Exposure-Response Efficacy Modeling to Support Trofinetide Dosing in Individuals with Rett Syndrome

INTRODUCTION

Trofinetide was recently approved for the treatment of Rett syndrome (RTT) on the basis of the efficacy and safety findings of the phase 3 LAVENDER study, which used a body weight-based dosing regimen. Exposure-response (E-R) efficacy modeling was used to characterize relationships between trofinetide exposure measures (maximum drug concentration and area under the concentration-time curve for the dosing interval of 0-12 h [AUC0-12]) and efficacy endpoints in RTT clinical studies to support the trofinetide dosing regimen.

METHODS

Efficacy endpoints were modeled using trofinetide exposure measures predicted from the population pharmacokinetic model and Bayesian estimates. The analysis population for each E-R model comprised individuals receiving placebo or trofinetide who had available trofinetide exposure measures. Efficacy endpoints were scores from the Rett Syndrome Behaviour Questionnaire (RSBQ), the Clinical Global Impression-Improvement, the Communication and Symbolic Behavior Scales Developmental Profile™ Infant-Toddler Checklist (CSBS-DP-IT) Social Composite, and the Rett Syndrome Clinician Rating of Ability to Communicate Choices (RTT-COMC).

RESULTS

Higher trofinetide exposure was associated with improvements in RSBQ, CSBS-DP-IT Social Composite, and RTT-COMC scores. Assuming target trofinetide AUC0-12 values of 800-1200 μg·h/mL, the reductions in RSBQ total scores at week 12 were approximately five- to seven-fold greater with trofinetide (range 3.55-4.94) versus placebo (0.76). Significant E-R relationships were also found for the CSBS-DP-IT Social Composite and RTT-COMC scores.

CONCLUSION

E-R efficacy modeling demonstrated significant relationships between trofinetide exposure and RSBQ, CSBS-DP-IT Social Composite, and RTT-COMC scores. Trofinetide is efficacious within the target exposure range, supporting the approved dosing regimen for trofinetide.

TRIAL REGISTRATION

NCT01703533, NCT02715115, NCT04181723.

Population pharmacokinetic modeling and target attainment analyses of rezafungin for the treatment of candidemia and invasive candidiasis

Rezafungin is a chemically and metabolically stable echinocandin with a longer half-life than other echinocandins, allowing for a once-weekly intravenous infusion versus a daily infusion. Rezafungin is approved in the US for the treatment of candidemia and/or invasive candidiasis and is in development for the prevention of invasive fungal disease caused by Candida, Aspergillus, and Pneumocystis spp. in immunosuppressed patients. A population pharmacokinetic (PPK) model was developed using data from five Phase 1, one Phase 2, and one Phase 3 study. The model found to best describe the available data was a three-compartment PPK model with first-order elimination characterized by the parameters clearance (CL), central volume (V1), peripheral volume (V23), intercompartmental clearance 1, and intercompartmental clearance 2. The variability model included correlated interindividual variability in CL, V1, and V23 and a proportional residual variability model. The following statistically significant covariates were identified: albumin concentrations on V23; body surface area (BSA) on CL, V1, and V23; and disease state on CL and V1. Disease states were defined as patients from the Phase 2 and Phase 3 studies and hepatically impaired subjects. Covariates of BSA, disease state, or albumin, included in the final model, were not associated with clinically meaningful changes in PK, nor were any other patient factors, indicating that a common dose regimen is adequate for all adult patients. Target attainment simulations were performed to estimate the probability of achieving PK/pharmacodynamic targets across the range of minimum inhibitory concentration values for six species of Candida.

Population pharmacokinetics and exposure-response analysis of a single dose of sotrovimab in the early treatment of patients with mild to moderate COVID-19

Sotrovimab is a recombinant human monoclonal antibody that has been shown to prevent progression to hospitalization or death in non-hospitalized high-risk patients with mild-to-moderate COVID-19 following either intravenous (IV) or intramuscular (IM) administration. Population pharmacokinetic (popPK) and exposure-response (ER) analyses were performed to characterize single dose sotrovimab PK and the relationship between exposure and response (probability of progression), as well as covariates that may contribute to between-participant variability in sotrovimab PK and efficacy following IV or IM administration. Sotrovimab PK was described by a two-compartment model with linear elimination; IM absorption was characterized by a sigmoid absorption model. PopPK covariate analysis led to the addition of the effect of body weight on systemic clearance and peripheral volume of distribution, sex on IM bioavailability and first-order absorption rate (KA), and body mass index on KA. However, the magnitude of covariate effect was not pronounced and was therefore not expected to be clinically relevant based on available data to date. For ER analysis, sotrovimab exposure measures were predicted using the final popPK model. An ER model was developed using the exposure measure of sotrovimab concentration at 168 hours that described the relationship between exposure and probability of progression within the ER dataset for COMET-TAIL. The number of risk factors (≤1 vs >1) was incorporated as an additive shift on the model-estimated placebo response but had no impact on overall drug response. Limitations in the ER model may prevent generalization of these results to describe the sotrovimab exposure-progression relationship across SARS-COV-2 variants.

