Effects of Omeprazole and Verapamil on the Pharmacokinetics, Safety, and Tolerability of Mavacamten: Two Drug-Drug Interaction Studies in Healthy Participants.

Two open-label, Phase 1 studies assessed the effects of omeprazole (a weak to moderate cytochrome P450 [CYP] 2C19 inhibitor) and verapamil (a moderate CYP3A4 inhibitor) on the pharmacokinetics, safety, and tolerability of mavacamten. In the omeprazole study, healthy participants received mavacamten 15 mg alone or with a 31-day course of omeprazole 20 mg once daily. In the verapamil study, healthy participants received mavacamten 25 mg alone or with a 28-day course of verapamil 240 mg once daily. In the omeprazole study, 27 of 29 randomized participants completed the study. Nine participants receiving mavacamten alone were normal metabolizers (NMs) of CYP2C19 substrates, and 6 were rapid metabolizers; 8 NMs and 6 rapid metabolizers received mavacamten + omeprazole. In both studies, mavacamten showed no safety signals and was generally well tolerated. Overall mavacamten exposure (area under the plasma concentration-time curve) increased by approximately 50% with omeprazole coadministration; maximum observed concentration (Cmax ), time to Cmax , and elimination half-life were not affected appreciably. In the verapamil study, 25 of 26 randomized participants received the study drug(s) and were included in the pharmacokinetic analyses; 24 completed the study. In the pharmacokinetic population, 12 participants received mavacamten alone (11 NMs, 1 poor metabolizer) and 13 received mavacamten + verapamil (7 NMs, 4 intermediate metabolizers, 2 poor metabolizers). Following verapamil coadministration in NMs and intermediate metabolizers, mavacamten area under the plasma concentration-time curve was minimally increased (by less than 20%), and Cmax was modestly increased (by 52%). These results suggest that mavacamten can be coadministered with weak CYP2C19 and moderate CYP3A4 inhibitors.

Physiologically Based Pharmacokinetic Modeling and Simulation of Mavacamten Exposure with Drug-Drug Interactions from CYP Inducers and Inhibitors by CYP2C19 Phenotype.

Mavacamten is a first-in-class, oral, selective, allosteric, reversible cardiac myosin inhibitor approved by the US Food and Drug Administration for the treatment of adults with symptomatic New York Heart Association functional class II-III obstructive hypertrophic cardiomyopathy. Mavacamten is metabolized in the liver, predominantly via cytochrome P450 (CYP) enzymes CYP2C19 (74%), CYP3A4 (18%), and CYP2C9 (8%). A physiologically-based pharmacokinetic (PBPK) model was developed using Simcyp version 19 (Certara, Princeton, NJ). Following model verification, the PBPK model was used to explore the effects of strong CYP3A4 and CYP2C19 inducers, and strong, moderate, and weak CYP2C19 and CYP3A4 inhibitors on mavacamten pharmacokinetics (PK) in a healthy population, with the effect of CYP2C19 phenotype predicted for poor, intermediate, normal, and ultrarapid metabolizers. The PBPK model met the acceptance criteria for all verification simulations (> 80% of model-predicted PK parameters within 2-fold of those observed clinically). A weak induction effect was predicted when mavacamten was administered with a strong CYP3A4 inducer in poor metabolizers. Moderate reductions in mavacamten exposure were predicted with a strong CYP2C19/CYP3A4 inducer in all CYP2C19 phenotypes. Except for the effect of strong CYP2C19 inhibitors on ultrarapid metabolizers, steady-state area under plasma concentration-time curve and maximum plasma concentration values were weakly affected (< 2-fold) or not affected (< 1.25-fold), regardless of CYP2C19 phenotype. In conclusion, a fit-for-purpose PBPK model was developed and verified, which accurately predicted the available clinical data and was used to simulate the potential impact of CYP induction and inhibition on mavacamten PKs, stratified by CYP2C19 phenotype.

Drug-Drug Interaction Potential of Mavacamten with Oral Contraceptives: Results from a Clinical Pharmacokinetic Study and a Physiologically Based Pharmacokinetic Model.

