Minocycline, an antibiotic that has immune-modulating properties and crosses the blood-brain barrier, appears to delay conversion to multiple sclerosis in patients who have an initial focal demyelinating event, according to a report published online June 1 in the New England Journal of Medicine.
Two small clinical trials involving patients with relapsing-remitting multiple sclerosis (MS) recently showed that minocycline reduces the number of lesions detected on MRI with gadolinium enhancement. So researchers led by Luanne M. Metz, MD, of the Cumming School of Medicine and the Hotchkiss Brain Institute, Calgary, Alta., conducted a randomized, double-blind, placebo-controlled trial at 12 Canadian MS clinics to determine whether the drug might delay conversion to MS after a first, clinically isolated demyelinating event, such as optic neuritis or a brainstem, cerebral, cerebellar, or myelopathy syndrome.
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The primary outcome of conversion to MS within 6 months of randomization occurred in 23 (32%) patients taking minocycline, compared with 41 (59%) taking placebo – a difference that exceeded the prespecified clinically meaningful difference between the two groups. After the data were adjusted to account for the number of brain lesions at baseline, the difference in risk at 6 months was 18.5 percentage points, a magnitude of effect that is similar to what has been reported for other therapies such as interferon beta-1b, interferon beta-1a, teriflunomide, and oral cladribine.
The findings were similar in every sensitivity and subgroup analysis. All secondary outcomes, such as the decrease in mean lesion volume and the mean number of new lesions after 6 months of treatment, also favored minocycline over placebo, the investigators said (N Engl J Med. 2017 June 1. doi: 10.1056/NEJMoa1608889).
Minocycline’s neuroprotective effect persisted through 12 months of follow-up, according to a post hoc analysis, but was no longer sustained at 24 months of follow-up, they noted. In addition, post hoc analyses showed that minocycline held no significant benefit over placebo with respect to relapse or disability outcomes at either 6 months or 24 months.
This study was supported by the Multiple Sclerosis Society of Canada. Dr. Metz reported receiving grant support from Hoffmann–La Roche outside of this work; her associates reported ties to numerous industry sources.