Optimizing high-drug-loaded spray-dried antibody fragment formulations for sustained delivery: influence of excipient composition and humidity on long-term stability

To facilitate the development of protein depots for sustained delivery, this study optimized spray-dried formulations of a model antibody fragment (Fab2) by evaluating the impact of excipient composition and environmental stress on long-term stability. Sucrose and trehalose were compared at low excipient-to-protein mass ratios (0.3:1 and 0.5:1), alongside the effects of polysorbate 20 and sodium chloride, under storage conditions mimicking physiological temperature (37 °C) at both low (sealed vials) and high (open vials) 80% relative humidity. While trehalose formulations exhibited significantly higher glass transition temperatures than sucrose-based systems, both disaccharides provided comparable protection against aggregation. Exposure to high humidity accelerated degradation across all formulations, resulting in massive particle growth, increased aggregation, and the formation of basic chemical variants including pyroglutamate and succinimide species. These findings underscore that while spray drying can engineer suitable particles for delivery, ensuring therapeutic viability requires maintaining specific excipient thresholds and strictly controlling moisture ingress.