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Gefapixant, a P2X3 receptor antagonist, has demonstrated efficacy in patients with refractory or unexplained chronic cough. We investigated the effect of renal impairment (RI) on the pharmacokinetics (PK) of gefapixant 50 mg in an open-label, single-dose study enrolling participants with moderate (n = 6) or severe (n = 6) RI, end-stage renal disease (ESRD; n = 6) under hemodialysis (HD) and non-HD conditions, and healthy matched controls (n = 6). Serial plasma and urine samples for gefapixant concentrations were collected at selected time points over 72 and 48 hours after dosing, respectively. Linear regression analysis predicted a 1.87-, 2.79-, and 3.76-fold higher exposure (area under the plasma concentration-time curve) for participants with mild, moderate, and severe RI, respectively, than that for healthy matched control participants. Categorical analysis exhibited a 2.98-, 4.43-, and 4.74-fold higher exposure for participants with moderate RI, severe RI, and ESRD, respectively, than that for healthy matched control participants. Apparent oral clearance and renal clearance was lower in participants with various degrees of RI, by 66% to 90%, compared with healthy matched control participants, explaining the increased gefapixant exposure with increasing degrees of renal impairment. Gefapixant area under the plasma concentration-time curve and maximum plasma concentration decreased by ≈25% under HD conditions compared to non-HD conditions. Single-dose administration of gefapixant was generally well tolerated in this study. The data from this trial informed the enrollment of phase 3 clinical trials that evaluated the efficacy and safety of gefapixant in2000 participants with refractory or unexplained chronic cough. Those efficacy and safety data, combined with analysis of population pharmacokinetics from across the entire development program, will be used to evaluate the magnitude of the renal impairment effect in the refractory or unexplained chronic cough population and to determine any dose adjustment recommendations.

Patients with chronic cough are typically female and have a mean age of ~ 60 years. However, initial pharmacokinetic (PK) characterization of the P2X3-receptor antagonist gefapixant, developed to treat refractory or unexplained chronic cough, was performed in healthy participants who were predominantly younger adult males. The objective of this Phase 1 study was to assess the safety, tolerability, and PK of gefapixant in younger (18-55 years) and older (65-80 years) males and females.A randomized, double-blind, placebo-controlled study was conducted. Healthy adult participants were stratified into 4 cohorts by age and sex (younger males/females and older males/females) and randomized 4:1 (younger adults) or 3:1 (older adults) to receive gefapixant 300 mg twice daily (BID) for 1 week, followed by gefapixant 600 mg BID for 2 weeks or placebo. Safety, tolerability, and PK were assessed.Of 36 randomized and treated participants, 28 (100%) receiving gefapixant and 6 (75%) receiving placebo reported ≥ 1 adverse event (AE). The most common treatment-related AEs in the gefapixant group were taste related. Predefined renal/urologic AEs were reported by 7 (25%) participants receiving gefapixant (all mild to moderate in severity). Gefapixant exposure was generally lower in younger males compared with younger females and older adults; however, differences may have been due to estimated glomerular filtration rate.The safety profile of gefapixant 300-600 mg BID was generally consistent with previous studies. Additional characterization of gefapixant PK as a function of age and sex using population PK modeling is warranted.

Background: Inhibition of PCSK9 (proprotein convertase subtilisin/kexin type 9)-low density lipoprotein receptor interaction with injectable monoclonal antibodies or small interfering RNA lowers plasma low density lipoprotein-cholesterol, but despite nearly 2 decades of effort, an oral inhibitor of PCSK9 is not available. Macrocyclic peptides represent a novel approach to target proteins traditionally considered intractable to small-molecule drug design. Methods: Novel mRNA display screening technology was used to identify lead chemical matter, which was then optimized by applying structure-based drug design enabled by novel synthetic chemistry to identify macrocyclic peptide (MK-0616) with exquisite potency and selectivity for PCSK9. Following completion of nonclinical safety studies, MK-0616 was administered to healthy adult participants in a single rising-dose Phase 1 clinical trial designed to evaluate its safety, pharmacokinetics, and pharmacodynamics. In a multiple-dose trial in participants taking statins, MK-0616 was administered once daily for 14 days to characterize the safety, pharmacokinetics, and pharmacodynamics (low density lipoprotein cholesterol). Results: MK-0616 displayed high affinity ( K i = 5pM) for PCSK9 in vitro and sufficient safety and oral bioavailability preclinically to enable advancement into the clinic. In Phase 1 clinical studies in healthy adults, single oral doses of MK-0616 were associated with >93% geometric mean reduction (95% CI, 84–103) of free, unbound plasma PCSK9; in participants on statin therapy, multiple–oral-dose regimens provided a maximum 61% geometric mean reduction (95% CI, 43–85) in low density lipoprotein cholesterol from baseline after 14 days of once-daily dosing of 20 mg MK-0616. Conclusions: This work validates the use of mRNA display technology for identification of novel oral therapeutic agents, exemplified by the identification of an oral PCSK9 inhibitor, which has the potential to be a highly effective cholesterol lowering therapy for patients in need.

Use of early predictive biomarkers of neurodegenerative disease in phase I clinical trials may improve the translation of novel drug therapies from preclinical development through late-stage studies. This article provides a categorical summary of promising biomarker approaches or clinical end points in molecular, cellular, metabolic, electrophysiological, or clinical function that can be used to predict or quantify the progression of neurodegenerative disorders and guide program support.

Letermovir is a human cytomegalovirus terminase inhibitor for the prophylaxis of cytomegalovirus infection and disease in allogeneic hematopoietic stem cell transplant recipients. The pharmacokinetics, safety, and tolerability of letermovir were assessed in healthy Japanese subjects in 2 phase 1 trials: trial 1-single ascending oral doses (240, 480, and 720 mg) and intravenous (IV) doses (240, 480, and 960 mg), and trial 2-multiple oral doses (240 and 480 mg once daily for 7 days). Following administration of oral single and multiple doses, letermovir was absorbed with a median time to maximum plasma concentration of 2 to 4 hours, and concentrations declined in a biphasic manner with a terminal half-life of ≈10 to 13 hours. The post absorption plasma concentration-time profile of letermovir following oral administration was similar to the profile observed with IV dosing. There was minimal accumulation with multiple-dose administration. Letermovir exposure in healthy Japanese subjects was ≈1.5- to 2.5-fold higher than that observed in non-Japanese subjects. Based on the population pharmacokinetic analysis, weight differences primarily accounted for the higher exposures observed in Asians. Letermovir was generally well tolerated following oral and IV administration to healthy Japanese subjects.

