Pharmacokinetic Interactions Between the Fixed-Dose Combination of Ezetimibe/Rosuvastatin 10/20 Mg and the Fixed-Dose Combination of Telmisartan/Amlodipine 80/5 Mg in Healthy Subjects.

Background: Management of hypertension and hyperlipidemia, which are common comorbid risk factors for cardiovascular diseases, require multiple medications. The development of a fixed-dose combination (FDC) containing ezetimibe, rosuvastatin, telmisartan, and amlodipine aims to enhance patient adherence and persistence, but the potential interactions among the four medications have not been studied. This study aimed to evaluate the pharmacokinetic (PK) interactions between the FDC of ezetimibe/rosuvastatin 10/20 mg (ER) and the FDC of telmisartan/amlodipine 80/5 mg (TA). Methods: An open-label, single-sequence, three-period, three-treatment crossover study was conducted in healthy male subjects. All subjects received ER for 7 days, TA for 9 days and ER combined with TA for 7 days during each treatment period. For PK analysis of total/free ezetimibe, rosuvastatin, telmisartan, and amlodipine, serial blood samples were collected for 24 hours at steady state. Safety profiles were assessed throughout the study. Results: Thirty-eight subjects were enrolled, and 34 subjects completed the study. The systemic exposure to each active ingredient after coadministration of the two FDCs was similar to that after each FDC alone. The geometric mean ratios and 90% confidence intervals for the maximum plasma concentration (µg/L) and the area under the plasma concentration-time curve (h·µg/L) of the combination therapy to monotherapy, assessed at steady state, were as follows: total ezetimibe, 1.0264 (0.8765-1.2017) and 0.9359 (0.7847-1.1163); free ezetimibe, 1.5713 (1.2821-1.9257) and 0.9941 (0.8384-1.1788); rosuvastatin, 2.1673 (1.7807-2.6379) and 1.1714 (0.9992-1.3733); telmisartan, 1.0745 (0.8139-1.4186) and 1.1057 (0.8379-1.4591); and amlodipine, 0.9421 (0.8764-1.0126) and 0.9603 (0.8862-1.0405). Both combination therapy and monotherapy were well tolerated by the subjects. Conclusion: The coadministration of ezetimibe/rosuvastatin 10/20 mg and ezetimibe/rosuvastatin 10/20 mg was well tolerated in healthy subjects, and the PK interaction between those two FDCs was not clinically significant.

Phase 1b study to assess the safety, tolerability, and clinical activity of pamiparib in combination with temozolomide in patients with locally advanced or metastatic solid tumors.

BACKGROUND: Pamiparib is a potent, selective, poly (ADP-ribose) polymerase 1/2 inhibitor that demonstrates synthetic lethality in cells with breast cancer susceptibility gene mutations or other homologous recombination deficiency. This two-stage phase 1b study (NCT03150810) assessed pamiparib in combination with temozolomide (TMZ) in adult patients with histologically confirmed locally advanced and metastatic solid tumors. METHODS: Oral pamiparib 60 mg was administered twice daily. During the dose-escalation stage, increasing doses of TMZ (40-120 mg once daily pulsed or 20-40 mg once daily continuous) were administered to determine the recommended dose to be administered in the dose-expansion stage. The primary objectives were to determine safety and tolerability, maximum tolerated/administered dose, recommended phase 2 dose and schedule, and antitumor activity of pamiparib in combination with TMZ. Pharmacokinetics of pamiparib and TMZ and biomarkers were also assessed. RESULTS: Across stages, 139 patients were treated (dose escalation, n = 66; dose expansion, n = 73). The maximum tolerated dose of TMZ, which was administered during dose expansion, was 7-day pulsed 60 mg once daily. The most common treatment-emergent adverse events (TEAEs) were anemia (dose escalation, 56.1%; dose expansion, 63.0%), nausea (dose escalation, 54.5%; dose expansion, 49.3%), and fatigue (dose escalation, 48.5%; dose expansion, 47.9%). In the dose-escalation stage, four patients experienced dose-limiting toxicities (three neutropenia and one neutrophil count decreased). No TEAEs considered to be related to study drug treatment resulted in death. Antitumor activity was modest, indicated by confirmed overall response rate (dose escalation, 13.8%; dose expansion, 11.6%), median progression-free survival (3.7 and 2.8 months), and median overall survival (10.5 and 9.2 months). Administration of combination therapy did not notably impact pamiparib or TMZ pharmacokinetics. CONCLUSIONS: Pamiparib in combination with TMZ had a manageable safety profile. Further investigation of the efficacy of this combination in tumor types with specific DNA damage repair deficiencies is warranted.

