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. A small Phase II trial of Copaxone plus minocycline showed favorable 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 patients with RRMS. Patients being treated with Rebif were randomized to oral placebo (n = 155) or minocycline 100 mg (n = 149) twice daily for 96 weeks. Data were presented at ECTRIMS in the fall of 2012,43 and disappointingly, minocycline did not provide significant improvement to either clinical or magnetic resonance imaging (MRI) outcomes. Further studies of minocycline are not thought to be warranted.
Another Phase III trial with 200 participants looking at minocycline is still ongoing. This trial will evaluate the effect of 100 mg of oral minocycline twice daily on the conversion of clinically isolated syndrome (CIS) to a diagnosis of MS at six and 24 months. It began in January 2009 and is scheduled for completion in December 2015. It will determine whether 100 mg of oral minocycline twice daily reduces the conversion of clinically isolated syndrome (CIS) to clinically active MS and if any treatment benefit seen after six months is maintained at two years.