Mavacamten is a potential inducer of cytochrome P450 (CYP) 3A4 and, as such, could reduce the exposure of the active components of oral contraceptives, ethinyl estradiol (EE) and norethindrone (NOR), where CYP3A4 is involved in metabolism. This study assessed if repeat doses of mavacamten led to a drug-drug interaction with EE and/or NOR. This was an open-label study in healthy women. In Period 1, participants received 35 mcg of EE and 1 mg of NOR. In Period 2, participants received oral loading doses of mavacamten 25 mg on Days 1-2, 15 mg/day on Days 3-17, and 35 mcg of EE and 1 mg of NOR on Day 15. Plasma concentrations of mavacamten, EE, and NOR were obtained before dosing and up to 72 hours after dosing. For EE only, a physiologically based pharmacokinetic model was used to simulate mavacamten-mediated CYP3A4 induction with EE for various CYP2C19 phenotypes. In total, 13 women were enrolled (mean age, 38.9 [standard deviation, 9.65] years). After mavacamten administration, modest increases in area under the concentration-time curves were observed for both EE and NOR. The maximum concentrations and half-lives for EE and NOR were not affected by coadministration with mavacamten. Criteria for bioequivalence were met or nearly met for EE and NOR exposure with geometric mean ratios between 0.8 and 1.25. All adverse events were mild. The physiologically based pharmacokinetic model predicted a less than 15% decrease in EE exposure across CYP2C19 phenotypes. Coadministration of mavacamten at a therapeutically relevant dose with EE and NOR did not decrease the exposure to either EE or NOR to a level that may lead to reduced effectiveness.

Performance Verification of CYP2C19 Enzyme Abundance Polymorphism Settings within the Simcyp Simulator v21.

Physiologically based pharmacokinetic (PBPK) modeling has a number of applications, including assessing drug−drug interactions (DDIs) in polymorphic populations, and should be iteratively refined as science progresses. The Simcyp Simulator is annually updated and version 21 included updates to hepatic and intestinal CYP2C19 enzyme abundance, including addition of intermediate and rapid metabolizer phenotypes and changes to the ultra-rapid metabolizer enzyme abundance, with implications for population clearance and DDI predictions. This work details verification of the updates with sensitive CYP2C19 substrates, omeprazole and lansoprazole, using available clinical data from literature. Multiple assessments were performed, including recovery of areas under the concentration-time curve (AUC) and Cmax from compiled datasets for each drug, recovery of victim DDI ratios with CYP2C19 and/or CYP3A4 inhibition and recovery of relative exposure between phenotypes. Simulated data were within respective acceptance criteria for >80% of omeprazole AUC values, >70% of lansoprazole AUC and Cmax, >60% of AUC and Cmax DDI ratios and >80% of exposure ratios between different phenotypes. Recovery of omeprazole Cmax was lower (>50−70% within 2-fold) and possibly attributed to the variety of formulations used in the clinical dataset. Overall, the results demonstrated that the updated data used to parameterize CYP2C19 phenotypes reasonably described the pharmacokinetics of omeprazole and lansoprazole in genotyped or phenotyped individuals.

Plasma and cerebrospinal fluid pharmacokinetics of ondansetron in humans.

AIMS: Changes in serotonergic sensory modulation associated with overexpression of 5-HT3 receptors in the central nervous system (CNS) have been implicated in the pathophysiology of neuropathic pain after peripheral nerve damage. 5-HT3 receptor antagonists such as ondansetron can potentially alleviate neuropathic pain, but have limited effectiveness, due potentially to limited CNS access. However, there is currently limited information on CNS disposition of systemically-administered 5-HT3 receptor antagonists. This study evaluated the cerebrospinal fluid (CSF) disposition of ondansetron, as a surrogate of CNS penetration. METHODS: Fifteen patients were given a single 16 mg intravenous 15 minute infusion of ondansetron, followed by serial blood and a single CSF sampling. Population pharmacokinetic (PK) modelling was implemented to describe the average and individual plasma and CSF profiles of ondansetron. A two-compartmental model was used to capture ondansetron plasma PK with a single CSF compartment to describe distribution to the CNS. RESULTS: The individual model-estimated CSF to plasma partition coefficients of ondansetron were between 0.09 and 0.20. These values were mirrored in the calculated CSF penetration ratios, ranging from 0.08 to 0.26. CONCLUSIONS: After intravenous administration, CSF concentrations of ondansetron were approximately 7-fold lower than those observed in the plasma. A model could be developed to describe individual CSF concentration-time profiles of ondansetron based on a single CSF data point. The low CSF penetration of ondansetron may explain its limited analgesic effectiveness, and affords an opportunity to explore enhancing its CNS penetration for targeting conditions such as neuropathic pain.

