CYP2B6*21 (c.1282C>A, p.P428T) – Uncertain function: CYP2B6*21 is assigned uncertain function. In vitro studies using cDNA expression systems found no or severely decreased enzyme activity for CYP2B6*21 (20517174, 21746968, 16272958, 30201214). However, there was no in vivo data available or data in human liver microsomes. Therefore, the consensus among experts was uncertain function based on inadequate evidence.