Exposure-response Modeling From the CLARITY Trial of Pimavanserin for Adjunctive Treatment of Major Depressive Disorder

In the 10-week, phase 2 CLARITY study of patients with major depressive disorder, adjunctive therapy to antidepressants with pimavanserin 34 mg once daily statistically significantly improved the Hamilton Depression Rating Scale (HAMD-17) total score (primary endpoint) and Sheehan Disability Scale (SDS) score (secondary endpoint) versus placebo. This analysis characterized the exposure-response (E-R) relationships of pimavanserin in this CLARITY patient population. Exposure measures were estimated for each patient based on population-pharmacokinetic empirical Bayesian estimates. E-R models were developed to describe exposure-efficacy (HAMD-17, SDS, and Clinical Global Impression-Improvement [CGI-I] scale) and exposure-safety relationships (Karolinska Sleepiness Scale [KSS], Massachusetts General Hospital Sexual Functioning Inventory [MGH-SFI], and adverse events [AEs] of headache, sedation, and somnolence) relationships. For the primary efficacy endpoint (HAMD-17 scores), a sigmoid maximum-effect model described the time course of response, and a linear function of pimavanserin exposure was statistically significant. HAMD-17 scores decreased steadily over time following placebo and pimavanserin treatment; separation from placebo increased as peak pimavanserin plasma concentration (C_max ) increased. At median pimavanserin C_max (34-mg dose), the reduction from baseline in HAMD-17 scores was -11.1 and -13.5 at weeks 5 and 10, respectively. Relative to placebo, the model predicted comparable reductions in HAMD-17 scores at weeks 5 and 10. Similar improvements in favor of pimavanserin were detected with SDS, CGI-I, MGH-SFI, and KSS scores. No E-R relationship was found for AEs. E-R modeling predicted a relationship between higher pimavanserin exposure and improvement in HAMD-17 score and improvement across multiple secondary efficacy endpoints.

Population Pharmacokinetics of Vericiguat in Patients with Heart Failure with Reduced Ejection Fraction: An Integrated Analysis

Vericiguat, a novel stimulator of soluble guanylate cyclase (sGC), is indicated for the treatment of patients following a hospitalization for heart failure or need for outpatient IV diuretics, with symptomatic chronic heart failure and ejection fraction less than 45%. Pharmacokinetic (PK) data from the phase II trial SOCRATES-REDUCED (SOluble guanylate Cyclase stimulatoR in heArT failurE Study) and the phase III trial VICTORIA (Vericiguat Global Study in Patients with Heart Failure with Reduced Ejection Fraction) were used to characterize vericiguat PK. A total of 8,092 concentration records from 2,321 participants (362 from SOCRATES-REDUCED and 1,959 from VICTORIA) were utilized for the development of the population PK (PPK) model. The final PK model was a one-compartment model with first-order absorption and linear elimination. Baseline body weight and time-varying body weight were identified as statistically significant covariates affecting apparent clearance (CL/F) and volume of distribution (V_c ), respectively. Age, sex, race, bilirubin, estimated glomerular filtration rate (eGFR), and albumin did not affect vericiguat PK. Baseline disease-related factors, such as left ventricular ejection fraction, New York Heart Association (NYHA) class, and N-terminal pro B-type natriuretic peptide (NT-proBNP), also did not influence vericiguat PK. Since vericiguat is a titrated drug, the impact of vericiguat PK on the titration to and maintenance of the target dose in VICTORIA was assessed. The distribution of steady-state doses in VICTORIA was similar across CL/F quartiles, suggesting that the ability to reach and maintain dosing at the target 10 mg dose was not related to vericiguat exposure.