Pharmacokinetic Modeling of the Impact of P-glycoprotein on Ondansetron Disposition in the Central Nervous System.

PURPOSE: Modulation of 5-HT3 receptor in the central nervous system (CNS) is a promising approach for treatment of neuropathic pain. The goal was to evaluate the role of P-glycoprotein (Pgp) in limiting exposure of different parts of the CNS to ondansetron (5-HT3 receptor antagonist) using wild-type and genetic knockout rat model. METHODS: Plasma pharmacokinetics and CNS (brain, spinal cord, and cerebrospinal fluid) disposition was studied after single 10 mg/kg intravenous dose. RESULTS: Pgp knockout resulted in significantly higher concentrations of ondansetron in all tested regions of the CNS at most of the time points. The mean ratio of the concentrations between KO and WT animals was 2.39-5.48, depending on the region of the CNS. Male and female animals demonstrated some difference in ondansetron plasma pharmacokinetics and CNS disposition. Mechanistic pharmacokinetic model that included two systemic disposition and three CNS compartments (with intercompartmental exchange) was developed. Pgp transport was incorporated as an efflux from the brain and spinal cord to the central compartment. The model provided good simultaneous description of all data sets, and all parameters were estimated with sufficient precision. CONCLUSIONS: The study provides important quantitative information on the role of Pgp in limiting ondansetron exposure in various regions of the CNS using data from wild-type and Pgp knockout rats. CSF drug concentrations, as a surrogate to CNS exposure, are likely to underestimate the effect of Pgp on drug penetration to the brain and the spinal cord.

Interspecies prediction of pharmacokinetics and tissue distribution of doxorubicin by physiologically-based pharmacokinetic modeling.

The aim of the study was to develop a physiologically-based pharmacokinetic (PBPK) model to describe and predict whole-body disposition of doxorubicin following intravenous administration. The PBPK model was established using previously published data in mice and included 10 tissue compartments: lungs, heart, brain, muscle, kidneys, pancreas, intestine, liver, spleen, adipose tissue, and plasma. Individual tissues were described by either perfusion-limited or permeability-limited models. All parameters were simultaneously estimated and the final model was able to describe murine data with good precision. The model was used for predicting doxorubicin disposition in rats, rabbits, dogs, and humans using interspecies scaling approaches and was qualified using plasma and tissue observed data. Reasonable prediction of the plasma pharmacokinetics and tissue distribution was achieved across all species. In conclusion, the PBPK model developed based on a rich dataset obtained from mice, was able to reasonably predict the disposition of doxorubicin in other preclinical species and humans. Applicability of the model for special populations, such as patients with hepatic impairment, was also demonstrated. The proposed model will be a valuable tool for optimization of exposure profiles of doxorubicin in human patients.

Is rat a good model for assessment of particulate-based taste-masked formulations?

Recently there has been an increased interest to develop specialised dosage forms that are better suited to specific patient populations, such as paediatrics and geriatrics. In these patient populations the acceptability of the oral dosage form can be paramount to the products success. However, many Active Pharmaceutical Ingredients (APIs) are known to cause an aversive taste response. One way to increase the acceptability and to enhance the palatability of the formulation is to design coated taste-masked particulate-based dosage forms. The masking of poorly tasting drugs with physical barriers such as polymer coatings can be utilised to prevent the release of drug within the oral cavity, thus preventing a taste response. However, currently, there are few assessment tools and models available to test the efficiency of these particulate-based taste-masked formulations. The rat brief access taste aversion model has been shown to be useful in assessment of taste for liquid dosage forms. However, the applicability of the rat model for particulate-based taste masked formulations is yet to be assessed. It is not understood whether dissolution, solubility and thus exposure of the drug to taste receptors would be the same in rat and human. Therefore, rat saliva must be compared to human saliva to determine the likelihood that drug release would be similar within the oral cavity for both species. In this study rat saliva was characterised for parameters known to be important for drug dissolution, such as pH, buffer capacity, surface tension, and viscosity. Subsequently dissolution of model bitter tasting compounds, sildenafil citrate and efavirenz, in rat saliva was compared to dissolution in human saliva. For all parameters characterised and for the dissolution of both drugs in rat saliva, a substantial difference was observed when compared to human saliva. This discrepancy in saliva parameters and dissolution of model drugs suggests that preclinical taste evaluation of particulate-based taste-masked formulations suggests rat is not a good model for predicting taste of solid dosage forms or undissolved drug where dissolution is required. Alternative preclinical in vivo models in other species, or improved biorelevant in vitro models should be considered instead.

