Pharmacokinetic interactions between the orexin receptor antagonist almorexant and the CYP3A4 inhibitors ketoconazole and diltiazem

The metabolism of the orexin-1 selective receptor antagonist nivasorexant

Nivasorexant was the first orexin-1 selective receptor antagonist entering clinical development. Despite encouraging preclinical evidence in animal models, a proof-of-concept trial in binge-eating patients recently failed to demonstrate its clinical utility in this population.Across species, nivasorexant clearance was driven by metabolism along seven distinct pathways, five of which were hydroxylation reactions in various locations of the molecule. The exact sites of metabolism were identified by means of mass spectrometry, the use of deuterated analogues, and finally confirmed by chemical references.CYP3A4 was the main cytochrome P450 enzyme involved in nivasorexant metabolism in vitro and accounting for about 90% of turnover in liver microsomes. Minor roles were taken by CYP2C9 and CYP2C19 but individually did not exceed 3-7%.In the rat, nivasorexant was mostly excreted via the bile after extensive metabolism, while urinary excretion was negligible. Only traces of the parent drug were detected in urine, bile, or faeces.

The Metabolism of the Dual Orexin Receptor Antagonist Daridorexant

Daridorexant is a dual orexin receptor antagonist developed for the treatment of insomnia disorder and has shown improvement in sleep outcomes and daytime functioning. The present work describes its biotransformation pathways in vitro and in vivo and provides a cross-species comparison between the animal species used in preclinical safety assessments and man.Daridorexant clearance is driven by metabolism along seven distinct pathways. Metabolic profiles were characterized by downstream products while primary metabolic products were of minor importance. The metabolic pattern differed between rodent species, with the rat reflecting the human pattern better than the mouse.In rodents, daridorexant is mostly excreted via the bile after extensive metabolism while urinary excretion was negligible in the rat. Only traces of parent drug were detected in urine, bile or faeces.Daridorexant has three major metabolites which are well covered in these preclinical safety species. All of them retain some residual affinity towards orexin receptors. However, none of these is considered to contribute to the pharmacological effect of daridorexant as their active concentrations in human brain are too low.

Effect of gastric pH and of a moderate CYP3A4 inducer on the pharmacokinetics of daridorexant, a dual orexin receptor antagonist

AIM

Daridorexant is a dual orexin receptor antagonist developed for the treatment of insomnia. The solubility of daridorexant is pH dependent and daridorexant has been shown to be a sensitive CYP3A4 substrate when co-administered with moderate CYP3A4 inhibitors. The purpose of this study was to assess the effect of an increased gastric pH on daridorexant pharmacokinetics (PK) and the extent of interaction when daridorexant is co-administered with a moderate CYP3A4 inducer.

METHODS

In this prospective, single-centre, randomized, open-label study, 24 male subjects consecutively received four treatments, i.e., daridorexant 50 mg single dose; famotidine 40 mg single dose + daridorexant 50 mg single dose; efavirenz 600 mg once a day (o.d.) during 10 days; and daridorexant 50 mg single dose + efavirenz 600 mg o.d. for 2 days. Plasma PK parameters of daridorexant were derived by noncompartmental analysis. Standard safety and tolerability evaluations were analysed descriptively.

RESULTS

When daridorexant administration was preceded by administration of famotidine, daridorexant C_max decreased by 39%, geometric means ratio (GMR) (90% confidence interval (90% CI)): 0.61 (0.50, 0.73). AUC_0-∞ remained unchanged. In the presence of steady-state efavirenz, daridorexant C_max , AUC_0-∞ , and t_½ decreased by approximately 35% (GMR (90% CI)): 0.65 (0.54, 0.78), 61% (0.39 (0.348, 0.44), and 35% (0.65 (0.58, 0.73), respectively. T_max remained unaffected. All treatments containing daridorexant were well tolerated.

CONCLUSION

Daridorexant 50 mg can be administered concomitantly with gastric pH modifiers or with moderate CYP3A4 inducers without dose adaptation based on efficacy observed at lower doses in Phase 3 studies.

