Performance of longitudinal item response theory models in shortened or partial assessments.

This work evaluates the performance of longitudinal item response (IR) theory models in shortened assessments using an existing model for part II and III of the MDS-UPDRS score. Based on the item information content, the assessment was reduced by removal of items in multiple increments and the models' ability to recover the item characteristics of the remaining items at each level was evaluated. This evaluation was done for both simulated and real data. The metric of comparison in both cases was the item information function. For real data, the impact of shortening on the estimated disease progression and drug effect was also studied. In the simulated data setting, the item characteristics did not differ between the full and the shortened assessments down to the lowest level of information remaining; indicating a considerable independence between items. In contrast when reducing the assessment in a real data setting, a substantial change in item information was observed for some of the items. Disease progression and drug effect estimates also decreased in the reduced assessments. These changes indicate a shift in the measured construct of the shortened assessment and warrant caution when comparing results from a partial assessment with results from the full assessment.

Effect of letermovir on levonorgestrel and ethinyl estradiol pharmacokinetics
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OBJECTIVE: Letermovir is an inhibitor of the terminase complex of cytomegalovirus (CMV) used as prophylactic therapy in CMV-seropositive allogeneic hematopoietic stem cell transplant recipients. As the combination oral contraceptive (COC) levonorgestrel/ethinyl estradiol (LNG/EE) may be coadministered in this target transplant population, the effects of letermovir on the pharmacokinetics (PK) of LNG and EE were investigated. MATERIALS AND METHODS: This was a phase I, open-label, fixed-sequence, two-period study conducted in healthy women (18 - 65 years old) of non-childbearing potential (protocol number: MK-8228 035). On day 1 of period 1, participants received a single dose of COC (LNG 0.15 mg/EE 0.03 mg). Following a 7-day washout, oral letermovir 480 mg was administered once-daily on days 1 - 12 of period 2, with a single dose of COC coadministered on day 8. Blood samples were collected to determine LNG and EE PK, and safety was assessed. RESULTS: The AUC0-∞ geometric mean ratios (90% confidence intervals) for COC + letermovir/COC alone were 1.36 (1.30, 1.43) for LNG and 1.42 (1.32, 1.52) for EE, indicating that letermovir coadministration increased COC exposure. Coadministration had no clinically-meaningful effect on Cmax, tmax, or apparent terminal T1/2 for either LNG or EE. All treatments were generally well tolerated. CONCLUSION: Letermovir coadministration with COC resulted in an increase in LNG and EE exposure in healthy adult women; however, levels were within the established safety margins. There was no decrease in LNG or EE exposure with no apparent risk of contraceptive failure on coadministration of letermovir and COC.
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Pharmacokinetics of fixed-dose combinations of empagliflozin/metformin compared with individual tablets in healthy subjects.

OBJECTIVE: To compare the pharmacokinetics of fixed-dose combination (FDC) tablets of empagliflozin/metformin with individual tablets taken together. METHODS: In 3 randomized, open-label studies, healthy subjects received a single FDC tablet of empagliflozin/metformin in 1 of 6 dose combinations (empagliflozin 12.5 mg or 5 mg; metformin 500 mg, 850 mg, or 1,000 mg) in 1 period and the individual tablets taken together under fed conditions in another period. Empagliflozin 12.5 mg/metformin 1,000 mg FDC and individual tablets were also given under fasted conditions. RESULTS: Adjusted geometric mean ratios (GMRs) of empagliflozin area under the plasma concentration-time curve (AUC(0-∞)) for the FDCs vs. individual tablets ranged from 97.92 to 106.00%, and 90% CIs ranged from 93.53 to 109.39%. Adjusted GMRs of empagliflozin maximum plasma concentrations (C(max)) for the FDCs vs. individual tablets ranged from 100.97 to 106.52%, and 90% CIs ranged from 95.86 to 118.35%. Adjusted GMRs of metformin AUC(0-∞) for the FDCs vs. individual tablets ranged from 96.25 to 101.61%, and 90% CIs ranged from 88.54 to 106.62%. Adjusted GMRs of metformin C(max) for the FDCs vs. individual tablets ranged from 93.83 to 102.95%, and 90% CIs ranged from 88.01 to 109.08%. Bioequivalence was also established under fasted conditions for empagliflozin 12.5 mg/metformin 1,000 mg FDC vs. individual tablets taken together. All treatments were well tolerated. CONCLUSION: Empagliflozin/metformin FDC tablets were found to be bioequivalent to individual tablets taken together at all tested dose strengths.