Solid dispersion systems for enhanced dissolution of poorly water-soluble candesartan cilexetil: In vitro evaluation and simulated pharmacokinetics studies.

BACKGROUND: Candesartan cilexetil (CC) is a selective angiotensin II receptor antagonist widely used to treat hypertension. CC is a substrate of P-glycoprotein (P-gp), causing its efflux to the intestinal lumen. It is also practically insoluble in water and has low oral bioavailability (14%). Thus, the current study aims to improve the in vitro dissolution of CC by developing solid dispersion systems (SDSs) and corroborating the in vitro results using a simulated pharmacokinetics study. METHODS: The SDSs were prepared using polyvinyl pyrrolidone (PVP) as a water-soluble polymer, Eudragit E100 (EE100) as a pH-dependent soluble carrier, and a combination of these two polymers. The saturation solubility and the dissolution rate studies of the prepared systems in three dissolution media were performed. The optimized system SE-EE5 was selected for further investigations, including DSC, XRD, FTIR, FESEM, DLS, TSEM, IVIVC convolution study, and stability studies. RESULTS: The solubility of CC significantly increased by a factor of 27,037.344 when formulated as a solid dispersion matrix using EE100 at a ratio of 1:5 (w/w) drug to polymer (SE-EE5 SD), compared to the solubility of the pure drug. The mechanism of solubility and dissolution rate enhancement of CC by the optimized SDS was found to be via the conversion of the crystalline CC into the amorphous form as well as nanoparticles formation upon dissolution at a pH below 5. The instrumental analysis tests showed good compatibility between CC and EE100 and there was no chemical interaction between the drug and the polymer. Moreover, the stability tests confirmed that the optimized system was stable after three months of storage at 25°C. CONCLUSION: The utilization of the solid dispersion technique employing EE 100 polymer as a matrix demonstrates significant success in enhancing the solubility, dissolution, and subsequently, the bioavailability of water-insoluble drugs like CC.

Pharmacokinetic Comparison of a Fixed-Dose Combination of Candesartan Cilexetil/Amlodipine/Atorvastatin Versus Co-administration of Individual Formulations in Healthy Participants.

INTRODUCTION: Fixed-dose combinations (FDCs) of angiotensin II receptor blockers, calcium channel blockers, and statins are conventional therapeutic interventions prescribed for cardiovascular diseases. This study aimed at drawing a comparison between the pharmacokinetics and safety of an FDC and the corresponding individual formulations in healthy subjects. METHODS: A randomized, open-label, single-dose, three-sequence, three-period, partially repeated crossover study was conducted with a cohort of healthy volunteers. A 14-day washout period was maintained between each of the three periods. In this study, candesartan cilexetil, amlodipine, and atorvastatin was administered orally as FDCs of 16/10/40 mg in study 1 and 16/5/20 mg in study 2. The maximum plasma concentration (Cmax) and area under the plasma concentration-time curve from time zero to the time of the last quantifiable concentration (AUClast) of candesartan, amlodipine, and atorvastatin were estimated as the geometric mean ratios (GMRs) and 90% confidence intervals (CIs) of the FDC to individual formulations. If the within-subject coefficient of variation (CVwr) of Cmax was greater than 0.3, the bioequivalence (BE) range calculated using the reference-scaled average bioequivalence was used to assess whether the 90% CI was within the BE range. RESULTS: The GMRs (90% CIs) for the AUClast for candesartan and amlodipine were 0.9612 (0.9158-1.0089)/0.9965 (0.9550-1.0397) and 1.0033 (0.9800-1.0271)/1.0067 (0.9798-1.0344), and the GMRs (90% CIs) for Cmax were 0.9600 (0.8953-1.0294)/0.9851 (0.9368-1.0359) and 1.0198 (0.9950-1.0453)/1.0003 (0.9694-1.0321) in studies 1 and 2, respectively. The extended BE ranges calculated from the CVwr of the Cmax of atorvastatin were 0.7814-1.2797 and 0.7415-1.3485, respectively. The GMRs (90% CIs) for the AUClast of atorvastatin were 1.0532 (1.0082-1.1003)/1.0252 (0.9841-1.0680), and the GMRs (90% CIs) for Cmax were 1.0630 (0.9418-1.1997)/0.9888 (0.8792-1.1120) in studies 1 and 2, respectively. CONCLUSION: The Cmax and AUClast values of candesartan cilexetil/amlodipine/atorvastatin 16/10/40 mg and 16/5/20 mg, respectively, were within the BE ranges. There were no clinically significant differences in safety between the two formulations. TRIAL REGISTRATION: ClinicalTrials.gov identifier, study 1: NCT04478097; study 2: NCT04627207.

