Lipid-based nanocarriers mediated Axitinib retinal delivery after topical instillation: Formulations setting up and in vivo evidence

Axitinib (AXB) is a multi-receptor tyrosine kinase inhibitor molecule. It acts by blocking the receptors for vascular endothelial growth factor (VEGFR) and platelet-derived growth factor (PDGFR), which are responsible for the development of neovascularization. To date, intravitreal injections of anti-VEGF have become the first-line medical treatment for diabetic macular oedema, a degeneration of diabetic retinopathy. Despite the efficacy of intravitreal injections, the complications of this type of administration are manifold. Our study aimed to design a nanotechnological formulation capable of delivering AXB to the retinal area after topical administration. Two different lipid-based formulations, namely solid lipid nanoparticles (SLN) and nanostructured lipid nanocarriers (NLC) were developed through a design of experiment (DoE) approach. The formulations possessed a mean particle size below 200 nm, low PDI values and a high drug encapsulation efficiency, thus designating them as suitable for ocular administration. Stability studies were performed at different storage conditions according to ICH guidelines. Strategies to improve AXB concentration in the retinal target were finally developed, such as using cationic lipids and increasing AXB loading in the nanocarriers. The in vivo PK studies indicated that cationic NLC loaded with AXB at 4 mM were the most efficient in delivering the drug to the retina, proposing them as a potential topical treatment for DR.