POS0579 ABSENCE OF ASSOCIATION BETWEEN ABATACEPT EXPOSURE LEVELS AND INITIAL INFECTION IN PATIENTS WITH RA: A POST HOC ANALYSIS OF THE RANDOMIZED, PLACEBO-CONTROLLED AVERT-2 STUDY

Background

Infections are the most commonly reported AE observed in patients with RA treated with immunosuppressive therapies and can be clinically significant. A recent review reported differences in the risk of infection for some biologics such as tocilizumab and TNF inhibitors.1 Abatacept selectively modulates T-cell co-stimulation and is approved for the treatment of RA. In patients with polyarticular-course juvenile idiopathic arthritis, no association was found between higher serum abatacept exposure and the incidence of infection.2 This has not been evaluated for adult patients with RA.

Objectives

To determine if higher serum abatacept exposure during treatment with SC abatacept was associated with increased risk of infection in adult patients with RA.

Methods

AVERT-2 (Assessing Very Early Rheumatoid arthritis Treatment-2) was a randomized, placebo-controlled study of SC abatacept + MTX vs abatacept placebo + MTX in MTX-naive, anti-citrullinated protein antibody–positive patients with early, active RA.3 A post hoc population pharmacokinetic (PK) analysis was performed using PK-evaluable patient data from the induction period (year 1) of AVERT-2. Association between steady-state abatacept exposure (min plasma concentration [Cmin], max plasma concentration [Cmax], and average plasma concentration [Cavg]) and first infection was evaluated using Kaplan–Meier plots of probability vs time on treatment by abatacept exposure quartiles and Cox proportional-hazards models.

Results

PK of SC abatacept was defined as a linear 2-compartment model with first-order absorption and first-order elimination. The findings of the updated PK analysis were consistent with those reported in prior population analyses of abatacept PK in adults with RA. The final model included effects of baseline body weight, estimated glomerular filtration rate, sex, age, albumin, MTX use, NSAID use, SJC, and race on abatacept clearance. The only covariate with a clinically relevant effect was higher body weight, which caused an increase in clearance and volume. Infections occurred in a total of 330/693 (47.6%; serious, 1.6%) patients treated with abatacept, and 134/301 (44.5%; serious, 1.3%) with placebo during the first year of AVERT-2. In patients taking abatacept, the mean (SD) study exposure to abatacept was 376 (60) days, while mean (SD) prednisone equivalent dose was 6.7 (3.8) mg/day and mean (SD) MTX dose was 9.6 (3.0) mg/week. No exposure–response relationship was observed between the probability of first infection and steady-state abatacept exposure quartiles (Cavg, Cmin, and Cmax), or compared with placebo (Figure 1A–C). Kaplan–Meier assessment also showed no increase in risk of infection with concomitant use of MTX and glucocorticoids.

Conclusion

No association was found between initial infection and steady-state abatacept exposure (Cavg, Cmin, Cmax) or MTX and glucocorticoid use in patients with RA treated with SC abatacept.

References

[1]Jani M, et al. Curr Opin Rheumatol 2019;31:285–92.

[2]Ruperto N, et al. J Rheumatol 2021;48:1073–81.

[3]Emery P, et al. Arthritis Rheumatol 2019;71(suppl 10):L11.

Acknowledgements

This study was sponsored by Bristol Myers Squibb. Writing and editorial assistance were provided by Fiona Boswell, PhD, of Caudex, and was funded by Bristol Myers Squibb. Support was provided by Sandra Overfield as Protocol Manager, and Prema Sukumar and Renfang Hwang as Data Science Leads.