Impact of P-gp inhibition on systemic exposure of pralsetinib and dosing considerations.

A study to determine the impact of cyclosporine (Neoral), an inhibitor of P-gp, on the pharmacokinetics of pralsetinib (trade name GAVRETO®) was conducted in 15 healthy adult volunteers. A single 200 mg dose of pralsetinib was administered orally alone and in combination with cyclosporine with a 9-day washout between treatments. Co-administration with cyclosporine resulted in a clinically relevant increase in pralsetinib maximum plasma concentration (Cmax) and area under the plasma concentration-time curve extrapolated to infinity (AUC0-∞) with associated geometric mean ratios (GMRs) and 90% confidence intervals (CIs) of 148% (109, 201) and 181% (136, 241), respectively. These findings provide insight into concomitant dosing of pralsetinib with inhibitors of P-gp given the increases in pralsetinib exposure observed when administered with cyclosporine. Based on these results, co-administration of pralsetinib with P-gp inhibitors is not recommended. In the event that co-administration cannot be avoided, it is recommended that the dose of pralsetinib be reduced.

A Population Pharmacokinetic Assessment of the Effect of Food on Selumetinib in Patients with Neurofibromatosis Type 1-Related Plexiform Neurofibromas and Healthy Volunteers.

Selumetinib is clinically used for pediatric patients with neurofibromatosis type 1 and symptomatic, inoperable plexiform neurofibromas. Until recently, selumetinib had to be taken twice daily, after 2 hours of fasting and followed by 1 hour of fasting, which could be inconvenient. This population analysis evaluated the effect of low- and high-fat meals on the pharmacokinetic (PK) parameters of selumetinib and its active metabolite N-desmethyl selumetinib. The dataset comprised 511 subjects from 15 clinical trials who received ≥1 dose of selumetinib and provided ≥1 measurable postdose concentration of selumetinib and N-desmethyl selumetinib. A 2-compartment model with sequential 0- and 1st-order delayed absorption and 1st-order elimination adequately described selumetinib PK characteristics. A 1-compartment model reasonably described N-desmethyl selumetinib PK characteristics over time simultaneously with selumetinib. Selumetinib geometric mean area under the concentration-time curve ratio (1-sided 90% confidence interval [CI] lower bound) was 76.9% (73.3%) with a low-fat meal and 79.3% (76.3%) with a high-fat meal versus fasting. The lower bound of the 1-sided 90% CI demonstrated a difference of <30% between fed and fasted states. Considering the flat exposure-response relationship within the dose range (20-30 mg/m2), the observed range of exposure, and the variability in the SPRINT trial, this was not considered clinically relevant.

Human metabolism of four synthetic benzimidazole opioids: isotonitazene, metonitazene, etodesnitazene, and metodesnitazene.

