Rs1800460

rs1800460 is a SNP in the TPMT gene, potentially encoding a variant incapable of detoxifying byproducts of certain antineoplastic and immunosuppressant drugs. In general, individuals must have two nonfunctioning TPMT alleles for the toxicity to be pronounced.

The risk allele for this SNP is rs1800460(A), and when it is the only variation in the TPMT gene, it encodes the TPMT*3B allele. While still rare, it is more common in Caucasians (4.5% of all alleles) than in African-Americans (0.8%). Note that if the same allele also carries the rs1142345(G) SNP, the allele is actually a TPMT*3A allele (OMIM).

The medicine 6-Mercaptopurine is metabolized by TPMT. Individual differences in TPMT activity associated with this SNP are now used to determine appropriate dosage range and interval for treatment.

[Wikipedia] thiopurine drugs metabolized by TPMT include azathioprine, mercaptopurine, and thioguanine