Simultaneous quantification of ondansetron and tariquidar in rat and human plasma using a high performance liquid chromatography-ultraviolet method.

Ondansetron, a widely used antiemetic agent, is a P-glycoprotein (P-gp) substrate and therefore expression of P-gp at the blood-brain barrier limits its distribution to the central nervous system (CNS), which was observed to be reversed by coadministration with P-gp inhibitors. Tariquidar is a potent and selective third-generation P-gp inhibitor, and coadministration with ondansetron has shown improved ondansetron distribution to the CNS. There is currently no reported bioanalytical method for simultaneously quantifying ondansetron with a third-generation P-gp inhibitor. Therefore, we aimed to develop and validate a method for ondansetron and tariquidar in rat and human plasma samples. A full validation was performed for both ondansetron and tariquidar, and sample stability was tested under various storage conditions. To demonstrate its utility, the method was applied to a preclinical pharmacokinetic study following coadministration of ondansetron and tariquidar in rats. The presented method will be valuable in pharmacokinetic studies of ondansetron and tariquidar in which simultaneous determination may be required. In addition, this is the first report of a bioanalytical method validated for quantification of tariquidar in plasma samples.

Lipophilic activated ester prodrug approach for drug delivery to the intestinal lymphatic system.

The intestinal lymphatic system plays an important role in the pathophysiology of multiple diseases including lymphomas, cancer metastasis, autoimmune diseases, and human immunodeficiency virus (HIV) infection. It is thus an important compartment for delivery of drugs in order to treat diseases associated with the lymphatic system. Lipophilic prodrug approaches have been used in the past to take advantage of the intestinal lymphatic transport processes to deliver drugs to the intestinal lymphatics. Most of the approaches previously adopted were based on very bulky prodrug moieties such as those mimicking triglycerides (TG). We now report a study in which a lipophilic prodrug approach was used to efficiently deliver bexarotene (BEX) and retinoic acid (RA) to the intestinal lymphatic system using activated ester prodrugs. A range of carboxylic ester prodrugs of BEX were designed and synthesised and all of the esters showed improved association with chylomicrons, which indicated an improved potential for delivery to the intestinal lymphatic system. The conversion rate of the prodrugs to BEX was the main determinant in delivery of BEX to the intestinal lymphatics, and activated ester prodrugs were prepared to enhance the conversion rate. As a result, an 4-(hydroxymethyl)-1,3-dioxol-2-one ester prodrug of BEX was able to increase the exposure of the mesenteric lymph nodes (MLNs) to BEX 17-fold compared to when BEX itself was administered. The activated ester prodrug approach was also applied to another drug, RA, where the exposure of the MLNs was increased 2.4-fold through the application of a similar cyclic activated prodrug. Synergism between BEX and RA was also demonstrated in vitro by cell growth inhibition assays using lymphoma cell lines. In conclusion, the activated ester prodrug approach results in efficient delivery of drugs to the intestinal lymphatic system, which could benefit patients affected by a large number of pathological conditions.

The Effect of Small Oligomeric Protein Aggregates on the Immunogenicity of Intravenous and Subcutaneous Administered Antibodies.

The role of aggregates in the immunogenicity of biologics is a major concern. A recent US FDA guidance on the issue suggests that a gap in knowledge exists regarding the type and size of aggregates involved in the immunogenicity of biologics. Furthermore, the guidance suggests that current techniques cannot capture the crucial stages of protein aggregation. Using a protein unfolding model developed earlier, we generated and classified aggregates of two therapeutic antibodies based on size and conformation. The immunogenic potential of these aggregates were then tested in a murine model. Our findings show that small native-like oligomeric aggregates (<100 nm) are more immunogenic toward the native protein than monomer and large non-native aggregates in the micron-size range, irrespective of route of administration [intravenous (i.v.) vs. subcutaneous (s.c.)]. Those smaller oligomeric aggregates represented 5%-20% of the total protein concentration in the test formulations. Furthermore, in vitro data suggest that TNF-α production by bone marrow-derived dendritic cells could serve as a predictive marker for increased immunogenic risk of aggregates after s.c. administration. The use of orthogonal techniques such as fluorescence anisotropy and quasielastic light scattering may be useful to detect these oligomeric aggregates.