Gefapixant (MK-7264, AF-219), a first-in-class P2X3 antagonist, is being developed as oral treatment for refractory or unexplained chronic cough. Based on in vitro data, gefapixant exerts inhibitory activity on the organic anion transporter (OAT) P1B1 transporter. Therefore, a drug-drug interaction study evaluating the potential effects of gefapixant on the OATP1B1 drug transporter, using pitavastatin as a sensitive probe substrate, was conducted. An open-label, 2-period, fixed-sequence study in 20 healthy adults 18 to 55 years old was conducted. In period 1, a 1-mg oral dose of pitavastatin was administered to each participant. After a ≥4-day washout, in period 2 participants received a 45-mg oral dose of gefapixant twice daily on days 1 through 4. On day 2 of period 2, pitavastatin was coadministered with the morning dose of gefapixant. Pitavastatin exposures following single-dose administration with and without multiple doses of gefapixant were similar: geometric mean ratio (90% confidence interval) of pitavastatin area under the plasma concentration-time curve from time 0 to infinity (AUC0-∞ ) (pitavastatin + gefapixant/pitavastatin alone) was 0.97 (0.93-1.02). The ratio of pitavastatin lactone AUC0-∞ to pitavastatin AUC0-∞ was also comparable between treatments. Administration of gefapixant and pitavastatin was generally well tolerated, with no safety findings of concern. These results support that gefapixant has a low potential to inhibit the OATP1B1 transporter.

Islatravir, an investigational nucleoside reverse transcriptase translocation inhibitor, is in clinical development for the treatment and prevention of HIV-1 infection. Because islatravir may be coadministered with other antiretroviral agents, assessment of potential drug-drug interactions are warranted. This phase 1, open-label, fixed-sequence, 2-period trial in adults without HIV (N = 12) assessed the safety and pharmacokinetic interactions of islatravir administered with dolutegravir and tenofovir disoproxil fumarate (TDF). In period 1, participants received a single oral dose of islatravir (20 mg). In period 2, participants received oral doses of dolutegravir (50 mg) and TDF (300 mg) once daily on days 1 through 11, with a single oral dose of islatravir (20 mg) coadministered on day 8. There were no clinically significant changes in islatravir, dolutegravir, or TDF pharmacokinetics following coadministration. Islatravir was generally well tolerated when administered alone or in combination with dolutegravir and TDF. Coadministration of islatravir, dolutegravir, and TDF is supported, with no clinically meaningful effect on pharmacokinetics, safety, or tolerability in participants without HIV.

Islatravir (MK-8591) is a highly potent type 1 human immunodeficiency virus (HIV-1) nucleoside reverse transcriptase translocation inhibitor with a long intracellular half-life that is in development for the prevention and treatment of HIV-1. We conducted a randomized, double-blind, placebo-controlled, phase 1 trial in adults without HIV-1 infection. Participants received islatravir or placebo subdermal implants for 12 weeks and were monitored throughout this period and after implant removal. The co-primary end points were safety and tolerability of the islatravir implant and pharmacokinetics, including concentration at day 85, of islatravir triphosphate in peripheral blood mononuclear cells (PBMCs). Secondary end points included additional pharmacokinetic parameters for islatravir triphosphate in PBMCs and the plasma pharmacokinetic profile of islatravir. Based on preclinical data, two doses were assessed: 54 mg (n = 8, two placebo) and 62 mg (n = 8, two placebo). The most frequently reported adverse events were mild-to-moderate implant-site reactions (induration, hematoma, pain). Throughout the 12-week trial, geometric mean islatravir triphosphate concentrations were above a pharmacokinetic threshold of 0.05 pmol per 106 PBMCs, which was estimated to provide therapeutic reverse transcriptase inhibition (concentration at day 85 (percentage of geometric coefficient of variation): 54 mg, 0.135 pmol per 106 cells (27.3); 62 mg, 0.272 pmol per 106 cells (45.2)). Islatravir implants at both doses were safe and resulted in mean concentrations above the pharmacokinetic threshold through 12 weeks, warranting further investigation of islatravir implants as a potential HIV prevention strategy. A subdermal implant of the HIV-1 antiretroviral islatravir delivers sustained drug release over 12 weeks in humans.

Background MK-8507 is a novel HIV-1 non-nucleoside reverse transcriptase inhibitor being developed for treatment of HIV-1 infection. MK-8507 has high antiviral potency in vitro and pharmacokinetic (PK) properties that support once-weekly dosing. Setting A phase 1, open-label, proof-of-concept study was conducted in treatment-naive adults with HIV-1 infection to assess monotherapy antiviral activity. Methods In 3 sequential panels, participants aged 18-60 years with baseline plasma HIV-1 RNA ≥10,000 copies/mL and CD4+ T-cell count >200/mm3 received a single oral dose of 40, 80, or 600 mg MK-8507 in the fasted state. Participants were assessed for HIV-1 RNA for at least 7 days, PK for 14 days, and safety and tolerability for 21 days post dose. Results A total of 18 participants were enrolled (6 per panel). The mean 7-day post-dose HIV-1 RNA reduction ranged from ∼1.2 to ∼1.5 log10 copies/mL across the doses assessed. One patient had a viral rebound associated with emergence of a F227C reverse transcriptase variant (per chain-termination method sequencing) 14 days post dose; this variant was found in a second participant by ultra-deep sequencing as an emerging minority variant. MK-8507 PK were generally dose-proportional and similar to observations in participants without HIV-1 infection in prior studies; mean MK-8507 half-life was 56-69 hours in this study. MK-8507 was generally well tolerated at all doses. Conclusions The robust antiviral activity, PK, and tolerability of MK-8507 support its continued development as part of a complete once-weekly oral regimen for HIV-1 treatment; combination therapy could mitigate the emergence of resistance-associated variants.

Islatravir (MK-8591) is a high-potency reverse transcriptase translocation inhibitor in development for the treatment of HIV-1 infection. Data from preclinical and clinical studies suggest that ~30% to 60% of islatravir is excreted renally and that islatravir is not a substrate of renal transporters. To assess the impact of renal impairment on the pharmacokinetics of islatravir, an open-label phase 1 trial was conducted with individuals with severe renal insufficiency (RI). A single dose of islatravir 60 mg was administered orally to individuals with severe RI (estimated glomerular filtration rate [eGFR]30 mL/min/1.73 m

Letermovir inhibits renal tubular organic anion transporter (OAT)3 in vitro and is predicted to inhibit OAT3 in vivo. Acyclovir, a substrate for OAT3, is likely to be co-administered with letermovir; therefore, letermovir may increase acyclovir concentrations. A drug-drug interaction (DDI) study was conducted in healthy participants (N = 16) to assess the effect of letermovir on acyclovir pharmacokinetics. On Day 1, participants received a single oral dose of 400 mg acyclovir; on Days 2-7, participants received oral doses of 480 mg letermovir once daily with a single oral dose of 400 mg acyclovir co-administered on Day 7. Co-administration with letermovir resulted in geometric mean ratios (90% CIs) for acyclovir AUC

Background:Islatravir (MK-8591) is a deoxyadenosine analog in development for the treatment and prevention of HIV-1 infection. An islatravir-eluting implant could provide an additional option for pre-exposure prophylaxis (PrEP).Setting:Previous data support a threshold islatravir triphosphate concentration for PrEP of 0.05 pmol/10(6) cells in peripheral blood mononuclear cells. Prototype islatravir-eluting implants were previously studied to establish general tolerability and pharmacokinetics (PKs) of islatravir relative to the threshold level.Methods:In this randomized, double-blind, placebo-controlled, phase 1 trial, a next-generation radiopaque islatravir-eluting implant (48 mg, 52 mg, or 56 mg) or placebo implant was placed for a duration of 12 weeks in participants at low risk of HIV infection. Safety and tolerability, as well as PK for islatravir parent and islatravir triphosphate from plasma and peripheral blood mononuclear cells, were assessed throughout placement and 8 weeks after removal.Results:In total, 36 participants (8 active and 4 placebo per dose arm) were enrolled and completed this study. Implants were generally well tolerated, with no discontinuations due to an adverse event, and no clear dose-dependence in implant-related adverse events. No clinically meaningful relationships were observed for changes in laboratory values, vital signs, or electrocardiogram assessments. Mean islatravir triphosphate levels at day 85 (0.101-0.561 pmol/10(6) cells) were above the PK threshold for all dose levels.Conclusion:Islatravir administered using a subdermal implant has the potential to be an effective and well-tolerated method for administering PrEP to individuals at risk of acquiring HIV-1.

