Lumicitabine, an orally administered nucleoside analog, in infants hospitalized with respiratory syncytial virus (RSV) infection: Safety, efficacy, and pharmacokinetic results.

Respiratory syncytial virus (RSV) infection is the leading cause of infant hospitalizations and mortality. Lumicitabine, an oral nucleoside analog was studied for the treatment of RSV. The phase 1b and phase 2b studies reported here assessed the safety, pharmacokinetics, and pharmacodynamics of lumicitabine in infants/neonates hospitalized with RSV. In the phase 1b study, infants (≥1 to ≤12 months) and neonates (<28 days) received a single-ascending or multiple-ascending doses (single loading dose [LD] then 9 maintenance doses [MD] of lumicitabine, or placebo [3:1]). In the phase 2b study, infants/children (28 days to ≤36 months old) received lumicitabine 40/20 mg/kg, 60/40 mg/kg LD/MD twice-daily or placebo (1:1:1) for 5 days. Safety, pharmacokinetics, and efficacy parameters were assessed over 28 days. Lumicitabine was associated with a dose-related increase in the incidence and severity of reversible neutropenia. Plasma levels of ALS-008112, the active nucleoside analog, were dose-proportional with comparable mean exposure levels at the highest doses in both studies. There were no significant differences between the lumicitabine groups and placebo in reducing viral load, time to viral non-detectability, and symptom resolution. No emergent resistance-associated substitutions were observed at the RSV L-gene positions of interest. In summary, lumicitabine was associated with a dose-related increase in the incidence and severity of reversible neutropenia and failed to demonstrate antiviral activity in RSV-infected hospitalized infants. This contrasts with the findings of the previous RSV-A adult challenge study where significant antiviral activity was noted, without incidence of neutropenia. Trial registration ClinicalTrials.gov Identifier: NCT02202356 (phase 1b); NCT03333317 (phase 2b).

Rilzabrutinib, a reversible covalent Bruton's tyrosine kinase inhibitor: Absorption, metabolism, excretion, and absolute bioavailability in healthy participants.

This single-center, open-label, non-randomized, two-part, phase I study was conducted (1) to evaluate the absolute oral bioavailability of rilzabrutinib 400 mg tablet following an i.v. microtracer dose of ~100 µg [14C]-rilzabrutinib (~1 µCi) and single oral dose of 400 mg rilzabrutinib tablet (part 1), and (2) to characterize the absorption, metabolism, and excretion (AME) of 14C-radiolabeled rilzabrutinib following single oral dose (300 mg) of [14C]-rilzabrutinib (~1000 µCi; administered as a liquid) in healthy male participants (part 2). A total of 18 subjects were enrolled (n = 8 in part 1; n = 10 in part 2). The absolute bioavailability of 400 mg rilzabrutinib oral tablet was low (<5%). In part 1, rilzabrutinib was absorbed rapidly after single oral dose of rilzabrutinib 400 mg tablet with a median (range) time to maximum concentration (Tmax ) value of 2.03 h (1.83-2.50 h). The geometric mean (coefficient of variation) terminal half-life following the oral dose and i.v. microtracer dose of ~100 µg [14C]-rilzabrutinib, were 3.20 (51.0%) and 1.78 (37.6%) h, respectively. In part 2, rilzabrutinib was also absorbed rapidly following single oral dose of 300 mg [14C]-rilzabrutinib solution with a median (range) Tmax value of 1.00 h (1.00-2.00 h). The majority of total radioactivity was in the feces for both non-bile collection subjects (92.9%) and bile collection subjects (87.6%), and ~5% of radioactivity was recovered in urine after oral administration. Urinary excretion of unchanged rilzabrutinib was low (3.02%). The results of this study advance the understanding of the absolute bioavailability and AME of rilzabrutinib and can help inform its further investigation.

Asia-Inclusive Clinical Research and Development Enabled by Translational Science and Quantitative Clinical Pharmacology: Toward a Culture That Challenges the Status Quo.