Following isotonitazene scheduling in 2019, the availability of alternative 2-benzylbenzimidazole opioids (nitazenes) on the global drug market increased, resulting in many fatalities worldwide. Nitazenes are potent µ-opioid receptor agonists with strong narcotic/analgesic effects, and their concentrations in biological matrices are low, making the detection of metabolite biomarkers of consumption crucial to document use in clinical and forensic settings. However, there is little to no data on the metabolism of the most recently available nitazenes, especially desnitro-analogues. The aim of the research was to assess isotonitazene, metonitazene, etodesnitazene, and metodesnitazene human metabolism and identify specific metabolite biomarkers of consumption. The four analogues were incubated with 10-donor-pooled human hepatocytes, and the incubates were analyzed by liquid chromatography-high-resolution tandem mass spectrometry and data mining with Compound Discoverer (Thermo Scientific); the analysis was supported by in silico metabolite predictions with GLORYx open-access software. Metabolites were identified in postmortem blood and/or urine samples from two metonitazene-positive and three etodesnitazene-positive cases following the same workflow, with and without glucuronide hydrolysis in urine, to confirm in vitro results. Twelve, nine, twenty-two, and ten metabolites were identified for isotonitazene, metonitazene, etodesnitazene, and metodesnitazene, respectively. The main transformations were N-deethylation at the N,N-diethylethanamine side chain, O-dealkylation, and further O-glucuronidation. In vitro and autopsy results were consistent, demonstrating the efficacy of the 10-donor-pooled human hepatocyte model to predict human metabolism. We suggest the parent and the corresponding O-dealkyl- and N-deethyl-O-dealkyl metabolites as biomarkers of exposure in urine after glucuronide hydrolysis, and the corresponding N-deethyl metabolite as additional biomarker in blood.

A phase 1 trial of the MEK inhibitor selumetinib in combination with pembrolizumab for advanced or metastatic solid tumors.

MEK inhibitors have immunomodulatory activity and potential for synergistic activity when combined with PD-1 inhibitors. We evaluated selumetinib (inhibitor of MEK1/2) plus pembrolizumab (anti‒PD-1 antibody) in patients with advanced/metastatic solid tumors. In this phase 1b study, adults with previously treated advanced/metastatic solid tumors received pembrolizumab 200 mg intravenously every 3 weeks plus selumetinib on days 1‒14 per 3-week cycle (2 weeks on/1 week off); selumetinib dosing began at 50 mg orally twice daily with escalation in 25 mg increments for ≤ 35 cycles. Primary endpoints were dose-limiting toxicities (DLTs), adverse events (AEs), and treatment discontinuations due to AEs. Thirty-two patients were enrolled. Dose escalation was completed up to selumetinib 125 mg twice daily. The target DLT rate of 30% was not reached at any dose level. In the selumetinib 100 mg group, 2/11 patients (18.2%) experienced DLTs (n = 1 grade 3 diarrhea, n = 1 grade 3 fatigue). In the selumetinib 125 mg group, 3/14 (21.4%) experienced DLTs (n = 1 grade 2 retinal detachment, n = 1 grade 3 retinopathy, n = 1 grade 3 stomatitis). Dose-related changes in pharmacokinetic exposures were observed for selumetinib and N-desmethyl selumetinib up to 100 mg (saturation at 125 mg). Two patients achieved partial responses (1 each with selumetinib 75 mg and 125 mg) for an objective response rate of 6%. The study was stopped early because of insufficient efficacy. Although the target DLT rate was not reached at any dose level and no new safety signals were identified, selumetinib plus pembrolizumab had limited antitumor activity in this population. Trial registration: ClinicalTrials.gov , NCT03833427.

Role of Bilastine in Allergic Rhinitis: A Narrative Review.

Allergic rhinitis (AR) is considered a trivial disease and is often self-treated with over-the-counter drugs and home remedies. However, AR is a contributing risk factor for asthma associated with complications, including chronic cough, eosinophilic esophagitis, and otitis media with effusion. In AR, inflammation is primarily mediated by histamines. Guidelines advise using second-generation oral H1 antihistamines as the primary treatment for AR. Second-generation H1 antihistamines strongly prefer the H1 receptor, limiting their ability to enter the central nervous system. Thus, they have minimal adverse effects. Among these H1 antihistamines, bilastine is highly specific for H1 receptors with a slight affinity for other receptors. It has a rapid and prolonged action, which reduces the need for frequent dosing and has better compliance. In the long term, bilastine is well-tolerated with minimal adverse effects. It is not associated with drug interactions, so dosage adjustment is unnecessary. Bilastine does not penetrate the brain and is nonsedating at 80 mg once daily. The low possibility of drug-drug interactions and pharmacokinetics of bilastine makes it suitable for elderly patients, even with compromised hepatic and renal function, without dose adjustment. This review comprehensively discusses the guidelines and the role of bilastine in treating AR. How to cite this article: Tiwaskar M, Vora A, Tewary K, et al. Role of Bilastine in Allergic Rhinitis: A Narrative Review. J Assoc Physicians India 2023;71(11):58-61.