Disclosure of Interests

Paul Emery Consultant of: AbbVie, AstraZeneca, Boehringer Ingelheim, Bristol Myers Squibb, Eli Lilly, Galapagos, Gilead, Janssen, Merck Sharp & Dohme, Novartis, Pfizer, Roche, Samsung, Grant/research support from: AbbVie, Bristol Myers Squibb, Eli Lilly, Novartis, Pfizer, Roche, Samsung, Roy Fleischmann Consultant of: Amgen, AbbVie, Bristol Myers Squibb, Gilead, GlaxoSmithKline, Novartis, Pfizer, Grant/research support from: Amgen, AbbVie, Arthrosi, Biosplice, Bristol Myers Squibb, Gilead, GlaxoSmithKline, Horizon, Novartis, Pfizer, Regeneron, TEVA, UCB, Robert Wong Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Karissa Lozenski Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Yoshiya Tanaka Speakers bureau: AbbVie, Amgen, Astellas, AstraZeneca, Boehringer Ingelheim, Bristol Myers Squibb, Chugai, Eisai, Eli Lilly, Gilead, Mitsubishi Tanabe, YL Biologics, Consultant of: AbbVie, Ayumi, Daiichi Sankyo, Eli Lilly, GlaxoSmithKline, Taisho, Sanofi, Grant/research support from: AbbVie, Asahi Kasei, Boehringer Ingelheim, Chugai, Corrona, Daiichi Sankyo, Eisai, Kowa, Mitsubishi Tanabe, Takeda, Vivian Bykerk Consultant of: Amgen, Bristol Myers Squibb, Genzyme Corporation, Gilead, Regeneron, UCB, Grant/research support from: Amgen, Bristol Myers Squibb, Genzyme Corporation, Pfizer, Regeneron, Sanofi Aventis, UCB, Clifton Bingham Consultant of: AbbVie, Bristol Myers Squibb, Eli Lilly, Janssen, Pfizer, Sanofi, Grant/research support from: Bristol Myers Squibb, Thomas Huizinga Speakers bureau: Abblynx, Abbott, Biotest AG, Bristol Myers Squibb, Crescendo Bioscience, Eli Lilly, Epirus, Galapagos, Janssen, Merck, Novartis, Pfizer, Roche, Sanofi- Aventis, UCB, Consultant of: Abblynx, Abbott, Biotest AG, Bristol Myers Squibb, Crescendo Bioscience, Eli Lilly, Epirus, Galapagos, Janssen, Merck, Novartis, Pfizer, Roche, Sanofi- Aventis, UCB, Grant/research support from: Abblynx, Abbott, Biotest AG, Bristol Myers Squibb, Crescendo Bioscience, Eli Lilly, Epirus, Galapagos, Janssen, Merck, Novartis, Pfizer, Roche, Sanofi- Aventis, UCB, Gustavo Citera Speakers bureau: AbbVie, Amgen, Bristol Myers Squibb, Eli Lilly, Janssen, Pfizer, Sandoz, Consultant of: AbbVie, Amgen, Bristol Myers Squibb, Pfizer, Grant/research support from: Pfizer, Yedid Elbez Consultant of: Bristol Myers Squibb, Employee of: Signifience, Vidya Perera Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Bindu Murthy Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Kelly Maxwell Consultant of: Bristol Myers Squibb, Employee of: Cognigen Corporation, Julie Passarell Consultant of: Bristol Myers Squibb, Employee of: Cognigen Corporation, William Hedrich: None declared, Daphne Williams Consultant of: Black Diamond Network, Joule, Syneos, Employee of: Bristol Myers Squibb.

Population Pharmacokinetic Modeling and Exposure-Response Analysis for Aripiprazole Once Monthly in Subjects With Schizophrenia

An intramuscular formulation of aripiprazole monohydrate dosed once monthly (AOM) was developed to address nonadherence with the approved oral tablets. A 3-compartment linear population pharmacokinetic model for oral and AOM doses was developed; relative bioavailability was estimated for AOM relative to oral dosing and body mass index and sex were significant predictors of AOM absorption rate constant (longer absorption half-life for women and absorption half-life increases with increasing body mass index). Aripiprazole apparent oral clearance for subjects with cytochrome P450 (CYP) 2D6 poor metabolizer status and in the presence of strong CYP2D6 inhibitors was approximately half that of subjects with CYP2D6 extensive metabolizer status and 24% lower in the presence of strong CYP3A4 inhibitors. Simulations of the population pharmacokinetics were conducted to evaluate the effect of different dose initiation strategies for AOM, the effects of CYP2D6 metabolizer status, coadministration of CYP2D6 and CYP3A4 inhibitors, and missed doses. An exposure-response model with an exponential hazard function of the model-predicted minimum concentration (C_min ) described the time to relapse. The hazard ratio (95% confidence interval) was 4.41 (2.89-6.75). Thus, a subject with a diagnosis of schizophrenia and C_min  ≥ 95 ng/mL is 4.41 times less likely to relapse relative to a subject with C_min  < 95 ng/mL.

Exposure-Response Analysis to Support Nivolumab Once Every 4 Weeks Dosing in Combination with Cabozantinib in Renal Cell Carcinoma

PURPOSE

A benefit:risk assessment for a less-frequent nivolumab 480 mg Q4W + cabozantinib 40 mg QD dosing regimen was predicted using modeling and simulation of clinical trial data from nivolumab monotherapy studies and from the nivolumab 240 mg Q2W + cabozantinib 40mg QD dosing regimen, which demonstrated clinical benefit versus sunitinib in previously untreated advanced renal cell carcinoma (aRCC) in the phase III CheckMate 9ER trial (NCT03141177).

EXPERIMENTAL DESIGN

Multivariable Cox proportional-hazards analyses were conducted using nivolumab monotherapy data in previously treated aRCC and data from CheckMate 9ER to evaluate progression-free survival (PFS), overall survival (OS), and grade {greater than or equal to}2 immune-mediated adverse events (IMAEs).

