Tetracycline Antibiotics

Experimental Medications: Other Therapeutic Strategies

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The tetracycline antibiotics, including minocycline and doxycycline, have immunomodulatory and neuroprotective activities. They appear to decrease the passage of lymphocytes across the blood-brain barrier. In 2009, a small double-blind, placebo controlled Phase II trial of Copaxone plus minocycline showed favorable magnetic resonance imaging (MRI) data, with minocycline decreasing gadolinium-enhancing activity by 50 percent over a period of six months. A subsequent 24-month trial showed a significant decrease in lesion activity and clinical status.

In a larger study of 305 patients called RECYCLINE, minocycline was used as an add-on to Rebif in people with RRMS. Patients being treated with Rebif were randomized to oral placebo or minocycline 100 mg twice daily for 96 weeks. Data were presented at ECTRIMS in the fall of 2012,26 and disappointingly, minocycline did not provide significant improvement to either clinical or MRI outcomes.

Another Phase III trial looking at minocycline reported positive data in fall 2015. This Canadian Phase III double-blind study began in 2009, and enrolled 142 individuals with a first clinical demyelinating event, i.e., clinically isolated syndrome (CIS). The participants were randomized to oral minocycline at 100 mg twice daily or to an identical placebo. Treatment was continued for up to two years, or until MS was confirmed. Those receiving minocycline had a 44.6-percent lower risk of conversion to MS at six months, and a 37.6-percent lower risk at 12 months, versus individuals taking a placebo. The authors suggest that with the known safety and low cost of minocycline, this medication could be considered for the initial treatment of individuals with a first clinical demyelinating event, particularly in geographic regions without access to approved disease-modifying therapies.

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