Biotransformation and mass balance of the SGLT2 inhibitor empagliflozin in healthy volunteers.

1. The absorption, biotransformation and excretion of empagliflozin, an SGLT2 inhibitor, were evaluated in eight healthy subjects following a single 50 mg oral dose of empagliflozin containing ∼100 µCi [(14)C]-empagliflozin. 2. Radioactivity was rapidly absorbed, with plasma levels peaking 1 h post-dose. Total exposure was lower in blood versus plasma, consistent with moderate (28.6-36.8%) red blood cell partitioning. Protein binding was 80.3-86.2%. 3. Most of the radioactive dose was recovered in urine (54.4%) and faeces (41.1%). Unchanged empagliflozin was the most abundant drug-related component in plasma, representing 75.5-77.4% of plasma radioactivity and 79.6% plasma radioactivity AUC0-12 h. Unchanged empagliflozin was the most abundant drug-related component in urine and faeces, representing 43.5% (23.7% of dose) and 82.9% (34.1% of dose) of radioactivity in urine and faeces, respectively. Six metabolites were identified in plasma: three glucuronide conjugates representing 4.7-7.1% of AUC0-12 h and three less abundant metabolites (<0.2-1.9% AUC0-12 h). The most abundant metabolites in urine were two glucuronide conjugates (7.8-13.2% of dose) and in faeces was a tetrahydrofuran ring-opened carboxylic acid metabolite (1.9% of dose). 4. To conclude, empagliflozin was rapidly absorbed and excreted primarily unchanged in urine and faeces. Unchanged parent was the major drug-related component in plasma. Metabolism was primarily via glucuronide conjugation.

Exposure-response modelling for empagliflozin, a sodium glucose cotransporter 2 (SGLT2) inhibitor, in patients with type 2 diabetes.

AIMS: To provide model-based clinical development decision support including dose selection guidance for empagliflozin, an orally administered sodium glucose cotransporter 2 inhibitor, through developed exposure-response (E-R) models for efficacy and tolerability in patients with type 2 diabetes mellitus (T2DM). METHODS: Five randomized, placebo-controlled, multiple oral dose studies of empagliflozin in patients with T2DM (n = 974; 1-100 mg once daily, duration ≤12 weeks) were used to develop E-R models for efficacy (glycosylated haemoglobin [HbA1c ], fasting plasma glucose [FPG] and urinary glucose excretion). Two studies (n = 748, 12 weeks) were used to evaluate tolerability E-R. RESULTS: The efficacy model predicted maximal decreases in FPG and HbA1c of 16% and 0.6%, respectively, assuming a baseline FPG concentration of 8 mm (144 mg dl(-1) ) and 10-25 mg every day empagliflozin targeted 80-90% of these maximums. Increases in exposure had no effect on incidence rates of hypoglycaemia (n = 4), urinary tract infection (n = 17) or genital/vulvovaginal-related (n = 16) events, although low prevalence rates may have precluded more accurate evaluation. CONCLUSIONS: E-R analyses indicated that 10 and 25 mg once daily empagliflozin doses achieved near maximal glucose lowering efficacy.

Pharmacokinetics of empagliflozin, a sodium glucose cotransporter 2 inhibitor, and simvastatin following co-administration in healthy volunteers.

