Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide with widespread distribution and exerting diverse biological functions. Among others, the neuropeptide has very strong cytoprotective effects mediated mainly through specific PAC1 receptors. Rapid degradation of PACAP by dipeptidyl-peptidase (DPP)-IV enzyme and its transmission through biological barriers are obstacles in systemic administration. Although intravitreal injections are a common practice in some ocular diseases, delivery of therapeutic agents in form of eye drops would be more convenient, and would lead to fewer side effects. Recently, we have proven that PACAP 1-27 and 1-38 in eye drops effectively counteract ischemic retinal degeneration. As this route of administration is a promising therapeutic strategy, it is worth investigating the stability and degradation of PACAP 1-27 and PACAP 1-38 solutions.
The drug’s stability in eye drops made with 4 common media was examined at both room temperature and + 4°C. According to the LC-MS, the highest stability was gained with water for injection and saline solution at +4°C. This meant 80-90% drug persistence after 2 weeks. The other two media (Solutio Ophthalmica cum Benzalkonio and Solvens viscosa pro oculoguttis cum thiomersalo) showed significantly lower stability, especially with PACAP 1-27 and when stored at room temperature.
The degradants are still being examined.