Background and Objectives Islatravir (MK-8591) is a novel nucleoside analogue in development for the treatment and prevention of HIV-1 infection. Doravirine is a non-nucleoside reverse transcriptase inhibitor indicated for the treatment of HIV-1 infection. This study evaluated the pharmacokinetics, safety, and tolerability of islatravir and doravirine coadministration in a double-blind, placebo-controlled, randomized, fixed-sequence study. Methods Adult participants without HIV infection were administered oral doravirine 100 mg (n = 10) or placebo (n = 4) once daily (QD) for 5 days, immediately followed by oral islatravir 2.25 mg (n = 10) or placebo QD (n = 4) for 14 days; islatravir 2.25 mg and doravirine 100 mg QD, or placebo QD, were then coadministered for 5 days. Pharmacokinetic and safety data were collected. Results Doravirine geometric least-squares mean ratios (90% confidence intervals (CIs)) of (doravirine + islatravir)/doravirine for the area under the plasma drug concentration-time curve over 24 h (AUC0–24h), maximum plasma concentration (Cmax), and plasma concentration at 24 h post-dose (C24h) were not meaningfully impacted. Islatravir geometric least-squares mean ratios (90% CI) of (islatravir + doravirine)/islatravir for AUC0–24h and Cmax were both close to unity, 1.06 (1.01, 1.12) and 1.08 (0.91, 1.27), respectively. All study regimens were generally well tolerated. Conclusion These results indicate that coadministration of islatravir and doravirine had no clinically meaningful effect on the pharmacokinetics of either drug, and support further clinical investigation of islatravir in combination with doravirine for the treatment of HIV-1 infection. Supplementary Information The online version contains supplementary material available at 10.1007/s40261-021-01046-1.

BACKGROUND Islatravir (MK-8591) is a novel nucleoside analog in development for the treatment and prevention of HIV-1 infection. Islatravir has potent antiviral activity and a long intracellular half-life. SETTING A 3-panel, randomized, double-blind, placebo-controlled, multiple-dose study in 36 adults without HIV evaluated the safety, tolerability, and pharmacokinetics of islatravir after daily administration. METHODS Islatravir or placebo was administered orally once daily for 42 days (5 mg) or 28 days (0.25 mg; 0.75 mg). Blood samples were taken at prespecified time points for pharmacokinetic analysis of islatravir (plasma) and islatravir-triphosphate (ISL-TP; peripheral blood mononuclear cells [PBMCs]). Rectal and vaginal tissue samples were also collected in a subset of participants. Safety and tolerability were evaluated throughout. RESULTS The pharmacokinetics of islatravir were approximately dose proportional, with concentrations approaching a steady state between days 14 and 21 in plasma and by day 28 for ISL-TP in PBMCs. Plasma exposure accumulation was 1.5-fold to 1.8-fold, and ISL-TP exposure accumulation was ∼10-fold. The apparent terminal half-life of ISL-TP was 177-209 hours. The ISL-TP pharmacokinetic trough threshold-the minimal concentration required for efficacy-of 0.05 pmol/106 cells was achieved after a single administration at all dose levels. Rectal and vaginal tissue also exhibited potentially therapeutic concentrations. Islatravir was generally well tolerated at all doses. CONCLUSIONS ISL-TP levels in PBMCs were above the threshold projected for antiviral efficacy against wild-type HIV after a single 0.25-mg dose. Multiple once-daily dosing of islatravir in adults without HIV was generally well tolerated up to doses of 5 mg administered for up to 6 weeks.

Development of monoclonal antibodies (mAbs) targeting immune-checkpoint receptors (IMRs) for the treatment of cancer is one of the most active areas of investment in the biopharmaceutical industry. A key decision in the clinical development of anti-IMR mAbs is dose selection. Dose selection can be challenging because the traditional oncology paradigm of administering the maximum tolerated dose is not applicable to anti-IMR mAbs. Instead, dose selection should be informed by the pharmacology of immune signaling. Engaging an IMR is a key initial step to triggering pharmacologic effects, and turnover (i.e., the rate of protein synthesis) of the IMR is a key property to determining the dose level needed to engage the IMR. Here, we applied the stable isotope labeling mass spectrometry technique using 13 C6 -leucine to measure the in vivo turnover rates of IMRs in humans. 13 C6 -leucine was administered to 10 study participants over 15 hours to measure 13 C6 -leucine enrichment kinetics in 2 IMR targets that have been clinically pursued in oncology: glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) and programmed death 1 (PD-1). We report the first measurements of GITR and PD-1 median half-lives associated with turnover to be 55.6 and ≥49.5 hours, respectively. The approach outlined here can be applied to other IMRs and, more generally, to protein targets.

Doravirine, a novel nonnucleoside reverse transcriptase inhibitor for the treatment of human immunodeficiency virus 1 (HIV-1), is predominantly cleared by cytochrome P450 (CYP) 3A4 and metabolized to an oxidative metabolite (M9). Coadministration with rifabutin, a moderate CYP3A4 inducer, decreased doravirine exposure. Based on nonparametric superposition modeling, a doravirine dose adjustment from 100 mg once daily to 100 mg twice daily during rifabutin coadministration was proposed. However, M9 exposure may also be impacted by induction, in addition to the dose adjustment. As M9 concentrations have not been quantified in previous clinical studies, a physiologically based pharmacokinetic model was developed to investigate the change in M9 exposure when doravirine is coadministered with CYP3A inducers. Simulations demonstrated that although CYP3A induction increases doravirine clearance by up to 4.4-fold, M9 exposure is increased by only 1.2-fold relative to exposures for doravirine 100 mg once daily in the absence of CYP3A induction. Thus, a 2.4-fold increase in M9 exposure relative to the clinical dose of doravirine is anticipated when doravirine 100 mg twice daily is coadministered with rifabutin. In a subsequent clinical trial, doravirine and M9 exposures, when doravirine 100 mg twice daily was coadministered with rifabutin, were found to be consistent with model predictions using rifampin and efavirenz as representative inducers. These findings support the dose adjustment to doravirine 100 mg twice daily when coadministered with rifabutin.