Access lag to innovative therapies in Asian populations continues to present a challenge to global health. Recent progressive changes in the global regulatory landscape, including newer guidelines, are enabling simultaneous global drug development and near-simultaneous global drug registration. The International Conference on Harmonization (ICH) E17 guideline outlines general principles for the design and analysis of multiregional clinical trials (MRCTs). We posit that translational research and quantitative clinical pharmacology tools are core enablers for Asia-inclusive global drug development aligned with ICH E17 principles. Assessment of ethnic sensitivity should be initiated early in the development lifecycle to inform the need for, and extent of, Asian phase I ethno-bridging data. Relevant ethno-bridging data may be generated as standalone Asian phase I trials, as part of Western First-In-Human trials, or under accelerated development settings as a lead-in phase in an MRCT. Quantitative understanding of human clearance mechanisms and pharmacogenetic factors is vital to forecasting ethnic sensitivity in drug exposure using physiologically-based pharmacokinetic models. Stratification factors to control heterogeneity in MRCTs can be identified by reverse translational research incorporating pharmacometric disease models and model-based meta-analyses. Because epidemiological variations can extend to the molecular level, quantitative systems pharmacology models may be useful in forecasting how molecular variation in therapeutic targets or pathway proteins across populations might impact treatment outcomes. Through prospective evaluation of conservation in drug- and disease-related intrinsic and extrinsic factors, a pooled East Asian region can be implemented in Asia-inclusive MRCTs to maximize efficiency in substantiating evidence of benefit-risk for the region at-large with a Totality of Evidence approach.

An evaluation of a supratherapeutic dose of inclisiran on cardiac repolarization in healthy volunteers: A phase I, randomized study.

Inclisiran is a small interfering RNA molecule that has been shown to provide an effective and sustained reduction in low-density lipoprotein cholesterol levels. This study aimed to determine whether a supratherapeutic dose of inclisiran affects cardiac repolarization and conduction in healthy volunteers. A phase I, randomized, double-blind, double-dummy, placebo- and positive-controlled, three-way crossover study was performed in 48 healthy volunteers. Volunteers were assigned to three treatments in a randomized sequence: a supratherapeutic dose of inclisiran sodium (900 mg), placebo, or moxifloxacin 400 mg as a positive control, with a minimum 7-day washout period between treatments. Continuous electrocardiogram monitoring was performed from >60 min before dosing until 48 h after dosing. Pharmacokinetics, pharmacodynamics, and safety were also assessed. Inclisiran, at a supratherapeutic dose, did not show a clinically significant effect on the QT interval (Fridericia correction formula [QTcF]; maximal placebo- and baseline-corrected change: 2.5 ms [90% confidence interval: 0.6, 4.5]) near the maximal plasma concentrations at 4 h. In addition, inclisiran did not show any effects on other electrocardiogram intervals or ST- and T-wave morphology. The positive control, moxifloxacin, demonstrated the expected changes in QTcF interval, validating the adequate sensitivity of the study. A supratherapeutic dose of inclisiran sodium (900 mg) had no effect on the QTcF interval or other electrocardiogram parameters, providing additional insight and reassurance regarding the safety profile of inclisiran.

Assessing the Combined Public Health Impact of Pharmaceutical Interventions on Pandemic Transmission and Mortality: An Example in SARS CoV-2.

To assess the combined role of anti-viral monoclonal antibodies (mAbs) and vaccines in reducing severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) transmission and mortality in the United States, an agent-based model was developed that accounted for social contacts, movement/travel, disease progression, and viral shedding. The model was calibrated to coronavirus disease 2019 (COVID-19) mortality between October 2020 and April 2021 (aggressive pandemic phase), and projected an extended outlook to estimate mortality during a less aggressive phase (April-August 2021). Simulated scenarios evaluated mAbs for averting infections and deaths in addition to vaccines and aggregated non-pharmaceutical interventions. Scenarios included mAbs as a treatment of COVID-19 and for passive immunity for postexposure prophylaxis (PEP) during a period when variants were susceptible to the mAbs. Rapid diagnostic testing paired with mAbs was evaluated as an early treatment-as-prevention strategy. Sensitivity analyses included increasing mAb supply and vaccine rollout. Allocation of mAbs for use only as PEP averted up to 14% more infections than vaccine alone, and targeting individuals ≥ 65 years averted up to 37% more deaths. Rapid testing for earlier diagnosis and mAb use amplified these benefits. Doubling the mAb supply further reduced infections and mortality. mAbs provided benefits even as proportion of the immunized population increased. Model projections estimated that ~ 42% of expected deaths between April and August 2021 could be averted. Assuming sensitivity to mAbs, their use as early treatment and PEP in addition to vaccines would substantially reduce SARS-CoV-2 transmission and mortality even as vaccination increases and mortality decreases. These results provide a template for informing public health policy for future pandemic preparedness.

