Population pharmacokinetic modelling of tremelimumab in patients with advanced solid tumours and the impact of disease status on time-varying clearance.

AIMS: Tremelimumab, a cytotoxic T-lymphocyte-associated protein 4 human monoclonal antibody of the immunoglobulin G2 κ isotype, has been studied in oncology clinical trials as both monotherapy and in combination with durvalumab. This study characterized the pharmacokinetics of tremelimumab as monotherapy and in combination with durvalumab and evaluated the impact of patient covariates on pharmacokinetics. METHODS: A pooled-analysis population pharmacokinetics model was built using NONMEM methodology. Pharmacokinetic data from 5 studies spanning different tumour types and therapy regimens were pooled for model development (956 patients). A dataset pooled from 4 additional studies was used for external validation (554 patients). Demographic and relevant clinical covariates were explored during model development. RESULTS: Tremelimumab exhibited linear pharmacokinetics, well described by a 2-compartment model, with time-varying clearance (0.276 L/day at baseline) associated primarily with therapy regimen and linked with changes in disease status. As monotherapy and combination therapy, tremelimumab clearance over 1 year increased by ~16% and decreased by ~17%, respectively. Pharmacokinetic behaviour was consistent across patient demographics and cancer subtypes. Patients with higher bodyweight and lower albumin levels at baseline had significantly higher clearance; however, no dosage adjustments are warranted. A flat dose (75 mg) was projected to provide comparable exposure to weight-based dosing (1 mg/kg) in adults. CONCLUSION: Tremelimumab exhibited linear pharmacokinetics but consistently opposite trends of time-varying clearance as monotherapy and in combination with durvalumab. Baseline bodyweight and albumin were significant covariates, but conversion from weight-based dosing at 1 mg/kg to flat dosing at 75 mg had no clinically relevant impact.

Physiologically Based Absorption Modelling to Explore the Formulation and Gastric pH Changes on the Pharmacokinetics of Acalabrutinib.

Acalabrutinib, a selective Bruton's tyrosine kinase inhibitor, is a biopharmaceutics classification system class II drug. The aim of this study was to develop a physiologically based pharmacokinetic (PBPK) model to mechanistically describe absorption of immediate release capsule formulation of acalabrutinib in humans. Integration of in vitro biorelevant measurements, dissolution studies and in silico modelling provided clinically relevant inputs for the mechanistic absorption PBPK model. The batch specific dissolution data were integrated in two ways, by fitting a diffusion layer model scalar to the drug product dissolution with integration of drug substance laser diffraction particle size data, or by fitting a product particle size distribution to the dissolution data. The latter method proved more robust and biopredictive. In both cases, the drug surface solubility was well predicted by the Simcyp simulator. The model using the product particle size distribution (P-PSD) for each clinical batch adequately captured the PK profiles of acalabrutinib and its active metabolite. Average fold errors were 0.89 for both Cmax and AUC, suggesting good agreement between predicted and observed PK values. The model also accurately predicted pH-dependent drug-drug interactions between omeprazole and acalabrutinib, which was similar across all clinical formulations. The model predicted acalabrutinib geometric mean AUC ratios (with omeprazole vs acalabrutinib alone) were 0.51 and 0.68 for 2 batches of formulations, which are close to observed values of 0.43 and 0.51~0.63, respectively. The mechanistic absorption PBPK model could be potentially used for future applications such as optimizing formulations or predicting the PK for different batches of the drug product.

Acalabrutinib CYP3A-mediated drug-drug interactions: Clinical evaluations and physiologically based pharmacokinetic modelling to inform dose adjustment strategy.

