Population exposure-response analysis of cabozantinib efficacy and safety endpoints in patients with renal cell carcinoma.

BACKGROUND: In the phase III METEOR trial, tyrosine kinase inhibitor cabozantinib significantly improved progression-free survival (PFS), objective response rate (ORR), and overall survival compared to everolimus in patients with advanced renal cell carcinoma (RCC) who had received prior VEGFR inhibitor therapy. In METEOR, RCC patients started at a daily 60-mg cabozantinib tablet (Cabometyx™) dose but could reduce to 40- or 20-mg to achieve a tolerated exposure. OBJECTIVES AND METHODS: Exposure-response (ER) models were developed to characterize the relationship between cabozantinib at clinically relevant exposures in RCC patients enrolled in METEOR and efficacy (PFS and tumor response) and safety endpoints. RESULTS: Compared to the average steady-state cabozantinib concentration for a 60-mg dose, exposures at simulated 40- and 20-mg starting doses were predicted to result in higher risk of disease progression or death [hazard ratios (HRs) of 1.10 and 1.39, respectively], lower maximal median reduction in tumor size (- 11.9 vs - 9.1 and - 4.5%, respectively), and lower ORR (19.1 vs 15.6 and 8.7%, respectively). The 60-mg exposure was also associated with higher risk for selected adverse events (AEs) palmar-plantar erythrodysesthesia syndrome (grade ≥ 1), fatigue/asthenia (grade ≥ 3), diarrhea (grade ≥ 3), and hypertension (predicted HRs of 2.21, 2.01, 1.78, and 1.85, respectively) relative to the predicted average steady-state cabozantinib concentration for a 20-mg starting dose. CONCLUSION: ER modeling predicted that cabozantinib exposures in RCC patients at the 60-mg starting dose would provide greater anti-tumor activity relative to exposures at simulated 40- and 20-mg starting doses that were associated with decreased rates of clinically relevant AEs.

A population pharmacokinetic model of cabozantinib in healthy volunteers and patients with various cancer types.

PURPOSE: An integrated population pharmacokinetic (popPK) model was developed to describe the pharmacokinetics (PK) of tyrosine kinase inhibitor cabozantinib in healthy volunteers (HVs) and patients with various cancer types and to identify any differences in cabozantinib PK across these populations. METHODS: Plasma concentration data used to develop the popPK model were obtained from nine clinical trials (8072 concentrations from 1534 HVs or patients) of cabozantinib in HVs and patients with renal cell carcinoma (RCC), medullary thyroid carcinoma (MTC), glioblastoma multiforme, castration-resistant prostate cancer, or other advanced malignancies. RESULTS: PK data across studies were adequately characterized by a two-compartment disposition model with dual first- and zero-order absorption processes and first-order elimination. Baseline demographic covariates (age, weight, gender, race, and cancer type) were generally predicted to have a small-to-moderate impact on apparent clearance (CL/F). However, MTC cancer type did show an approximately 93% higher CL/F relative to HVs following chronic dosing, resulting in approximately 40-50% lower predicted steady-state cabozantinib plasma concentrations. CONCLUSION: This popPK analysis showed cabozantinib CL/F values to be higher for patients with MTC and may account for the higher dosage required in this patient population (140-mg) to achieve plasma exposures comparable to those in patients with RCC and other tumor types administered a 60-mg cabozantinib tablet dose. Possible factors that may underlie the higher cabozantinib clearance observed in MTC patients are discussed.

Dosing celecoxib in pediatric patients with juvenile rheumatoid arthritis.

The objective was to derive dosing recommendations for the use of celecoxib in patients with juvenile rheumatoid arthritis (JRA) using pharmacokinetic (PK) and exposure-response data. PK and efficacy data from a randomized, double-blind, 12-week study of celecoxib dosed at 3 and 6 mg/kg twice a day (bid) as an investigational suspension formulation in 152 JRA patients aged 2 to 17 years, PK data from 36 adult RA patients, and relative bioavailability data in healthy adults comparing suspension or capsule sprinkles with the commercial capsule were analyzed. Typical oral clearance (L/h) values were 40% and 24% lower in patients weighing 10 and 25 kg, respectively, compared with a 70-kg patient. Longitudinal, logistic pharmacodynamic models incorporating linear effects of dose/area under the plasma concentration-time curve (AUC) over 0 to 12 hours (AUC(0-12)) suggested that the percentage of responders increased with celecoxib exposure. Systemic exposures (AUC) were similar for the suspension, capsule sprinkles, and intact capsule. Administration of a 50-mg bid capsule (or sprinkles) for patients weighing 10 to 25 kg and 100 mg bid for patients >25 kg was predicted to yield similar exposures and response rates as those observed in the JRA trial. Doses and dosage forms not studied in the JRA trial were approved based on the results of this analysis.

Population pharmacokinetics of pegaptanib in patients with neovascular, age-related macular degeneration.

