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Purpose ACT-541468 is a novel dual orexin receptor antagonist (DORA) under development for the treatment of insomnia. In vitro studies suggested a significant role of CYP3A4 in ACT-541468 metabolism and an impact on CYP3A4 activity. Methods Subsequently, two clinical cross-over studies investigated the victim ( n  = 14 healthy subjects) and perpetrator ( n  = 20) potential of 25 mg ACT-541468 with respect to CYP3A4. The effect of food intake on the pharmacokinetics of ACT-541468 was also investigated. Results Moderate CYP3A4 inhibition by diltiazem (240 mg/day) increased the C max and AUC 0–∞ of ACT-541468 by 1.4-fold (90% confidence interval (CI): 1.2–1.6) and 2.4-fold (90% CI: 2.0–2.8), respectively, and prolonged t ½ by 80% (90% CI: 60–90) without affecting t max . Single- and multiple-dose administration of 25 mg ACT-541468 had no impact on the pharmacokinetics of the sensitive substrate midazolam and its main metabolite 1-hydroxy midazolam indicated by 90% CI of the geometric mean ratios of C max and AUC within bioequivalence criteria and by an unchanged t max . After a high-fat high-calorie breakfast, the pharmacokinetic profile of 25 mg ACT-541468 showed a decrease of C max by 24% (90% CI: 17–31) and a delay of t max by approximately 2 h (90% CI: 1.4–2.4), whereas t ½ and AUC 0–24 remained essentially unchanged. ACT-541468 given alone or in combination with diltiazem, midazolam, or food was safe and well tolerated. Conclusions Overall, ACT-541468 has been determined as CYP3A4 substrate but without any perpetrator drug–drug interaction potential regarding CYP3A4 in humans. Food affected ACT-541468 absorption without modifying overall exposure.

Tramadol and codeine are metabolized by CYP2D6 and are subject to drug-gene and drug-drug interactions. This interim analysis examined prescribing behavior and efficacy in 102 individuals prescribed tramadol or codeine while receiving pharmaco-genotyping as part of the INGENIOUS trial (NCT02297126). Within 60 days of receiving tramadol or codeine, clinicians more frequently prescribed an alternative opioid in ultrarapid and poor metabolizers (odds ratio: 19.0; 95% CI: 2.8-160.4) as compared with normal or indeterminate metabolizers (p = 0.01). After adjusting the CYP2D6 activity score for drug-drug interactions, uncontrolled pain was reported more frequently in individuals with reduced CYP2D6 activity (odds ratio: 0.50; 95% CI: 0.25-0.94). Phenoconversion for drug-drug and drug-gene interactions is an important consideration in pharmacogenomic implementation; drug-drug interactions may obscure the potential benefits of genotyping.

Ulotaront (SEP‐363856) is a TAAR1 agonist, with 5‐HT1A agonist activity, currently in clinical development for the treatment of schizophrenia. In vitro studies indicate ulotaront is an OCT2‐specific inhibitor with IC50 of 1.27 μM. The primary objective of this study is to determine if a single dose of ulotaront affects the PK of metformin, an index substrate of OCT2, in subjects with schizophrenia. In a randomized, single‐blind, 2‐period crossover study, 25 adults with schizophrenia received a single dose of metformin‐HCl 850 mg (approximately 663 mg metformin) with and without coadministration of 100 mg ulotaront. The plasma samples were analyzed by fully validated LC–MS/MS methods. The primary PK endpoints for metformin were AUCinf, AUClast, Cmax, and tmax. The highest‐anticipated clinical dose of ulotaront (100 mg) had no statistically significant effect on the PK of a single dose of metformin based on Cmax and AUCinf. Geometric least squares mean ratios were 89.98% and 110.63%, respectively, with the 90% confidential interval (CI) for each parameter contained within 80%–125%. Median tmax was comparable across the treatments. Ulotaront does not act as a perpetrator of OCT2‐mediated DDI against metformin. Co‐administration of ulotaront is not expected to require dose adjustment of metformin or other drugs cleared by OCT2. Plasma and urine pharmacokinetic parameters of metformin along and in combination with ulotaront.