OBJECTIVE: This study was undertaken to investigate potential drugdrug interactions between the sodium glucose cotransporter 2 inhibitor empagliflozin and simvastatin. MATERIALS AND METHODS: In this open-label, randomized crossover trial, healthy volunteers (median (range) age 36.5 (20 - 50) years) received 3 single-dose treatments: 25 mg empagliflozin (n = 18), 40 mg simvastatin (n = 17), and 25 mg empagliflozin with 40 mg simvastatin (n = 18). RESULTS: Based on standard criteria, simvastatin had no effect on empagliflozin area under the plasma concentration-time curve (AUC(0-∞), adjusted geometric mean ratio (GMR): 102.05; 90% CI: 98.90 - 105.29) or maximum plasma concentration (C(max), GMR: 109.49; 90% CI: 96.91 - 123.69). There were only minor deviations in simvastatin AUC(0-∞) (GMR: 101.26; 90% CI: 80.06 - 128.07) and C(max) (GMR: 97.18; 90% CI: 76.30 - 123.77) when co-administered with empagliflozin. Empagliflozin had no effect on AUC(0-∞) (GMR: 104.87; 90% CI: 90.09 - 122.07) or C(max) (GMR: 97.27; 90% CI: 84.90 - 111.44) of simvastatin acid, the active metabolite of simvastatin. Adverse events (AEs) were reported for 6 subjects on empagliflozin, 4 on simvastatin, and 5 on co-administered treatment. No serious AEs or investigator-defined drug-related AEs were reported. CONCLUSION: No relevant drug-drug interaction was observed, and pharmacokinetic results suggest that no dose adjustments for either drug are necessary when empagliflozin and simvastatin are co-administered. Empagliflozin was well tolerated when administered alone or in combination with simvastatin.

The sodium glucose cotransporter 2 inhibitor empagliflozin does not prolong QT interval in a thorough QT (TQT) study.

BACKGROUND: Empagliflozin is a potent, selective sodium glucose cotransporter 2 (SGLT2) inhibitor in development as an oral antidiabetic treatment. This QT interval study assessed potential effects of empagliflozin on ventricular repolarisation and other electrocardiogram (ECG) parameters. METHODS: A randomised, placebo-controlled, single-dose, double-blind, five-period crossover study incorporating a novel double-placebo period design to reduce sample size, while maintaining full statistical power. TREATMENTS: single empagliflozin doses of 25 mg (therapeutic) and 200 mg (supratherapeutic), matching placebo and open-label moxifloxacin 400 mg (positive control). Triplicate 12-lead ECGs of 10 second duration were recorded at baseline and during the first 24 hours after dosing. The primary endpoint was mean change from baseline (MCfB) in the population heart rate-corrected QT interval (QTcN) between 1-4 hours after dosing. RESULTS: Thirty volunteers (16 male, 14 female, mean [range] age: 34.5 [18-52] years) were randomised. The placebo-corrected MCfB in QTcN 1-4 hours after dosing was 0.6 (90% CI: -0.7, 1.9) ms and -0.2 (-1.4, 0.9) ms for empagliflozin 25 mg and 200 mg, respectively, below the ICH E14 defined threshold of regulatory concern 10 ms. Assay sensitivity was confirmed by a placebo-corrected MCfB in QTcN 2-4 hours post-dose of 12.4 (10.7, 14.1) ms with moxifloxacin 400 mg. Empagliflozin tolerability was good for all volunteers; 23.3% experienced adverse events (AEs) with empagliflozin and 27.6% with placebo. The most frequent AE was nasopharyngitis. CONCLUSIONS/INTERPRETATION: Single doses of empagliflozin 25 mg and 200 mg were not associated with QTcN prolongation and were well tolerated in healthy volunteers. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01195675.

Pharmacokinetics of empagliflozin, a sodium glucose cotransporter-2 (SGLT2) inhibitor, and metformin following co-administration in healthy volunteers.