The anti-vascular endothelial growth factor (VEGF) aptamer pegaptanib is eliminated primarily by renal clearance. Because renal function declines with age, pegaptanib exposure in patients with age-related macular degeneration (AMD) may increase. Therefore, a population pharmacokinetic (PK) analysis of pegaptanib was undertaken in Western and Asian AMD patients to determine the influence of renal function on apparent pegaptanib clearance (CL). Pegaptanib (0.3-3 mg per eye) was administered every 4 to 6 weeks to 262 AMD patients in 4 studies. Pegaptanib exposures (area under the concentration-time curve [AUC] and maximum plasma concentration) after 8 doses were similar to exposures following the first dose, consistent with the absence of plasma accumulation. A 1-compartment model parameterized in terms of the absorption rate constant, apparent volume of distribution, and CL was used to describe the pegaptanib plasma concentration data. Creatinine clearance (CLCR), body weight (WT), and age influenced pegaptanib PK. Decreasing CLCR from 70 to 30 mL/min doubled AUC. After adjustment for CLCR, WT, and age, the model predicted no race differences in CL or AUC. Given that the therapeutic 0.3 mg per eye dose of pegaptanib results in exposures one-tenth of those observed following the well-tolerated 3-mg dose, these results suggest that no dose adjustment is warranted for AMD patients with moderate renal insufficiency (CLCR >30 mL/min).

Modeling dropout from adverse event data: impact of dosing regimens across pregabalin trials in the treatment of generalized anxiety disorder.

Dizziness represents a major determinant of dropout in the treatment of generalized anxiety disorder with pregabalin. Titration (dose escalation) regimens based on clinical judgment were implemented to mitigate this adverse event and reduce patient dropout across clinical trials. Dropout is an important treatment failure endpoint, which can be analyzed using time-to-event models that incorporate daily dosing or other time-varying information. A parametric discrete-time dropout model with daily dizziness severity score as a covariate afforded a systematic, model-based assessment of titration dosing strategies, with model predictions evaluated against corresponding nonparametric estimates. A Gompertz hazard function adequately described the decreasing dropout hazard over time for individuals with severe or moderate dizziness and a lower, constant hazard for individuals reporting no dizziness or mild dizziness. Predictive performance of the model was adequate based on external validation with an independent trial and other goodness-of-fit criteria. Prospective simulations highlight the utility of this approach in reducing dropout based on examination of untested titration scenarios for future generalized anxiety disorder or other trials.

Exposure-response analysis in patients with schizophrenia to assess the effect of asenapine on QTc prolongation.

An exposure-response (E-R) analysis using linear mixed effects modeling was conducted on data from a thorough QTc trial for asenapine in 148 patients with schizophrenia. In a parallel design, patients received asenapine 5 mg twice daily (BID) for 10 days (10d) followed by 10 mg BID (6d), asenapine 15 mg BID (10d) followed by 20 mg BID (6d), quetiapine 375 mg BID (for assay sensitivity; 16d) or placebo (16d). Triplicate 12-lead electrocardiograms and concentration measurements were obtained on day -1 (baseline), 1, 10, and 16 at 8 scheduled times on each day. At mean C(max) for all asenapine doses, the E-R model predicted that the mean QTcF increase was less than 5 milliseconds, the International Conference on Harmonisation-established threshold for clinical concern. The model predicted a mean increase of 7 to 8 milliseconds for quetiapine. The corresponding upper bounds of the 95% confidence intervals were 7.5 milliseconds and 11.2 milliseconds for asenapine and quetiapine, respectively.

The pharmacokinetics of etanercept in patients with end-stage renal disease on haemodialysis.

Inflammation is strongly associated with malnutrition and cardiovascular risk in patients with chronic renal failure on haemodialysis (HD). The acute-phase inflammatory response, defined by the increased synthesis of positive acute-phase proteins, is stimulated by the production of such cytokines as interleukin 6 (IL-6), interleukin 1 (IL-1) and tumour necrosis factor-alpha TNF-alpha The availability of cytokine antagonists allows testing of the hypothesis that suppression of inflammation reverses the malnutrition-inflammation syndrome in HD patients. Etanercept is a soluble TNF-alpha receptor fusion protein used to suppress inflammation in rheumatoid and psoriatic arthritis. Its metabolism in HD patients is unknown. In a study designed to test the safety and pharmacokinetics of etanercept in HD patients, etanercept was administered to six HD patients with albumin levels above 4.2 g dL(-1) and C-reactive protein levels <5 mg L(-1) (five men, one woman, age range 34-59 years). Etanercept (25 mg) was administered subcutaneously twice weekly immediately after dialysis for 13-16 weeks. Etanercept concentrations were measured pre- and post-dialysis by ELISA. Concentrations were compared graphically to assess whether, firstly, dialysis affects etanercept apparent clearance and, secondly, etanercept kinetics were similar between HD patients and the more extensively studied psoriasis population with normal renal function (PS). The second stage examined model-based parameter predictions of the terminal elimination rate constant (k) for HD patients. Steady-state etanercept levels were comparable between HD and PS patients. Treatment with HD had no effect on etanercept levels. When etanercept was discontinued, the terminal rate constant for HD patients was not significantly different from that observed in PS patients. No adverse effects were noted during the 3-month treatment phase and subsequent 6-month follow-up. Albumin and C-reactive protein levels did not change in these non-inflamed patients during the study period. The pharmacokinetics of etanercept in patients with chronic renal failure on HD are similar to patients with normal renal function. It is, therefore, feasible to administer etanercept to HD patients without adjusting the dose.