Intravitreal Suspension Formulations of Integrin–linked Kinase Inhibitors

Abstract

Abstract: : Purpose: The in–vivo testing of novel ocular agents in animal models can be facilitated by directly injecting slow release formulations of compounds into the vitreous. We have formulated novel small molecule inhibitors of integrin–linked kinase (ILK) in suspensions to deliver test doses into the eye over an extended period of time. Assessment of compound levels in the posterior segment and vitreous using a qualified bioanalytical method was performed. Methods: Preparations of ILK inhibitors were suspended in carboxymethylcellulose (CMC) solutions at 40 mg/mL and 10 mg/mL of active substance. The particle size was estimated by microscopy and by light scattering techniques. The suspensions (5 µL) were administered into the vitreous humor of anaesthetized animals. A bioanalytical method using mass spectrometry was developed to measure concentrations of compounds extracted from vitreous and the posterior segment of rat eyes. The dissolution and stability of the suspension formulations was assessed in water (pH 7.3) to simulate vitreous fluid. Results: An extraction method was qualified over a compound concentration range of 20 to 2000 ng/g. Using an internal standard, intra/inter–assay precision and accuracy, and analyte recovery were satisfactory. The compound suspensions having particle sizes less than 100 µm were injectable through a 30 gauge needle and were well tolerated in vivo. In simulated vitreous fluid, high concentrations of compound were maintained for over 7 days. Conclusions: Suspension formulations of ILK inhibitors are suitable for intravitreal injection into rat eyes. The tissue levels of ILK inhibitors in rat ocular tissue and vitreous fluid will be compared to levels predicted by in vitro dissolution testing.

Keywords: retina • vitreous • drug toxicity/drug effects