Weber Benjamin, Hochhaus Guenther
Department of Pharmaceutics, College of Pharmacy, Center of Pharmacometrics and Systems Pharmacology, University of Florida, Gainesville, Florida, USA.
AAPS J. 2015 Jul;17(4):999-1010. doi: 10.1208/s12248-015-9768-y. Epub 2015 May 2.
The role of plasma pharmacokinetics (PK) for assessing bioequivalence at the target site, the lung, for orally inhaled drugs remains unclear. A validated semi-mechanistic model, considering the presence of mucociliary clearance in central lung regions, was expanded for quantifying the sensitivity of PK studies in detecting differences in the pulmonary performance (total lung deposition, central-to-peripheral lung deposition ratio, and pulmonary dissolution characteristics) between test (T) and reference (R) inhaled fluticasone propionate (FP) products. PK bioequivalence trials for inhaled FP were simulated based on this PK model for a varying number of subjects and T products. The statistical power to conclude bioequivalence when T and R products are identical was demonstrated to be 90% for approximately 50 subjects. Furthermore, the simulations demonstrated that PK metrics (area under the concentration time curve (AUC) and C max) are capable of detecting differences between T and R formulations of inhaled FP products when the products differ by more than 20%, 30%, and 25% for total lung deposition, central-to-peripheral lung deposition ratio, and pulmonary dissolution characteristics, respectively. These results were derived using a rather conservative risk assessment approach with an error rate of <10%. The simulations thus indicated that PK studies might be a viable alternative to clinical studies comparing pulmonary efficacy biomarkers for slowly dissolving inhaled drugs. PK trials for pulmonary efficacy equivalence testing should be complemented by in vitro studies to avoid false positive bioequivalence assessments that are theoretically possible for some specific scenarios. Moreover, a user-friendly web application for simulating such PK equivalence trials with inhaled FP is provided.
血浆药代动力学（PK）在评估口服吸入药物在靶部位（肺）的生物等效性方面的作用仍不明确。一个经过验证的半机制模型，考虑到肺中央区域存在黏液纤毛清除功能，被扩展用于量化PK研究在检测试验（T）和参比（R）吸入丙酸氟替卡松（FP）产品之间肺部性能差异（全肺沉积、中央与外周肺沉积率以及肺部溶解特性）时的敏感性。基于该PK模型，针对不同数量的受试者和T产品模拟了吸入FP的PK生物等效性试验。当T和R产品相同时，得出生物等效性结论的统计效能在约50名受试者时被证明为90%。此外，模拟结果表明，当吸入FP产品的T和R制剂在全肺沉积、中央与外周肺沉积率以及肺部溶解特性方面分别相差超过20%、30%和25%时，PK指标（浓度-时间曲线下面积（AUC）和Cmax）能够检测出它们之间的差异。这些结果是使用一种较为保守的风险评估方法得出的，错误率<10%。因此，模拟结果表明，对于比较缓慢溶解的吸入药物肺部疗效生物标志物的临床研究，PK研究可能是一种可行的替代方法。肺部疗效等效性测试的PK试验应以体外研究作为补充，以避免在某些特定情况下理论上可能出现的假阳性生物等效性评估。此外，还提供了一个用户友好的网络应用程序，用于模拟吸入FP的此类PK等效性试验。
