Effects of Different Carriers on the Stability and Pharmacokinetic Performance of Cucurbitacin B Solid Dispersions

Cucurbitacin B (CuB) is a highly oxidized tetracyclic triterpenoid classified as a Biopharmaceutics Classification System class (BCS) IV drug. Its poor solubility and low permeability significantly limit its clinical use. In an initial study, a solid dispersion formulation, CuB-PLX 407-SD, was developed and showed significantly improved dissolution rate and bioavailability. However, long-term storage led to evident crystallization and other aging-related issues, raising concerns about its stability. This study aimed to evaluate the effects of different carrier materials on the dissolution and stability of CuB solid dispersions (CuB-SD) and to assess the bioavailability of the most stable formulation. Dissolution behavior was characterized using SEM, DSC, XRPD, and FT-IR. The stability of CuB-SDs was evaluated under high-humidity storage conditions (25℃/95% RH). Relative crystallinity, and dissolution profiles were measured at scheduled intervals to identify the most stable formulation. The in vitro dissolution results indicated that all tested solid dispersions enhanced the dissolution rate of CuB. Stability analysis showed that CuB-SDs formulations using the amorphous carrier PVP VA64 and the semi-crystalline carrier PLX 407 exhibited superior stability, with PVP VA64 demonstrating the best performance. Compared to the active pharmaceutical ingredient, both CuB-PVP VA64-SD and CuB-PLX 407-SD formulations achieved substantial improvements in relative bioavailability.