Statins Increase the Bioavailability of Fixed-Dose Combination of Sofosbuvir/Ledipasvir by Inhibition of P-glycoprotein.

BACKGROUND: Coadministration of statins and direct acting antiviral agents is frequently used. This study explored the effects of both atorvastatin and lovastatin on pharmacokinetics of a fixed-dose combination of sofosbuvir/ledipasvir "FDCSL". METHODS: 12 healthy volunteers participated in a randomized, three-phase crossover trial and were administered a single atorvastatin dose 80 mg plus tablet containing 400/90 mg FDCSL, a single lovastatin dose 40 mg plus tablet containing 400/90 mg FDCSL, or tablets containing 400/90 mg FDCSL alone. Liquid chromatography-tandem mass spectrometry was used to analyze plasma samples of sofosbuvir, ledipasvir and sofosbuvir metabolite "GS-331007" and their pharmacokinetic parameters were determined. RESULTS: Atorvastatin caused a significant rise in sofosbuvir bioavailability as explained by increasing in AUC0-∞ and Cmax by 34.36% and 11.97%, respectively. In addition, AUC0-∞ and Cmax of GS-331007 were increased by 73.73% and 67.86%, respectively after atorvastatin intake. Similarly, co-administration of lovastatin with FDCSL increased the bioavailability of sofosbuvir, its metabolite (AUC0-∞ increase by 17.2%, 17.38%, respectively, and Cmax increase by 12.03%, 22.24%, respectively). However, neither atorvastatin nor lovastatin showed a change in ledipasvir bioavailability. Hepatic elimination was not affected after statin intake with FDCSL. Compared to lovastatin, atorvastatin showed significant increase in AUC0-∞ and Cmax of both sofosbuvir and its metabolite. CONCLUSIONS: Both atorvastatin and lovastatin increased AUC of sofosbuvir and its metabolite after concurrent administration with FDCSL. Statins' P-glycoprotein inhibition is the attributed mechanism of interaction. The increase in sofosbuvir bioavailability was more pronounced after atorvastatin intake. Close monitoring is needed after co-administration of atorvastatin and FDCSL.

Effects of ABCB1 and ABCG2 polymorphisms on the pharmacokinetics of abemaciclib.

PURPOSE: Adverse events after the use of the CDK4/6 inhibitor abemaciclib are dose-dependent. However, its pharmacokinetics varies among individuals. Abemaciclib is reportedly transported by P-glycoprotein and breast cancer resistance protein. Therefore, we evaluated whether ABCB1 and ABCG2 polymorphisms are pharmacokinetic predictive factors of abemaciclib. METHODS: A total of 45 patients with breast cancer taking abemaciclib (150 mg twice per day) for 2 weeks were evaluated to determine the associations among abemaciclib concentration; adverse events; and ABCB1 1236 T > C, 2677G > T/A, 3435C > T, and ABCG2 421C > A gene polymorphisms. RESULTS: The trough concentration of abemaciclib was significantly higher in the group with grade 2 or greater neutropenia and thrombocytopenia than in those with grades 0 or 1. For ABCB1 2677G > T/A polymorphisms, the concentration of abemaciclib tended to be higher in the homozygous group (TT + AT) than in the wild-type + heterozygous group (GG + GA + GT) (median [range], 222.8 [80.5-295.8] ng/mL vs. 113.5 [23.6-355.2] ng/mL, P = 0.09), Moreover, the ABCB1 2677G > T/A homozygous group had a higher tendency of abemaciclib withdrawal or dose reduction within 4 weeks than the wild-type + heterozygous group (odds ratio, 4.22; 95% confidence interval, 0.86-20.7; P = 0.08). No significant association was observed among abemaciclib concentration; adverse reactions; and ABCB1 1236 T > C, 3435C > T, and ABCG2 421C > A polymorphisms. CONCLUSION: ABCB1 2677G > T/A polymorphism might be a predictor of the pharmacokinetics and tolerability of abemaciclib.