To develop a framework for evaluating the resorption effects of Cathepsin K (CatK) inhibitors and to inform dose regimen selection, a pharmacokinetic/pharmacodynamic (PK/PD) model for odanacatib (ODN) was developed based upon data from Phase 1 studies. Pooled PK/PD data from 11 studies (N = 249) were fit reasonably to a population inhibitory sigmoid Emax model. Body weight on E0 (baseline uNTx/Cr, urinary N-terminal telopeptide normalized by creatinine) and age on Emax (fractional inhibition of the biomarker response) were significant covariates for biomarker response. Simulations of typical osteoporosis patients (by age, sex and weight) indicated minimal differences between sexes in concentration-uNTx/Cr relationship. There was no evidence that regimen (daily vs. weekly dosing) influenced the PK/PD relationship of resorption inhibition for odanacatib. PK/PD models based on data from odanacatib (ODN) Phase 1 studies demonstrated that uNTx/Cr was an appropriate bone resorption biomarker for assessment of the effects of a CatK inhibitor. The models also identified the determinants of response in the PK/PD relationship for ODN (body weight on E0 and age on Emax).

What is known and objective Doravirine is a non-nucleoside reverse transcriptase inhibitor indicated for the treatment of human immunodeficiency virus (HIV)-1 infection. This phase 1 study in healthy adults investigated the pharmacokinetics, safety and tolerability of long-acting parenteral (LAP) microsuspension formulations of doravirine administered as an intramuscular (IM) injection. Methods After confirmation of tolerability and safety of oral doravirine, 36 participants were randomized 1:1:1 to receive IM doravirine 200 mg as Treatment A (1 × 1 mL, 20% [200 mg/mL] suspension), B (1 × 0.66 mL, 30% [300 mg/mL] suspension) or C (2 × 0.5 mL, 20% suspension). Blood samples were taken as venous plasma, venous dried blood spots (DBS) and fingerstick DBS. Results and discussion Plasma concentration-time profiles following IM treatments demonstrated rapid initial doravirine release, with initial peak ~4 days post-injection, followed by decline over the next ~6 days; a second peak was reached at ~24-36 days, corresponding to prolonged and sustained release, with measurable concentrations up to Day 183. Treatment C was associated with highest peak concentrations and shortest time to maximum concentration. Elimination half-lives for all IM formulations were prolonged versus oral administration (~46-58 days vs ~11-15 hours). Oral doravirine and IM doravirine were generally well tolerated; injection-site pain was the most common adverse event for IM doravirine. Doravirine concentrations from DBS samples showed strong correlations to venous plasma concentrations. What is new and conclusions Novel doravirine LAP IM injection formulations investigated in this study demonstrated sustained plasma doravirine concentrations over a course of >20 weeks.

Novel therapeutics for pulmonary arterial hypertension (PAH) with improved safety/tolerability profiles are needed to address continued high rates of morbidity/mortality.This Phase 1 study evaluated efficacy/safety of inhaled single-dose MK-5475, an investigational, small-molecule stimulator of soluble guanylate cyclase designed for inhaled delivery via a dry-powder inhaler device, in participants with PAH (Clinicaltrials.gov: NCT03744637). Eligible participants were 18-70 years of age; body mass index ≤35 kg/mMK-5475 was generally well tolerated without systemic side effects on blood pressure or heart rate up to 24 h post dose. With respect to the primary pharmacodynamic outcome, mean reductions in pulmonary vascular resistance ranged from 21% to 30% across 120 μg and 360 μg doses.Treatment with inhaled single-dose MK-5475 showed rapid and sustained reductions in pulmonary vascular resistance and increases in pulmonary blood volume. MK-5475 was generally well tolerated versus placebo without vasodilatory systemic side effects. The promising pulmonary selectivity and favorable safety/tolerability profile of MK-5475 seen in this study of adult participants with PAH lays the foundation for further clinical development.

Background: More efficient screening methods are needed to improve the ability to identify and follow genetic cohorts in Parkinson’s disease (PD). Objective: To explore the use of the electronic medical records (EMRs) to identify participants with PD. Methods: Using an algorithm previously developed in collaboration with Maccabi Healthcare Services (MHS), approximately 5,200 participants with PD were identified, more than 3,200 were screened, and 837 participants were enrolled and genotyped for leucine-rich repeat kinase 2 (LRRK2) and beta-glucocerebrosidase (GBA) variants. Questionnaires were completed to ascertain Ashkenazi Jewish (AJ) ancestry and family history of PD. Results: Among 837 participants with PD, 82% were 65 years and older and 72% had a family history of AJ ancestry. Among those with AJ ancestry, 15.6% reported having relatives with PD. The frequency of observed mutations for LRRK2 and GBA genes combined was approximately 15.4%. The frequency of observed LRRK2 mutation was 6.1% overall and 7.2% from those with AJ ancestry; and for GBA mutation was 9.3% overall and 11.2% from those with AJ ancestry. Conclusion: Although the frequency of observed mutations in this study was lower than anticipated, mutation carriers were enriched among those with a family history of AJ ancestry increasing nearly 2-3-fold, from 3% –7% (LRRK2) and 4% –11% (GBA). The identification (and selection) of PD patients through EMRs prior to genotyping is a viable approach, to establish a genetically defined cohort of patients with PD for clinical research.

Insulin molecules of size much greater than natural insulin have been synthesized and studied with the intention of widening the therapeutic window between adequate glycemic control and hypoglycemia as compared with conventional insulins. MK-1092 is a synthetic insulin dimer with favorable properties demonstrated in preclinical studies. Here, we report the results of the first-in-human, randomized, double-blind, active-control, single ascending dose trial of MK-1092, conducted in healthy adults, adults with type 1 diabetes (T1D), and adults with type 2 diabetes (T2D). MK-1092 was well tolerated in all study populations, and no dose-related adverse events were identified across the evaluated dose range (4-64 nmol/kg). Circulating concentrations of MK-1092 were approximately dose-proportional. Maximum glucose infusion rate (GIR) and 24-hour time-weighted average GIR were evaluated under euglycemic clamp conditions. These pharmacodynamic measurements were approximately dose-proportional in all study populations; at similar doses, the GIR parameters were lower in adults with T2D than in healthy adults or adults with T1D, likely due to the influence of insulin resistance. At doses ≥ 16 nmol/kg, MK-1092 had similar or greater effects than glargine 3 nmol/kg (0.5 units/kg) on increasing GIR in each study population and on suppressing free fatty acids and ketone generation in adults with T1D. MK-1092 did not prevent a subsequent high dose of lispro from increasing the GIR in healthy adults. Additional studies in adults with T1D and T2D are needed to further evaluate the safety, tolerability, and efficacy profile of MK-1092 and its potential for differentiation from more conventional insulins. (ClinicalTrials.gov: NCT03170544).

Gefapixant is a P2X3-receptor antagonist being developed for treatment of refractory or unexplained chronic cough. Four phase 1 studies were conducted in healthy participants that bridged the early-phase gefapixant formulation (F01) to the phase 3 (F04A) and intended commercial (F04B) formulations. In addition, food and proton pump inhibitor (PPI) coadministration effects on gefapixant exposure were assessed. The gefapixant free base formulation (F01) was used in the initial early-phase clinical studies. Adding citric acid to the F01 formulation (to generate F02) enhanced drug solubilization, resulting in similar bioavailability and mitigating food and gastric pH effects. The subsequently developed gefapixant citrate salt formulation (F04) achieved exposures that were comparable to F02 in the fed state (90%CIs of geometric mean ratios for area under the plasma concentration-time curve from time 0 extrapolated to infinity and maximum observed concentration were within 0.80 and 1.25) and were not meaningfully affected by food or PPIs (90%CIs of geometric mean ratios for area under the plasma concentration-time curve from time 0 extrapolated to infinity and maximum observed concentration were within 0.80 and 1.25). Minor compositional changes were made to generate the F04A and F04B formulations. In vitro dissolution studies were used to bridge F04 to F04A, and clinical bioequivalence was then established between F04A and F04B. These data support use of the proposed commercial gefapixant formulation without significant food and PPI effects.

