Topical Trabodenoson Is Neuroprotective in a Rodent Model of Anterior Ischemic Optic Neuropathy (rNAION)

Ischemic Optic Neuropathy: A Review of Current and Potential Future Pharmacotherapies

The treatment of arteritic anterior ischemic optic neuropathy (AAION), non-arteritic ischemic optic neuropathy (NAAION), and posterior ischemic optic neuropathy (PION) is a topic of ongoing research with mixed evidence on some pharmacotherapies and a need for more consensus. This manuscript provides an overview of these conditions' current, potential future, and attempted pharmacotherapies. AAION's current treatment regimen consists of high-dose steroids, with methotrexate, tocilizumab, and abatacept, being the most viable steroid-sparing therapy candidates. As for NAAION, the treatments being tried are vast, with mixed evidence supporting each modality. Similarly, despite the various treatment options explored, there still needs to be a universally effective therapy for PION. More research is needed to formulate an agreed-upon treatment regimen for these conditions.

Neuroprotective Strategies for Nonarteritic Anterior Ischemic Optic Neuropathy: A Systematic Review

PURPOSE

Nonarteritic anterior ischemic optic neuropathy (NAION) is the second most common form of optic neuropathy. Most patients show no improvement over time. Until now, there is still no definitive therapy for NAION. The available literatures on the possible treatment of NAION are quite diverse and controversial. Neuroprotection strategies have been suggested as one of the potential treatments for NAION. This review aims to critically evaluate the literature on neuroprotective strategy for NAION.

METHODS

This report was written in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines. We performed a systematic literature search in Pubmed, Science Direct, Proquest, and Cochrane databases. Only neuroprotective agents that directly work in protecting neurons were included. The outcome of interest in this review is retinal ganglion cell density and apoptosis for animal studies and retinal nerve fiber layer thickness for human studies.

RESULTS

The systematic search identified 591 studies of which 24 met the eligibility criteria, including 21 animal studies and three human studies. Only a few of the studies evaluated the same treatments, showing how diverse neuroprotector treatments are currently being evaluated as NAION treatment. From 21 animal studies, 14 studies showed significantly higher retinal ganglion cell density (1.49- to 2.81-fold) with neuroprotective treatment compared to control group. Two of three human studies in this review had also found a beneficial effect of preserving retinal nerve fiber layer thickness in NAION patients.

CONCLUSIONS

This review suggests the potential of neuroprotection as a viable option in the quest for an effective treatment strategy for NAION. Further studies, particularly clinical studies, are necessary to establish its efficacy in NAION patients.

Neuroprotection and Neuroregeneration Strategies Using the rNAION Model: Theory, Histology, Problems, Results and Analytical Approaches

Nonarteritic anterior ischemic optic neuropathy (NAION) is the most common cause of sudden optic nerve (ON)-related vision loss in humans. Study of this disease has been limited by the lack of available tissue and difficulties in evaluating both treatments and the window of effectiveness after symptom onset. The rodent nonarteritic anterior ischemic optic neuropathy model (rNAION) closely resembles clinical NAION in its pathophysiological changes and physiological responses. The rNAION model enables analysis of the specific responses to sudden ischemic axonopathy and effectiveness of potential treatments. However, there are anatomic and genetic differences between human and rodent ON, and the inducing factors for the disease and the model are different. These variables can result in marked differences in lesion development between the two species, as well as in the possible responses to various treatments. These caveats are discussed in the current article, as well as some of the species-associated differences that may be related to ischemic lesion severity and responses.

Anti-NOGO Antibody Neuroprotection in a Rat Model of NAION

Purpose

To evaluate the efficacy and mechanisms of anti-NOGO receptor monoclonal antibody 11C7mAb in a rat model of nonarteritic anterior ischemic optic neuropathy (rNAION).