CYP450 polymorphisms result in variable rates of drug metabolism. CYP drug-drug interactions can contribute to altered drug effectiveness and safety. The primary objective was to determine the percentage of emergency department (ED) patients with cytochrome 2C19 (CYP2C19) drug-drug interactions. The secondary objective was to determine the prevalence of CYP2C19 polymorphisms in a US ED population. We conducted a prospective observational study in an urban academic ED with 72,000 annual visits. Drug ingestion histories for the 48 hours preceding ED visit were obtained; each drug was coded as CYP2C19 substrate, inhibitor, inducer, or not CYP2C19 dependent. Ten percent of patients were randomized to undergo CYP2C19 genotyping using the Roche Amplichip. A total of 502 patients were included; 61% were female, 65% were white, and median age was 39 years (interquartile range, 22-53). One hundred thirty-one (26.1%) patients had taken at least 1 CYP2C19-dependent home drug. Eighteen (13.7%) patients who were already taking a CYP2C19-dependent drug were given or prescribed a CYP2C19-dependent drug while in the ED. Among the 53 patients genotyped, 52 (98%) were extensive metabolizers and 1 was a poor metabolizer. In a population of ED patients, more than a quarter had taken a CYP2C19-dependent drug in the preceding 48 hours, but few were given or prescribed another CYP2C19-dependent drug in the ED. On genotyping analysis, CYP2C19 polymorphisms were uncommon in our cohort. We conclude that changing prescribing practice due to CYP2C19 drug-drug interaction or genotype is unlikely to be useful in most US ED populations.

Background and Objectives: St John’s wort (SJW; Hypericum perforatum ) has been one of the most commonly used herbal remedies for mood disorders. This study aimed to investigate the effect of SJW, a pregnane X receptor (PXR) agonist, on the pharmacokinetics and pharmacodynamics of repaglinide, a widely consumed glucose-lowering drug. Methods: In a two-phase, randomized, crossover study with a 4-week washout period between phases, 15 healthy subjects with specific solute carrier organic anion transporter family member 1B1 ( SLCO1B1 ) genotypes were given pretreatment with SJW 325 mg or placebo three times daily for 14 days, and a single dose of repaglinide 1mg was administered followed by 75 g glucose at 15 minutes after repaglinide administration. Results: In all subjects, SJW had no effect on the total area under the plasma concentration-time curve from time zero to infinity (AUC∞), the peak plasma concentration (C max ) or the elimination half-life (t ½ ) of repaglinide. In addition, SJW had no significant effect on the blood glucose-lowering and insulin-elevating effects of repaglinide. Conclusion: Consumption of SJW for 14 days had no clinically significant effect on the pharmacokinetics and pharmacodynamics of repaglinide.

Currently, most guidelines on drug-drug interaction (DDI) neither consider the potential effect of genetic polymorphism in the strength of the interaction nor do they account for the complex interaction caused by the combination of DDI and drug-gene interaction (DGI) where there are multiple biotransformation pathways, which is referred to as drug-drug-gene interaction (DDGI). In this systematic review, we report the impact of pharmacogenetics on DDI and DDGI in which three major drug-metabolizing enzymes - CYP2C9, CYP2C19 and CYP2D6 - are central. We observed that several DDI and DDGI are highly gene-dependent, leading to a different magnitude of interaction. Precision drug therapy should take pharmacogenetics into account when drug interactions in clinical practice are expected.

The narrow therapeutic range and wide interpatient variability in dose requirement make anticoagulation response to coumarin derivatives unpredictable. As a result, patients require frequent monitoring to avert adverse effects and maintain therapeutic efficacy. Polymorphisms in and jointly account for about 40% of the interindividual variability in dose requirements. To date, several pharmacogenetic-guided dosing algorithms for coumarin derivatives, predominately for warfarin, have been developed. However, the potential benefit of these dosing algorithms in terms of their safety and clinical utility has not been adequately investigated in randomized settings. The European Pharmacogenetics of Anticoagulant Therapy (EU-PACT) trial will assess, in a single-blinded and randomized controlled trial with a follow-up period of 3 months, the safety and clinical utility of genotype-guided dosing in daily practice for the three main coumarin derivatives used in Europe. The primary outcome measure is the percentage time in the therapeutic range for international normalized ratio. This report describes the design and protocol for the trial.