OBJECTIVE: This open-label study investigated potential drug-drug interactions between empagliflozin and metformin. METHODS: 16 healthy men received treatment A (empagliflozin 50 mg q.d. for 5 days), treatment B (empagliflozin 50 mg q.d. for 4 days with metformin 1,000 mg b.i.d. for 3 days and 1,000 mg q.d. on Day 4) and treatment C (metformin 1,000 mg b.i.d. for 3 days and 1,000 mg q.d .on Day 4) in the sequence AB then C, or C then AB. RESULTS: Metformin had no clinically relevant effect on the area under the steady state plasma concentration-time curve (AUC(τ,ss) geometric mean ratio (GMR): 96.9; 90% CI: 92.3 - 101.7) or the maximum plasma concentration at steady state (C(max,ss) GMR: 100.5; 90% CI: 88.8 - 113.7) of empagliflozin. Similarly, empagliflozin had no clinically relevant effect on AUC(τ,ss) (GMR: 100.7; 90% CI: 95.9 - 105.6) or C(max,ss) (GMR: 103.6; 90% CI: 96.5 - 111.2) of metformin. The renal clearance of empagliflozin and metformin were unaffected by co-administration. Both drugs were well tolerated alone and in combination and did not cause hypoglycemia. CONCLUSIONS: These data support co-administration of empagliflozin and metformin without dose adjustment.

Effect of food on the pharmacokinetics of empagliflozin, a sodium glucose cotransporter 2 (SGLT2) inhibitor, and assessment of dose proportionality in healthy volunteers.

OBJECTIVES: Empagliflozin is an orally available, potent and highly selective inhibitor of the sodium glucose cotransporter 2 (SGLT2). This study was undertaken to investigate the effect of food on the pharmacokinetics of 25 mg empagliflozin and to assess dose proportionality between 10 mg and 25 mg empagliflozin under fasted conditions. MATERIALS AND METHODS: In this open-label, 3-way, cross-over study, 18 healthy volunteers received 3 single doses of empagliflozin in a randomized sequence (25 mg empagliflozin under fasted conditions, 25 mg empagliflozin after a high-fat, high-calorie breakfast and 10 mg empagliflozin under fasted conditions), each separated by a washout period of at least 7 days. Serial plasma samples were collected at selected time points over a period of 72 hours. RESULTS: Administration with food had no clinically relevant effect on the area under the plasma concentration-time curve (AUC0-∞) of empagliflozin (geometric mean ratio (GMR): 84.04, 90% confidence interval (CI): 80.86 - 87.34). The decrease observed in the maximum plasma concentrations (Cmax) of empagliflozin (GMR: 63.22, 90% CI: 56.74 - 70.44) when administered with food was not considered clinically meaningful. The increases in AUC0-∞ and Cmax for 10 mg vs. 25 mg empagliflozin administered under fasting conditions were roughly dose-proportional, as demonstrated by the slope ß of the regression lines being slightly less than 1 (slope ß for AUC0-∞: 0.94, 95% CI: 0.90 - 0.97; slope ß for Cmax: 0.91, 95% CI: 0.80 - 1.01). Empagliflozin was well tolerated under fed and fasting conditions. CONCLUSIONS: The results support administration of empagliflozin tablets independently of food. Increases in empagliflozin exposure under fasting conditions were roughly dose-proportional between 10 mg and 25 mg empagliflozin.

Exposure-Response Analyses of Letermovir Following Oral and Intravenous Administration in Allogeneic Hematopoietic Cell Transplantation Recipients.

The cytomegalovirus (CMV) viral terminase inhibitor letermovir is approved for prophylaxis of CMV infection and disease in adult CMV-seropositive allogeneic hematopoietic stem cell transplantation recipients. In a phase III trial (NCT02137772), letermovir significantly reduced clinically significant CMV infection (CS-CMVi) rate vs. placebo through Week 24 (primary end point) and Week 14 (secondary end point) post transplantation. Here, exposure-response relationships were investigated using efficacy and selected safety end points from the phase III trial to inform the proposed clinical dose. Post hoc exposure estimates were derived from a population pharmacokinetic model. No significant exposure dependencies were found for CS-CMVi through Week 24 or Week 14 among letermovir-treated participants. Evaluated covariates had no impact on exposure-efficacy relationships and letermovir plasma exposure did not affect time of CS-CMVi onset. There was no dependence between adverse event incidence and letermovir exposure. These results support current dosing recommendations in several countries and regions, including the United States and European Union.