Summary: Background: We report on the safety and immunogenicity of V591, a measles vector-based SARS-CoV-2 vaccine candidate. Methods: In this multicentre, randomised, placebo-controlled, double-blind, phase 1/2 trial, healthy adults with no history of COVID-19 disease were assigned to intramuscular injection of V591 or placebo (4:1 ratio). In part 1, younger adults (18-55 years) received V591 median tissue culture infectious dose (TCID50)-levels of 1×105 or 1×106 or placebo, 56 days apart. In part 2, younger and older (>55 years) adults received a single dose of one of four (104/105/106/107) or one of two (105/106) V591 TCID50 levels, respectively, or placebo. Primary outcome: safety/tolerability. Secondary outcome: humoral immunogenicity. ClinicalTrials.gov: NCT04498247. Findings: From August–December 2020, 444 participants were screened and 263 randomised (210 V591; 53 placebo); 262 received at least one and 10 received two doses of V591 or placebo. Adverse events were experienced by 140/209 (67.0%) V591 dose-group participants and 37/53 (69.8%) placebo-group participants following injection 1; most frequent were fatigue (57 [27.3%] vs 20 [37.7%]), headache (57 [27.3%] vs 19 [35.8%]), myalgia (35 [16.7%] vs 10 [18.9%]), and injection-site pain (35 [16.7%] vs 4 [7.5%]). No deaths nor vaccine-related serious adverse events occurred. At Day 29, no anti-SARS-CoV-2 spike serum neutralising antibody and IgG-responses were identified in placebo or the three lower V591 dose-groups; responses were detected with V591 1×107 TCID50, although titres were lower than convalescent serum. Interpretation: V591 was generally well tolerated, but immunogenicity was insufficient to warrant continued development. Funding: Merck Sharp & Dohme, Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA.

Introduction Hormonal contraceptives are among the most effective forms of reversible contraception, but many other compounds, including some antiretrovirals, have clinically meaningful drug–drug interactions (DDIs) with hormonal contraceptives. Islatravir is a novel human immunodeficiency virus nucleoside reverse transcriptase translocation inhibitor currently in clinical development for treatment and prevention of HIV infection. A phase 1 clinical trial was conducted to evaluate the DDI of islatravir and the combination of oral contraceptive levonorgestrel (LNG)/ethinyl estradiol (EE). Methods This was an open‐label, two‐period, fixed‐sequence, DDI clinical trial in healthy, postmenopausal or bilaterally oophorectomized females aged 18 through 65 years in the United States between October 2016 and January 2017. A single dose of LNG 0.15 mg/EE 0.03 mg was given followed by a 7‐day washout. Islatravir, 20 mg, was then dosed once weekly for 3 weeks; a single dose of LNG 0.15 mg/EE 0.03 mg was given concomitantly with the third dose of islatravir. Pharmacokinetic samples for plasma LNG and EE concentrations were collected pre‐dose and up to 120 hours post‐dose in each period. Safety and tolerability were assessed throughout the trial by clinical assessments, laboratory evaluations and examination of adverse events. Results and Discussion Fourteen participants were enrolled. The pharmacokinetics of LNG and EE were not meaningfully altered by co‐administration with islatravir. For the comparison of (islatravir + LNG/EE)/(LNG/EE alone), the geometric mean ratios (GMRs) (90% confidence intervals [CIs]) for LNG AUC0–inf and C max were 1.13 (1.06, 1.20) and 0.965 (0.881, 1.06), respectively. For EE, the GMRs (90% CI) for AUC0–inf and C max were 1.05 (0.981, 1.11) and 1.02 (0.971, 1.08), respectively. Co‐administration of all three drugs was generally well tolerated. Conclusions The results of this trial support the use of LNG/EE contraceptives in combination with islatravir without dose adjustment.

Mobile health (mHealth) technologies have the potential to capture dense patient data on the background of real-life behavior. Merck & Co., Inc. (Kenilworth, NJ), in collaboration with Koneksa Health, conducted a phase I clinical trial to validate cardiovascular mHealth technologies for concordance with traditional approaches and to establish sensitivity to detect effects of pharmacological intervention. This two-part study enrolled 18 healthy male subjects. Part I, a 5-day study, compared mHealth measures of heart rate (HR) and blood pressure (BP) to those from traditional methods. Hypotheses of similarity, in the clinic and at home, were tested individually for HR, systolic BP, and diastolic BP, at a 2-sided 0.05 alpha level, with a prespecified criterion for similarity being the percentage differences between the 2 measurements within 15%. Part II, a 7-day, 3-period randomized balanced crossover study, evaluated the mHealth technology's ability to detect effects of bisoprolol and salbutamol. Hypotheses that the changes from baseline in HR were greater in the bisoprolol (reduction in HR) and salbutamol (increase in HR) groups compared with no treatment were tested, at a 1-sided 0.05 alpha level. Linear mixed-effects models, Pearson's correlation coefficients, summary statistics, and exploratory plots were applied to analyze the data. The mHealth measures of HR and BP were demonstrated to be similar to those from traditional methods, and sensitive to changes in cardiovascular parameters induced by bisoprolol and salbutamol.

Fine-needle aspiration (FNA) for serial hepatic sampling may be an efficient and less invasive alternative to core needle biopsy (CNB), the current standard for liver tissue sampling. In this randomized, open-label trial in 31 participants with hepatitis C virus genotype 1 infection (NCT01678131/Merck protocol PN048), we evaluated the feasibility of using FNA to obtain human liver tissue samples appropriate for measuring hepatic pharmacokinetics (PK), using vaniprevir as a tool compound. The primary end point was successful retrieval of liver tissue specimens with measurable vaniprevir concentrations at two of three specified FNA time points. Twenty-nine patients met the primary end point and, therefore, were included in the PK analyses. Hepatic vaniprevir concentrations obtained with FNA were consistent with known vaniprevir PK properties. The shape of liver FNA and CNB concentration-time profiles were comparable. In conclusion, FNA may be effective for serial tissue sampling to assess hepatic drug exposure in patients with liver disease.

A significant regulatory gap exists to facilitate global development of therapeutics for nononcology severely debilitating or life-threatening diseases or conditions (SDLTs). In a 2017 publication, a streamlined approach to the development of treatments for SDLTs was proposed to facilitate earlier and continued patient access to new, potentially beneficial therapeutics.1 However, a major hindrance to broad adoption of this streamlined approach has been the lack of universally accepted, objective criteria to define SDLTs. This article serves to extend the 2017 publication by further addressing the challenge of defining SDLT scope in order to stimulate broader discussion and facilitate development of regional and ultimately international guidelines on the development of therapeutics for SDLTs. Using case examples, we describe key attributes of SDLTs and provide criteria for consideration of an SDLT scope definition.

