Model-Based Analysis of Biopharmaceutic Experiments To Improve Mechanistic Oral Absorption Modeling: An Integrated in Vitro in Vivo Extrapolation Perspective Using Ketoconazole as a Model Drug.

Mechanistic modeling of in vitro data generated from metabolic enzyme systems (viz., liver microsomes, hepatocytes, rCYP enzymes, etc.) facilitates in vitro-in vivo extrapolation (IVIV_E) of metabolic clearance which plays a key role in the successful prediction of clearance in vivo within physiologically-based pharmacokinetic (PBPK) modeling. A similar concept can be applied to solubility and dissolution experiments whereby mechanistic modeling can be used to estimate intrinsic parameters required for mechanistic oral absorption simulation in vivo. However, this approach has not widely been applied within an integrated workflow. We present a stepwise modeling approach where relevant biopharmaceutics parameters for ketoconazole (KTZ) are determined and/or confirmed from the modeling of in vitro experiments before being directly used within a PBPK model. Modeling was applied to various in vitro experiments, namely: (a) aqueous solubility profiles to determine intrinsic solubility, salt limiting solubility factors and to verify pKa; (b) biorelevant solubility measurements to estimate bile-micelle partition coefficients; (c) fasted state simulated gastric fluid (FaSSGF) dissolution for formulation disintegration profiling; and (d) transfer experiments to estimate supersaturation and precipitation parameters. These parameters were then used within a PBPK model to predict the dissolved and total (i.e., including the precipitated fraction) concentrations of KTZ in the duodenum of a virtual population and compared against observed clinical data. The developed model well characterized the intraluminal dissolution, supersaturation, and precipitation behavior of KTZ. The mean simulated AUC0-t of the total and dissolved concentrations of KTZ were comparable to (within 2-fold of) the corresponding observed profile. Moreover, the developed PBPK model of KTZ successfully described the impact of supersaturation and precipitation on the systemic plasma concentration profiles of KTZ for 200, 300, and 400 mg doses. These results demonstrate that IVIV_E applied to biopharmaceutical experiments can be used to understand and build confidence in the quality of the input parameters and mechanistic models used for mechanistic oral absorption simulations in vivo, thereby improving the prediction performance of PBPK models. Moreover, this approach can inform the selection and design of in vitro experiments, potentially eliminating redundant experiments and thus helping to reduce the cost and time of drug product development.

Identification of M4205─A Highly Selective Inhibitor of KIT Mutations for Treatment of Unresectable Metastatic or Recurrent Gastrointestinal Stromal Tumors.

The treatment of gastrointestinal stromal tumors (GISTs) driven by activating mutations in the KIT gene is a prime example of targeted therapy for treatment of cancer. The approval of the tyrosine kinase inhibitor imatinib has significantly improved patient survival, but emerging resistance under treatment and relapse is observed. Several additional KIT inhibitors have been approved; still, there is a high unmet need for KIT inhibitors with high selectivity and broad coverage of all clinically relevant KIT mutants. An imidazopyridine hit featuring excellent kinase selectivity was identified in a high-throughput screen (HTS) and optimized to the clinical candidate M4205 (IDRX-42). This molecule has a superior profile compared to approved drugs, suggesting a best-in-class potential for recurrent and metastatic GISTs driven by KIT mutations.

Evaluating the predictability of the in vitro transfer model and in vivo rat studies as a surrogate to investigate the supersaturation and precipitation behaviour of different Albendazole formulations for humans.

The present study investigated the ability of the in vitro transfer model and an in vivo pharmacokinetic study in rats to investigate the supersaturation and precipitation behaviour of albendazole (ABZ) relative to data from a human intestinal aspiration study reported in the literature. Two lipid based formulation systems, a hydroxypropyl-ß-cyclodextrin (HPßCD) solution and the addition of a crystallization inhibitor (HPMC-E5) on the behaviour of ABZ was investigated. These formulations were investigated to represent differences in their ability to facilitate supersaturation within the small intestine. Overall, both the in vitro transfer model and the in vivo rat study were able to rank order the formulations (as aqueous suspension±HPMC

Prediction of Ketoconazole absorption using an updated in vitro transfer model coupled to physiologically based pharmacokinetic modelling.

