updated September 2026.
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