AIMS: Clinical drug interaction studies with itraconazole and rifampicin have demonstrated that acalabrutinib is a sensitive substrate of CYP3A. A physiologically based pharmacokinetic (PBPK) model was developed based on the data of these studies. One of the active CYP3A metabolites, ACP-5862, was identified but never studied in a drug interaction scenario. This study aims to evaluate both parent and metabolite exposure change with coadministration of moderate CYP3A inhibitors and its impact on safety and efficacy. METHODS: In an open label, randomized, 2-period study, we investigated the effect of coadministration of fluconazole or isavuconazole on the pharmacokinetics of acalabrutinib. Bruton tyrosine kinase receptor occupancy and safety were compared between different treatments. Experimental data were compared to PBPK simulation results. RESULTS: Least square means of acalabrutinib maximum plasma concentration and area under the curve increased 1.37 (1.14-1.64) and 1.60 (1.45-1.77)-fold in the presence of isavuconazole and 1.48 (1.10-1.98) and 2.16 (1.94-2.40)-fold in the presence of fluconazole, respectively. For ACP-5862, these values are 0.72 (0.63-0.82) and 0.91 (0.86-0.97) fold for isavuconazole and 0.65 (0.49-0.87) and 0.95 (0.91-0.99) fold for fluconazole coadministration. The PBPK model was able to recover acalabrutinib and ACP-5862 PK profiles in the study. Bruton tyrosine kinase receptor occupancy change was minimal in the presence of isavuconazole. There were no deaths, serious adverse events (AEs), or subject discontinuation due to AEs in this study. Only mild (Grade 1) AEs were reported during the study, by 17% of the study population. CONCLUSION: Our results demonstrate the impact of fluconazole and isavuconazole on the pharmacokinetics of acalabrutinib and ACP-5862, and suggest that no dose adjustment is needed for concomitant administration with moderate CYP3A inhibitors. the current PBPK model can be used to propose dose adjustment for drug interactions via CYP3A.

Selecting the dosage of ceftazidime-avibactam in the perfect storm of nosocomial pneumonia.

PURPOSE: Ceftazidime-avibactam is a novel ß-lactam/ß-lactamase inhibitor combination recently approved in Europe and the USA for the treatment of adults with hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP), among other indications. In the phase III REPROVE trial (NCT01808092), ceftazidime-avibactam demonstrated non-inferiority to meropenem for the treatment of patients with nosocomial pneumonia (NP), including VAP. As ceftazidime-avibactam was not studied in patients with NP prior to REPROVE, selecting an appropriate dosage regimen in the "perfect storm" of NP required careful consideration of potential determinants and confounders of response specific to the NP patient population. METHODS: This review describes the series of preclinical studies and pharmacokinetic/pharmacodynamic (PK/PD) analyses that supported ceftazidime-avibactam dosage selection for patients with NP/VAP (2000/500 mg by 2-h intravenous infusion every 8 h, adjusted for renal function). In parallel, important considerations for antibiotic dosage selection in patients with NP are highlighted, including adequate drug penetration into the lungs, the suitability of murine-derived plasma PK/PD targets, evaluation of MIC distributions against clinical bacterial isolates from patients with NP, and consideration of PK in patients with NP, who are often critically ill. These analyses also supported the European approval of ceftazidime-avibactam for adults with HAP, including VAP, before the completion of REPROVE. CONCLUSIONS: This work serves as a successful practical example of dosage design for a new antibacterial drug therapy in the indication of NP, including VAP, where previous drug therapies have failed, possibly as a result of evaluation of too few variables, thereby limiting the accuracy of pharmacodynamic predictions.

Physiologically based pharmacokinetic modeling to predict exposures in healthy Japanese subjects with different CYP2C19 phenotypes: Esomeprazole case study
.

PURPOSE: The objective of this study was to improve the predictive performance of cytochrome P450 (CYP) 2C19 substrates in Japanese subjects using physiologically based pharmacokinetic (PBPK) modeling. MATERIALS AND METHODS: Esomeprazole, a CYP2C19 substrate, was selected as a test compound, and the Simcyp simulator was used for pharmacokinetic prediction. The compound file of esomeprazole model developed in healthy Caucasian subjects was applied directly. The population file "Sim-Japanese" in Simcyp was adopted to predict esomeprazole pharmacokinetics in Japanese, while CYP2C19 enzyme abundances in the liver and the gastrointestinal tract for homozygous extensive metabolizers (homo EMs), heterozygous extensive metabolizers (hetero EMs), and poor metabolizers (PMs) were adjusted to be the same as in Caucasians. RESULTS: The PBPK model predicted esomeprazole exposure after 10-, 20-, and 40-mg doses in Japanese subjects within 1.5-fold of observed values in all three -CYP2C19 phenotypes. The reported concentration-time profiles were mostly well-captured within the 95% prediction intervals. CONCLUSION: By adjusting CYP2C19 enzyme abundances levels in the Japanese population, the systemic exposure of esomeprazole in Japanese subjects can be reasonably extrapolated using a PBPK model developed in Caucasian subjects. This analysis serves as a case application for assessing the predictive performance of CYP2C19 substrate in Japanese subjects by using PBPK modeling approach.

