(W1230-08-52) Testing Formulation Effects of Itraconazole in a Miniaturized Precipitation Set-Up

Purpose: The number of New Chemical Entities (NCEs) exhibiting unfavorable biopharmaceutical properties has increased over the years. As mitigation strategy, the development of enabling formulations has proven useful. In vitro assays capable of characterizing enabling formulations for their potential to improve in vivo absorption are of high interest. For weakly basic drugs, this may include the assessment of intestinal precipitation in vitro. During research, the availability of compounds is often limited. Therefore, small-scale assays that require low amounts of the compound are preferred. This study aims to investigate the potential of a miniaturized precipitation setup for characterizing precipitation to differentiate between two formulations of the weakly basic drug itraconazole.

Methods: The products under investigation included capsules containing an amorphous solid dispersion (ASD), a solution with a high concentration of Hydroxypropyl-β-Cyclodextrin (HP-β-CD), and the drug substance itself. The results of the in vitro precipitation tests were compared to human bioavailability data obtained from the open literature. The experimental setup comprised two compartments: the donor compartment, simulating the stomach, and the acceptor compartment, representing the intestine. The setup uses a 1:210 scale-down of the gastric and intestinal volumes of 250 mL. For 25 minutes, 1.2 mL of gastric media (Simulated Gastric Fluid sine pepsin (SGFsp), pH 2.0) was transferred into 1.2 mL of intestinal media (double-buffered, double-concentrated Fasted State Simulated Intestinal Fluid) at 37 °C. A dose of 0.96 mg (1/210^th of the 200 mg dose applied in the in vivo study¹) was applied. The drug was either dissolved (solution) or dispersed (capsule and drug substance) in SGFsp pH 2.0 for 15 minutes at 37 °C prior to the transfer. Samples were taken at specified time points and analyzed using Ultra High-Performance Liquid Chromatography. To assess the precipitation behavior of the various formulations, the relative area under the curve (AUC_rel) was calculated, representing the measured precipitation profile divided by the theoretical transfer profile (no precipitation). An AUC_rel of 100% indicates no precipitation of the drug during the assay. The experiments were conducted in triplicate.

Results: The concentration of dissolved itraconazole from the ASD formulation ranged between 10 and 15 µg/mL. By contrast, the concentrations for the HP-β-CD solution were typically higher, with concentrations between 30 and 40 µg/mL. When compared to the solubility of itraconazole in Fasted State Simulated Intestinal Fluid, which is reported to be 0.3 µg/mL³, both formulations exhibited supersaturation. The calculated AUC_rel was 11% ± 4% for the solution, and thus approximately 3.5-old higher compared to the AUC_rel of the capsule (3.17% ± 0.23%). For the drug substance, the concentrations obtained in the acceptor compartment were below 1 µg/mL, rendering them non-evaluable. An in vivo study involving five volunteers showed that the AUC_0-8h for the solution was, on average, 3.0-fold higher than that of the capsules¹. Other set-ups such as the BioGIT, which includes a reservoir compartment, yielded comparable concentrations, with values typically ranging from 5 to 15 µg/mL for the capsule and approximately 50 µg/mL for the HP-β-CD solution. However, the solution, exhibited much higher initial concentrations, exceeding 200 µg/mL at the 5-minute timepoint.²

Conclusion: This study details the application of a miniaturized precipitation assay to characterize the precipitation behavior of three different itraconazole formulations. Supersaturation in the duodenal compartment was observed for both formulations (ASD capsule and HP-β-CD solution). While human bioavailability data indicated a 3.0-fold higher AUC_0-8h for the solution compared to the capsule, the in vitro assay predicted an approximately 3.5-fold higher AUC_rel for the solution. This example demonstrates how a miniaturized precipitation assay can be used to forecast luminal dissolution, precipitation, and drug absorption for enabling formulations. Given the limited compound requirements, combined with the simplicity in terms of assay setup, the precipitation assay is well suited for formulation selection in preformulation. Further investigations, particularly with other drugs and formulations, are needed to further validate the predictiveness of the assay.

References: 1. Brouwers, J., Geboers, S., Mols, R., Tack, J., Augustijns, P., 2017. Gastrointestinal behavior of itraconazole in humans - Part 1: Supersaturation from a solid dispersion and a cyclodextrin-based solution. International Journal of Pharmaceutics 525 (1), 211–217. https://doi.org/10.1016/j.ijpharm.2017.04.029.
2. Kourentas, A., Vertzoni, M., Symillides, M., Hens, B., Brouwers, J., Augustijns, P., Reppas, C., 2016. In vitro evaluation of the impact of gastrointestinal transfer on luminal performance of commercially available products of posaconazole and itraconazole using BioGIT. International Journal of Pharmaceutics 515 (1-2), 352–358. https://doi.org/10.1016/j.ijpharm.2016.10.018.
3. Yamashita, T., Ozaki, S., Kushida, I., 2011. Solvent shift method for anti-precipitant screening of poorly soluble drugs using biorelevant medium and dimethyl sulfoxide. International Journal of Pharmaceutics 419 (1-2), 170–174. https://doi.org/10.1016/j.ijpharm.2011.07.045.