Population pharmacokinetics of losmapimod in healthy subjects and patients with rheumatoid arthritis and chronic obstructive pulmonary diseases.

BACKGROUND AND OBJECTIVE: Losmapimod is an orally available, potent p38 mitogen-activated protein kinase inhibitor. It is in development as an anti-inflammatory drug in different therapeutic areas. Clinical studies have shown that losmapimod is well tolerated and safe in humans and several studies have shown its pharmacological effect in the target diseases. The aim of this work was to develop a population pharmacokinetic model and to explore the covariates affecting the pharmacokinetics of losmapimod using data collected from healthy volunteers and patients with rheumatoid arthritis (RA) and chronic obstructive pulmonary diseases (COPD). SUBJECTS AND METHODS: The plasma concentration data were pooled from four of the losmapimod clinical studies, with 30 healthy subjects, 23 subjects with RA and 24 subjects with COPD. Non-linear mixed-effects modelling was used to build a base model to characterize the structure and describe the variability of the pharmacokinetics of losmapimod. The available demographic covariates were explored to further explain the inter-subject variability. New data generated from another RA study with 34 subjects were used to validate the final model. All modelling was conducted using NONMEM(®) VI. RESULTS: A two-compartment model with first-order elimination and time-dependent first-order absorption was found to best fit the concentration-time profiles of losmapimod following oral administration. The first phase of the absorption was more variable than the second phase for most of the subjects in the dataset. There was no apparent difference in the structure of the pharmacokinetic model among healthy subjects and patients with RA and COPD. A slightly higher residual error was associated with COPD patients compared with the healthy and RA subjects. Three demographic covariates, namely sex, age and bodyweight, were retained in the final model to explain the inter-individual variability on pharmacokinetic parameters apparent total oral clearance (CL/F), apparent volume of distribution of the central compartment (V(1)) and the first-order absorption rate constant (k(a)). Most of the fixed effect parameters (θ(pop,j) and θ for covariate) of the final model were estimated with good precision (% relative standard error [RSE] ≤30 %). The inter-individual variability was precisely estimated (%RSE ≤30 %) for clearance and k(a), but less precise for inter-compartmental clearance and volumes of distribution. The mean clearance following oral administration of losmapimod was approximately 31.2 L/h (95 % CI 27.7-35.2) for males and 24.6 L/h (95 % CI 22.1-27.3) in females. CONCLUSION: The population pharmacokinetic model described in this work well characterized the pharmacokinetic profile of losmapimod following administration of a single oral dose and repeated oral doses in healthy subjects and patients with RA and COPD. Although sex, bodyweight and age were significant factors influencing some pharmacokinetic parameters of losmapimod, the relatively small magnitude of the effect did not result in concerns for dose adjustment.

Re-introduction of a novel approach to the use of stable isotopes in pharmacokinetic studies.

The purpose of this investigation is to evaluate the scientific benefits of a novel approach in using stable isotopes to reduce the number of subjects needed to perform relative bioavailability and bioequivalence pharmacokinetic studies for formulations that are qualitatively and quantitatively the same and quality by design (QbD) pharmacokinetic studies. The stable isotope approach was investigated using simulations to determine the impact this approach would have on the estimation of variability and, subsequently, the sample size for a bioequivalence study. A biostudy was conducted in dogs in a two period crossover to explore the viability of the stable isotope approach. For a drug product with within-subject variability (CV(w)) of 50% and assuming a correlation of 0.95 between the enriched and non-enriched pharmacokinetics (PK), simulations showed that the variability can be reduced by 70% and the required sample size can be reduced by 90% while maintaining 90% power to demonstrate bioequivalence. The dog study showed a strong correlation (R(2), > 0.99) between the enriched and non-enriched area under the curve and maximum observed concentration, and a significant reduction in the variability (reduction in % coefficient of variation from 79.9% to 6.3%). Utilization of a stable isotope approach can markedly improve the efficiency and accuracy of bioavailability and bioequivalence studies particularly for highly variable drugs in formulations that are qualitatively and quantitatively the same and for studies designed for QbD investigations.

A phase I study of cantuzumab mertansine administered as a single intravenous infusion once weekly in patients with advanced solid tumors.

PURPOSE: The purpose is to determine the maximum-tolerated dose, assess the toxicities, characterize the pharmacokinetic behavior, and seek preliminary evidence of biological activity of cantuzumab mertansine when administered as a weekly i.v. infusion without interruption. EXPERIMENTAL DESIGN: Patients with incurable solid tumors that expressed the target antigen for cantuzumab mertansine, CanAg, were treated with doses of cantuzumab mertansine ranging from 40 to 138 mg/m(2). The maximum-tolerated dose was defined as the highest dose at which no more than 1 of 6 patients experienced dose-limiting toxicity. Plasma concentrations of cantuzumab mertansine and total humanized antibody were determined, and area under the plasma concentration-time curve (to the last measured concentration) was calculated. RESULTS: Thirty-nine patients received a total of 280 weekly doses of cantuzumab mertansine. Acute, transient elevation of the hepatic transaminases and reversible fatigue were identified as the dose-limiting toxicities at the highest dose level. The maximum-tolerated dose was determined to be 115 mg/m(2)/week. Evidence of clinical activity was noted in 3 patients. Pharmacokinetic analyses revealed that the pharmacokinetic variability was moderate, without evidence of dose dependency. Furthermore, the drug had a long terminal half-life ( approximately 40 h). CONCLUSIONS: This study identified a safe and tolerable dose of the novel immunoconjugate prodrug cantuzumab mertansine. The evidence of antitumor activity suggests that additional clinical development is warranted, with a focus on tumors that express high levels of CanAg and which are known to be sensitive to antimicrotubule agents.

A randomized study of the effect of oral lamotrigine and hydromorphone on pain and hyperalgesia following heat/capsaicin sensitization.

In this randomized double-blind placebo-controlled study, the analgesic effect of oral lamotrigine (400 mg) on cutaneous sensitization induced with the heat/capsaicin sensitization model was compared with the effect of oral hydromorphone (8 mg) in healthy volunteers. In a separate session, intravenous remifentanil (0.10 microg.kg(-1).min(-1)) and placebo were administered. This session was used as an additional reference comparator. Outcome measures were the areas of secondary hyperalgesia to brush and von Frey hair stimulation and the painfulness of noxious thermal stimulation in nonsensitized skin. Compared with placebo, both intravenous remifentanil and oral hydromorphone significantly suppressed secondary hyperalgesia and acute thermal nociception. Oral lamotrigine did not reduce secondary hyperalgesia or acute thermal nociception but produced side effects of severity comparable with that of oral hydromorphone. Although lamotrigine is efficacious in the management of some types of chronic neuropathic pain, the lack of effect of this agent on human experimental pain suggests that its analgesic effects depend on nerve injury-associated abnormalities, which cannot be simulated in healthy human volunteers.