The Roles of CYP2C19 and CYP3A4 in Voriconazole Pharmacogenetics

Voriconazole is a triazole antifungal agent used to treat serious fungal infections. It is primarily used in immunocompromised patients, such as those undergoing organ transplantation. CYP2C19 is the primary enzyme responsible for voriconazole metabolism. CYP3A4, CYP3A5 and CYP2C9 also play a role, secondary to CYP2C19. The influence of genetic polymorphisms in CYP2C19 is well documented in clinical studies, and the Clinical Pharmacogenetics Implementation Consortium (CPIC) recently released guideline for voriconazole dosing based on CYP2C19 genotype.

In the August issue of Clinical Pharmacology and Therapeutics, Gautier-Veyret et al wrote a perspective piece discussing two retrospective studies showing that genetic variations in CYP3A4 gene may influence voriconazole trough concentrations, suggesting that in addition to CYP2C19, CYP3A4 should also be genotyped for voriconazole dosing.

In response to this, CPIC guideline authors Walsh et al acknowledged the different opinions on the role of CYP3A4 in voriconazole pharmacokinetics and clarified the reasons why CPIC authors feel there is NOT sufficient evidence to recommend altered voriconazole dosing based on genetic polymorphisms in CYP3A4/CYP3A5.

For further details see both articles in the August edition of Clinical Pharmacology and Therapeutics:

1, Response to "Pharmacogenetics of Voriconazole: CYP2C19 but Also CYP3A4 Need to Be Genotyped" - The Role of CYP3A4 and CYP3A5 Polymorphisms in Clinical Pharmacokinetics of Voriconazole.

Walsh TJ, Moriyama B, Penzak SR, Klein TE, Caudle KE.

Clin Pharmacol Ther. 2017 Aug;102(2):190. doi: 10.1002/cpt.681. Epub 2017 Apr 29. 

PMID: 28455946

2, Pharmacogenetics of Voriconazole: CYP2C19 but Also CYP3A4 Need to Be Genotyped.

Gautier-Veyret E, Fonrose X, Stanke-Labesque F.

Clin Pharmacol Ther. 2017 Aug;102(2):189. doi: 10.1002/cpt.662. Epub 2017 May 26. 

PMID: 28182291

3, CPIC guideline for voriconazole and CYP2C19

4, Voriconazole pathway on PharmGKB

Curators' Favorite Papers

The Impact of Whole-Genome Sequencing on the Primary Care and Outcomes of Healthy Adult Patients: A Pilot Randomized Trial

Jason L. Vassy, MD, MPH, SM; Kurt D. Christensen, PhD, MPH; Erica F. Schonman, MPH; Carrie L. Blout, MS, CGC; Jill O. Robinson, MA; Joel B. Krier, MD; Pamela M. Diamond, PhD; Matthew Lebo, PhD; Kalotina Machini, PhD; Danielle R. Azzariti, MS, CGC; Dmitry Dukhovny, MD, MPH; David W. Bates, MD, MSc; Calum A. MacRae, MD, PhD; Michael F. Murray, MD; Heidi L. Rehm, PhD; Amy L. McGuire, JD, PhD; and Robert C. Green, MD, MPH for the MedSeq Project

This study, published  in the Annals of Internal Medicine, received a lot of attention in prominent media outlets including Wired, STAT, NPR, Washington Post and Science Magazine. As part of the MedSeq project, 100 healthy adults were recruited by 9 primary care providers (PCP), themselves briefed on genomics and how to refer patients to genetics experts. All patients gave a detailed family history (FH) but were randomized to get either whole genome sequencing (WGS) (WGS +FH) or not (FH) and were surveyed at 6 months regarding follow-up care and well-being. The study authors uncovered monogeneic disease risk (MDR) variants in 11 patients, but only 2 manifested the phenotype (fundus albipunctatus and subclinical porphyria). 48 of 50 subjects had a pharmacogenetic variant in a gene affecting one of five drugs (warfarin, clopidogrel, simvastatin, metformin, and digoxin) and results were added to electronic health records (EHR). PCPs recommended new clinical actions in 16% and 34% of FH and WGS+ FH patients, respectively. At 6 months, 30% and 41% of patients made health behavior changes in the FH and WGS-FH groups, respectively, but no significant differences in self-reported health, anxiety or depression scores emerged between groups. Overall, the authors conclude that identification of MDR variants did not improve short-term health outcomes, and results do not support the routine use of WGS in healthy patients. However, the authors note that the ability of PCPs to adequately manage patient results, their use of EHR, and their appropriate referrals to genetic specialists, as well as self-reported patient well-being after receiving results are encouraging signs that indicate a favorable environment for WGS in future studies and specific clinical care situations.

You can read the study here and more information about the pharmacogenetics of warfarin, clopidogrel, simvastatin, metformin, and digoxin is available at PharmGKB.