Drug-Drug Interaction of Letermovir and Atorvastatin in Healthy Participants.

Letermovir (MK-8228/AIC246) is a cytomegalovirus (CMV) DNA terminase complex inhibitor for CMV prophylaxis in adult patients undergoing hematopoietic stem cell transplant. It is cytochrome P450 (CYP) 3A inhibitor and inhibits organic anion transporting polypeptide 1B1/3 and breast cancer resistance protein transporters. Atorvastatin (ATV), a commonly used treatment for hypercholesterolemia, is a substrate of organic anion transporting polypeptide 1B1, potentially breast cancer resistance protein, and CYP3A. As letermovir may be coadministered with ATV, the effect of multiple-dose letermovir 480 mg once daily on the pharmacokinetics of single-dose ATV 20 mg and its metabolites (ortho-hydroxyatorvastatin [o-OH-ATV] and para-hydroxyatorvastatin [p-OH-ATV]) was evaluated in an open-label trial in healthy female adults (N = 14). ATV area under the plasma concentration-time curve from time 0 to infinity and maximum plasma concentration (Cmax ) increased ≈3-fold with letermovir coadministration. The time to ATV Cmax also increased, while apparent clearance decreased. The exposures of o-OH-ATV and p-OH-ATV were comparable in the presence versus absence of letermovir; however, o-OH-ATV Cmax decreased by 60% with coadministration, while p-OH-ATV Cmax was similar. Due to the increase in ATV exposure with letermovir coadministration, statin-associated adverse events such as myopathy should be closely monitored following coadministration. The dose of ATV should not exceed 20 mg daily when coadministered with letermovir.

Quantitative systems pharmacology in neuroscience: Novel methodologies and technologies.

The development and application of quantitative systems pharmacology models in neuroscience have been modest relative to other fields, such as oncology and immunology, which may reflect the complexity of the brain. Technological and methodological advancements have enhanced the quantitative understanding of brain physiology and pathophysiology and the effects of pharmacological interventions. To maximize the knowledge gained from these novel data types, pharmacometrics modelers may need to expand their toolbox to include additional mathematical and statistical frameworks. A session was held at the 10th annual American Conference on Pharmacometrics (ACoP10) to highlight several recent advancements in quantitative and systems neuroscience. In this mini-review, we provide a brief overview of technological and methodological advancements in the neuroscience therapeutic area that were discussed during the session and how these can be leveraged with quantitative systems pharmacology modeling to enhance our understanding of neurological diseases. Microphysiological systems using human induced pluripotent stem cells (IPSCs), digital biomarkers, and large-scale imaging offer more clinically relevant experimental datasets, enhanced granularity, and a plethora of data to potentially improve the preclinical-to-clinical translation of therapeutics. Network neuroscience methodologies combined with quantitative systems models of neurodegenerative disease could help bridge the gap between cellular and molecular alterations and clinical end points through the integration of information on neural connectomics. Additional topics, such as the neuroimmune system, microbiome, single-cell transcriptomic technologies, and digital device biomarkers, are discussed in brief.

Population pharmacokinetics of letermovir following oral and intravenous administration in healthy participants and allogeneic hematopoietic cell transplantation recipients.

Letermovir is indicated for prophylaxis of cytomegalovirus infection and disease in allogeneic hematopoietic stem cell transplant (HSCT) recipients. Two-stage population pharmacokinetic (PK) modeling of letermovir was conducted to support dose rationale and evaluate the impact of intrinsic/extrinsic factors. Data from healthy phase I study participants over a wide dose range were modeled to evaluate the effects of selected intrinsic factors, including pharmacogenomics; next, phase III HSCT-recipient data at steady-state following clinical doses were modeled. The model in HSCT recipients adequately described letermovir PK following both oral or i.v. administration, and was consistent with the healthy participant model at steady-state clinical doses. Intrinsic factor effects were not clinically meaningful. These staged analyses indicate that letermovir PK in HSCT recipients and healthy participants differ only with respect to bioavailability and absorption rate. The HSCT recipient model was suitable for predicting exposure for exposure-response analysis supporting final dose selection.