Methods

The rNAION was induced in one eye of 20 Long-Evans rats, which were studied in 10 groups of two rats, each group containing a sham rat receiving intravitreal injections of vehicle and a treatment rat receiving intravitreal injections of 11C7mAb. Fellow eyes served as naïve controls. The rats were tested using flash electroretinograms (ERGs), flash visual evoked potentials (VEPs), and optical coherence tomography (OCT). Thirty days after induction, they were euthanized, and the eyes were prepared for immunohistochemistry (two groups), hematoxylin and eosin staining (two groups) or transmission electron microscopy (TEM; six groups).

Results

Ninety-five percent of the VEP amplitude was preserved in eyes treated with 11C7mAb, versus 69% in the control eyes. Immunohistochemistry revealed a large reduction in microglia and extrinsic macrophages with axon sparing. In addition to axon preservation, TEM also showed reduced extracellular debris and only slight myelin damage compared with the vehicle-treated animals. There were no significant differences in retinal ganglion cell counts, nor was there a difference in optic nerve swelling as measured by OCT. ERGs were used to exclude eyes with retinal vascular occlusions, an occasional complication of the induction technique.

Conclusions

The 11C7mAb preserves optic nerve integrity and reduces inflammation in rNAION.

Translational Relevance

This study evaluates the efficacy of an anti-NOGO receptor antibody in a rat model of NAION, a disorder that currently has no universally-acknowledged treatment.

Adenosine: The common target between cancer immunotherapy and glaucoma in the eye

Adenosine, an endogenous purine nucleoside, is a well-known actor of the immune system and the inflammatory response both in physiologic and pathologic conditions. By acting upon particular, G-protein coupled adenosine receptors, i.e., A1, A2- a & b, and A3 receptors mediate a variety of intracellular and immunomodulatory actions. Several studies have elucidated Adenosine's effect and its up-and downstream molecules and enzymes on the anti-tumor response against several types of cancers. We have also targeted a couple of molecules to manipulate this pathway and get the immune system's desired response in our previous experiences. Besides, the outgrowth of the studies on ocular Adenosine in recent years has significantly enhanced the knowledge about Adenosine and its role in ocular immunology and the inflammatory response of the eye. Glaucoma is the second leading cause of blindness globally, and the recent application of Adenosine and its derivatives has shown the critical role of the adenosine pathway in its pathophysiology. However, despite a very promising background, the phase III clinical trial of Trabodenoson failed to achieve the non-inferiority goals of the study. In this review, we discuss different aspects of the abovementioned pathway in ophthalmology and ocular immunology; following a brief evaluation of the current immunotherapeutic strategies, we try to elucidate the links between cancer immunotherapy and glaucoma in order to introduce novel therapeutic targets for glaucoma.

Trabodenoson on trabecular meshwork rejuvenation: a comprehensive review of clinical data

INTRODUCTION

Trabodenoson is an adenosine mimetic acting selectively at the A1 receptor (A1R) subtype, involved in multiple signaling pathways including matrix metalloproteinase (MMP-2) associated with glaucoma pathological processes. It has been developed as a Phase 3 candidate for the treatment of patients with primary open-angle glaucoma (POAG) or ocular hypertension (OH).

AREA COVERED

This review summarizes the molecular traits of Trabodenoson in intraocular pressure (IOP) regulations and provides a scientific interpretation of the Phase 2 clinical study results. This article sheds light on the root causes of the two pivotal Phase 3 clinical trial failures in patients with POAG or OH; it further highlights the discovery of MMP-2 in trabecular meshwork (TM) rejuvenation, which has strategic importance in long-term glaucoma patient care.

EXPERT OPINION

Trabodenoson is a BID glaucoma eye drop with a possible QD dose as maintenance. Its Phase 3 pivotal clinical trials failed at the wrong dose and dosing regimen because of the misinterpretation of the complex IOP results from the Phase 2 monotherapy and combination studies. The future development should focus on the TM benefits whilst unleashing its potential of neural protection through nanoparticle eye drops, medical coating, and sustained release drug delivery.