RESULTS

Nivolumab 240 mg Q2W + cabozantinib versus nivolumab showed improvement in PFS (HR, 0.38; 95% CI, 0.31-0.47), OS (HR, 0.63 95% CI, 0.46-0.85), and increased risk of grade {greater than or equal to}2 IMAEs (HR, 2.19; 95% CI, 1.79-2.67). Nivolumab exposure was not a predictor of PFS/OS or grade {greater than or equal to}2 IMAEs. Lower nivolumab clearance, male sex, higher baseline bodyweight, and Karnofsky performance (100) were each associated with PFS/OS improvements. Region and IMDC poor score were negative OS predictors. Age, baseline albumin, and programmed death ligand-1 status were not significant PFS/OS predictors. Cabozantinib was a significant grade {greater than or equal to}2 IMAE predictor, driven by diarrhea and hepatic events. Model-predicted PFS/OS and grade {greater than or equal to}2 IMAE rates were similar (<2.5% difference) for nivolumab 240 mg Q2W + cabozantinib and 480 mg Q4W + cabozantinib.

CONCLUSIONS

Comparable benefit:risk was predicted for nivolumab 480 mg Q4W + cabozantinib and nivolumab 240 mg Q2W + cabozantinib.

Relationship of the Calcitonin Gene-Related Peptide Monoclonal Antibody Galcanezumab Pharmacokinetics and Capsaicin-Induced Dermal Blood Flow in Healthy Subjects

Galcanezumab, a humanized monoclonal antibody targeting calcitonin gene-related peptide, was recently approved for migraine prophylaxis. The pharmacokinetic/pharmacodynamic (PK/PD) relationship between galcanezumab concentration and inhibition of capsaicin-induced dermal blood flow (CIDBF) was evaluated using first-in-human data following 6 single subcutaneous doses (1 to 600 mg) or multiple (4) 150-mg doses every 2 weeks in 7 cohorts (7 actively treated subjects and 2 placebo-treated healthy subjects). Galcanezumab pharmacokinetics were best described by a 1-compartment model with delayed first-order absorption/linear elimination. Apparent estimates (between-subject variability) of clearance, volume of distribution, absorption rate constant, and lag time were 0.0106 L/h (27%CV), 11.2 L (21%CV), 0.0192 h^-1 (89%CV), and 0.202 hours, respectively. Estimated elimination half-life was about 30 days. An effect compartment link model described the concentration-effect relationship; estimated maximum inhibitory effect was 70.5%, and 50% maximum inhibitory effect concentration (IC₅₀ ) was 1060 ng/mL. Galcanezumab showed dose- and concentration-dependent potent and durable inhibition of CIDBF. Simulated effect compartment concentrations were maintained above IC₅₀ after 12 weeks of dosing. Near-maximal CIDBF inhibition occurred with 150 mg biweekly for 12 weeks lasting ≥24 weeks or with ≥30 mg every 2 weeks or 195 mg every 13 weeks. Quantitative modeling of galcanezumab PK/PD supported dose selection for the phase 2 proof-of-concept study.

Absence of Association Between Abatacept Exposure and Initial Infection in Patients With Juvenile Idiopathic Arthritis

OBJECTIVE

To assess the relationship between infection risk and abatacept (ABA) exposure levels in patients with polyarticular-course juvenile idiopathic arthritis (pJIA) following treatment with subcutaneous (SC) and intravenous (IV) ABA.

METHODS

Data from 2 published studies (ClinicalTrials.gov: NCT01844518, NCT00095173) of ABA treatment in pediatric patients were analyzed. One study treated patients aged 2-17 years with SC ABA and the other treated patients aged 6-17 years with IV ABA. Association between serum ABA exposure measures and infection was evaluated using Kaplan-Meier plots of probability of first infection vs time on treatment by ABA exposure quartiles and log-rank tests. Number of infections by ABA exposure quartiles was investigated.

RESULTS

Overall, 343 patients were included in this analysis: 219 patients received SC ABA and 124 patients received IV ABA. Overall, 237/343 (69.1%) patients had ≥ 1 infection over 24 months. No significant difference in time to first infection across 4 quartiles of ABA exposure levels was observed in the pooled (P = 0.45), SC (2-5 yrs: P = 0.93; 6-17 yrs: P = 0.48), or IV (P = 0.50) analyses. Concomitant use of methotrexate and glucocorticoids (at baseline and throughout) with ABA did not increase infection risk across the ABA exposure quartiles. There was no evidence of association between number of infections and ABA exposure quartiles. No opportunistic infections related to ABA were reported.