Population pharmacokinetic analysis of esomeprazole in Japanese subjects with various CYP2C19 phenotypes.

WHAT IS KNOWN AND OBJECTIVE: Esomeprazole, the S-isomer of omeprazole, is a proton pump inhibitor which has been approved by over 125 countries, also known as NEXIUM® . Esomeprazole was developed to provide further improvement on efficacy for acid-related diseases with higher systemic bioavailability due to the less first-pass metabolism and lower plasma clearance. Esomeprazole is primarily metabolized by CYP2C19. Approximately <1% of Caucasians and 5%-10% of Asians have absent CYP2C19 enzyme activity. Although the influence of various CYP2C19 phenotypes on esomeprazole pharmacokinetics has been studied, this is the first report in the Japanese population where 27 low CYP2C19 metabolizers were included. METHODS: In this study, a population PK model describing the PK of esomeprazole was developed to understand the difference of CYP2C19 phenotypes on clearance in the Japanese population. The model quantitatively assessed the influence of CYP2C19 phenotype on esomeprazole PK in healthy Japanese male subjects after receiving repeated oral dosing. The inhibition mechanism of esomeprazole on CYP2C19 activity was also included in the model. RESULTS AND DISCUSSION: CYP2C19 phenotype and dose were found as statistically significant covariates on esomeprazole clearance. The apparent clearance at 10-mg dose was 17.32, 9.77 and 7.37 (L/h) for homozygous extensive metabolizer, heterozygous extensive metabolizer and poor metabolizer subjects, respectively. And the apparent clearance decreased as dose increased. WHAT IS NEW AND CONCLUSION: The established population PK model well described the esomeprazole PK and model-predicted esomeprazole PK was in good agreement with external clinical data, suggesting the robustness and applicability of the current model for predicting esomeprazole PK.

Ceftaroline fosamil doses and breakpoints for Staphylococcus aureus in complicated skin and soft tissue infections.

Objectives: To describe the pharmacokinetic/pharmacodynamic (PK/PD) modelling and microbiological data that were used to support the recent European approval of ceftaroline fosamil 600 mg q8h by 2 h intravenous (iv) infusion for patients with complicated skin and soft tissue infections (cSSTIs) caused by Staphylococcus aureus with ceftaroline MICs of 2 or 4 mg/L, and the associated EUCAST MIC breakpoint update for q8h dosing (intermediate = 2 mg/L and resistant >2 mg/L). Methods: A population PK model for ceftaroline and ceftaroline fosamil was developed using PK data from 21 clinical studies. The final model was used to simulate PTA in patients with cSSTI receiving ceftaroline fosamil 600 mg q12h by 1 h iv infusion or 600 mg q8h by 2 h iv infusion. PTA was calculated by MIC for S. aureus PK/PD targets derived from preclinical studies (27% fT>MIC for stasis, 31% fT>MIC for 1 log10 kill and 35% fT>MIC for 2 log10 kill) and compared with S. aureus ceftaroline MIC distributions from a 2013 global surveillance study. Results: The final population PK model based on 951 subjects adequately described ceftaroline and ceftaroline fosamil PK. High PTA (>90%) was predicted for the ceftaroline fosamil 600 mg q12h dosage regimen against S. aureus isolates with ceftaroline MICs ≤2 mg/L. Greater than 90% PTA was predicted for the ceftaroline fosamil 600 mg q8h dosage regimen against S. aureus with ceftaroline MICs ≤4 mg/L. Conclusions: The approved ceftaroline fosamil dosage regimens for adults and adolescents with cSSTI achieve high PTA against S. aureus at the associated EUCAST breakpoints.

Population pharmacokinetic analysis of danvatirsen supporting flat dosing switch.