A thorough QTc study to evaluate the effects of oral rilzabrutinib administered alone and with ritonavir in healthy subjects.

This study aimed to define the clinically relevant supratherapeutic dose of rilzabrutinib, an oral Bruton tyrosine kinase (BTK) inhibitor, and evaluate potential effects of therapeutic and supratherapeutic exposures on cardiac repolarization in healthy subjects. This was a two-part phase I study (anzctr.org.au ACTRN12618001036202). Part A was a randomized, open-label, three-period, single-dose crossover study (n = 12) with rilzabrutinib 100 mg ± ritonavir 100 mg or rilzabrutinib 1200 mg. Part B was a randomized, double-blind, placebo-controlled, four-way, single-dose crossover study (n = 39) with matched placebo, rilzabrutinib 400 mg ± ritonavir 100 mg, or moxifloxacin (positive control). Primary objectives: part A - pharmacokinetics (PK) of rilzabrutinib ± ritonavir, safety, and optimal dose for Part B; Part B - effect of rilzabrutinib therapeutic and supratherapeutic concentration on electrocardiogram (ECG) parameters. ECGs and PK samples were serially recorded before and post-dose. In part A, rilzabrutinib 100 mg + ritonavir led to 17-fold area under the concentration-time curve (AUC0-∞ ) and 7-fold maximum plasma concentration (Cmax ) increases over rilzabrutinib alone. Rilzabrutinib 1200 mg was discontinued due to mild-to-moderate gastrointestinal intolerance. In Part B, rilzabrutinib 400 mg + ritonavir increased rilzabrutinib mean AUC0-∞ from 454 to 3800 ng h/mL and Cmax from 144 to 712 ng/mL. The concentration-QTc relationship was slightly negative, shallow (-0.01 ms/ng/mL [90% CI -0.016 to -0.001]), and an effect >10 ms on QTcF could be excluded within the observed range of plasma concentrations, up to 2500 ng/mL. Safety was similar to other studies of rilzabrutinib. In conclusion, rilzabrutinib, even at supratherapeutic doses, had no clinically relevant effects on ECG parameters, including the QTc interval.

Pharmacokinetics and pharmacodynamics of inclisiran, a small interfering RNA therapy, in patients with hepatic impairment.

BACKGROUND: Inclisiran, a small interfering RNA molecule, reduces low-density lipoprotein cholesterol (LDL-C) by inhibiting production of proprotein convertase subtilisin/kexin type 9 (PCSK9) in the liver. OBJECTIVE: To investigate the pharmacokinetics, pharmacodynamics, and safety of inclisiran in patients with mild or moderate hepatic impairment (HI) vs participants with normal hepatic function (NHF). METHODS: In this single-center, open-label, parallel-group study, patients with mild (Child-Pugh A) or moderate (Child-Pugh B) HI and with NHF, matched by age, body mass index, sex, and race (if possible), received a single subcutaneous therapeutic dose of inclisiran (300 mg). Pharmacokinetic profiles, pharmacodynamic endpoints (PCSK9 and LDL-C), and safety were assessed. RESULTS: Twenty-eight participants completed the study (mild HI: n = 10; moderate HI: n = 6; NHF: n = 12). Inclisiran achieved maximum plasma concentration at 4-6 h and was undetectable in plasma at 48 h in most participants, irrespective of liver function. Inclisiran exposure was 1.24-fold higher in the mild HI vs NHF groups (90% confidence interval [CI] 1.01-1.53) and 2.03-fold higher in the moderate HI vs NHF groups (90% CI 1.60-2.58). LDL-C and PCSK9 plasma levels decreased from baseline up to the last assessment on Day 60 in all groups, with a similar response in NHF and mild HI groups but a less pronounced and more varied decrease in the moderate HI group. Inclisiran was generally safe and well tolerated. CONCLUSION: The pharmacokinetic exposure of inclisiran increased by up to two fold in patients with moderate HI compared with those with NHF, while pharmacodynamic effects remained relatively unchanged. Inclisiran is generally safe and well tolerated in patients with mild or moderate HI, with no dose adjustment needed. However, a larger, long-term clinical trial would help to further evaluate the long-term safety profile of inclisiran in patients with liver disease.