CONCLUSION

In patients aged 2-17 years with pJIA, no evidence of association between higher levels of exposure to IV ABA or SC ABA and incidence of infection was observed.

Effect of Fremanezumab Monthly and Quarterly Doses on Efficacy Responses

OBJECTIVE

Exposure-response (E-R) models were developed to provide a description of the time-course of treatment effect for monthly and quarterly dosing regimens of fremanezumab.

BACKGROUND

Fremanezumab is a monoclonal antibody for preventive treatment of episodic migraine (EM) and chronic migraine (CM). In phase 2b and 3 clinical studies of fremanezumab, significant reductions in migraine and headache days and other clinical endpoints were observed for patients with EM and patients with CM. Development of E-R models relating individual-specific measures of drug exposure to clinical endpoints provides a more granular understanding of the expected effects of different doses on therapeutic outcomes by accounting for variability in pharmacokinetic (PK) properties.

METHODS

Data from 2 phase 2b and 2 phase 3 studies of adults with EM or CM were used. Individual exposures were calculated from a population PK model and related to monthly migraine days in EM and moderate-severe (M/S) headache days in CM. Model-based stochastic simulations were performed to compare predicted responses for the various treatment regimens.

RESULTS

The effect of average fremanezumab concentration compared to placebo on the reduction in migraine days and M/S headache days was predicted by the models to be similar for 225 mg monthly and 675 mg once quarterly over time for both EM and CM patients. Both regimens were associated with better response than placebo. A similar percent of EM and CM responders was predicted across the range of observed body weights.

CONCLUSIONS

Exposure-response evaluations showed that both monthly (225 mg) and quarterly (675 mg) fremanezumab dosing regimens were appropriate in achieving clinical benefit in adult patients with EM or CM.

Population Pharmacokinetic and Pharmacokinetic/Pharmacodynamic Modeling of Weight-Based Intravenous Reslizumab Dosing

Reslizumab 3.0 mg/kg has demonstrated efficacy in clinical studies of patients with eosinophilic asthma and a history of exacerbations. A population pharmacokinetic (PK) model was developed to determine whether 3.0 mg/kg weight-based dosing is appropriate to obtain consistent reslizumab exposures in all patients. PK data in healthy volunteers and patients ≥12 years with moderate to severe asthma, eosinophilic asthma, or nasal polyposis were analyzed from 4 phase 1, 2 phase 2, and 2 phase 3 studies of intravenous (IV) reslizumab (N = 804). Covariates evaluated included age, race, sex, baseline weight, renal and liver function, concomitant medications, and antidrug antibody status. Exposure-response models were developed to characterize key efficacy (blood eosinophil levels, forced expiratory volume in 1 second [FEV₁ ], Asthma Control Questionnaire [ACQ-7] scores), and safety end points (muscle disorder adverse events [AEs]). Vial-based dosing was evaluated as an alternative to weight-based dosing. IV reslizumab PK was accurately described by a 2-compartment PK model with 0-order input and first-order elimination. Body weight was the only covariate that significantly influenced PK parameters. However, with weight-based dosing, comparable steady-state exposures were observed across high and low body weights. Greater eosinophil lowering and longer response duration were observed with increasing dose; exposure-related effects on FEV₁ and ACQ-7 were also seen, demonstrating the clinical importance of a dosing regimen to optimize reslizumab exposure. The probability of a muscle disorder AE appeared to increase with increasing exposure. Steady-state exposure measures were similar for both dosing regimens, showing vial-based dosing as an alternative method of achieving the benefits of weight-based dosing.

Relationship Between Plasma Concentrations and Clinical Effects of Cariprazine in Patients With Schizophrenia or Bipolar Mania

Population pharmacokinetic/pharmacodynamic modeling (via NONMEM) was used to describe longitudinal exposure‐response relationships for total cariprazine (sum of cariprazine and its major active metabolites) in 2,558 patients with schizophrenia or bipolar mania. Drug exposure metrics were explored for potential relationships with efficacy and safety end points. Total cariprazine exposures were significantly related to reductions in Positive and Negative Syndrome Scale (PANSS) or Young Mania Rating Scale (YMRS) total scores in schizophrenia or bipolar mania, respectively, via a maximum effect (E_max)‐type relationship. Typical steady‐state plasma concentrations after 3 and 4.5 mg/day were associated with 50% of maximum typical reductions in PANSS and YMRS total scores, respectively. Time‐weighted cariprazine exposures had significant relationships with the probability of common adverse events (AEs). Dose increase was associated with increased efficacy but was also associated with an increase in AEs. Results of these pharmacokinetic/pharmacodynamic analyses support that the recommended dose range (1.5–6 mg/day for schizophrenia and 3–6 mg/day for bipolar mania) provides an appropriate benefit‐risk balance between cariprazine efficacy and safety.

