Topical axitinib is a potent inhibitor of corneal neovascularization

Anti-angiogenic and antioxidant effects of axitinib in human retinal endothelial cells: implications in diabetic retinopathy

Diabetic retinopathy is a secondary microvascular complication of diabetes mellitus. This disease progresses from two stages, non-proliferative and proliferative diabetic retinopathy, the latter characterized by retinal abnormal angiogenesis. Pharmacological management of retinal angiogenesis employs expensive and invasive intravitreal injections of biologic drugs (anti-vascular endothelial growth factor agents). To search small molecules able to act as anti-angiogenic agents, we focused our study on axitinib, which is a tyrosine kinase inhibitor and represents the second line treatment for renal cell carcinoma. Axitinib is an inhibitor of vascular endothelial growth factor receptors, and among the others tyrosine kinase inhibitors (sunitinib and sorafenib) is the most selective towards vascular endothelial growth factor receptors 1 and 2. Besides the well-known anti-angiogenic and immune-modulatory functions, we hereby explored the polypharmacological profile of axitinib, through a bioinformatic/molecular modeling approach and in vitro models of diabetic retinopathy. We showed the anti-angiogenic activity of axitinib in two different in vitro models of diabetic retinopathy, by challenging retinal endothelial cells with high glucose concentration (fluctuating and non-fluctuating). We found that axitinib, along with inhibition of vascular endothelial growth factor receptors 1 (1.82 ± 0.10; 0.54 ± 0.13, phosphorylated protein levels in fluctuating high glucose vs . axitinib 1 µM, respectively) and vascular endothelial growth factor receptors 2 (2.38 ± 0.21; 0.98 ± 0.20, phosphorylated protein levels in fluctuating high glucose vs . axitinib 1 µM, respectively), was able to significantly reduce (p < 0.05) the expression of Nrf2 (1.43 ± 0.04; 0.85 ± 0.01, protein levels in fluctuating high glucose vs . axitinib 1 µM, respectively) in retinal endothelial cells exposed to high glucose, through predicted Keap1 interaction and activation of melanocortin receptor 1. Furthermore, axitinib treatment significantly (p < 0.05) decreased reactive oxygen species production (0.90 ± 0.10; 0.44 ± 0.06, fluorescence units in high glucose vs . axitinib 1 µM, respectively) and inhibited ERK pathway (1.64 ± 0.09; 0.73 ± 0.06, phosphorylated protein levels in fluctuating high glucose vs . axitinib 1 µM, respectively) in HRECs exposed to high glucose. The obtained results about the emerging polypharmacological profile support the hypothesis that axitinib could be a valid candidate to handle diabetic retinopathy, with ancillary mechanisms of action.

Intralesional Axitinib Injection Mitigates Hypertrophic Scar by Inhibiting Angiogenesis Pathway: A Preliminary Study in a Rabbit Ear Model

Objective

High levels of VEGF and excessive angiogenesis contribute significantly to hypertrophic scar (HS) formation. Our study aimed to preliminarily investigate the effect of axitinib, a selective VEGF receptor tyrosine kinase inhibitor, on angiogenesis of HS and to explore its possible mechanism in a rabbit ear model.

Methods

Ten male New Zealand white rabbits were used to establish HS models and then randomised to the control and axitinib groups. The scar tissues in the two groups were injected with axitinib or normal saline, and they were evaluated after one month of treatment. Macroscopic scar thickness, vascularity and pliability, as well as histopathological analysis including HE staining and Masson staining and scar elevation index (SEI) between two groups were compared. Immunohistochemical staining of CD31 in two groups was conducted to assess the degree of angiogenesis in HS tissue. The protein expression of protein kinase B (AKT) and ribosomal protein S6 kinase (p70S6K) and their phosphorylation levels in both groups were examined by Western blot analysis.

Results

The macroscopic and histological observation showed intralesional axitinib injection significantly reduced scar thickness, vascularity and pliability of HS in the rabbit ear model. The value of SEI in HE assessment was also significantly declined in the axitinib group. Furthermore, immunohistochemical analysis revealed that axitinib suppressed the expression of CD31 in HS tissue, and the mean IOD for blood vessels was significantly lower in the axitinib-treated group. Additionally, axitinib effectively attenuated the protein expression of p70S6K, p-AKT and p-p70S6K by Western blot analysis.

