In vitro evaluation of the metabolic enzymes and drug interaction potential of triapine.

PURPOSE: To investigate the metabolic pathways of triapine in primary cultures of human hepatocytes and human hepatic subcellular fractions; to investigate interactions of triapine with tenofovir and emtricitabine; and to evaluate triapine as a perpetrator of drug interactions. The results will better inform future clinical studies of triapine, a radiation sensitizer currently being studied in a phase III study. METHODS: Triapine was incubated with human hepatocytes and subcellular fractions in the presence of a number of inhibitors of drug metabolizing enzymes. Triapine depletion was monitored by LC-MS/MS. Tenofovir and emtricitabine were co-incubated with triapine in primary cultures of human hepatocytes. Triapine was incubated with a CYP probe cocktail and human liver microsomes, followed by LC-MS/MS monitoring of CYP specific metabolite formation. RESULTS: Triapine was not metabolized by FMO, AO/XO, MAO-A/B, or NAT-1/2, but was metabolized by CYP450s. CYP1A2 accounted for most of the depletion of triapine. Tenofovir and emtricitabine did not alter triapine depletion. Triapine reduced CYP1A2 activity and increased CYP2C19 activity. CONCLUSION: CYP1A2 metabolism is the major metabolic pathway for triapine. Triapine may be evaluated in cancer patients in the setting of HIV with emtricitabine or tenofovir treatment. Confirmatory clinical trials may further define the in vivo triapine metabolic fate and quantify any drug-drug interactions.

Feasibility of clinical pharmacist-led CYP2C19 genotyping for patients receiving non-emergent cardiac catheterization in an integrated health system

Objective: To assess the feasibility of clinical pharmacist-led CYP2C19 genotype-guided P2Y12 inhibitor antiplatelet drug therapy recommendations to cardiologists in an outpatient cardiology practice. Methods: This was a prospective, open-labeled, single-arm study conducted in an integrated healthcare delivery system between March 1, 2013 and January 23, 2014. Patients requiring non-emergent cardiac catheterization were included. A clinical pharmacist provided interpretation and recommendations from genotyping results. The feasibility of implementing CYP2C19 genotype-guided antiplatelet therapy was assessed by the: 1) percentage of patients approached who consented to CYP2C19 genotyping, 2) percentage of patients with CYP2C19 genotyping results available prior to cardiac catheterization, and 3) percentage of clinical pharmacist CYP2C19 genotype-based antiplatelet recommendations accepted by cardiologists. Results: Of the 43 patients identified for potential recruitment, 22 of these were eligible for study enrollment and 6 (27%) patients consented and received CYP2C19 genotyping. All patients had genotyping results available prior to catheterization and all clinical pharmacists’ antiplatelet therapy recommendations were accepted by the patients’ cardiologists. Three patients had the CYP2C19 wild-type (*1/*1) genotype and the clinical pharmacist recommended clopidogrel therapy. CYP2C19 variant genotypes (i.e., *1/*2, *1/*17, and *2/*17) were found in the other three patients; alternative antiplatelet therapy was recommended for the patient with the *1/*2 genotype, while clopidogrel was recommended for those with *1/*17 and *2/*17 genotypes. Conclusion: A relatively small proportion of patients undergoing non-emergent cardiac catheterization consented to pharmacogenetic testing; however, their cardiologists were receptive to clinical pharmacists conducting such testing and providing corresponding pharmacotherapy recommendations. Future studies should identify patient barriers to pharmacogenetic testing (AU)

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