Outcomes of toll-like receptors’ antagonism in steroid-resistant optic neuritis; a pilot study

To investigate the safety and outcomes of off-label immunomodulator Mycobacterium w. (Mw), a TLR 9 antagonist in steroid-resistant idiopathic unilateral optic neuritis.

Case series. Eight patients with documented idiopathic unilateral optic neuritis who did not improve with methyl prednisolone followed by oral steroids as per the Optic Neuritis Treatment Trial (ONTT) were administered Mw 5 ml in 500 ml normal saline, 30 days after the last of dose of steroids had been administered. The dose was repeated at 3 months. Outcome measures monitoring the change in the best-corrected visual acuity (BCVA), pupillary reaction, colour vision, visual field (VF) examination (when possible), fundus examination and photography, visually evoked potential (VEP) testing. BCVA, pupillary reaction, and color vision were monitored immediately prior to steroid therapy, on days 1 and 7 post steroid therapy, pre Mw administration (i.e., 30 days after the last dose of steroids had been completed) and post Mw administration on days 1, 7, 30, 90, 120 and 180. VF, VEP and fundus photography was performed immediately prior to steroid administration, 30 days after the last dose of steroids (i.e., immediately prior to Mw), and days 30, 90,120 and 180 post Mw administration.

There were five females and three males in an age range of 30–54 years. Six patients were available for follow-up at 6 months. All patients showed improvement in visual acuity, colour vision & pupillary reaction. Visual field monitoring was possible in four patients; all four had a centrocecal scotoma that persisted post steroid therapy but resolved 1 month post Mw therapy. Three out of five patients who had disc edema were available for all follow-ups, and showed resolution of disc edema post Mw therapy. The disc edema had persisted post steroid therapy. No adverse events were seen. The 2nd dose did not improve any of the said parameters. There was no recurrence of the disease up to the end of the follow-up period.

Mw appears to improve steroid resistant optic neuritis; future randomized clinical trials would help affirm this observation.