Phase 1 clinical trial evaluating safety, exposure and pharmacodynamics of BTK inhibitor tolebrutinib (PRN2246, SAR442168).

Bruton's tyrosine kinase (BTK), expressed in B cells and cells of innate immunity, including microglia, is an essential signaling element downstream of the B-cell receptor and Fc-receptors. Tolebrutinib (PRN2246, SAR442168) is a potent BTK inhibitor that covalently binds the kinase, resulting in durable inhibition with the potential to target inflammation in the periphery and central nervous system (CNS). Tolebrutinib crosses the blood-brain barrier and potently inhibits BTK in microglial cells isolated from the CNS. A first-in-human randomized, double-blind, placebo-controlled study of tolebrutinib was conducted. The trial design consisted of five single ascending dose arms with oral administration of a single dose of 5, 15, 30, 60, and 120 mg (n = 6 per arm, n = 2 placebo), five multiple ascending dose arms with oral administration of 7.5, 15, 30, 60, and 90 mg (n = 8 per arm, n = 2 placebo) over 10 days, and one arm (n = 4) in which cerebral spinal fluid (CSF) exposure was measured 2 h after a single 120 mg dose. Tolebrutinib was well-tolerated in the study and all treatment-related treatment emergent adverse events were mild. Tolebrutinib was rapidly absorbed following oral administration with a rapid half-life of ~ 2 h. Peripheral BTK occupancy was assessed at various timepoints by an enzyme-linked immunosorbent assay-based readout using an irreversible probe. Assessments demonstrated extensive and prolonged peripheral BTK occupancy at steady-state with once daily doses as low as 7.5 mg. Further, CSF exposure was demonstrated 2 h after administration at 120 mg.

Blueprint for pandemic response: Focus on translational medicine, clinical pharmacology and pharmacometrics.

Perhaps the most important lesson learned from the COVID-19 pandemic is that of preparedness. Enhanced surveillance systems for early threat detection will be crucial to maximizing response time for implementation of public health measures and mobilization of resources in containing an emerging pandemic. Recent outbreaks have been dominated by viral pathogens, with RNA respiratory viruses being the most likely to have pandemic potential. These should therefore be a preparedness priority. Tools in the areas of virology, drug discovery, clinical pharmacology, translational medicine and pharmacometrics should be considered key components in the rapid identification and development of existing and novel interventions for a pandemic response. Prioritization of therapeutics should be based on in vitro activity, likelihood of achieving effective drug concentrations at the site of action, and safety profile at the doses that will be required for clinical efficacy. Deployment strategies must be tailored to the epidemiology of the disease, and the adequacy of the response should be re-evaluated in view of evolving epidemiological factors. An interdisciplinary framework integrating drug pharmacology, viral kinetics, epidemiology and health economics could help optimize the deployment strategy by improving decision-making around who to treat, when to treat, and with what type of intervention for optimal outcomes. Lastly, while an effective vaccine will ultimately end a pandemic, antiviral drug intervention guided by clinical pharmacology principles will continue to play a critical role in any pandemic response.

Model-Informed Drug Development for Anti-Infectives: State of the Art and Future.

Model-informed drug development (MIDD) has a long and rich history in infectious diseases. This review describes foundational principles of translational anti-infective pharmacology, including choice of appropriate measures of exposure and pharmacodynamic (PD) measures, patient subpopulations, and drug-drug interactions. Examples are presented for state-of-the-art, empiric, mechanistic, interdisciplinary, and real-world evidence MIDD applications in the development of antibacterials (review of minimum inhibitory concentration-based models, mechanism-based pharmacokinetic/PD (PK/PD) models, PK/PD models of resistance, and immune response), antifungals, antivirals, drugs for the treatment of global health infectious diseases, and medical countermeasures. The degree of adoption of MIDD practices across the infectious diseases field is also summarized. The future application of MIDD in infectious diseases will progress along two planes; "depth" and "breadth" of MIDD methods. "MIDD depth" refers to deeper incorporation of the specific pathogen biology and intrinsic and acquired-resistance mechanisms; host factors, such as immunologic response and infection site, to enable deeper interrogation of pharmacological impact on pathogen clearance; clinical outcome and emergence of resistance from a pathogen; and patient and population perspective. In particular, improved early assessment of the emergence of resistance potential will become a greater focus in MIDD, as this is poorly mitigated by current development approaches. "MIDD breadth" refers to greater adoption of model-centered approaches to anti-infective development. Specifically, this means how various MIDD approaches and translational tools can be integrated or connected in a systematic way that supports decision making by key stakeholders (sponsors, regulators, and payers) across the entire development pathway.

