pH Modulation as a Key Strategy for Developing a Stable Lyotropic Liquid Crystal Formulation of Octreotide Acetate

Background: Lyotropic liquid crystal (LLC) systems provide sustained release and convenient administration for peptide delivery. Octreotide, a first-line somatostatin analogue, has previously been formulated into LLC systems mainly using the hydrochloride salt. Here, we investigated the acetate salt, which is widely used in marketed products, but presents unique challenges in LLC formulation due to poor stability. Methods: We demonstrate that pH adjustment is a critical determinant for successfully incorporating octreotide acetate into a stable LLC system. By employing 3M HCl-EtOH to adjust pH to approximately 5.7, we obtained a formulation that maintained >90% drug content after 3 months at 40 °C and >98% after 12 months at 4 °C. Results: Structural analyses confirmed the coexistence of cubic and hexagonal mesophases, supporting controlled release. In vivo pharmacokinetic studies in rats further demonstrated sustained-release behavior, as evidenced by prolonged systemic exposure and an extended half-life. Pharmacokinetic profiles were comparable to those of an octreotide hydrochloride LLC. Conclusions: These findings highlight pH modulation as an essential strategy for stabilizing octreotide acetate in LLC systems, providing a foundation for extending LLC technology to clinically relevant salt forms of peptide therapeutics.