Evaluation of the impact of the polymer end groups and molecular weight on in vitro and in vivo performances of PLGA based in situ forming implants for ketoprofen

In situ forming implants are appealing long-acting dosage forms for both preclinical and clinical applications due to their simple manufacturing process and easy delivery. This study aims to develop extended-release in situ forming solid implants for subcutaneous administration using two types of commercially available triblock poly (lactic-co-glycolic acid)-poly (ethylene glycol)-poly (lactic-co-glycolic acid) (PLGA-PEG-PLGA) polymers, with either an acid or ester end group. Both types of polymers instantly form in situ implants when injected directly into an aqueous medium. The performance of these implants, containing a model compound ketoprofen, was evaluated by comparing the in vitro drug release profiles with the in vivo performance following subcutaneous administration in rats. Analytical characterizations of two representative in situ implants were conducted to understand their structural impact on polymer degradation and drug release. All tested in situ forming implants demonstrated prolonged drug release profiles both in vitro and in vivo. This study illustrates the successful preparation of sustained-release in situ forming implant formulations for ketoprofen using commercially available polymers, with the molecular weight and the end group of the polymers affecting their degradation and the drug release from the in situ formed implants.