We have previously described a midazolam limited sampling strategy employing a population pharmacokinetic (PK) approach to estimate constitutive cytochrome P450 (CYP) 3A activity. This study evaluated expansion of this approach to estimate CYP3A constitutive, inhibitory, and induction activities. Midazolam concentrations (n = 4441) from adults (n = 152) were obtained from previous studies after single, oral, or intravenous administration with intensive sample collection. Data were fit to a 2-compartment population PK model that incorporated CYP3A conditions as covariates for clearance (CL), volume of distribution, and bioavailability (F). Limited sampling models using single- or 2-time point concentrations were compared with full PK profiles using the empiric Bayesian post hoc estimations of midazolam area under the plasma concentration-time curve derived from the population PK model. Ketoconazole, rifampin, and pleconaril were significant covariates of CL, while ketoconazole, rifampin, and grapefruit juice were significant covariates for F. Typical midazolam CL and F estimates were 32.9 L/h and 0.31 for the constituent state, while the ratio of inducer/inhibitor for midazolam CL and CL/F for the induced/inhibited (rifampin/ketoconazole) states were 14.2 and 85.3. Upon comparison to the population PK model, the majority of evaluated single- and 2-time point limited sampling models estimated area under the plasma concentration-time curve had unacceptable r2 and/or unacceptable bias and precision. Exclusively during CYP3A inhibitory conditions, the 4- and 6-hour limited sampling model had acceptable limits of r2 , bias, and precision. Consequently, development of a single- or 2-time point midazolam limited sampling model for general, widespread use to simultaneously evaluate various CYP3A conditions remains elusive.

For pharmacokinetics characterization of a therapeutic insulin dimer, an ultrasensitive plasma method was required due to the expected low circulating levels in humans. A bioanalytical strategy combining immunoprecipitation enrichment with liquid chromatography - tandem mass spectrometry (LC-MS/MS) analysis of the intact protein offers the opportunity to resolve the analyte from endogenous and exogenous insulin and insulin analogs. Nonetheless, interference from complex background matrix was observed limiting reliable measurements at the low concentration range. A sample preparation approach incorporating protein precipitation and immunoprecipitation was developed and optimized to further reduce sample complexity prior to LC-MS/MS analysis. This approach enabled a deeper level of selectivity and presented a cleaner mass spectrometric detection that may otherwise be confounded. Sample preparation was automated to allow high throughput analysis. The method reached a limit of quantitation at 0.3 ng/mL (25 pM), and a linear dynamic range from 0.3 to 300 ng/mL. Results were highly reproducible, with intra-day and inter-day precision and bias below 11%. Furthermore, the organic solvent treatment involved in protein precipitation is expected to improve assay resistance to the bias introduced by endogenous protein binding such as that exerted by anti-drug antibodies. The method was successfully applied to support clinical pharmacokinetics studies. This approach may potentially be adapted to bioanalysis of low abundance proteins.

MK-8507 is a novel HIV-1 non-nucleoside reverse transcriptase inhibitor in clinical development with potential for once-weekly oral administration for the treatment of HIV-1 infection. Two randomized, double-blind, placebo-controlled phase 1 studies in adults without HIV-1 evaluated the safety, tolerability, and pharmacokinetics of single and multiple doses of MK-8507; drug interaction with midazolam (a cytochrome P450 3A4 substrate) and food effect were also assessed. In Study 1, 16 participants received oral ascending single doses of MK-8507 (2-400 mg) or placebo in an alternating fashion. In Study 2, 24 participants received ascending single doses of MK-8507 (400-1200 mg) or placebo and multiple doses (once weekly for 3 weeks) of MK-8507 (100-400 mg) or placebo. MK-8507 pharmacokinetics were approximately dose proportional at 2-1200 mg. MK-8507 had a time to maximum concentration of 2-7 hours and a mean terminal half-life of ∼58-84 hours. MK-8507 doses ≥100 mg achieved a plasma concentration at 168 hours post-dose (7 days) associated with antiviral efficacy. A high-fat meal had no clinically meaningful effect on MK-8507 pharmacokinetics, and MK-8507 400 mg once weekly had no clinically meaningful effect on midazolam pharmacokinetics. Single and multiple doses of MK-8507 were generally well tolerated. No trends with dose and no clinically meaningful changes were observed in vital signs, electrocardiograms, and laboratory safety tests. The pharmacokinetics and safety data are supportive of once-weekly oral administration and support further clinical investigation of MK-8507 for the treatment of HIV-1 infection. Over the last 3 decades, substantial improvements have been made in oral HIV antiretroviral therapies (ART), which now offer people living with HIV (PLWH) the potential for a near-normal life expectancy (1, 2). To achieve this, individuals must maintain life-long viral suppression, which requires daily administration of efficacious medication (3). Issues surrounding tolerability, complicated regimens, and treatment fatigue from daily dosing can lead to poor adherence and suboptimal viral suppression (3-6). Regimens can become complex when there is the need to take multiple pills, requirement to take a medication fasted or with food, or the potential for interactions with other medications, including those required to treat HIV-related comorbidities (3, 78). New treatment options that are not only highly effective but also offer excellent tolerability, a high barrier to resistance, favorable drug interaction profiles, and the potential for less frequent dosing remain the focus of much clinical research (7, 9). While 1 pill once a day meets the needs of many PLWH, for others daily administration poses challenges, including treatment fatigue and daily reminders and/or stigma associated with ART (10, 11). While treatment regimens that can be taken less often than daily are attractive to many PLWH, the long-acting injectable combination of cabotegravir/rilpivirine is currently the only treatment option available without daily dosing; however, administration requires injection by a health care professional (12), potentially posing other challenges.

MK-8507 is an investigational HIV-1 nonnucleoside reverse transcriptase inhibitor being developed for the treatment of HIV-1 infection. MK-8507 contains 2 trifluoromethyl groups that may result in fluoride release through metabolism, but the extent of MK-8507-related fluoride release in humans has yet to be determined. This double-blind, placebo-controlled, 2-period, parallel-group, multiple-dose trial in healthy participants without HIV-1 who were administered a fluoride-restricted diet and once-weekly doses of MK-8507 aimed to estimate the relationship between MK-8507 dose and fluoride exposure. A total of 15 adult male and 3 adult female (of non-childbearing potential) participants were randomized to receive MK-8507 200 mg (n = 6), MK-8507 800 mg (n = 6), or placebo (n = 6). Change from baseline in mean daily fluoride excretion averaged over 7 days following the administration of MK-8507 200 mg resulted in a net mean increase of 19.8 μmol (90% confidence interval, 12.2-27.4) relative to placebo and did not exceed 57 μmol, a threshold related to the mean difference between the daily reference dose set by the US Environmental Protection Agency and the average dietary fluoride intake in the United States. However, daily urinary fluoride excretion exceeded the threshold following administration of 800 mg MK-8507 (75.1 μmol [90% confidence interval, 67.5-82.7]). Assuming a linear relationship between MK-8507 dose and estimated mean daily fluoride released at steady-state, data interpolation suggests that the US Environmental Protection Agency reference dose for fluoride would not be exceeded in most patients when administering MK-8507 at doses currently under clinical investigation (≤400 mg once weekly).

