Long-acting injectable in situ gel of rasagiline: a patented product development

Rasagiline has a certain potential in neuroprotection and delaying the progression of Parkinson's disease (PD). However, the poor pharmacokinetics (PK) characteristics of conventional oral tablets and poor medication compliance limit the optimal efficacy of rasagiline. Based on this, we designed and optimized a sustained-release rasagiline in situ gel based on in vitro release and in vivo PK results. Among them, we found for the first time that aluminum hydroxide can effectively shorten the lag phase and promote early and late release, making the daily release more uniform. After subcutaneous administration of the optimized gel formulation at a monthly dose, the C_max (64 ng/ml) was lower than that of free rasagiline (494 ng/ml) administered subcutaneously at a daily dose and comparable to that of oral administration of Azilect^® (59.1 ng/ml) at a daily dose. In the meantime, the plasma concentration of rasagiline was mainly maintained at 5-10 ng/ml for about 1 month, and the active metabolite 1-aminoindane in plasma was also able to maintain a steady state. The rasagiline in situ gel has suitable viscosity and injectability, good repeatability of subcutaneous injection, and controllable impurities and can achieve sustained release in vivo with small burst release, which may have the clinical application advantages of maximizing the disease-modifying effect of rasagiline and improving medication compliance. The rasagiline in situ gel was optimized through the feedback of in vitro release and in vivo pharmacokinetics (PK), in which the addition of aluminum hydroxide had a modulating effect on uniform release. The gel has low burst release and maintains steady-state blood drug concentration for about 1 month.