Conclusion

Our study suggests that intralesional injection of axitinib can effectively attenuate HS by reducing angiogenesis in the rabbit ear model, and this inhibitory effect may be mediated by suppression of AKT/p70S6K signaling pathway. It indicates that axitinib may be a promising option for the treatment of HS in the future.

Research progress of VEGFR small molecule inhibitors in ocular neovascular diseases

Angiogenesis is the biological process in which existing blood vessels generate new ones and it is essential for body growth and development, wound healing, and granulation tissue formation. Vascular endothelial growth factor receptor (VEGFR) is a crucial cell membrane receptor that binds to VEGF to regulate angiogenesis and maintenance. Dysregulation of VEGFR signaling can lead to several diseases, such as cancer and ocular neovascular disease, making it a crucial research area for disease treatment. Currently, anti-VEGF drugs commonly used in ophthalmology are mainly four macromolecular drugs, Bevacizumab, Ranibizumab, Conbercept and Aflibercept. Although these drugs are relatively effective in treating ocular neovascular diseases, their macromolecular properties, strong hydrophilicity, and poor blood-eye barrier penetration limit their efficacy. However, VEGFR small molecule inhibitors possess high cell permeability and selectivity, allowing them to traverse and bind to VEGF-A specifically. Consequently, they have a shorter duration of action on the target, and they offer significant therapeutic benefits to patients in the short term. Consequently, there is a need to develop small molecule inhibitors of VEGFR to target ocular neovascularization diseases. This review summarizes the recent developments in potential VEGFR small molecule inhibitors for the targeted treatment of ocular neovascularization diseases, with the aim of providing insights for future studies on VEGFR small molecule inhibitors.

Identification of the Major Degradation Pathways of Selumetinib

Selumetinib is administered orally in capsule form and is indicated for the treatment of neurofibromatosis. To facilitate dosage adjustments, liquid preparations, such as solutions or suspensions, are to be developed. This led, first, to determine the stability profile of soluble or dispersed selumetinib and, secondly, to look for ways to stabilize the active substance. The degradation kinetics of selumetinib as a function of stress conditions were determined and compared. The degradation products were detected and identified by LC-HRMSⁿ. In solution, selumetinib is sensitive to oxidation and degrades by photooxidation. In both cases, the side chain represented by the oxoamide group is concerned, leading to the formation of an amide derivative for the first case and an ester derivative for the second. The identification of such degradation mechanisms allowed us to study, in a targeted way, processes aiming at stabilizing the active molecule.

Magic Bullets: The Coming Age of Meaningful Pharmacological Control of the Corneal Responses to Injury and Disease

Corneal injuries from chemical burns, mechanical trauma, infections, immunological rejections, surgical complications, and some diseases are commonly associated with persistent epithelial defects (PED), neurotrophic epitheliopathy, scarring fibrosis, corneal neovascularization (CNV), and/or corneal endothelial damage that lead to vision loss. Several Food and Drug Administration (FDA) approved medications have recently become available, are currently in clinical trials, or are likely to enter clinical trials in the near future. For example, a 2-week course of topical human recombinant nerve growth factor is frequently an effective treatment for corneal neurotrophic epitheliopathy associated with PEDs. Topical losartan, an angiotensin converting enzyme II receptor antagonist that also inhibits TGF beta signaling, has been shown to effectively decrease myofibroblast generation and scarring fibrosis in alkali burn injury and Descemetorhexis rabbit models. Small molecule topical tyrosine kinase inhibitors, such as sunitinib and axitinib, FDA approved as chemotherapeutic agents to treat specific cancers, have also been found to be effective topical inhibitors of CNV in animal and human trials. Rho-kinase inhibitors, such as ripasudil and netarsudil, that are currently approved agents for the treatment of glaucoma in some countries, have been shown to stimulate corneal endothelial proliferation in animal studies and human trials, and may accelerate the regeneration of Descemet's membrane. These agents, as well as other drugs in development, will be used in targeted combinations to treat corneal pathophysiology associated with epithelial healing disorders, stromal scarring fibrosis, CNV, and corneal endothelial injury during the next decade.

