Optic neuritis - Emerging treatments

Neuroprotective and remyelinating treatments

Optic neuritis is increasingly used as a paradigm for multiple sclerosis (MS) treatment, in particular for neuroprotective and remyelinating treatments, and more clinical trials are performed specifically in optic neuritis.[59] The advantages of this are multiple: clinical outcomes such as visual acuity are easily quantified; the use of visual evoked potentials (VEP) and optical coherence tomography (OCT) allows precise measurements of conduction velocity through the optic nerve and retinal layer thickness, thus giving indirect measures of remyelination and axonal loss, respectively.

Amiloride

Amiloride is a diuretic in clinical use and has been shown to block the acid-sensing ion channel, which allows an influx of sodium and calcium in the demyelinated and inflamed optic nerve. Blocking this channel therefore may have neuroprotective effects. One phase 2 clinical trial, which compared amiloride versus placebo for treating patients with acute optic neuritis, did not show an effect on protecting the retinal nerve fiber layer thickness.[60]

Phenytoin

Phenytoin, a widely used anticonvulsant that may have neuroprotective properties due to its sodium channel blocking action, has been tested in a phase 2 trial. The study found a significant decrease in the amount of loss of the retinal nerve fiber layer, the primary outcome measure, in the phenytoin group compared with placebo, confirming the potential for neuroprotection with phenytoin.[61]

Opicinumab

A monoclonal antibody against LINGO, an endogenous inhibitor of remyelination. One multicenter international trial assessed remyelination in the first episode of optic neuritis after treatment with opicinumab or placebo. Although overall there was no evidence of remyelination, the trial showed some promise and opicinumab warrants future study.[62]

Clemastine

A sedating antihistamine with immunosuppressant properties. The ReBUILd trial of clemastine, in people with MS with evidence of past optic neuritis, showed remyelination as evidenced by improved visual evoked potentials.[63]

Emerging treatments for neuromyelitis optica spectrum disorder (NMOSD)

Advances in the treatment of NMOSD and the need for aggressive treatment have led to a number of emerging therapies for this condition in the last few years.[64] Most such therapies employ B cell depletion (e.g., inebilizumab), complement activation blockade (e.g., ravulizumab), or blockade of the critical cytokine IL-6 or its receptor (e.g., satralizumab).[65][66][67][68][69][70] Inebilizumab, satralizumab, and ravulizumab are approved in the US and Europe for the treatment of adult patients with anti-aquaporin-4 (AQP4) antibody-positive NMOSD.