Preclinical Bioavailability Strategy for Decisions on Clinical Drug Formulation Development: An In Depth Analysis
The aim of the presented retrospective analysis was to verify whether a previously proposed Janssen Biopharmaceutical Classification System (BCS)-like decision tree, based on preclinical bioavailability data of a solution and suspension formulation, would facilitate informed decision making on the clinical formulation development strategy. In addition, the predictive value of (in vitro) selection criteria, such as solubility, human permeability, and/or a clinical dose number (Do), were evaluated, potentially reducing additional supporting formulation bioavailability studies in animals. The absolute (Fabs,sol) and relative (Frel, susp/sol) bioavailability of an oral solution and suspension, respectively, in rat or dog and the anticipated BCS classification were analyzed for 89 Janssen compounds with 28 of these having Frel,susp/sol and Fabs,sol in both rat and dog at doses around 10 and 5 mg/kg, respectively. The bioavailability outcomes in the dog aligned well with a BCS-like classification based upon the solubility of the active pharmaceutical ingredient (API) in biorelevant media, while the alignment was less clear for the bioavailability data in the rat. A retrospective analysis on the clinically tested formulations for a set of 12 Janssen compounds confirmed that the previously proposed animal bioavailability-based decision tree facilitated decisions on the oral formulation type, with the dog as the most discriminative species. Furthermore, the analysis showed that based on a Do for a standard human dose of 100 mg in aqueous and/or biorelevant media, a similar formulation type would have been selected compared to the one suggested by the animal data. However, the concept of a Do did not distinguish between solubility enhancing or enabling formulations and does not consider the API permeability, and hence, it produces the risk of slow and potentially incomplete oral absorption of an API with poor intestinal permeability. In cases where clinical dose estimations are available early in development, the preclinical bioavailability studies and dose number calculations, used to guide formulation selection, may be performed at more relevant doses instead of the proposed standard human dose. It should be noted, however, that unlike in late development, there is uncertainty on the clinical dose estimated in the early clinical phases because that dose is usually only based on in vitro and/or in vivo animal pharmacology models, or early clinical biomarker information. Therefore, formulation strategies may be adjusted based on emerging data supporting clinical doses. In summary, combined early information on in vitro-assessed API solubility and permeability, preclinical suspension/solution bioavailability data in relation to the intravenous clearance, and metabolic pathways of the API can strengthen formulation decisions. However, these data may not always fully distinguish between conventional (e.g., to be taken with food), enhancing, and enabling formulations. Therefore, to avoid overinvestment in complex and expensive enabling technologies, it is useful to evaluate a conventional and solubility (and/or permeability) enhancing formulation under fasted and fed conditions, as part of a first-in-human study or in a subsequent early human bioavailability study, for compounds with high Do, a low animal Frel,susp/sol, or low Fabs,sol caused by precipitation of the solubilized API.