Danvatirsen is a Generation 2.5 antisense oligonucleotide under clinical development. Population PK modelling was conducted using data from 3 available danvatirsen Phase I/II studies in oncology patients to investigate the impact of flat dosing on exposure compared to ideal body weight-based dosing. A total of 126 patients who received danvatirsen doses ranging from 1 to 4 mg/kg as monotherapy or in combination with durvalumab, most at 3 mg/kg (n = 70), was used in the danvatirsen population PK analysis. A 2-compartment model with linear elimination described the data well. Covariate analysis revealed ideal body weight was not a significant covariate on the PK of danvatirsen; nor was age, sex or race. The model-based simulation suggested that steady state weekly AUC and Cmax were very similar between 3 mg/kg and 200 mg flat dosing (geometric mean of AUC: 62.5 vs. 63.4 mg h/L and Cmax: 26.2 vs. 26.5 mg/L for two dose groups) with slightly less overall between-subject variability in the flat dosing regimen. The switch to flat dosing was approved by multiple regulatory agencies, including FDA, EMA, PMDA and ANSM. Several ongoing studies have been evaluating flat dosing. Interim analysis from an ongoing study (D5660C00016, NCT03421353) has shown the observed steady state concentration from 200 mg flat dose is in agreement with the model predictions. The population PK model could be further utilized in subsequent exposure-response efficacy and safety modelling.

Simplified Aztreonam Dosing in Patients with End-Stage Renal Disease: Results of a Monte Carlo Simulation.

The manufacturer-recommended aztreonam dosing for patients with creatinine clearance values of <10 ml/min/1.73 m2 is complex. It is not known whether simpler posthemodialysis dosing administered once daily or thrice weekly can reliably achieve pharmacodynamic goals. We found that 1 or 2 g administered once daily after hemodialysis had >90% probability of target attainment up to MICs of 4 or 8 mg/liter, respectively. Thrice-weekly dosing should generally be avoided, except in nonsevere infections with MICs of ≤0.5 mg/liter.

Population pharmacokinetics of the MEK inhibitor selumetinib and its active N-desmethyl metabolite: data from 10 phase I trials.

AIMS: The aims of the study were to characterize the pharmacokinetics (PK) of selumetinib (AZD6244; ARRY-142886), a mitogen-activated protein kinase kinase (MEK) 1/2 inhibitor in clinical development for various indications, and its N-desmethyl metabolite in healthy volunteers, and evaluate clinically important covariates. METHODS: A pooled-population PK analysis was performed using a nonlinear mixed-effects approach with plasma concentration data from 346 subjects who received single oral doses of selumetinib 20-75 mg across 10 phase I studies. Absolute bioavailability was determined using intravenous [14 C] selumetinib. RESULTS: A two-compartment linear model with sequential zero-first order absorption and a lag time for the zero-order process was described for selumetinib PK. N-desmethyl metabolite disposition was described by a single compartment with linear elimination, without back transformation. The parent-only and joint models generally described pooled data adequately. For the median subject, not taking interacting drugs, estimates for clearance (CL) and central volume of distribution (V2) for selumetinib in the final joint model were 12.7 l h-1 and 35.6 l, respectively. Food effects, comedication with itraconazole [a cytochrome P450 (CYP) 3A4 inhibitor], fluconazole (a CYP2C19 inhibitor) and rifampicin (a CYP3A4 inducer) and formulation effects were incorporated into the base model a priori. Race and hepatic function were also influential in the PK model. Additional covariates affecting selumetinib disposition identified from covariate analysis were age on V2, bilirubin on CL, and weight on CL and V2. CONCLUSIONS: Analysis confirmed previous clinical pharmacology study findings of drug-drug interactions and food effects, with additional covariates that influence selumetinib and N-desmethyl selumetinib PK identified. Dose modifications based on these additional covariates were not considered necessary.

Development of a physiologically based pharmacokinetic model to predict the effects of flavin-containing monooxygenase 3 (FMO3) polymorphisms on itopride exposure.

Itopride, a substrate of FMO3, has been used for the symptomatic treatment of various gastrointestinal disorders. Physiologically based pharmacokinetic (PBPK) modeling was applied to evaluate the impact of FMO3 polymorphism on itopride pharmacokinetics (PK). The Asian populations within the Simcyp simulator were updated to incorporate information on the frequency, activity and abundance of FMO3 enzyme with different phenotypes. A meta-analysis of relative enzyme activities suggested that FMO3 activity in subjects with homozygous Glu158Lys and Glu308Gly mutations (Lys158 and Gly308) in both alleles is ~47% lower than those carrying two wild-type FMO3 alleles. Individuals with homozygous Lys158 and Gly308 mutations account for about 5% of the total population in Asian populations. A CLint of 9 µl/min/pmol was optimised for itopride via a retrograde approach as human liver microsomal results would under-predict its clearance by ~7.9-fold. The developed itopride PBPK model was first verified with three additional clinical studies in Korean and Japanese subjects resulting in a predicted clearance of 52 to 69 l/h, which was comparable to those observed (55 to 88 l/h). The model was then applied to predict plasma concentration-time profiles of itopride in Chinese subjects with wild type or homozygous Lys158 and Gly308 FMO3 genotypes. The ratios of predicted to observed AUC of itopride in subjects with each genotype were 1.23 and 0.94, respectively. In addition, the results also suggested that for FMO3 metabolised drugs with a safety margin of 2 or more, proactive genotyping FMO3 to exclude subjects with homozygous Lys158/Gly308 alleles may not be necessary.

