Translational model to predict pulmonary pharmacokinetics and efficacy in man for inhaled bronchodilators.

Translational pharmacokinetic (PK) models are needed to describe and predict drug concentration-time profiles in lung tissue at the site of action to enable animal-to-man translation and prediction of efficacy in humans for inhaled medicines. Current pulmonary PK models are generally descriptive rather than predictive, drug/compound specific, and fail to show successful cross-species translation. The objective of this work was to develop a robust compartmental modeling approach that captures key features of lung and systemic PK after pulmonary administration of a set of 12 soluble drugs containing single basic, dibasic, or cationic functional groups. The model is shown to allow translation between animal species and predicts drug concentrations in human lungs that correlate with the forced expiratory volume for different classes of bronchodilators. Thus, the pulmonary modeling approach has potential to be a key component in the prediction of human PK, efficacy, and safety for future inhaled medicines.

Identification of novel substrates and structure-activity relationship of cellular uptake mediated by human organic cation transporters 1 and 2.

Recently the clinical importance of human organic cation transporters 1 (hOCT1/SLC22A1) and 2 (hOCT2/SLC22A2) in drug disposition, for example, clearance, toxicity, and drug-drug interactions, have been highlighted [Annu. Rev. Pharmacol. Toxicol. 2012, 52, 249-273; Nat. Rev. Drug Discovery 2010, 9 (3), 215-236]. Consequently, there is an extensive need for experimental assessment of structure-transport relationships as well as tools to predict drug uptake by these transporters in ADMET (absorption, distribution, metabolism, excretion, toxicity) investigations. In the present study, we developed a robust assay for screening unlabeled compound uptake by hOCT1 and hOCT2 using transfected HEK293 cells. For the first time, an extensive data set comprising uptake of 354 compounds is presented. As expected, there was a large overlap in substrate specificity between the two organic cation transporters. However, several compounds selectively taken up by either hOCT1 or hOCT2 were identified. In particular, a chemical series of phenylthiophenecarboxamide ureas was identified as selective hOCT1 substrates. Moreover, the drivers for transport differed: molecular volume was the most important determinant of hOCT1 substrates, whereas H-bonding parameters like polar surface area (PSA) dominated for hOCT2.