rs28399504 is a SNP in the CYP2C19 gene, potentially encoding the CYP2C19*4 variant. This variant has been linked to poor metabolism of compounds like mephenytoin. It is also known as M1V or Met1Val.[Clopidogrel Efficacy
[PMID 23130019] Frequencies of 23 functionally significant variant alleles related with metabolism of antineoplastic drugs in the chilean population: comparison with caucasian and asian populations.