Phase I Study Assessing the Pharmacokinetic Profile, Safety, and Tolerability of a Single Dose of Ceftazidime-Avibactam in Hospitalized Pediatric Patients.

This study aimed to investigate the pharmacokinetics (PK), safety, and tolerability of a single dose of ceftazidime-avibactam in pediatric patients. A phase I, multicenter, open-label PK study was conducted in pediatric patients hospitalized with an infection and receiving systemic antibiotic therapy. Patients were enrolled into four age cohorts (cohort 1, ≥12 to <18 years; cohort 2, ≥6 to <12 years; cohort 3, ≥2 to <6 years; cohort 4, ≥3 months to <2 years). Patients received a single 2-h intravenous infusion of ceftazidime-avibactam (cohort 1, 2,000 to 500 mg; cohort 2, 2,000 to 500 mg [≥40 kg] or 50 to 12.5 mg/kg [<40 kg]; cohorts 3 and 4, 50 to 12.5 mg/kg). Blood samples were collected to describe individual PK characteristics for ceftazidime and avibactam. Population PK modeling was used to describe characteristics of ceftazidime and avibactam PK across all age groups. Safety and tolerability were assessed. Thirty-two patients received study drug. Mean plasma concentration-time curves, geometric mean maximum concentration (Cmax), and area under the concentration-time curve from time zero to infinity (AUC0-∞) were similar across all cohorts for both drugs. Six patients (18.8%) reported an adverse event, all mild or moderate in intensity. No deaths or serious adverse events occurred. The single-dose PK of ceftazidime and avibactam were comparable between each of the 4 age cohorts investigated and were broadly similar to those previously observed in adults. No new safety concerns were identified. (This study has been registered at ClinicalTrials.gov under registration no. NCT01893346.).

Pharmacokinetics, metabolism and excretion of [(14)C]-lanicemine (AZD6765), a novel low-trapping N-methyl-d-aspartic acid receptor channel blocker, in healthy subjects.

1.(1S)-1-phenyl-2-(pyridin-2-yl)ethanamine (lanicemine; AZD6765) is a low-trapping N-methyl-d-aspartate (NMDA) channel blocker that has been studied as an adjunctive treatment in major depressive disorder. The metabolism and disposition of lanicemine was determined in six healthy male subjects after a single intravenous infusion dose of 150 mg [(14)C]-lanicemine. 2.Blood, urine and feces were collected from all subjects. The ratios of Cmax and AUC(0-∞) of lanicemine to plasma total radioactivity were 84 and 66%, respectively, indicating that lanicemine was the major circulating component with T1/2 at 16 h. The plasma clearance of lanicemine was 8.3 L/h, revealing that lanicemine is a low-clearance compound. The mean recovery of radioactivity from urine was 93.8% of radioactive dose. 3.In urine samples, 10 metabolites of lanicemine were identified. Among which, an O-glucuronide conjugate (M1) was the most abundant metabolite (∼11% of the dose in excreta). In plasma, the circulatory metabolites were identified as a para-hydroxylated metabolite (M1), an O-glucuronide (M2), an N-carbamoyl glucuronide (M3) and an N-acetylated metabolite (M6). The average amount of each of metabolite was less than 4% of total radioactivity detected in plasma or urine. 4.In conclusion, lanicemine is a low-clearance compound. The unchanged drug and metabolites are predominantly eliminated via urinary excretion.

Physiologically based pharmacokinetic modeling to predict complex drug-drug interactions: a case study of AZD2327 and its metabolite, competitive and time-dependent CYP3A inhibitors.