Pharmacologic effects of oseltamivir in immunocompromised adult patients as assessed by population PK/PD analysis and drug-disease modelling for dosing regimen optimization.

AIM: Pharmacologic effects were analysed to determine a dose recommendation for oseltamivir in immunocompromised (IC) adults with influenza. METHODS: Quantitative clinical pharmacology methods were applied to data from 160 adult IC patients (aged 18-78 years) from two studies (NV20234, 150 patients; NV25118, 10 patients) who received oseltamivir 75-200 mg twice daily for up to 10 days. An established population-pharmacokinetic (PK) model with additional effects on oseltamivir and oseltamivir carboxylate (OC) clearance described the PK characteristics of oseltamivir in IC patients versus otherwise healthy (OwH) patients from previous clinical trials. Estimated PK parameters were used to evaluate exposure-response relationships for virologic endpoints (time to cessation of viral shedding, viral load measures and treatment-emergent resistance). A drug-disease model characterized the viral kinetics of influenza accounting for the effect of OC on viral production. RESULTS: Oseltamivir clearance was 32.5% lower (95% confidence interval [CI], 26.1-38.8) and OC clearance was 33.7% lower (95% CI, 23.2-44.1) in IC versus OwH patients. No notable exposure-response relationships were identified for exposures higher than those achieved after conventional dose oseltamivir 75 mg, which appeared to be close to the maximum effect of oseltamivir. Simulations of the drug-disease model predicted that initiating treatment within 48 hours of symptom onset had maximum impact, and a treatment duration of 10 days was favourable over 3-5 days to limit viral rebound. CONCLUSIONS: Our findings support the use of conventional-dose oseltamivir 75 mg twice daily for 10 days in the treatment of IC adult patients with influenza.

Using in silico viral kinetic models to guide therapeutic strategies during a pandemic: An example in SARS-CoV-2.

AIMS: We propose the use of in silico mathematical models to provide insights that optimize therapeutic interventions designed to effectively treat respiratory infection during a pandemic. A modelling and simulation framework is provided using SARS-CoV-2 as an example, considering applications for both treatment and prophylaxis. METHODS: A target cell-limited model was used to quantify the viral infection dynamics of SARS-CoV-2 in a pooled population of 105 infected patients. Parameter estimates from the resulting model were used to simulate and compare the impact of various interventions against meaningful viral load endpoints. RESULTS: Robust parameter estimates were obtained for the basic reproduction number, viral release rate and infected-cell mortality from the infection model. These estimates were informed by the largest dataset currently available for SARS-CoV-2 viral time course. The utility of this model was demonstrated using simulations, which hypothetically introduced inhibitory or stimulatory drug mechanisms at various target sites within the viral life-cycle. We show that early intervention is crucial to achieving therapeutic benefit when monotherapy is administered. In contrast, combination regimens of two or three drugs may provide improved outcomes if treatment is initiated late. The latter is relevant to SARS-CoV-2, where the period between infection and symptom onset is relatively long. CONCLUSIONS: The use of in silico models can provide viral load predictions that can rationalize therapeutic strategies against an emerging viral pathogen.

Accelerating Clinical Evaluation of Repurposed Combination Therapies for COVID-19.

As the global COVID-19 pandemic continues, unabated and clinical trials demonstrate limited effective pharmaceutical interventions, there is a pressing need to accelerate treatment evaluations. Among options for accelerated development is the evaluation of drug combinations in the absence of prior monotherapy data. This approach is appealing for a number of reasons. First, combining two or more drugs with related or complementary therapeutic effects permits a multipronged approach addressing the variable pathways of the disease. Second, if an individual component of a combination offers a therapeutic effect, then in the absence of antagonism, a trial of combination therapy should still detect individual efficacy. Third, this strategy is time saving. Rather than taking a stepwise approach to evaluating monotherapies, this strategy begins with testing all relevant therapeutic options. Finally, given the severity of the current pandemic and the absence of treatment options, the likelihood of detecting a treatment effect with combination therapy maintains scientific enthusiasm for evaluating repurposed treatments. Antiviral combination selection can be facilitated by insights regarding SARS-CoV-2 pathophysiology and cell cycle dynamics, supported by infectious disease and clinical pharmacology expert advice. We describe a clinical evaluation strategy using adaptive combination platform trials to rapidly test combination therapies to treat COVID-19.