Evaluation of Long-Lasting Potential of Suprachoroidal Axitinib Suspension Via Ocular and Systemic Disposition in Rabbits

Purpose

Axitinib, a tyrosine kinase inhibitor, is a potent inhibitor of vascular endothelial growth factor (VEGF) receptors −1, −2 and −3. Suprachoroidal (SC) delivery of axitinib, combined with pan-VEGF inhibition activity of axitinib, has the potential to provide additional benefits compared to the current standard of care with intravitreal anti–VEGF-A agents. This study evaluated the ocular pharmacokinetics and systemic disposition of axitinib after SC administration in rabbits.

Methods

Rabbits received axitinib as either a single SC injection (0.03, 0.10, 1.00, or 4.00 mg/eye; n = 4/group) or a single intravitreal injection (1 mg/eye; n = 4/group) in three separate studies. Axitinib concentrations were measured in several ocular compartments and in plasma at predetermined timepoints for up to 91 days. The pharmacokinetics parameters were estimated by noncompartmental analysis.

Results

A single SC injection of axitinib suspension (1 mg/eye) resulted in an 11-fold higher mean axitinib exposure in the posterior eye cup, compared with intravitreal injection. Sustained levels of axitinib in the retinal pigment epithelium–choroid–sclera (RCS) and retina were observed throughout the duration of studies after a single SC axitinib injection (0.1 and 4.0 mg/eye), with low exposure in the vitreous humor, aqueous humor, and plasma. Axitinib levels in the RCS were 3 to 5 log orders higher than the reported in vitro (VEGF receptor–2 autophosphorylation inhibition) 50% inhibitory concentration value after 0.1 and 4.0 mg/eye dose levels throughout the 65-day and 91-day studies, respectively.

Conclusions

This study demonstrates that SC axitinib suspension has a favorable pharmacokinetics profile with potential as a long-acting therapeutic candidate targeted to affected choroid and retinal pigment epithelium in neovascular age-related macular degeneration.

Translational Relevance

Suprachoroidal axitinib suspension has potential to decrease the treatment burden in neovascular age-related macular degeneration, as a long-acting therapeutic candidate, and could yield greater efficacy, as a potent tyrosine kinase pan-VEGF inhibitor, compared with current standard anti-VEGF-A therapies.

Suprachoroidal Delivery of Small Molecules, Nanoparticles, Gene and Cell Therapies for Ocular Diseases

Suprachoroidal drug delivery technology has advanced rapidly and emerged as a promising administration route for a variety of therapeutic candidates, in order to target multiple ocular diseases, ranging from neovascular age-related macular degeneration to choroidal melanoma. This review summarizes the latest preclinical and clinical progress in suprachoroidal delivery of therapeutic agents, including small molecule suspensions, polymeric entrapped small molecules, gene therapy (viral and nonviral nanoparticles), viral nanoparticle conjugates (VNCs), and cell therapy. Formulation customization is critical in achieving favorable pharmacokinetics, and sustained drug release profiles have been repeatedly observed for multiple small molecule suspensions and polymeric formulations. Novel therapeutic agents such as viral and nonviral gene therapy, as well as VNCs, have demonstrated promise in animal studies. Several of these suprachoroidally-administered therapies have been assessed in clinical trials, including small molecule suspensions of triamcinolone acetonide and axitinib, viral vector RGX-314 for gene therapy, and VNC AU-011. With continued drug delivery research and optimization, coupled with customized drug formulations, suprachoroidal drug delivery may address large unmet therapeutic needs in ophthalmology, targeting affected tissues with novel therapies for efficacy benefits, compartmentalizing therapies away from unaffected tissues for safety benefits, and achieving durability to relieve the treatment burden noted with current agents.