4-{(R)-(3-Aminophenyl)[4-(4-fluorobenzyl)-piperazin-1-yl]methyl}-N,N-diethylbenzamide (AZD2327) is a highly potent and selective agonist of the δ-opioid receptor. AZD2327 and N-deethylated AZD2327 (M1) are substrates of cytochrome P450 3A (CYP3A4) and comprise a complex multiple inhibitory system that causes competitive and time-dependent inhibition of CYP3A4. The aim of the current work was to develop a physiologically based pharmacokinetic (PBPK) model to predict quantitatively the magnitude of CYP3A4 mediated drug-drug interaction with midazolam as the substrate. Integrating in silico, in vitro and in vivo PK data, a PBPK model was successfully developed to simulate the clinical accumulation of AZD2327 and its primary metabolite. The inhibition of CYP3A4 by AZD2327, using midazolam as a probe drug, was reasonably predicted. The predicted maximum concentration (Cmax) and area under the concentration-time curve (AUC) for midazolam were increased by 1.75 and 2.45-fold, respectively, after multiple dosing of AZD2327, indicating no or low risk for clinically relevant drug-drug interactions (DDI). These results are in agreement with those obtained in a clinical trial with a 1.4 and 1.5-fold increase in Cmax and AUC of midazolam, respectively. In conclusion, this model simulated DDI with less than a two-fold error, indicating that complex clinical DDI associated with multiple mechanisms, pathways and inhibitors (parent and metabolite) can be predicted using a well-developed PBPK model.

Development of physiologically based pharmacokinetic model to evaluate the relative systemic exposure to quetiapine after administration of IR and XR formulations to adults, children and adolescents.

Quetiapine is an atypical antipsychotic drug with a high permeability, moderate solubility and defined as a Biopharmaceutics Classification System class ll compound. The pharmacokinetics (PK) of the quetiapine immediate-release (IR) formulation has been studied in both adults and children, but the quetiapine extended-release (XR) formulation has only been conducted in adults. The purpose of the current study was to use physiologically based pharmacokinetic modeling (PBPK) quantitatively to predict the PK of the XR formulation in children and adolescents. Using a 'learn and confirm' approach, PBPK models were developed employing in vitro ADME and physicochemical data, clinical PK data of quetiapine IR/XR in adults and clinical PK data of quetiapine IR in children. These models can predict well the effects of CYP3A4 inhibition and induction on the PK of quetiapine, the PK profile of quetiapine IR in children and adults, and the PK profile of quetiapine XR in adults. The AUC and Cmax ratios (children vs adults) for the different age groups were in reasonable agreement with the observed ratios. In addition, the PBPK model predicted that children and adolescents are likely to achieve a similar exposure following administration of either the XR formulation once daily or the IR formulation twice daily at similar total daily doses. The results from the study can help inform dosing regimens in pediatrics using the quetiapine XR formulation.

Population Pharmacokinetics of Capivasertib in Patients with Advanced or Metastatic Solid Tumours.

