CYP2C9*15 is assigned no function based on limited evidence. CYP2C9*15 is defined by a nonsense mutation which results in a premature stop codon resulting in a significant truncation of the protein. In an in vitro study, CYP2C9*15 did not result in detectable protein expression (16099926). CYP2C9*15 was not included in subsequent in vitro studies because it is a null allele resulting in no protein formation (23752738). Therefore, consensus among experts was no function with an activity value of 0 based on limited evidence as it was determined the phenotypes containing this allele would be clinically distinct from phenotypes comprising normal and decreased function alleles.