Clinical and virological responses to a broad-spectrum human monoclonal antibody in an influenza virus challenge study.

Influenza A infections cause significant seasonal morbidity and mortality as well as periodic pandemic infections. Currently, no approved therapies exist for patients hospitalized with influenza. The efficacy of VIS410, a broadly neutralizing human immunoglobulin IgG1 monoclonal antibody engineered to bind to the stem region of group 1 and 2 influenza A hemagglutinins, was explored in experimental human influenza infection. Healthy volunteers were inoculated with influenza A/California/07/2009 (H1N1) and received a single dose of VIS410 or placebo 24 h later. Subjects were monitored for symptoms, viral shedding, and safety, including cytokine measurements. The primary efficacy endpoint was the area under the curve (AUC) of viral load (VL) in the VIS410 group versus placebo. VIS410 treatment was associated with a 76% reduction in median VL AUC as measured by qRT-PCR (p = 0.024). Similar VIS410 antiviral activity was observed by virus culture, with a 91% reduction in median VL AUC by TCID50 (p = 0.019) compared to placebo-treated volunteers. Influenza symptoms were generally mild or moderate, with a trend toward faster resolution in VIS410-treated subjects. Treatment with VIS410 was generally safe, with an increase in gastrointestinal events that were largely mitigated by pre-treatment with oral diphenhydramine (50 mg) in combination with 600 mg of ibuprofen. Transient elevation of specific cytokines (IL-8 and TNFα) were associated with gastrointestinal adverse events. Treatment with VIS410 did not interfere with the endogenous immune response to influenza A. These data indicate that VIS410 may provide therapeutic benefit in influenza A infection. TRIAL REGISTRATION: ClinicaTtrials.gov Identification NCT02468115; https://clinicaltrials.gov/ct2/show/NCT02468115?term=NCT02468115&rank=1).

Respiratory syncytial virus-A dynamics and the effects of lumicitabine, a nucleoside viral replication inhibitor, in experimentally infected humans.

Background: Respiratory syncytial virus (RSV) causes high morbidity, with mortality rates approaching or exceeding that of influenza in adult and infant patient populations, respectively. Lumicitabine (ALS-008176 or JNJ-64041575) is an oral nucleoside analogue prodrug in clinical development to treat RSV infections. This prodrug converts to plasma-circulating ALS-8112, and then to the 5'-active nucleoside triphosphate (NTP) form within host cells. We conducted an RSV-A challenge study in healthy adults to evaluate lumicitabine's activity during an active RSV infection. Objectives: To develop a semi-mechanistic mathematical model describing RSV kinetics, and the pharmacokinetics (PK) and pharmacodynamics (PD) of lumicitabine during treatment. Methods: Nasopharyngeal viral load and concentrations of ALS-8112 and ALS-8144 (uridine metabolite) were measured frequently over the study duration. Population viral kinetic and PK/PD models were developed using NONMEM. The RSV life-cycle was described using a target-cell-limited model that included a physiological delay. Results: The estimated clearances of ALS-8112 and ALS-8144 were 54.2 and 115 L/h/70 kg, respectively. A semi-physiological model was linked to predict ALS-8112 conversion to active intracellular NTP. Extensive and rapid RSV reduction occurred after lumicitabine treatment (EC50 = 1.79 µM), with >99% viral inhibition at 2 h after loading dose. Simulated NTP exposures and time to EC50 attainment suggested that rapid therapeutic effects and reduced dosing frequency are achievable in adult and paediatric patients. Conclusions: The semi-mechanistic model characterizes RSV kinetics and the antiviral effectiveness of lumicitabine in an adult challenge population. This model is applicable to guide dose selection in adult and paediatric patients.

A pharmacokinetic/viral kinetic model to evaluate treatment of chronic HCV infection with a non-nucleoside polymerase inhibitor.

