Correlation of in vivo and in vitro release data for rh-INFα lipid implants

Previous in vitro experiments had shown that rh-INFα releasing tristearin implants feature promising properties making them an excellent tool for the delivery of therapeutic proteins. Sustained release for periods up to one month could be achieved, associated with high protein stabilization. The objective of this study was to investigate for the first time the in vivo release properties of these implants in rabbits and to establish an in vivo–in vitro correlation. Computer modeling was used to simulate rh-INFα serum levels based on pharmacokinetic data. Protein serum concentrations on therapeutically relevant nearly constant levels could be detected for 9 days. Modeling revealed that in vivo release correlated closely with the release monitored in vitro.