Identification of the Benzoimidazole Compound as a Selective FLT3 Inhibitor by Cell-Based High-Throughput Screening of a Diversity Library.

Internal tandem duplication in the FLT3 receptor tyrosine kinase (FLT3/ITD mutation) occurs in approximately 25% of acute myeloid leukemia (AML) patients. To specifically target this driver mutation in AML, we assessed and compared the cell-based cytotoxicity of a diversity library (10,000 compounds) against the normal cell line BaF3 and the isogenic leukemic cell line BaF3/ITD. A benzoimidazole scaffold-based compound (HP1142) was identified as the most selective compound against a series of murine and human leukemia cells with FLT3/ITD. Novel benzoimidazole compounds were further designed to improve the aqueous solubility of HP1142. The most potent compound, HP1328, demonstrated desirable pharmaceutical and pharmacokinetic properties. Treatment with HP1328 significantly reduced the leukemia burden and prolonged the survival of mice with FLT3/ITD leukemia. Our findings establish the specific activity of the benzoimidazole compound against FLT3/ITD leukemia and warrant further investigation in this subset of leukemia patients with poor prognosis.

A Vaccine against Benzimidazole-Derived New Psychoactive Substances That Are More Potent Than Fentanyl.

New psychoactive substance (NPS) opioids have proliferated within the international drug market. While synthetic opioids are traditionally composed of fentanyl analogues, benzimidazole-derived isotonitazene and its derivatives are the current NPS opioids of concern. Hence, in this study, we implement immunopharmacotherapy wherein antibodies are produced with high titers and nanomolar affinity to multiple benzimidazole-derived NPS opioids (BNO). Notably, these antibodies blunt psychoactive and physiological repercussions from BNO exposure, which was observed through antinociception, whole-body plethysmography, and blood-brain biodistribution studies. Moreover, we detail previously unreported pharmacokinetics of these drugs, which explains the struggle of traditional pharmaceutical opioid antagonists against BNO substances. These findings provide further insight into the in vivo effects of BNO drugs and the development of effective broad-spectrum therapeutics against NPS opioids.

A phase I study of veliparib with cyclophosphamide and veliparib combined with doxorubicin and cyclophosphamide in advanced malignancies.

PURPOSE: Veliparib (V), an oral poly(ADP-ribose) polymerase (PARP) inhibitor, potentiates effects of alkylating agents and topoisomerase inhibitors in preclinical tumor models. We conducted a phase I trial of V with iv cyclophosphamide (C) and V plus iv doxorubicin (A) and C. METHODS: Objectives were to establish the maximum tolerated dose (MTD) of the combinations, characterize V pharmacokinetics (PK) in the presence and absence of C, measure PAR in peripheral blood mononuclear cells (PBMCs) and γH2AX in circulating tumor cells (CTCs). In Group 1, dose escalations of V from 10 to 50 mg every 12 h Days 1-4 plus C 450 to 750 mg/m2 Day 3 in 21-day cycles were evaluated. In Group 2, V doses ranged from 50 to 150 mg every 12 h Days 1-4 with AC (60/600 mg/m2) Day 3 in 21-day cycles. In Group 3, patients received AC Day 1 plus V Days 1-7, and in Group 4, AC Day 1 plus V Days 1-14 was given in 21-day cycles to evaluate effects on γH2AX foci. RESULTS: Eighty patients were enrolled. MTD was not reached for V and C. MTD for V and AC was V 100 mg every 12 h Days 1-4 with AC (60/600 mg/m2) Day 3 every 21 days. V PK appears to be dose-dependent and has no effect on the PK of C. Overall, neutropenia and anemia were the most common adverse events. Objective response in V and AC treated groups was 22% (11/49). Overall clinical benefit rate was 31% (25/80). PAR decreased in PBMCs. Percentage of γH2AX-positive CTCs increased after treatment with V and AC. CONCLUSION: V and AC can be safely combined. Activity was observed in patients with metastatic breast cancer.