Exposure-response (E-R) analysis of efficacy of pegvorhyaluronidase alfa (PEGPH20) in combination with nab-paclitaxel + gemcitabine (AG) in patients (Pts) with metastatic pancreatic ductal adenocarcinoma

e15746

Background: PEGPH20 depolymerizes extracellular matrix hyaluronan (HA) and is an investigational agent for the treatment of pts with HA-accumulating tumors. HALO-109-202 (260 pts) was conducted to evaluate the effect of PEGPH20 + AG in pts with mPDA. Methods: E-R models were developed to evaluate the relationship between PEGPH20 exposure and efficacy, including time to PFS, time to OS, and overall response (OR). Results: The final E-R PFS model was a Cox proportional hazards model that included effects of PEGPH20 Cmax and baseline tumor biopsy HA (high or low). Higher PEGPH20 Cmax was associated with a lower risk of radiological progression. Pts with baseline HA≥ 50% (HA-high) tumor biopsy were at a lower risk of radiological progression with PEGPH20 treatment. A similar E-R model evaluated the effect of PEGPH20 on OS, including effects of dose-adjusted PEGPH20 concentration 7 days postdose (D7 Conc), liver metastases, and baseline tumor burden. The model-predicted influence of PEGPH20 D7 Conc on risk of death indicated that with increasing PEGPH20 D7 Conc, the predicted risk of death decreases. Pts with liver metastases and higher baseline tumor burden were predicted to have a higher risk of death. The final E-R efficacy model for OR probability was a linear function of dose-adjusted PEGPH20 AUC in Cycle 1, where increasing exposure was related to a higher predicted OR probability. Conclusions: The E-R analyses demonstrate that improvements in PFS and OS with PEGPH20 + AG is PEGPH20 exposure-dependent, supporting 3 µg/kg as an appropriate dose for further development and emphasizing the need for sufficient PEGPH20 exposure for improved therapeutic effect. Clinical trial information: NCT01839487. [Table: see text]

Exposure-safety and efficacy response relationships and population pharmacokinetics of eslicarbazepine acetate

Objectives

Eslicarbazepine acetate (ESL) is a once‐daily (QD) oral antiepileptic drug (AED) for focal‐onset seizures (FOS). Pharmacokinetic (PK) and pharmacodynamic (PD) models were developed to assess dose selection, identify significant AED drug interactions, and quantitate relationships between exposure and safety and efficacy outcomes from Phase 3 trials of adjunctive ESL.

Methods

Eslicarbazepine (the primary active metabolite of ESL) population PK was evaluated using data from 1351 subjects enrolled in 14 studies (11 Phase 1 and three Phase 3 studies) after multiple oral doses ranging from 400 to 1200 mg. Population PK and PD models related individual eslicarbazepine exposures to safety outcomes and efficacy responses.

Results

Eslicarbazepine PK was described by a one‐compartment model with linear absorption and elimination. The probability of a treatment‐emergent adverse event (TEAE; dizziness, headache, or somnolence) was higher with an initial dose of ESL 800 mg than with an initial dose of ESL 400 mg QD. Body weight, sex, region, and baseline use of carbamazepine (CBZ) or lamotrigine were also found to influence the probability of TEAEs. Eslicarbazepine exposure influenced serum sodium concentration, standardized seizure frequency, and probability of response; better efficacy outcomes were predicted in patients not from Western Europe (WE; vs WE patients) and those not taking CBZ (vs taking CBZ) at baseline.

Conclusions

Pharmacokinetic and PK/PD modeling were implemented during the development of ESL for adjunctive treatment of FOS in adults. This quantitative approach supported decision‐making during the development of ESL, and contributed to dosing recommendations and labeling information related to drug interactions.

