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Selumetinib (ARRY-142886), an oral, potent and highly selective allosteric mitogen-activated protein kinase kinase 1/2 inhibitor, is approved by the US Food and Drug Administration for the treatment of pediatric patients aged ≥2 years with neurofibromatosis type 1 with symptomatic, inoperable plexiform neurofibromas. A physiologically based pharmacokinetic (PBPK) model was constructed to predict plasma concentration-time profiles of selumetinib, and to evaluate the impact of coadministering moderate cytochrome P450 (CYP) 3A4/2C19 inhibitors/inducers. The model was also used to extrapolate pharmacokinetic exposures from older children with different body surface area to guide dosing in younger children. This model was built based on physiochemical data and clinical in vivo drug-drug interaction (DDI) studies with itraconazole and fluconazole, and verified against data from an in vivo rifampicin DDI study and an absolute bioavailability study. The pediatric model was updated by changing system-specific input parameters using the Simcyp pediatric module. The model captured the observed selumetinib pharmacokinetic profiles and the interactions with CYP inhibitors/inducers. The predictions from the PBPK model showed a DDI effect of 30% to 40% increase or decrease in selumetinib exposure when coadministered with moderate CYP inhibitors or inducers, respectively, which was used to inform dose management and adjustments. The pediatric PBPK model was applied to simulate exposures in specific body surface area brackets that matched those achieved with a 25 mg/m2 dose in SPRINT clinical trials. The pediatric PBPK model was used to guide the dose for younger patients in a planned pediatric clinical study.

Selumetinib (AZD6244, ARRAY-142886) is a mitogen-activated protein kinase kinase inhibitor that has been tested for treatment of non-small cell lung cancer (NSCLC). Selumetinib (75 mg twice daily) plus docetaxel in patients with advanced NSCLC has been assessed in phase 2 (SELECT-2) and phase 3 (SELECT-1) clinical trials. The objective of the current analysis was to investigate the exposure-response relationship of selumetinib in these 2 clinical trials, based on the development of a population pharmacokinetic (PopPK) model for selumetinib and its active metabolite, N-desmethyl selumetinib, in patients with NSCLC. A PopPK model using data from seven phase 1 studies was first developed and served as prior information for the development of the patient PopPK model. The pharmacokinetics (PK) of selumetinib and N-desmethyl selumetinib were modeled simultaneously. A two-compartment model with zero-first order absorption and first-order elimination reasonably described the selumetinib PK. The N-desmethyl metabolite of selumetinib was described by a one-compartment model with first-order elimination. The final PK parameter estimates were similar between patients with NSCLC and patients in the phase 1 population. Selumetinib apparent clearance and central volume of distribution were 11.9 L/h and 32.1 L, respectively, in patients. Individual selumetinib exposure metrics were estimated to investigate the correlation between exposure and efficacy/safety endpoints observed in NSCLC studies. There was no significant difference in progression-free survival (the primary endpoint) among the different quartiles of exposure. Similarly, no significant correlation was observed between selumetinib exposure and other secondary efficacy or safety endpoints. The conclusions are in accordance with the reported clinical findings.

Zolmitriptan is a serotonin (5-HT) 1B/1D receptor agonist effective for the treatment of migraine. This analysis aimed to develop a population pharmacokinetic (PK) model for zolmitriptan and its active metabolite in adults and adolescents and provide appropriate dosing regimens to be used in clinical trials for children 6–11 years old. The data from a single-dose clinical study of 5.0-mg zolmitriptan nasal spray (ZNS) conducted in adult and adolescent patients with migraine between migraine attacks was applied. Similar plasma concentration profiles of zolmitriptan and its metabolite, 183C91, were observed in adults and adolescents. A 1-compartment model with first-order absorption and first-order elimination reasonably described the zolmitriptan PK. With a portion of elimination of zolmitriptan being treated as the conversion from zolmitriptan to 183C91, the disposition of 183C91 was described by a 1-compartment model with first-order elimination. The estimated typical apparent volume of distribution and clearance of zolmitriptan were 136 L and 121 L/h, respectively, with 56.5% and 42.6% between-subject variability, respectively. Based on the simulation results with the final population PK model, a body weight–based dosing scheme of 5.0 and 2.5 mg ZNS in children greater than and less than 50 kg is recommended to achieve exposures similar to those of the adult and adolescent population administered 5.0 mg ZNS. The recommended doses for children to achieve exposure similar to that observed in adults given 2.5 mg ZNS are 2.5 mg (≥50 kg) and 1.0 mg (15–50 kg). These dosing regimens could be used in future clinical trials.

