Has the era of individualised medicine arrived for antifungals? A review of antifungal pharmacogenomics.

Treatment or prophylaxis of invasive fungal infection in recipients of haemopoietic SCT (HSCT) may require management of coexistent malnutrition, organ dysfunction and GVHD, all of which create added potential for inter- and intra-patient variations in drug metabolism as well as drug interactions. Polymorphism is common in genes encoding pathway components of antifungal drug metabolism such as enzymes (cytochrome P450 (CYP450), glutathione S-transferase, N-acetyltransferase and uridine 5'-diphospho-glucuronosyltransferase), uptake transporters (organic cationic transporter, novel organic cationic transporter, organic anion transporter protein (OATP), organic anion transport (OAT), and peptide tranporter) and efflux transporters (breast cancer resistance protein, bile sale export pump (BSEP), multidrug and toxin extrusion type transporter, multidrug resistance protein (MRP), OAT, permeability glycoprotein (P-gp), and urate transporter). Specific polymorphisms may be generalised throughout a population or largely confined to ethnic groups. CYP450 enzymes, especially 2C9 and 2C19, exhibit extensive polymorphism and are central to the metabolism of azole antifungals and their interactions with other drugs including calcineurin inhibitors, cytotoxics and benzodiazepines. Polymorphism may ultimately affect drug efficacy: CYP2C19 variation leads to a fivefold variation in voriconazole levels between individuals. Anticipated routine provision of pharmacogenomic data in the future for new drugs, together with accumulating knowledge about established agents, challenge physicians to assimilate and apply that information to drug prescribing. Increasing availability of pharmacogenomic data may strengthen demand for rapid turn-around therapeutic drug monitoring of antifungal agents in HSCT recipients.