The aim of this study was to optimize the in vitro transfer model and to increase its biorelevance to more accurately mimic the in vivo supersaturation and precipitation behaviour of weak basic drugs. Therefore, disintegration of the formulation, volumes of the stomach and intestinal compartments, transfer rate, bile salt concentration, pH range and paddle speed were varied over a physiological relevant range. The supersaturation and precipitation data from these experiments for Ketoconazole (KTZ) were coupled to physiologically based pharmacokinetic (PBPK) model using Stella® software, which also incorporated the disposition kinetics of KTZ taken from the literature, in order to simulate the oral absorption and plasma profile in humans. As expected for a poorly soluble weak base, KTZ demonstrated supersaturation followed by precipitation under various in vitro conditions simulating the proximal small intestine with the results influenced by transfer rate, hydrodynamics, volume, bile salt concentration and pH values. When the in vitro data representing the "average" GI conditions was coupled to the PBPK model, the simulated profiles came closest to the observed mean plasma profiles for KTZ. In line with the high permeability of KTZ, the simulated profiles were highly influenced by supersaturation whilst precipitation was not predicted to occur in vivo. A physiological relevant in vitro "standard" transfer model setup to investigate supersaturation and precipitation was established. For translating the in vitro data to the in vivo setting, it is important that permeability is considered which can be achieved by coupling the in vitro data to PBPK modelling.

Advances and challenges in PBPK modeling--Analysis of factors contributing to the oral absorption of atazanavir, a poorly soluble weak base.

Many active pharmaceutical ingredients (APIs) exhibit a highly variable pharmacokinetic (PK) profile. This behavior may be attributable to pre-absorptive, absorptive and/or post-absorptive factors. Pre-absorptive factors are those related to dosage form disintegration, drug dissolution, supersaturation, precipitation and gastric emptying. Absorptive factors are involved with drug absorption and efflux mechanisms, while drug distribution and clearance are post-absorptive factors. This study aimed to investigate the relative influence of the aforementioned parameters on the pharmacokinetic profile of atazanavir, a poorly soluble weakly basic compound with highly variable pharmacokinetics. The pre-absorptive behavior of the drug was examined by applying biorelevant in vitro tests to reflect upper gastrointestinal behavior in the fasted and fed states. The in vitro results were implemented, along with permeability and post-absorptive data obtained from the literature, into physiologically based pharmacokinetic (PBPK) models. Sensitivity analysis of the resulting plasma profiles revealed that the pharmacokinetic profile of atazanavir is affected by an array of factors rather than one standout factor. According to the in silico model, pre-absorptive and absorptive factors had less impact on atazanavir bioavailability compared to post-absorptive parameters, although active drug efflux and extraction appear to account for the sub-proportional pharmacokinetic response to lower atazanavir doses in the fasted state. From the PBPK models it was concluded that further enhancement of the formulation would bring little improvement in the pharmacokinetic response to atazanavir. This approach may prove useful in assessing the potential benefits of formulation enhancement of other existing drug products on the market.

A toolbox for the upscaling of ethanolic human serum albumin (HSA) desolvation.

Nanoparticles consisting of human serum albumin (HSA) play an emerging role in the development of new drug delivery systems. Many of these protein-based colloidal carriers are prepared by the well-known desolvation technique, which has shown to be a robust and reproducible method for the laboratory-scale production of HSA nanoparticles. The aim of the present study was to upscale the ethanolic desolvation process utilizing the paddle stirring systems Nanopaddle I and II in combination with a HPLC pump in order to find the optimal conditions for the controlled desolvation of up to 2000 mg of the protein. For characterization of the HSA nanoparticles particle size, zeta potential as a function of the pH, polydispersity index and particle content were investigated. The particle content was determined by microgravimetry and by a turbidimetry to allow optimized in-process control for the novel desolvation technique. Furthermore the sedimentation coefficient was measured by analytical ultracentrifugation (AUC) to gain deeper insight into the size distribution of the nanoparticles. The formed nanocarriers were freeze dryed to achieve a solid preparation for long-term storage and further processing. Particles ranging in size between 251.2 ± 27.0 and 234.1 ± 1.5 nm and with a polydispersity index below 0.2 were achieved.