Nonclinical and pharmacokinetic assessments to evaluate the potential of tedizolid and linezolid to affect mitochondrial function

Prolonged treatment with the oxazolidinone linezolid is associated with myelosuppression, lactic acidosis, and neuropathies, toxicities likely caused by impairment of mitochondrial protein synthesis (MPS). To evaluate the potential of the novel oxazolidinone tedizolid to cause similar side effects, nonclinical and pharmacokinetic assessments were conducted. In isolated rat heart mitochondria, tedizolid inhibited MPS more potently than did linezolid (average [± standard error of the mean] 50% inhibitory concentration [IC50] for MPS of 0.31 ± 0.02 μM versus 6.4 ± 1.2 μM). However, a rigorous 9-month rat study comparing placebo and high-dose tedizolid (resulting in steady-state area under the plasma concentration-time curve values about 8-fold greater than those with the standard therapeutic dose in humans) showed no evidence of neuropathy. Additional studies explored why prolonged, high-dose tedizolid did not cause these mitochondriopathic side effects despite potent MPS inhibition by tedizolid. Murine macrophage (J774) cell fractionation studies found no evidence of a stable association of tedizolid with eukaryotic mitochondria. Monte Carlo simulations based on population pharmacokinetic models showed that over the course of a dosing interval using standard therapeutic doses, free plasma concentrations fell below the respective MPS IC50 in 84% of tedizolid-treated patients (for a median duration of 7.94 h) and 38% of linezolid-treated patients (for a median duration of 0 h). Therapeutic doses of tedizolid, but not linezolid, may therefore allow for mitochondrial recovery during antibacterial therapy. The overall results suggest that tedizolid has less potential to cause myelosuppression and neuropathy than that of linezolid during prolonged treatment courses. This, however, remains a hypothesis that must be confirmed in clinical studies.

Exposure-response analyses of tigecycline tolerability in healthy subjects

Tigecycline exposure (area under the concentration-time curve [AUC((0-infinity))] and maximum serum concentration [C(max)]) and first occurrence of nausea and vomiting were evaluated in 136 healthy subjects after 12.5- to 300-mg single doses. Nausea was more frequent in females (46%, 10/22) compared with males (31%, 11/36) after 100-mg doses. Most nausea (vomiting) events occurred < or =4 h (<6 h) after tigecycline. For doses < or =100 mg, the median duration of nausea and vomiting was approximately 5 h. Based on logistic regression, increased exposure (AUC((0-infinity)) >C(max)) to tigecycline results in an increased rate of nausea (P < or = .0001; = .0022) and vomiting (P < or = .0001; = .0006). At the median AUC((0-infinity)) (C(max)) for the 50-mg dose group, the probability of nausea and vomiting was 0.26 (0.29) and 0.07 (0.11), respectively. Model-predicted rates of nausea and vomiting were comparable with those observed for the tetracycline class of antibiotics, with tolerable rates predicted after 50-mg doses of tigecycline.

Pharmacodynamics of fluoroquinolones against Streptococcus pneumoniae in patients with community-acquired respiratory tract infections

Fluoroquinolone antibiotic agents have demonstrated efficacy in the treatment of respiratory tract infections. This analysis was designed to examine the relationship between drug exposure, as measured by the free-drug area under the concentration-time curve at 24 h (AUC(24))/MIC ratio, and clinical and microbiological responses in patients with community-acquired respiratory tract infections involving Streptococcus pneumoniae. The study population included 58 adult patients (34 males, 24 females) who were enrolled in either of two phase III, randomized, multicenter, double-blind studies of levofloxacin versus gatifloxacin for the treatment of community-acquired pneumonia or acute exacerbation of chronic bronchitis. Clearance equations from previously published population pharmacokinetic models were used in conjunction with dose and adjusted for protein binding to estimate individual patient free-drug AUC(24)s. In vitro susceptibility was determined in a central laboratory by broth microdilution in accordance with NCCLS guidelines. Pharmacodynamic analyses were performed on data from all evaluable patients with documented S. pneumoniae infection using univariate and multivariable logistic regression; pharmacodynamic breakpoints were estimated using Classification and Regression Tree analysis. A statistically significant (P = 0.013) relationship between microbiological response and the free-drug AUC(24)/MIC ratio was detected. At a free-drug AUC(24)/MIC ratio of <33.7, the probability of a microbiological response was 64%, and at a free-drug AUC(24)/MIC ratio of >33.7, it was 100% (P < 0.01). These findings may provide a minimum target free-drug AUC(24)/MIC ratio for the treatment of infections involving S. pneumoniae with fluoroquinolone antibiotics and provide a paradigm for the selection of fluoroquinolones to be brought forward from drug discovery into clinical development and dose selection for clinical trials. Further, when target free-drug AUC(24)/MIC ratios are used in conjunction with stochastic modeling techniques, these findings may be used to support susceptibility breakpoints for fluoroquinolone antibiotics and S. pneumoniae.