BACKGROUND AND OBJECTIVE: Overactivation of the PI3K/AKT pathway can occur in many cancers. Capivasertib is a potent, selective pan-AKT inhibitor. The objectives of this analysis were to develop a population pharmacokinetic model for capivasertib and to quantitatively assess the impact of intrinsic and extrinsic factors on the pharmacokinetics of capivasertib. METHODS: Pharmacokinetic data from four phase I and II studies were combined. Capivasertib was administered orally at a dose range of 80-800 mg twice daily over 28-day and 21-day cycles as monotherapy or in combination with paclitaxel or fulvestrant, using continuous dosing or one of two intermittent dosing schedules: either 4 days on, 3 days off (4/3) or 2 days on, 5 days off (2/5). Several models and approaches were tested for their ability to describe capivasertib disposition. The covariates assessed included dose, schedule, age, body weight, race, sex, creatinine clearance, hepatic function, renal function, smoking status, food effect, formulation, and concomitant use with paclitaxel, fulvestrant, cytochrome P450, family 3, subfamily A (CYP3A) inducers, CYP3A inhibitors and acid-reducing agents. RESULTS: A total of 3963 capivasertib plasma concentrations from 441 patients were included. Capivasertib pharmacokinetics was adequately described by a three-compartment model where the apparent clearance (CL/F) presented a moderate time-dependent and dose-dependent clearance. Following oral administration of multiple doses of capivasertib (400 mg twice daily; [4/3]), the initial CL/F was 62.2 L/h (between-subject variability 39.3%), and after approximately 120 hours, CL/F decreased by 18%. The effective half-life was 8.34 h. Steady state was predicted to be reached on every third and fourth dosing day each week from the second week with exposure levels that produced robust inhibition of AKT but not of other related kinases. The area under the plasma concentration-time curve and maximum plasma concentration of capivasertib were proportional between the dose levels of 80-480 mg after multiple doses but more than proportional beyond 480 mg. Schedule, age, race, sex, creatinine clearance, hepatic function, renal function, smoking status and concomitant use with fulvestrant, CYP3A inducers, CYP3A inhibitors or acid-reducing agents were not significant covariates for capivasertib pharmacokinetics. Concomitant use of paclitaxel, food effect and formulation statistically significantly affected capivasertib pharmacokinetics, but the effect was low. Body weight was statistically significantly related to capivasertib CL/F, with a 12% reduction in CL/F at steady state and a 14% increase in the area under the curve for 12 hours at steady state and maximum concentration at steady state at a lower body weight (47 kg vs 67 kg reference). CONCLUSIONS: Capivasertib pharmacokinetics showed moderate between-subject variability, and most covariates assessed had no significant impact. Body weight, dose, concomitant use of paclitaxel, food effect and formulation showed statistically significant effects. However, these were predicted to impact exposure to capivasertib by <20% and were not expected to be clinically relevant. Based on the population pharmacokinetics, no a priori dose adjustment is needed for intrinsic and extrinsic factors.

Clinical Pharmacology Strategies for Bispecific Antibody Development: Learnings from FDA-Approved Bispecific Antibodies in Oncology.

Bispecific antibodies, by enabling the targeting of more than one disease-associated antigen or engaging immune effector cells, have both advantages and challenges compared with a combination of two different biological products. As of December 2023, there are 11 U.S. Food and Drug Administration-approved BsAb products on the market. Among these, 9 have been approved for oncology indications, and 8 of these are CD3 T-cell engagers. Clinical pharmacology strategies, including dose-related strategies, are critical for bispecific antibody development. This analysis reviewed clinical studies of all approved bispecific antibodies in oncology and identified dose-related perspectives to support clinical dose optimization and regulatory approvals, particularly in the context of the Food and Drug Administration's Project Optimus: (1) starting doses and dose ranges in first-in-human studies; (2) dose strategies including step-up doses or full doses for recommended phase 2 doses or dose level(s) used for registrational intent; (3) restarting therapy after dose delay; (4) considerations for the introduction of subcutaneous doses; (5) body weight vs. flat dosing strategy; and (6) management of immunogenicity. The learnings arising from this review are intended to inform successful strategies for future bispecific antibody development.

Modeling of Proliferating CD4 and CD8 T-Cell Changes to Tremelimumab Exposure in Patients with Unresectable Hepatocellular Carcinoma.

The STRIDE (Single Tremelimumab Regular Interval Durvalumab) regimen of single-dose tremelimumab 300 mg, plus durvalumab 1,500 mg every 4 weeks demonstrated potential for long-term survival in studies of unresectable hepatocellular carcinoma (uHCC; Study 22 and HIMALAYA). The aim of this analysis was to investigate changes in proliferating CD4+ Ki67+ and CD8+ Ki67+ T cells and their relationship with tremelimumab exposure in patients with uHCC. Median cell count, change from baseline, and percent change from baseline in CD4+ and CD8+ T cells peaked around 14 days after STRIDE. A model of CD4+ and CD8+ T cell response to tremelimumab exposure was developed. Patients with lower baseline T cell counts had a greater percent change from baseline in T cell response to tremelimumab, and baseline T-cell count was included in the final model. With the full covariate model, the half-maximal effective concentration (EC50 ) of tremelimumab was 6.10 µg/mL (standard error = 1.07 µg/mL); > 98.0% of patients were predicted to have a minimum plasma concentration greater than EC50 with tremelimumab 300 or 750 mg. For EC75 (9.82 µg/mL), 69.5% and 98.2% of patients were predicted to exceed the EC75 with tremelimumab 300 and 750 mg, respectively. This analysis supports the clinical hypothesis that combination anti-cytotoxic T-lymphocyte-associated antigen 4 (anti-CTLA-4) and anti-programmed cell death ligand-1 (anti-PD-L1) therapy primes an immune response that may then be sustained by anti-PD-L1 monotherapy and supports the clinical utility of the STRIDE regimen in patients with uHCC. These insights may also help inform dose selection of anti-CTLA-4 plus anti-PD-L1 combination strategies.