Inhibitory effect of resveratrol on the pharmacokinetics of ticagrelor in vivo and in vitro

This study was to evaluate the effect of resveratrol on the pharmacokinetics of ticagrelor in rats and the metabolism of ticagrelor in human cytochrome P450 (CYP) 3A4 (CYP3A4) and liver microsomes. Eighteen Sprague-Dawley rats were randomly divided into three groups: group A (control group), group B (50 mg/kg resveratrol), and group C (150 mg/kg resveratrol). After 30 min administration of resveratrol, a single dose of ticagrelor (18 mg/kg) was administered orally. The in vitro experiment was performed to examine the influence of resveratrol on ticagrelor metabolism in CYP3A4*1, human, and rat liver microsomes. Serial biological samples were assayed by validated ultra high-performance liquid chromatography - tandem mass spectrometer methods. For the in vivo study, the area under the concentration-time curve and mean peak plasma concentrations of ticagrelor in group B and C appeared to be significantly higher than the control group, while volume of distribution in terminal phase and apparent clearance of ticagrelor in group B and C were significantly decreased. For the in vitro study, resveratrol exhibited an inhibitory effect on CYP3A4*1, human and rat liver microsomes. The half-maximal inhibitory concentration values of resveratrol were 56.75 μM, 69.07 μM, and 14.22 μM, respectively. Our results indicated that resveratrol had an inhibitory effect on the metabolism of ticagrelor in vitro and in vivo. Further research should focus on the clinical combination of resveratrol with ticagrelor, and ticagrelor plasma concentration should be monitored to avoid the occurrence of adverse reaction.

Effect of severe renal impairment on pharmacokinetics, safety, and tolerability of lemborexant

The primary aim of this study was to examine the effect of severe renal impairment (SRI) on the pharmacokinetics of lemborexant, a dual orexin receptor antagonist indicated for the treatment of insomnia. A phase 1 multicenter, single‐dose, open‐label, parallel‐group study was conducted in subjects with SRI not requiring dialysis (estimated glomerular filtration rate 15–29 ml/min/1.73 m²; n = 8) compared with demographically matched healthy subjects with normal renal function (n = 8). Plasma levels of lemborexant and its metabolites were measured over 240 h following a single oral 10‐mg dose administered in the morning. Relative to subjects with normal renal function, lemborexant maximum plasma concentration (C_max) was similar, whereas area under the plasma concentration–time curve from zero to time of last quantifiable concentration (AUC_(0‐t)) and AUC from zero to infinity (AUC_(0‐inf)) were about 1.5‐fold higher in subjects with SRI. The geometric mean ratios (90% confidence interval) were 104.8 (77.4–142.0), 150.5 (113.2–200.3), and 149.8 (113.1–198.6) for C_max, AUC_(0‐t), and AUC_(0‐inf), respectively. In both groups, the median lemborexant time to C_max (t_max) was 1 h, and the mean unbound fraction of lemborexant was ~7%. For the M4, M9, and M10 metabolites, C_max was reduced ~20% and exposure (AUC_(0‐t) and AUC_(0‐inf)) was ~1.4‐ to 1.5‐fold higher in subjects with SRI versus healthy subjects; t_max was delayed ~1.5–2 h for M4 and M10. All treatment‐emergent adverse events were mild or moderate. Lemborexant pharmacokinetics were not sufficiently altered to warrant a dose adjustment for subjects with renal impairment.

Effects of ketoconazole on cyclophosphamide metabolism: evaluation of CYP3A4 inhibition effect using the in vitro and in vivo models

Cyclophosphamide (CP) is widely used in anticancer therapy regimens and 2-dechloroethylcyclophosphamide (DECP) is its side-chain dechloroethylated metabolite. N-dechloroethylation of CP mediated by the enzyme CYP3A4 yields nephrotoxic and neurotoxic chloroacetaldehyde (CAA) in equimolar amount to DECP. This study aimed to evaluate the inhibitory effect of ketoconazole (KTZ) on CP metabolism through in vitro and in vivo drug-drug interaction (DDI) research. Long-term treatment of KTZ induces hepatic injury; thus single doses of KTZ at low, middle, and high levels (10, 20, and 40 mg/kg) were investigated for pharmacokinetic DDI with CP. Our in vitro human liver microsome modeling approach suggested that KTZ inhibited CYP3A4 activity and then decreased DECP exposure. In addition, an UHPLC-MS/MS method for quantifying CP, DECP, and KTZ in rat plasma was developed and fully validated with a 4 min analysis coupled with a simple and reproducible one-step protein precipitation. A further in vivo pharmacokinetic study demonstrated that combination use of CP (10 mg/kg) and KTZ (10, 20, and 40 mg/kg) in rats caused a KTZ dose-dependent decrease in main parameters of DECP (C_max, T_max, and AUC_0-∞) and provided magnitude exposure of DECP (more than a 50% AUC decrease) as a consequence of CYP3A inhibition but had only a small effect on the CP plasma concentration. Our results suggested that combination usage of a CYP3A4 inhibitor like KTZ may decrease CAA exposure and thus intervene against CAA-induced adverse effects in CP clinical treatment.