Application of biorelevant in vitro assays for the assessment and optimization of ASD-based formulations for pediatric patients

Amorphous solid dispersions (ASD) have been a successful formulation strategy to overcome the poor aqueous solubility of many novel drugs, but the development of pediatric formulations presents a special challenge due to variable gastrointestinal conditions in children. It was the aim of this work to design and apply a staged biopharmaceutical test protocol for the in vitro assessment of ASD-based pediatric formulations. Ritonavir was used as a model drug with poor aqueous solubility. Based on the commercial ASD powder formulation, a mini-tablet and a conventional tablet formulation were prepared. Drug release from the three formulations was studied in different biorelevant in vitro assays (i.e. MicroDiss, two-stage, transfer model, tiny-TIM) to consider different aspects of human GI physiology. Data from the two-stage and transfer model tests indicated that by controlled disintegration and dissolution excessive primary precipitation can be prevented. However, this advantage of the mini-tablet and tablet formulation did not translate into better performance in tiny-TIM. Here, the in vitro bioaccessibility was comparable for all three formulations. In the future, the staged biopharmaceutical action plan established herein will support the development of ASD-based pediatric formulations by improving the mechanistic understanding so that formulations are developed for which drug release is robust against variable physiological conditions.

Mucin-Protected Caco-2 Assay to Study Drug Permeation in the Presence of Complex Biorelevant Media

The poor solubility and permeability of compounds beyond Lipinski’s Rule of Five (bRo5) are major challenges for cell-based permeability assays. Due to their incompatibility with gastrointestinal components in biorelevant media, the exploration of important questions addressing food effects is limited. Thus, we established a robust mucin-protected Caco-2 assay to allow the assessment of drug permeation in complex biorelevant media. To do that, the assay conditions were first optimized with dependence of the concentration of porcine mucin added to the cells. Mucin-specific effects on drug permeability were evaluated by analyzing cell permeability values for 15 reference drugs (BCS class I–IV). Secondly, a sigmoidal relationship between mucin-dependent permeability and fraction absorbed in human (f_a) was established. A case study with venetoclax (BCS class IV) was performed to investigate the impact of medium complexity and the prandial state on drug permeation. Luminal fluids obtained from the tiny-TIM system showed a higher solubilization capacity for venetoclax, and a better read-out for the drug permeability, as compared to FaSSIF or FeSSIF media. In conclusion, the mucin-protected Caco-2 assay combined with biorelevant media improves the mechanistic understanding of drug permeation and addresses complex biopharmaceutical questions, such as food effects on oral drug absorption.

The relevance of supersaturation and solubilization in the gastrointestinal tract for oral bioavailability: An in vitro vs. in vivo approach

The influence of supersaturation and solubilization on oral absorption was assessed independently from the dissolution process for the non-formulated model drugs celecoxib and telmisartan. In vitro, physicochemical characterization and biphasic dissolution were used to characterize the supersaturation and solubilization effects of three water soluble polymers (copovidone, methylcellulose and Soluplus®) on the drugs. While celecoxib precipitated in a crystalline form resulting in pronounced stabilization of supersaturation, telmisartan precipitated as a highly energetic amorphous form and the potential of the polymers to enhance its solubility was subsequently, limited. In vivo, for the crystalline precipitating celecoxib, supersaturation and solubilization increased its oral bioavailability up to 10-fold. On the contrary, the amorphous precipitating telmisartan did not benefit from the limited stabilization in terms of oral exposure. Amongst all investigated in vitro tests the biphasic dissolution test was the most predictive in relation to supersaturation. However, for the potential micellar solubilization and the respective impact in the aqueous/organic interface, prediction accuracy of the biphasic dissolution test was limited in combination with Soluplus®. Despite the hetergeneous micellar distribution in vitro and permeation in vivo, the biphasic approach could clearly show the supersaturation potential on bioavailability (BA) for celecoxib on the one hand and the inferiority of supersaturation on BA for telmisartan.

Solubility and Stability Enhanced Oral Formulations for the Anti-Infective Corallopyronin A

Novel-antibiotics are urgently needed to combat an increase in morbidity and mortality due to resistant bacteria. The preclinical candidate corallopyronin A (CorA) is a potent antibiotic against Gram-positive and some Gram-negative pathogens for which a solid oral formulation was needed for further preclinical testing of the active pharmaceutical ingredient (API). The neat API CorA is poorly water-soluble and instable at room temperature, both crucial characteristics to be addressed and overcome for use as an oral antibiotic. Therefore, amorphous solid dispersion (ASD) was chosen as formulation principle. The formulations were prepared by spray-drying, comprising the water-soluble polymers povidone and copovidone. Stability (high-performance liquid chromatography, Fourier-transform-infrared spectroscopy, differential scanning calorimetry), dissolution (biphasic dissolution), and solubility (biphasic dissolution, Pion's T3 apparatus) properties were analyzed. Pharmacokinetic evaluations after intravenous and oral administration were conducted in BALB/c mice. The results demonstrated that the ASD formulation principle is a suitable stability- and solubility-enhancing oral formulation strategy for the API CorA to be used in preclinical and clinical trials and as a potential market product.

PROTAC-mediated crosstalk between E3 ligases

Small-molecule heterobifunctional degraders can effectively control protein levels and are useful research tools.