Pharmacological Potential of Small Molecules for Treating Corneal Neovascularization

Under healthy conditions, the cornea is an avascular structure which allows for transparency and optimal visual acuity. Its avascular nature is maintained by a balance of proangiogenic and antiangiogenic factors. An imbalance of these factors can result in abnormal blood vessel proliferation into the cornea. This corneal neovascularization (CoNV) can stem from a variety of insults including hypoxia and ocular surface inflammation caused by trauma, infection, chemical burns, and immunological diseases. CoNV threatens corneal transparency, resulting in permanent vision loss. Mainstay treatments of CoNV have partial efficacy and associated side effects, revealing the need for novel treatments. Numerous natural products and synthetic small molecules have shown potential in preclinical studies in vivo as antiangiogenic therapies for CoNV. Such small molecules include synthetic inhibitors of the vascular endothelial growth factor (VEGF) receptor and other tyrosine kinases, plus repurposed antimicrobials, as well as natural source-derived flavonoid and non-flavonoid phytochemicals, immunosuppressants, vitamins, and histone deacetylase inhibitors. They induce antiangiogenic and anti-inflammatory effects through inhibition of VEGF, NF-κB, and other growth factor receptor pathways. Here, we review the potential of small molecules, both synthetics and natural products, targeting these and other molecular mechanisms, as antiangiogenic agents in the treatment of CoNV.

Comparison of the effect of topical bevacizumab and sorafenib in experimental corneal neovascularization

PURPOSE

The purpose of this study was to compare the neovascularization inhibiting the effect of topical bevacizumab and sorafenib and to determine the effective dose of sorafenib.

MATERIAL AND METHODS

Forty-two healthy Wistar albino rats were randomly divided into six groups. The right corneas of all rats except group 1 were cauterised with silver nitrate. Group 2 received DMSO, group 3 received topical bevacizumab (5 mg/dL, 3 times a day) and group 4, 5 and 6 received topical sorafenib (2.5 mg/dl, 5 mg/dL, 7.5 mg/dL, 2 times a day respectively), between days 1 and 7. Corneal photographs were taken on day 8 and the corneal neovascular area percentage was calculated. Following decapitation, the corneas were removed to determine the levels of VEGF ELİSA and corneal immune staining. The Mann-Whitney U-test was used for statistical analysis.

RESULTS

The neovascular corneal area percentage was statistically significantly lower in the treatment groups than group 2 (p < 0.05). The intensity of VEGF immune staining was also lower in groups 3, 5 and 6 from the group 2. Group 3, 5 and 6 were no significant differences compared to group 1. The VEGF ELİSA levels were statistically significantly lower in group 3, 5 and 6 compared to group 2 (p < 0.05). There was no statistically difference between VEGF ELİSA levels of group 2 and 4 (p > 0.05).

CONCLUSIONS

Sorafenib was as effective as bevacizumab in the regression of corneal neovascularization. The effect of sorafenib seems to be dose-dependent. The low doses and twice a day administration are important advantages of sorafenib.

Comparison of the Therapeutic Efficacies of Topical Rivoceranib and Topical Bevacizumab in a Murine Model of Corneal Neovascularization

Background and Objectives: Corneal neovasculariziation (CNV) is a serious vision-threatening complication; however, all therapeutics have their clinical limitations. The aim of this study is to investigate the efficacy of topical rivoceranib compared with topical bevacizumab in a murine model of corneal neovascularization (CNV). Materials and Methods: Murine CNV was induced by means of total de-epithelization and alkali burn. Mice were divided into five groups according to topical treatment: untreated control, phosphate-buffered saline (PBS), 0.1% and 0.5% rivoceranib, and 0.5% bevacizumab. CNV area and index were measured 7 and 14 days after treatment. After corneal tissues were excised at day 14, the blood and lymphatic vessels were quantified by cluster of differentiation 31 (CD31) and lymphatic vessel endothelial hyaluronan receptor 1 (LYVE1) immunofluorescence, respectively. Results: After 14 days, treatment groups with 0.1% and 0.5% rivoceranib and 0.5% bevacizumab showed a decrease in CNV area and index compared with the untreated and PBS groups (all p < 0.01). Blood and lymphatic vascularization significantly decreased in the 0.5% rivoceranib and 0.5% bevacizumab groups, as measured by CD31 and LYVE1 immunofluorescence. There was no significant difference of vascularization between the 0.5% rivoceranib and bevacizumab groups. Conclusions: Topical application of rivoceranib could effectively decrease CNV equivalent to topical bevacizumab in a murine model.