BACKGROUND: Viral kinetic models have proven useful in characterizing treatment effectiveness during HCV therapy with interferon (IFN) as well as with direct-acting antivirals (DAAs). METHODS: Here we use a pharmacokinetic/viral kinetic (PK/VK) model to describe HCV RNA kinetics during treatment with setrobuvir, a non-nucleosidic inhibitor of the HCV NS5B polymerase enzyme. Using PK data from three studies in healthy volunteers and PK and VK data from a Phase I study, where setrobuvir was administered for 3 days, we fitted a two-compartment PK model with first-order absorption and lag-time, an Emax pharmacodynamics model and a standard biphasic VK model. RESULTS: Setrobuvir's EC50 and Hill coefficient and the viral clearance rate were significantly different (P=0.014, P<0.001 and P=0.004, respectively) between patients infected with HCV subtypes 1b and 1a, leading to an increased viral load decline in patients infected with genotype 1b virus. CONCLUSIONS: Understanding the combined effects of PK/VK on the performance of a non-nucleoside polymerase inhibitor such as setrobuvir could provide valuable insights into their use in combination with other DAAs as well as to optimize future therapy. Further, our work suggests that patients infected with subtype 1a would need higher doses than those infected with subtype 1b to achieve the same effectiveness. Whether this is true for other non-nucleoside polymerase inhibitors needs to be examined.

A phase I trial of PRN1008, a novel reversible covalent inhibitor of Bruton's tyrosine kinase, in healthy volunteers.

AIM: To evaluate the safety, tolerability, and pharmacokinetics/pharmacodynamics of PRN1008, a novel Bruton's tyrosine kinase (BTK) inhibitor, in healthy volunteers, and thus determine the dose range for future clinical studies. METHODS: This was a two-part randomized, placebo controlled study in healthy volunteers using a liquid formulation. Part I was a single ascending dose design with dose levels of 50-1200 mg (n = 6 active, two placebos per cohort); Part II was a multiple ascending dose design, with dose regimens ranging from 300 to 900 mg daily, either four times or twice daily for 10 days. Plasma pharmacokinetics, adverse events, vital signs, electrocardiograms and laboratory parameters were assessed. BTK occupancy in peripheral blood mononuclear cells was evaluated as a marker of target engagement. RESULTS: PRN1008 was rapidly absorbed following oral administration, and was safe and well tolerated in all dose regimens evaluated in both single and multiple doses. PRN1008 demonstrated a large volume of distribution, and a half-life of approximately 3-4 h. BTK occupancy of >90% was observed within 4 h after dosing in both single and multiple dose regimens, and was closely linked to maximum plasma concentration. BTK occupancy decay was slow (-1.6% h-1 ), and occupancy was sustained despite drug concentrations being undetectable. No severe or serious adverse events occurred, and the most common adverse events were gastrointestinal in nature. CONCLUSIONS: PRN1008 was safe and well-tolerated following oral administration, and achieved high, sustained levels of BTK occupancy in peripheral blood mononuclear cells.

Interdisciplinary pharmacometrics linking oseltamivir pharmacology, influenza epidemiology and health economics to inform antiviral use in pandemics.

AIMS: A modular interdisciplinary platform was developed to investigate the economic impact of oseltamivir treatment by dosage regimen under simulated influenza pandemic scenarios. METHODS: The pharmacology module consisted of a pharmacokinetic distribution of oseltamivir carboxylate daily area under the concentration-time curve at steady state (simulated for 75 mg and 150 mg twice daily regimens for 5 days) and a pharmacodynamic distribution of viral shedding duration obtained from phase II influenza inoculation data. The epidemiological module comprised a susceptible, exposed, infected, recovered (SEIR) model to which drug effect on the basic reproductive number (R0 ), a measure of transmissibility, was linked by reduction of viral shedding duration. The number of infected patients per population of 100 000 susceptible individuals was simulated for a series of pandemic scenarios, varying oseltamivir dose, R0 (1.9 vs. 2.7), and drug uptake (25%, 50%, and 80%). The number of infected patients for each scenario was entered into the health economics module, a decision analytic model populated with branch probabilities, disease utility, costs of hospitalized patients developing complications, and case-fatality rates. Change in quality-adjusted life years was determined relative to base case. RESULTS: Oseltamivir 75 mg relative to no treatment reduced the median number of infected patients, increased change in quality-adjusted life years by deaths averted, and was cost-saving under all scenarios; 150 mg relative to 75 mg was not cost effective in low transmissibility scenarios but was cost saving in high transmissibility scenarios. CONCLUSION: This methodological study demonstrates proof of concept that the disciplines of pharmacology, disease epidemiology and health economics can be linked in a single quantitative framework.