Population Pharmacokinetic-Pharmacodynamic Model of Oxfendazole in Healthy Adults in a Multiple Ascending Dose and Food Effect Study and Target Attainment Analysis.

Oxfendazole is a potent veterinary antiparasitic drug undergoing development for human use to treat multiple parasitic infections. Results from two recently completed phase I clinical trials conducted in healthy adults showed that the pharmacokinetics of oxfendazole is nonlinear, affected by food, and, after the administration of repeated doses, appeared to mildly affect hemoglobin concentrations. To facilitate oxfendazole dose optimization for its use in patient populations, the relationship among oxfendazole dose, pharmacokinetics, and hemoglobin concentration was quantitatively characterized using population pharmacokinetic-pharmacodynamic modeling. In fasting subjects, oxfendazole pharmacokinetics was well described by a one-compartment model with first-order absorption and elimination. The change in oxfendazole pharmacokinetics when administered following a fatty meal was captured by an absorption model with one transit compartment and increased bioavailability. The effect of oxfendazole exposure on hemoglobin concentration in healthy adults was characterized by a life span indirect response model in which oxfendazole has positive but minor inhibitory effect on red blood cell synthesis. Further simulation indicated that oxfendazole has a low risk of posing a safety concern regarding hemoglobin concentration, even at a high oxfendazole dose of 60 mg/kg of body weight once daily. The final model was further used to perform comprehensive target attainment simulations for whipworm infection and filariasis at various dose regimens and target attainment criteria. The results of our modeling work, when adopted appropriately, have the potential to greatly facilitate oxfendazole dose regimen optimization in patient populations with different types of parasitic infections.

LC-MS/MS bioanalytical method for quantification of binimetinib and venetoclax, and their pharmacokinetic interaction.

Aim: Because of several prospective benefits, binimetinib (BMT)-venetoclax (VTC) combination can be a better therapeutic strategy to treat cancer. Results: An LC-MS/MS method for simultaneous quantification of BMT and VTC in rat plasma has been developed and validated. Specificity, accuracy, precision and stability results met the acceptance criteria for validation. Accuracy and precisions at all quality control levels were <15%. The study revealed that co-administration of BMT and VTC has no significant effect on their pharmacokinetics. Conclusion: The developed method can provide accurate results for quantification of BMT and VTC over the range of 5-500 ng/ml. The reported pharmacokinetic interaction study results will be useful for future consideration of the combined treatment of BMT and VTC in anticancer chemotherapy regimens.

A Rapid and Sensitive Liquid Chromatography-Tandem Mass Spectrometry Bioanalytical Method for the Quantification of Encorafenib and Binimetinib as a First-Line Treatment for Advanced (Unresectable or Metastatic) Melanoma-Application to a Pharmacokinetic Study.

The combination regimen targeting BRAF and MEK inhibition, for instance, encorafenib (Braftovi™, ENF) plus binimetinib (Mektovi®, BNB), are now recommended as first-line treatment in patients with unresectable or metastatic melanoma with a BRAF V600-activating mutation. Patients treated with combination therapy of ENF and BNB demonstrated a delay in resistance development, increases in antitumor activity, and attenuation of toxicities compared with the activity of either agent alone. However, the pharmacokinetic profile of the FDA-approved ENF and BNB is still unclear. In this study, a rapid and sensitive LC-MS/MS bioanalytical method for simultaneous quantification of ENF and BNB in rat plasma was developed and validated. Chromatography was performed on an Agilent Eclipse plus C18 column (50 mm × 2.1 mm, 1.8 µm), with an isocratic mobile phase composed of 0.1% formic acid in water/acetonitrile (67:33, v/v, pH 3.2) at a flow rate of 0.35 mL/min. A positive multiple reaction monitoring (MRM) mode was chosen for detection and the process of analysis was run for 2 min. Plasma samples were pre-treated using protein precipitation with acetonitrile containing spebrutinib as the internal standard (IS). Method validation was assessed as per the FDA guidelines for the determination of ENF and BNB over concentration ranges of 0.5-3000 ng/mL (r2 ≥ 0.997) for each drug (plasma). The lower limits of detection (LLOD) for both drugs were 0.2 ng/mL. The mean relative standard deviation (RSD) of the results for accuracy and precision was ≤ 7.52%, and the overall recoveries of ENF and BNB from rat plasma were in the range of 92.88-102.28%. The newly developed approach is the first LC-MS/MS bioanalytical method that can perform simultaneous quantification of ENF and BNB in rat plasma and its application to a pharmacokinetic study. The mean result for Cmax for BNB and ENF was found to be 3.43 ± 0.46 and 16.42 ± 1.47 µg/mL achieved at 1.0 h for both drugs, respectively. The AUC0-∞ for BNB and ENF was found to be 18.16 ± 1.31 and 36.52 ± 3.92 µg/mL.h, respectively. On the other hand, the elimination half-life (t1/2kel) parameters for BNB and ENF in the rat plasma were found to be 3.39 ± 0.43 h and 2.48 ± 0.24 h, and these results are consistent with previously reported values.