The Dutch Pharmacogenetics Working Group (DPWG) aims to facilitate pharmacogenetics implementation in clinical practice by developing evidence-based guidelines to optimize pharmacotherapy based on pharmacogenetic test results. The current guideline describes the gene-drug interaction between CYP2D6 and venlafaxine, mirtazapine and duloxetine. In addition, the interaction between CYP2C19 and mirtazapine and moclobemide is presented. The DPWG identified a gene-drug interaction that requires therapy adjustment for CYP2D6 and venlafaxine. However, as the side effects do not appear to be related to plasma concentrations, it is not possible to offer a substantiated advice for dose reduction. Therefore, the DPWG recommends avoiding venlafaxine for CYP2D6 poor and intermediate metabolisers. Instead, an alternative antidepressant, which is not, or to a lesser extent, metabolized by CYP2D6 is recommended. When it is not possible to avoid venlafaxine and side effects occur, it is recommended to reduce the dose and monitor the effect and side effects or plasma concentrations. No action is required for ultra-rapid metabolisers as kinetic effects are minimal and no clinical effect has been demonstrated. In addition, a gene-drug interaction was identified for CYP2D6 and mirtazapine and CYP2C19 and moclobemide, but no therapy adjustment is required as no effect regarding effectiveness or side effects has been demonstrated for these gene-drug interactions. Finally, no gene-drug interaction and need for therapy adjustment between CYP2C19 and mirtazapine and CYP2D6 and duloxetine were identified. The DPWG classifies CYP2D6 genotyping as being “potentially beneficial” for venlafaxine, indicating that genotyping prior to treatment can be considered on an individual patient basis.

PurposeIsoniazid (INH) is prescribed both for the prophylaxis as well as the treatment of tuberculosis. It is primarily metabolized through acetylation by a highly polymorphic enzyme, N-acetyl transferase 2 (NAT2), owing to which significant variable systemic drug levels have been reported among slow and rapid acetylators. Furthermore, many drugs, like phenytoin, diazepam, triazolam, etc., are known to show toxic manifestation when co-administered with INH and it happens prominently among slow acetylators. Additionally, it is revealed in in vitro inhibition studies that INH carries noteworthy potential to inhibit CYP2C19 and CYP3A4 enzymes. However, CYP inhibitory effect of INH gets masked by opposite enzyme-inducing effect of rifampicin, when used in combination. Thus, distinct objective of this study was to fill the knowledge gaps related to gene-drug-drug interactions (DDI) potential of INH when given alone for prophylactic purpose.MethodsWhole body-PBPK models of INH were developed and verified for both slow and fast acetylators. The same were then utilized to carry out prospective DDI studies with CYP2C19 and CYP3A4 substrates in both acetylator types.ResultsThe results highlighted likelihood of significant higher blood levels of CYP2C19 and CYP3A4 substrate drugs in subjects receiving INH pre-treatment. It was also re-established that interaction was more likely in slow acetylators, as compared to rapid acetylators.ConclusionThe novel outcome of the present study is the indication that prescribers should give careful consideration while advising CYP2C19 and CYP3A4 substrate drugs to subjects who are on prophylaxis INH therapy, and are slow to metabolic acetylation.

Implementation of pharmacogenetic testing to guide drug prescribing has potential to improve drug response and prevent adverse events. Robust data exist for more than 30 gene-drug pairs linking genotype to drug response phenotypes; however, it is unclear which pharmacogenetic tests, if implemented, would provide the greatest utility for a given patient population. To project the proportion of veterans in the US Veterans Health Administration (VHA) with actionable pharmacogenetic variants and evaluate how testing might be associated with prescribing decisions. This cross-sectional study included veterans who used national VHA pharmacy services from October 1, 2011, to September 30, 2017. Data analyses began April 26, 2018, and were completed February 6, 2019. Receipt of level A drugs based on VHA pharmacy dispensing records. Projected prevalence of actionable pharmacogenetic variants among VHA pharmacy users based on variant frequencies from the 1000 Genomes Project and veteran demographic characteristics; incident number of level A prescriptions, and proportion of new level A drug recipients projected to carry an actionable pharmacogenetic variant. During the study, 7 769 359 veterans (mean [SD] age, 58.1 [17.8] years; 7 021 504 [90.4%] men) used VHA pharmacy services. It was projected that 99% of VHA pharmacy users would carry at least 1 actionable pharmacogenetic variant. Among VHA pharmacy users, 4 259 153 (54.8%) received at least 1 level A drug with 1 188 124 (15.3%) receiving 2 drugs, and 912 189 (11.7%) receiving 3 or more drugs. The most common incident prescriptions during the study were tramadol (923 671 new recipients), simvastatin (533 928 new recipients), citalopram (266 952 new recipients), and warfarin (205 177 new recipients). Gene-drug interactions projected to have substantial clinical impacts in the VHA population include the interaction of SLCO1B1 with simvastatin (1 988 956 veterans [25.6%]), CYP2D6 with tramadol (318 544 veterans [4.1%]), and CYP2C9 or VKORC1 with warfarin (7 163 349 veterans [92.2%]). Clinically important pharmacogenetic variants are highly prevalent in the VHA population. Almost all veterans would carry an actionable variant, and more than half of the population had been exposed to a drug affected by these variants. These results suggest that pharmacogenetic testing has the potential to affect pharmacotherapy decisions for commonly prescribed outpatient medications for many veterans.