Development and optimization of an in vitro release assay for evaluation of liposomal irinotecan formulation

Onivyde®, a pegylated irinotecan liposomal formulation, is approved by the USFDA for treating metastatic pancreatic adenocarcinoma. Despite the substantial interest in developing its generic versions, the unique structural and manufacturing complexities of liposomal formulations pose challenges. In this study, we address this gap by developing a robust in vitro release test (IVRT) using dialysis membrane techniques. The release of Onivyde® is influenced by several key factors, including the composition of the release medium, temperature, initial formulation concentration, the materials and molecular weight cut-offs of dialysis bags, and the pH of the release medium. Our optimized IVRT for Onivyde® incorporates a release medium containing 5 mM ammonium bicarbonate in a HEPES solution with a pH of 7.4. Additionally, the method includes an initial formulation concentration of 4.6 µg/mL and 50 kDa dialysis bags, while maintaining a temperature of 37 °C with continuous agitation at 80 rpm. This optimized IVR assay effectively differentiates between varying qualities of irinotecan liposomal formulations. Our findings contribute to optimizing IVRT for liposomal irinotecan formulations, enabling better quality control procedures. This assay serves as a reliable tool for evaluating generic irinotecan liposomal formulations, aiding in their development and ensuring in vitro comparability.