The CYP2C9*1 allele is assigned as a normal function allele by CPIC. Patients carrying the CYP2C9*1 allele in combination with another normal function allele may have increased metabolism and decreased plasma concentrations of siponimod as compared to patients carrying at least one decreased or no function alleles. Other genetic and clinical factors may also influence the metabolism of siponimod. This annotation only covers the pharmacokinetic relationship between CYP2C9 and siponimod and does not include evidence about clinical outcomes.