A Disease Progression Model to Quantify the Nonmotor Symptoms of Parkinson's Disease in Participants With Leucine-Rich Repeat Kinase 2 Mutation.

Leucine-rich repeat kinase 2 (LRRK2) inhibitors are currently in clinical development as interventions to slow progression of Parkinson's disease (PD). Understanding the rate of progression in PD as measured by both motor and nonmotor features is particularly important in assessing the potential therapeutic effect of LRRK2 inhibitors in clinical development. Using standardized data from the Critical Path for Parkinson's Unified Clinical Database, we quantified the rate of progression of the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part I (nonmotor aspects of experiences of daily living) in 158 participants with PD who were carriers and 598 participants with PD who were noncarriers of at least one of three different LRRK2 gene mutations (G2019S, R1441C/G, or R1628P). Age and disease duration were found to predict baseline disease severity, while presence of at least one of these three LRRK2 mutations was a predictor of the rate of MDS-UPDRS Part I progression. The estimated progression rate in MDS-UPDRS Part I was 0.648 (95% confidence interval: 0.544, 0.739) points per year in noncarriers of a LRRK2 mutation and 0.259 (95% confidence interval: 0.217, 0.295) points per year in carriers of a LRRK2 mutation. This analysis demonstrates that the rate of progression based on MDS-UPDRS Part I is ~ 60% lower in carriers as compared with noncarriers of LRRK2 gene mutations.

Challenges in Alzheimer's Disease Drug Discovery and Development: The Role of Modeling, Simulation, and Open Data.

Alzheimer's disease (AD) is the leading cause of dementia worldwide. With 35 million people over 60 years of age with dementia, there is an urgent need to develop new treatments for AD. To streamline this process, it is imperative to apply insights and learnings from past failures to future drug development programs. In the present work, we focus on how modeling and simulation tools can leverage open data to address drug development challenges in AD.

Development of a Disease Progression Model for Leucine-Rich Repeat Kinase 2 in Parkinson's Disease to Inform Clinical Trial Designs.

A quantitative assessment of Parkinson's disease (PD) progression is critical for optimizing clinical trials design. Disease progression model was developed using pooled data from the Progression Marker Initiative study and the Incidence of Cognitive Impairment in Cohorts with Longitudinal Evaluation in Parkinson's Disease study. Age, gender, concomitant medication, and study arms were predictors of baseline. A mutation in the leucine-rich repeat kinase 2 (LRRK2) encoding gene was associated with the disease progression rate. The progression rate in subjects with PD who carried LRRK2 mutation was slightly slower (~0.170 points/month) than that in PD subjects without the mutation (~0.222 points/month). For a nonenriched placebo-controlled clinical trial, approximately 70 subjects/arm would be required to detect a drug effect of 50% reduction in the progression rate with 80% probability, whereas 85, 93, and 100 subjects/arm would be required for an enriched clinical trial with 30%, 50%, and 70% subjects with LRRK2 mutations, respectively.

In vitro-in vivo correlation for nevirapine extended release tablets.

An in vitro-in vivo correlation (IVIVC) for four nevirapine extended release tablets with varying polymer contents was developed. The pharmacokinetics of extended release formulations were assessed in a parallel group study with healthy volunteers and compared with corresponding in vitro dissolution data obtained using a USP apparatus type 1. In vitro samples were analysed using HPLC with UV detection and in vivo samples were analysed using a HPLC-MS/MS assay; the IVIVC analyses comparing the two results were performed using WinNonlin. A Double Weibull model optimally fits the in vitro data. A unit impulse response (UIR) was assessed using the fastest ER formulation as a reference. The deconvolution of the in vivo concentration time data was performed using the UIR to estimate an in vivo drug release profile. A linear model with a time-scaling factor clarified the relationship between in vitro and in vivo data. The predictability of the final model was consistent based on internal validation. Average percent prediction errors for pharmacokinetic parameters were <10% and individual values for all formulations were <15%. Therefore, a Level A IVIVC was developed and validated for nevirapine extended release formulations providing robust predictions of in vivo profiles based on in vitro dissolution profiles.