Rifampin has acute inhibitory and chronic inductive effects that can cause complex drug-drug interactions. Rifampin inhibits transporters including organic-anion-transporting polypeptide (OATP)1B and P-glycoprotein (P-gp), and induces enzymes and transporters including cytochrome P450 3A, UDP-glucuronosyltransferase (UGT)1A, and P-gp. This study aimed to separate inhibitory and inductive effects of rifampin on letermovir disposition and elimination (indicated for cytomegalovirus prophylaxis in hematopoietic stem cell transplant recipients). Letermovir is a substrate of UGT1A1/3, P-gp, and OATP1B, with its clearance primarily mediated by OATP1B. Letermovir (single-dose) administered with rifampin (single-dose) resulted in increased letermovir exposure through transporter inhibition. Chronic coadministration with rifampin (inhibition plus potential OATP1B induction) resulted in modestly decreased letermovir exposure vs. letermovir alone. Letermovir administered 24 hours after the last rifampin dose (potential OATP1B induction) resulted in markedly decreased letermovir exposure. These data suggest rifampin may induce transporters that clear letermovir; the modestly reduced letermovir exposure with chronic rifampin coadministration likely reflects the net effect of inhibition and induction. OATP1B endogenous biomarkers coproporphyrin (CP) I and glycochenodeoxycholic acid-sulfate (GCDCA-S) were also analyzed; their exposures increased after single-dose rifampin plus letermovir, consistent with OATP1B inhibition and prior reports of inhibition by rifampin alone. CP I and GCDCA-S exposures were substantially reduced with letermovir administered 24 hours after the last dose of rifampin vs. letermovir plus chronic rifampin coadministration. This study suggests that OATP1B induction may contribute to reduced letermovir exposure after chronic rifampin administration, although given the complexity of letermovir disposition alternative mechanisms are not fully excluded.

Gefapixant (MK-7264, AF-219) is a first-in-class P2X3 antagonist in development for refractory or unexplained chronic cough. Gefapixant is primarily cleared by renal excretion. To assess the importance of the multidrug and toxin extrusion protein 1 (MATE1) and MATE2K transporters in the elimination of gefapixant, a drug-drug interaction study was conducted evaluating the effect of coadministration of a single dose of pyrimethamine, a competitive inhibitor of MATE1 and MATE2K, on the single-dose pharmacokinetics of gefapixant in healthy participants. Safety and tolerability were also assessed. In this open-label, 2-period, fixed-sequence study, a 45-mg dose of gefapixant was administered to 12 participants in period 1. After a 7-day washout, a 50-mg dose of pyrimethamine was administered 3 hours before a 45-mg dose of gefapixant in period 2. Compared with the administration of gefapixant alone, concomitant dosing of gefapixant with pyrimethamine increased the total gefapixant plasma exposure (area under the plasma concentration-time curve from time 0 to infinity) by 24%, reduced gefapixant renal clearance by 30%, and increased gefapixant mean terminal half-life from 7.7 to 10.3 hours. The most frequently reported adverse events were dysgeusia, hypogeusia, and dry mouth; all adverse events were considered of mild intensity and resolved by the end of the study. These results support that MATE1 and/or MATE2K contribute to the renal clearance of gefapixant, but the effect of inhibition of these transporters on gefapixant pharmacokinetics is not considered clinically meaningful.

Anacetrapib is a novel, powerful cholesteryl ester transfer protein (CETP) inhibitor with bidirectional lipid regulation, which was developed for dyslipidemia. The aim of this study is to evaluate the single- and multiple-dose pharmacokinetics (PK), safety and tolerability of anacetrapib in healthy Chinese subjects and assess the PK difference between Chinese and other populations. Forty subjects were enrolled in an open-label study consisting of three panels (50 mg single dose; 100 mg single dose followed by 100 mg once-daily multiple doses for 10 days; a 200 mg single dose). Safety and tolerability were evaluated by monitoring adverse events, laboratory safety tests, ECGs, vital signs and physical examination. PK were evaluated and compared with historical data in black and white subjects. Anacetrapib was absorbed after administration of a single oral dose, with a median Tmax of 3.0–5.0 h and elimination half-life of 105.3–122.3 h. The AUC and Cmax of anacetrapib increased in a slightly less than dose-proportional manner over a dose range of 50–200 mg. Once-daily administration of 100 mg of anacetrapib for 10 days resulted in a median Tmax of 5.0 h with an apparent half-life of 193.7 h on Day 10 of multiple dosing. Anacetrapib accumulation ratios (Day 10 of multiple dosing/Day 1) were 1.39 (AUC0–24 h), 1.11 (Cmax) and 2.57 (C24 h). The PK properties of anacetrapib in Chinese subjects are comparable to those observed in the black population and in white subjects. Single and once-daily administration of anacetrapib was generally well tolerated in healthy Chinese subjects observed in this study. chinadrugtrials.org.cn identifier number CTR20130983.

Islatravir (MK-8591) is a novel nucleoside analog in development for the treatment and prevention of HIV-1 infection. Islatravir has potent antiviral activity and a long intracellular half-life.A 3-panel, randomized, double-blind, placebo-controlled, multiple-dose study in 36 adults without HIV evaluated the safety, tolerability, and pharmacokinetics of islatravir after daily administration.Islatravir or placebo was administered orally once daily for 42 days (5 mg) or 28 days (0.25 mg; 0.75 mg). Blood samples were taken at prespecified time points for pharmacokinetic analysis of islatravir (plasma) and islatravir-triphosphate (ISL-TP; peripheral blood mononuclear cells [PBMCs]). Rectal and vaginal tissue samples were also collected in a subset of participants. Safety and tolerability were evaluated throughout.The pharmacokinetics of islatravir were approximately dose proportional, with concentrations approaching a steady state between days 14 and 21 in plasma and by day 28 for ISL-TP in PBMCs. Plasma exposure accumulation was 1.5-fold to 1.8-fold, and ISL-TP exposure accumulation was ∼10-fold. The apparent terminal half-life of ISL-TP was 177-209 hours. The ISL-TP pharmacokinetic trough threshold-the minimal concentration required for efficacy-of 0.05 pmol/106 cells was achieved after a single administration at all dose levels. Rectal and vaginal tissue also exhibited potentially therapeutic concentrations. Islatravir was generally well tolerated at all doses.ISL-TP levels in PBMCs were above the threshold projected for antiviral efficacy against wild-type HIV after a single 0.25-mg dose. Multiple once-daily dosing of islatravir in adults without HIV was generally well tolerated up to doses of 5 mg administered for up to 6 weeks.

Islatravir (MK‐8591) is a nucleoside analogue in development for the treatment and prevention of HIV‐1. Two phase 1 trials were conducted during initial evaluation of islatravir: rising single doses (Study 1) and rising multiple doses (Study 2) of oral islatravir in male and female participants without HIV (aged 18–60 years). Safety, tolerability, and pharmacokinetics of islatravir (plasma) and islatravir‐triphosphate (peripheral blood mononuclear cells) were assessed. In Study 1, 24 participants, assigned to 1 of 3 panels, received alternating single doses of islatravir in a fasted state from 5 mg to 400 mg, or placebo, over 3 dosing periods; a 30 mg dose was additionally assessed following a high‐fat meal. In Study 2, 8 participants per dose received 3 once‐weekly doses of 10, 30, or 100 mg islatravir or placebo in a fasted state. For each panel in both trials, 6 participants received active drug and 2 received placebo. Islatravir was generally well‐tolerated, with no serious adverse events or discontinuations due to adverse events. Islatravir was rapidly absorbed (median time to maximum plasma concentration 0.5 hours); plasma half‐life was 49–61 h; intracellular islatravir‐triphosphate half‐life was 118–171 h. Plasma exposure increased in an approximately dose‐proportional manner; there was no meaningful food effect. There was a modest degree of intracellular islatravir‐triphosphate accumulation after multiple weekly dosing. After single oral doses of islatravir greater than or equal to 5 mg, intracellular islatravir‐triphosphate levels were comparable to levels associated with efficacy in preclinical studies. These results warrant continued clinical investigation of islatravir.

