Gao, G.F.G.F.GaoAshtikar, M.M.AshtikarKojima, R.R.KojimaYoshida, T.T.YoshidaKaihara, M.M.KaiharaTajiri, T.T.TajiriShanehsazzadeh, S.S.ShanehsazzadehModh, H.H.ModhWacker, M.G.M.G.Wacker2022-03-062022-03-062021https://publica.fraunhofer.de/handle/publica/26893810.1016/j.jconrel.2020.11.0552-s2.0-85097654310Today, tacrolimus represents a cornerstone of immunosuppressive therapy for liver and kidney transplants and remains subject of preclinical and clinical investigations, aiming at the development of long-acting depot formulations for subcutaneous injection. One major challenge arises from establishing in vitro-in vivo correlations due to the absence of meaningful in vitro methods predictive for the in vivo situation, together with a strong impact of multiple kinetic processes on the plasma concentration-time profile. In the present approach, two microsphere formulations were compared with regards to their in vitro release and degradation characteristics. A novel biorelevant medium provided the physiological ion and protein background. Release was measured using the dispersion releaser technology under accelerated conditions. A release of 100% of the drug from the carrier was achieved within 7 days. The capability of the in vitro performance assay was verified by the level A in vitro-in vivo correlation analysis. The contributions of in vitro drug release, drug degradation, diffusion rate and lymphatic transport to the absorption process were quantitatively investigated by means of a mechanistic modelling approach. The degradation rate, together with release and diffusion characteristics provides an estimate of the bioavailability and therefore can be a guide to future formulation development.en615Predicting drug release and degradation kinetics of long-acting microsphere formulations of tacrolimus for subcutaneous injectionjournal article