Pharmacokinetic Drug-Drug Interactions Between Letermovir and the Immunosuppressants Cyclosporine, Tacrolimus, Sirolimus, and Mycophenolate Mofetil.

Letermovir (AIC246, MK-8228) is a human cytomegalovirus terminase inhibitor indicated for the prophylaxis of cytomegalovirus infection and disease in allogeneic hematopoietic stem cell transplant recipients that is also being investigated for use in other transplant settings. Many transplant patients receive immunosuppressant drugs, of which several have narrow therapeutic ranges. There is a potential for the coadministration of letermovir with these agents, and any potential effect on their pharmacokinetics (PK) must be understood. Five phase 1 trials were conducted in 73 healthy female participants to evaluate the effect of letermovir on the PK of cyclosporine, tacrolimus, sirolimus, and mycophenolic acid (active metabolite of mycophenolate mofetil [MMF]), as well as the effect of cyclosporine and MMF on letermovir PK. Safety and tolerability were also assessed. Coadministration of letermovir with cyclosporine, tacrolimus, and sirolimus resulted in 1.7-, 2.4-, and 3.4-fold increases in area under the plasma concentration-time curve and 1.1-, 1.6-, and 2.8-fold increases in maximum plasma concentration, respectively, of the immunosuppressants. Coadministration of letermovir and MMF had no meaningful effect on the PK of mycophenolic acid. Coadministration with cyclosporine increased letermovir area under the plasma concentration-time curve by 2.1-fold and maximum plasma concentration by 1.5-fold, while coadministration with MMF did not meaningfully affect the PK of letermovir. Given the increased exposures of cyclosporine, tacrolimus, and sirolimus, frequent monitoring of concentrations should be performed during administration and at discontinuation of letermovir, with dose adjustment as needed. These data support the reduction in clinical dosage of letermovir (to 240 mg) upon coadministration with cyclosporine.

Molecular Neuroimaging of the Dopamine Transporter as a Patient Enrichment Biomarker for Clinical Trials for Early Parkinson's Disease.

The Critical Path for Parkinson's (CPP) Imaging Biomarker and Modeling and Simulation working groups aimed to achieve qualification opinion by the European Medicines Agency (EMA) Committee for Medical Products for Human Use (CHMP) for the use of baseline dopamine transporter neuroimaging for patient selection in early Parkinson's disease clinical trials. This paper describes the regulatory science strategy to achieve this goal. CPP is an international consortium of three Parkinson's charities and nine pharmaceutical partners, coordinated by the Critical Path Institute.

Dopamine Transporter Neuroimaging as an Enrichment Biomarker in Early Parkinson's Disease Clinical Trials: A Disease Progression Modeling Analysis.

Given the recognition that disease-modifying therapies should focus on earlier Parkinson's disease stages, trial enrollment based purely on clinical criteria poses significant challenges. The goal herein was to determine the utility of dopamine transporter neuroimaging as an enrichment biomarker in early motor Parkinson's disease clinical trials. Patient-level longitudinal data of 672 subjects with early-stage Parkinson's disease in the Parkinson's Progression Markers Initiative (PPMI) observational study and the Parkinson Research Examination of CEP-1347 Trial (PRECEPT) clinical trial were utilized in a linear mixed-effects model analysis. The rate of worsening in the motor scores between subjects with or without a scan without evidence of dopamine transporter deficit was different both statistically and clinically. The average difference in the change from baseline of motor scores at 24 months between biomarker statuses was -3.16 (90% confidence interval [CI] = -0.96 to -5.42) points. Dopamine transporter imaging could identify subjects with a steeper worsening of the motor scores, allowing trial enrichment and 24% reduction of sample size.