CYP3A43 is a cytochrome P450 enzyme that catalyzes monooxygenase reactions involving steroid metabolism, particularly testosterone 6-beta-hydroxylase activity and estrogen 16-alpha-hydroxylase activity. It is expressed primarily in prostate, liver, kidney, pancreas, and testis 12. The enzyme shares 71–76% amino acid identity with other CYP3A family members (CYP3A4, CYP3A5, CYP3A7) but displays markedly lower enzymatic activity and protein expression compared to CYP3A4 13. Unlike CYP3A4, CYP3A43 is selectively induced by dexamethasone and rifampicin, but not by proton-pump inhibitors or St. John's wort 4. CYP3A43 contributes to metabolism of certain xenobiotics including alprazolam and has been associated with antipsychotic drug response; the rs680055 missense variant significantly influenced antipsychotic response in schizophrenia patients 5. Genetic variation in CYP3A43, particularly the CYP3A43*3 allele, has been associated with family history-positive prostate cancer, likely reflecting its role in testosterone metabolism 6. Recent evidence suggests CYP3A43 expression suppresses lung adenocarcinoma proliferation and migration, indicating a potential tumor-inhibitory role 7. Clinical applications targeting CYP3A43-mediated metabolism have included protease inhibitors such as ritonavir and cobicistat for HIV treatment, though CYP3A43's quantitative contribution to drug metabolism remains modest relative to CYP3A4 1.