Aztreonam is a monocyclic β-lactam antibiotic often used to treat infections caused by Enterobacteriaceae or Pseudomonas aeruginosa. Despite the long history of clinical use, population pharmacokinetic modeling of aztreonam in renally impaired patients is not yet available. The aims of this study were to assess the impact of renal impairment on aztreonam exposure and to evaluate dosing regimens for patients with renal impairment. A population model describing aztreonam pharmacokinetics following intravenous administration was developed using plasma concentrations from 42 healthy volunteers and renally impaired patients from 2 clinical studies. The final pharmacokinetic model was used to predict aztreonam plasma concentrations and evaluate the probability of pharmacodynamic target attainment (PTA) in patients with different levels of renal function. A 2-compartment model with first-order elimination adequately described aztreonam pharmacokinetics. The population mean estimates of aztreonam clearance, intercompartmental clearance, volume of distribution of the central compartment, and volume of distribution of the peripheral compartment were 4.93 L/h, 9.26 L/h, 7.43 L, and 6.44 L, respectively. Creatinine clearance and body weight were the most significant variables to explain patient variability in aztreonam clearance and volume of distribution, respectively. Simulations using the final pharmacokinetic model resulted in a clinical susceptibility break point of 4 and 8 mg/L, respectively, based on the clinical use of 1- and 2-g loading doses with the same or reduced maintenance dose every 8 hours for various renal deficiency patients. The population pharmacokinetic modeling and PTA estimation support adequate PTAs (>90% PTA) from the aztreonam label for dose adjustment of aztreonam in patients with moderate and severe renal impairment.

A population model describing quetiapine pharmacokinetics (PK) in Western and Chinese patients following oral administration of immediate-release (IR) and extended-release (XR) formulations was developed using plasma concentrations in 127 patients from 5 studies with quetiapine IR and/or XR in Western patients and 1 study with quetiapine XR in Chinese patients. A 1-compartmental model with first-order absorption and first-order elimination adequately described the quetiapine PK. The typical apparent volume of distribution and elimination rate constant of quetiapine were 574 L and 0.12 h(-) (1) , respectively. The estimated population absorption rate constants were 1.46 and 0.10 h(-1) for quetiapine IR and XR, respectively. Covariate analysis revealed that race was not a significant covariate influencing the PK of quetiapine. Simulation conducted with the final quetiapine population PK model predicted that the administration of a 200-mg twice-daily dose of quetiapine IR in Chinese patients would achieve a steady-state AUC (AUCss ) ± standard deviation of 3087 ± 1480 ng · h/mL, which is in close agreement with the reported value (3538 ± 1728 ng · h/mL). The model also predicted that once-daily administration of 300 mg quetiapine IR or XR would achieve similar exposure in terms of AUCss in Chinese patients.

The objectives of the present study were to evaluate safety and tolerability as well as the effects of multiple doses of lanicemine on the pharmacokinetics of a CYP3A substrate, midazolam. A total of 46 healthy volunteers were enrolled in the open-label, fixed-sequence, nonrandomized study. All volunteers received an oral dose of 5 mg of midazolam alone or after 6 days of 150 mg daily intravenous infusion of lanicemine. Lanicemine reached a plasma Cmax of 1.51 μg/mL after 150 mg daily dosing to steady state. The geometric mean CL, Vss, and t1/2 of lanicemine were 8.1 L/h, 122.0 L, and 10.4 hours, respectively. The geometric least-squares mean ratios and 90% confidence intervals for midazolam AUC0- ∞ , and Cmax were within the 80% to 125% limits when lanicemine plus midazolam treatment was compared with midazolam alone, demonstrating that daily dosing with 150 mg of lanicemine for 6 days had no effect on CYP3A activity. Comprehensive physiologically based pharmacokinetic modeling using in vitro and in silico findings also indicated lanicemine would have little impact on the pharmacokinetics of CYP3A substrate, such as midazolam. In addition, lanicemine and midazolam administered alone or in combination were generally safe and well tolerated.