Islatravir (MK-8591) is a highly potent type 1 human immunodeficiency virus (HIV-1) nucleoside reverse transcriptase translocation inhibitor with a long intracellular half-life that is in development for the prevention and treatment of HIV-1. We conducted a randomized, double-blind, placebo-controlled, phase 1 trial in adults without HIV-1 infection. Participants received islatravir or placebo subdermal implants for 12 weeks and were monitored throughout this period and after implant removal. The co-primary end points were safety and tolerability of the islatravir implant and pharmacokinetics, including concentration at day 85, of islatravir triphosphate in peripheral blood mononuclear cells (PBMCs). Secondary end points included additional pharmacokinetic parameters for islatravir triphosphate in PBMCs and the plasma pharmacokinetic profile of islatravir. Based on preclinical data, two doses were assessed: 54 mg (n = 8, two placebo) and 62 mg (n = 8, two placebo). The most frequently reported adverse events were mild-to-moderate implant-site reactions (induration, hematoma, pain). Throughout the 12-week trial, geometric mean islatravir triphosphate concentrations were above a pharmacokinetic threshold of 0.05 pmol per 10

Gefapixant (MK-7264) is a P2X3 receptor antagonist in development for refractory or unexplained chronic cough. In vitro, gefapixant is a substrate of the renal efflux transporters MATE1 and -2K and an inhibitor of the hepatic uptake transporter OATP1B. The potential for gefapixant drug-drug interactions (DDI) was assessed using the probe compounds, pyrimethamine (PYR, a MATE inhibitor) and pitavastatin (PITA, an OATP1B substrate). Two Phase 1 open-label fixed-sequence trials were conducted to assess the single-dose pharmacokinetics (PK) of gefapixant and PITA, respectively. In Trial 1, 12 participants received 45 mg gefapixant alone in Period 1 and, in Period 2, received gefapixant three hours after a single dose of 50 mg PYR. In Trial 2, 20 participants received 1 mg PITA alone in Period 1 and, in Period 2, received 45 mg gefapixant for 4 days; PITA was coadministered with the third dose of gefapixant. Intensive PK samples, including urine in Trial 1, were collected after each dose of the respective victim drugs. Gefapixant and PITA PK (geometric mean ratios [GMR]) are summarized as follows. Coadministration of PYR and gefapixant resulted in clinically insignificant increases in gefapixant, attributable to reduced renal clearance. Gefapixant coadministration did not affect PITA exposure. These trials indicate that gefapixant has minimal potential for clinical DDI involving the interrogated transporters.

Doravirine (MK-1439) is a novel non-nucleoside reverse transcriptase inhibitor indicated for the combination treatment of human immunodeficiency virus type-1 (HIV-1) infection. The recommended dose is 100 mg once daily. This review summarizes the pharmacokinetics of doravirine, the influence of intrinsic factors, and its drug–drug interaction (DDI) profile. Following oral administration, doravirine is rapidly absorbed (median time to maximum plasma concentration, 1–4 h) and undergoes cytochrome P450 (CYP)3A-mediated oxidative metabolism. Steady-state geometric means for AUC0–24, C24, and Cmax in individuals with HIV-1 following administration of doravirine 100 mg once daily are 37.8 μM·h, 930 nM, and 2260 nM, respectively. Age, gender, severe renal impairment, and moderate hepatic impairment have no clinically meaningful effect on doravirine pharmacokinetics, and there is limited potential for DDIs. No dose adjustment is necessary when doravirine is co-administered with strong CYP3A inhibitors. However, doravirine is contraindicated with strong CYP3A inducers (e.g., rifampin), and dose adjustment of doravirine is recommended for co-administration with the moderate CYP3A inducer, rifabutin. Included in this review are clinical trial data from phase I pharmacokinetic trials, including DDI trials and trials in participants with renal and hepatic disease but without HIV-1 infection (N = 326), as well as phase I, II, and III safety and efficacy trials in participants living with HIV-1 (N = 991). Based on these data, the pharmacokinetic profile of doravirine supports its use in diverse populations living with HIV-1 and allows co-administration with various antiretroviral agents and treatments for commonly occurring co-morbidities. Electronic supplementary material The online version of this article (10.1007/s40261-020-00934-2) contains supplementary material, which is available to authorized users.

Cathepsin K (CatK) is a cysteine protease abundantly expressed by osteoclasts and localized in the lysosomes and resorption lacunae of these cells. CatK is the principal enzyme responsible for the degradation of bone collagen. Odanacatib is a selective, reversible inhibitor of CatK at subnanomolar potency. The pharmacokinetics of odanacatib have been extensively studied and are similar in young healthy men, postmenopausal women and elderly men, and were qualitatively similar throughout Phase 1 development and in‐patient studies. Following 3 weeks of 50 mg once weekly dosing the geometric mean area under the curve from 0 to 168 hours was 41.1 μM h, the concentration at 168 hours was 126 nM and the harmonic mean apparent terminal half‐life was 84.8 hr. Odanacatib exposure increased in a less than dose proportional manner due to solubility limited absorption. It is estimated that approximately 70% of the absorbed dose of odanacatib is eliminated via metabolism, 20% is excreted as unchanged drug in the bile or faeces, and 10% is excreted as unchanged drug in the urine. The systemic clearance was low (approximately 13 mL/min). Odanacatib decreases the degradation of bone matrix proteins and reduces the efficiency of bone resorption with target engagement confirmed by a robust decrease in serum C‐telopeptides of type 1 collagen (approximately 60%), urinary aminoterminal crosslinked telopeptides of type 1 collagen to creatinine ratio (approximately 50%) and total urine deoxypyridinoline/Cr (approximately 30%), with an increase in serum cross‐linked carboxy‐terminal telopeptide of type 1 collagen (approximately 55%). The 50‐mg weekly dosing regimen evaluated in Phase 3 achieved near maximal reduction in bone resorption throughout the treatment period. The extensive clinical programme for odanacatib, together with more limited clinical experience with other CatK inhibitors (balicatib and ONO‐5334), provides important insights into the clinical pharmacology of CatK inhibition and the potential role of CatK in bone turnover and mineral homeostasis. Key findings include the ability of this mechanism to: (i) provide sustained reductions in resorption markers, increases in bone mineral density, and demonstrated fracture risk reduction; (ii) be associated with relative formation‐sparing effects such that sustained resorption reduction is achieved without accompanying meaningful reductions in bone formation; and (iii) lead to increases in osteoclast number as well as other osteoclast activity (including build‐up of CatK enzyme), which may yield transient increases in resorption following treatment discontinuation and the potential for nonmonotonic responses at subtherapeutic doses.