CYP2B6*30 (CYP2B7-CYP2B6 hybrid gene) – No function: CYP2B6*30 is assigned no function. This allele has a hybrid gene consisting of CYP2B6 (exons 1-4) and CYP2B7 (exons 5-9) harboring 15 amino acid changes compared to the protein encoded by the CYP2B6*1 reference. Among those is a premature stop codon (p.R378X) which is also found in CYP2B6*28 (23164804). This allele has been found in a duplication structure; it remains uncertain, however, whether the other gene in the duplication is a *1, *4 or *6 (or potentially other). Although CYP2B6*30 has no function, the function of this duplication allele depends on the nature of the other gene copy. One in vitro study found that primary human hepatocytes of subjects with a CYP2B6*30 had significantly lower mRNA and protein expression and enzyme activity compared to the *1 reference (28181240). The same study also showed that the AUC for 4-OH-cyclophosphamide was significantly lower for patients with *1/*30 compared to *1/*1 (28181240). In this study, the presence of a CYP2B6*30 was inferred by subjects having three gene copies and sequence analysis of the *30; however, the study did not provide any information regarding the nature of the second gene copy of the duplication. Therefore, consensus among experts was no function based on limited evidence.