Physiologically based pharmacokinetic modeling of candesartan related to CYP2C9 genetic polymorphism in adult and pediatric patients.

Candesartan cilexetil is an angiotensin II receptor blocker and it is widely used to treat hypertension and heart failure. This drug is a prodrug that rapidly converts to candesartan after oral administration. Candesartan is metabolized by cytochrome P450 2C9 (CYP2C9) enzyme or uridine diphosphate glucurinosyltransferase 1A3, or excreted in an unchanged form through urine, biliary tract and feces. We investigated the effect of genetic polymorphism of CYP2C9 enzyme on drug pharmacokinetics using physiologically based pharmacokinetic (PBPK) modeling. In addition, by introducing the age and ethnicity into the model, we developed a model that can propose an appropriate dosage regimen taking into account the individual characteristics of each patient. To evaluate the suitability of the model, the results of a clinical trial on twenty-two healthy Korean subjects and their CYP2C9 genetic polymorphism data was applied. In this study, PK-Sim® was used to develop the PBPK model of candesartan.

Elucidation of Metabolic and Disposition Pathways for Maribavir in Nonhuman Primates through Mass Balance and Semi-Physiologically Based Modeling Approaches.

Maribavir is in phase 3 clinical development for treatment of cytomegalovirus infection/disease in transplant recipients. Previous research conducted using only intact cynomolgus monkeys indicated biliary secretion as the primary elimination pathway for maribavir and that maribavir undergoes enterohepatic recirculation (EHR). To clarify the exact mechanisms of maribavir's EHR behavior, we studied its clearance pathways using intravenously administered 14C-labeled maribavir in intact and bile duct-cannulated (BDC) monkeys and constructed a semi-physiologically based pharmacokinetic (PBPK) model. Total radioactivity metabolite profiles in plasma and excreta were quantitatively determined along with plasma maribavir concentrations. Intact animals showed significantly lower clearance and longer half-lives in both total radioactivity and parent concentration in plasma than BDC monkeys. The primary in vitro and in vivo metabolic pathway for maribavir in monkey is direct glucuronidation; N-dealkylation and renal clearance are minor pathways. In BDC monkeys, 73% of dose was recovered as maribavir glucuronides in bile, and 3% of dose was recovered as parent in bile and feces; in intact animals' feces, 58% of dose was recovered as parent, and no glucuronides were detected. Therefore, EHR of maribavir occurs through biliary secretion of maribavir glucuronides, and this is followed by hydrolysis of glucuronides in the gut lumen and subsequent reabsorption of parent. A semi-PBPK model constructed from physiologic, in vitro, and in vivo BDC monkey data is capable of projecting maribavir's pharmacokinetic and EHR behavior in intact animals after intravenous or oral dosing and could be applied to modeling other xenobiotics that are subject to similar EHR processes. SIGNIFICANCE STATEMENT: Through both mass balance and semi-physiologically based pharmacokinetic (semi-PBPK) modeling approaches, this study mechanistically and quantitatively elucidates maribavir's enterohepatic recirculation (EHR) behavior in monkeys, which occurs via extensive direct glucuronidation, biliary secretion of these glucuronides, luminal hydrolysis of glucuronides to parent, and subsequent reabsorption of the parent. The study also identifies important drug- and animal-specific parameters that determine the EHR kinetics, and the semi-PBPK model is readily applicable to other drugs that undergo similar metabolic and recirculation mechanisms.