Design and Development of Long-acting Formulation for the Treatment of Posterior Segment Eye Diseases

Abstract

Age-related macular degeneration (AMD) is a chronic eye ailment characterized by gradual loss of central vision. Currently, intravitreal injections of anti-VEGF agents are used to manage AMD. However, these injections only halt the progression of the disease. Furthermore, the currently available anti-VEGF agents in the market exhibit a short half-life and hence require frequent administration. Sustained delivery of anti-VEGF agents remains a challenge to deliver across anatomic locations. Innovations in nanotechnology, implantable devices, and formulation strategies hold promise for overcoming these challenges and improving the efficacy of anti-VEGF agents. Polymeric implants with high drug loading capacity can provide sustained delivery of anti-VEGF agents without any complications. Thus, in the present study, an attempt has been made to develop a technique for fabricating cylindrical biodegradable implants which can deliver anti-VEGF agents over 12 months. Small molecule i.e. carotenoid based implants was also developed and characterized in the present study for AMD. Electrospinning has proven to be highly effective in producing small cylindrical tubes, thus makes it as an ideal method for implant production. In this study, it was used to create implants that could be loaded with anti-VEGF agents while still being compatible with a 21 G needle administration. A multi-faceted approach was employed for the development of implants, integrating the techniques of electrospinning, sintering, and salt leaching. Bevacizumab was selected as a model anti-VEGF agent in the present study with aim to reduce administration frequency of intravitreal injections. The FDA-approved polymer Poly(caprolactone) was employed for the fabrication of implants. Furthermore, the developed cylindrical implant was optimized for polymer concentration, anti-VEGF concentration, electrospinning, sintering, salt leaching parameters and characterized for salt leaching, biodegradation, FTIR, DSC, FE-SEM, tensile strength, and GPC analysis. The results of the developed cylindrical implant after the biodegradation study for six months confirm the biodegradation with reduction of molecular weight of the polymer. This was confirmed by the FE-SEM and GPC study. DSC and FTIR overlay indicated good physical and chemical stability of developed implants. The anti-VEGF loaded implants were characterized by Far-UV CD, Near UV-CD, AT-FTIR, SEC-HPLC, CEX-HPLC, In vitro drug release, bioassay, ex vivo injection feasibility and stability study. The Far-UV CD analysis revealed a distinct beta-sheet structure at 217-218 nm, while the Near-UV CD analysis represented the presence of Phenylalanine at 256-265 nm, Tyrosine at 284-285 nm and Tryptophan at 290 nm in the anti-VEGF agent. The spectral analysis conducted by FTIR provides conclusive evidence of the presence of primary and secondary amines peak at wavenumber 1635.64 cm-1 and 1543-1555 cm-1 . The SEC and CEX HPLC examination of implant purity consistently yielded robust results, specifically between 96-96.5 %, demonstrating the anti-VEGF agent's strength. The developed cylindrical implants showed a nonporous morphology, which controls the release of anti-VEGF drugs for twelve months. In vitro bioassay shows that the polymeric implants effectively maintain anti-VEGF potency. The injection feasibility study utilizing the goat eye model employed a non-surgical approach, delivering the implant through the sclera with a 21 G needle. Remarkably, the implant successfully traversed the ocular structures, reaching the posterior segment of the goat eye. In summary, the positive results obtained for the bevacizumab nanoporous sustained-release implant paved the way for the validation and subsequent recognition of the ranibizumab implant as a promising therapeutic modality confirmed by the drug release studies. Therefore, it is evident that the potential of the developed methodology extends to the exploration of similar monoclonal antibodies (mAbs). Further, these studies expanded to encompass small molecules such as carotenoids to develop nanofiber-based implants. Notably, carotenoids possess a solid nature, and their successful integration into the nanofiber matrix was achieved, as opposed to the hollow cylinder-based implant design employed for monoclonal antibodies (mAbs). However, they exhibited a sustained release profile of two months only. Furthermore, it is stated that the optimum parameters for macromolecules require adjustments before being used in the development of small molecule implants due to considerable differences in their physicochemical and biological properties. Overall, these findings suggest that the developed electrospun polymeric implants have the potential to revolutionize the treatment of vascular related diseases, offering extended-release durations, reduced administration frequency, and potentially lower costs. The study opens avenues for further exploration of similar monoclonal antibodies and underscores the importance of tailored approaches for different types of therapeutic agents.