Population Pharmacokinetics and Exposure-Response Analysis for the CTLA-4 Inhibitor Tremelimumab in Metastatic NSCLC Patients in the Phase III POSEIDON Study.

Blockade of CTLA-4 by tremelimumab combined with anti-PD-L1 durvalumab and chemotherapy provided increased antitumor activity and long-term survival benefits in first-line metastatic non-small cell lung cancer (mNSCLC) in the phase III POSEIDON study. We performed population pharmacokinetic modeling for tremelimumab using data from 1,605 patients across 6 studies (including POSEIDON) in multiple tumors (lung cancer, bladder cancer, malignant mesothelioma, and other solid tumors), and identified a 2-compartment model with linear and time-varying clearance for tremelimumab. Cox proportional hazard regression models were applied to 326 patients with mNSCLC from POSEIDON to evaluate the association between exposure metrics and efficacy end points, adjusting for baseline prognostic covariates. Improved progression-free survival (PFS) and overall survival (OS) in the tremelimumab arm (in combination with durvalumab and chemotherapy) was associated with higher tremelimumab exposure (e.g., minimum concentration at 5th dose (Cmin,dose5 ) and area under the curve at 5th dose (AUCdose5 )). However, further case-matching analyses yielded hazard ratios for the comparison of tremelimumab-treated patients in the Cmin,dose5 quartile 1 (Q1) subgroup with matched chemotherapy-treated patients of 1.04 (95% confidence interval (CI): 0.76-1.44) for OS and 0.99 (95% CI: 0.72-1.36) for PFS, suggesting that the observed apparent exposure-response relationship might be confounded. No relationship between tremelimumab exposure and safety (grade ≥3 treatment-emergent adverse events [AEs], AEs of special interest, or discontinuation due to AEs) was identified. These results support the consistent benefit observed with tremelimumab 75 mg every 3 weeks for up to 5 doses in combination with durvalumab and chemotherapy in POSEIDON as first-line therapy for mNSCLC.

Exposure-Response Analyses of Tremelimumab Monotherapy or in Combination with Durvalumab in Patients with Unresectable Hepatocellular Carcinoma.

PURPOSE: A novel single-dose regimen of 300 mg tremelimumab in combination with durvalumab [Single Tremelimumab Regular Interval Durvalumab (STRIDE)] has demonstrated a favorable benefit-risk profile in the phase I/II Study 22 (NCT02519348) and phase III HIMALAYA study (NCT03298451). This study evaluated the pharmacokinetics, exposure-response, and exposure-pharmacodynamics relationships of tremelimumab in patients with unresectable hepatocellular carcinoma (uHCC). PATIENTS AND METHODS: A previous tremelimumab population pharmacokinetic model was validated using data from parts 2 and 3 of Study 22. Exposure-response analyses explored relationships of tremelimumab exposure with efficacy and safety. Pharmacokinetics and pharmacodynamics relationships were evaluated using linear and nonlinear regression models. RESULTS: The observed pharmacokinetics of tremelimumab in uHCC were consistent with predictions; no significant covariates were identified. Tremelimumab exposure was not significantly associated with adverse events, objective response rate, or progression-free survival. Overall survival (OS) was longer for patients with tremelimumab exposure, minimum serum drug concentration (Cmin1) ≥ median versus Cmin1 < median (18.99 months vs. 10.97 months), but this exposure-survival analysis might be confounded with baseline characteristics of albumin level and neutrophil to lymphocyte ratio, which had a significant impact on OS (P = 0.0004 and 0.0001, respectively). The predicted Cmin1 of tremelimumab in STRIDE regimen (12.9 µg/mL) was greater than the estimated concentration of tremelimumab eliciting half-maximal increases (EC50 = 5.24 µg/mL) in CD8+Ki67+ T-cell counts. CONCLUSIONS: Our findings support novel insights into tremelimumab pharmacokinetics and exposure-response relationships in HCC and support the clinical utility of the STRIDE regimen in patients with uHCC.