Minocycline for multiple sclerosis
Last updated Aug. 26, 2025, by Margarida Maia, PhD
Fact-checked by Inês Martins, PhD
What is minocycline for MS?
Minocycline is an oral antibiotic that has been investigated as a treatment for certain forms of multiple sclerosis (MS), but has failed to demonstrate definitive signs of efficacy in clinical trials.
Due to disappointing results, some trials of minocycline were terminated early, and it is not clear if minocycline will continue to be tested as a possible treatment for MS.
Administered twice daily in the form of oral tablets, the therapy was specifically tested in people with clinically isolated syndrome (CIS) — a first episode of symptoms suggestive of MS — and relapsing-remitting MS (RRMS).
Minocycline was first approved in the U.S. in 1971 for treating bacterial infections, but the medication also has potent immunomodulatory, anti-inflammatory, and neuroprotective properties. These were expected to help reduce disease activity and potentially slow the progression of MS.
Specifically, minocycline has been shown to reduce the activity of immune cells involved in MS and prevent them from entering the brain and spinal cord. It can also reduce the release of inflammatory molecules and protect cells from damage.
Therapy Snapshot
| Treatment Name: | Minocycline |
| Administration: | Oral tablets |
| Clinical Testing: | Development status is unknown after trials have mostly shown negative results in people with MS. |
Minocycline in MS clinical trials
Minocycline has been tested either on its own or in combination with other medications in several clinical trials for RRMS and CIS.
- A Phase 2 trial called GA 9014 (NCT00203112) tested oral minocycline as an add-on to Copaxone (glatiramer acetate) in 44 adults with RRMS. After nine months, the combination led to a reduction in relapse risk and in the number of inflammatory and new or enlarging lesions compared with Copaxone plus a placebo. However, these differences failed to reach statistical significance.
- Another Phase 2 trial, RECYCLINE (NCT01134627), enrolled 305 adults with RRMS and tested a combination of oral minocycline plus Rebif (interferon beta‑1a) over nearly two years. While some positive trends were observed, the trial failed to meet the main goal of showing that the combination could significantly extend the time to a first relapse compared with Rebif plus a placebo. No significant differences were also observed in other measures, including relapse rates and disability worsening, leading to the trial’s early termination.
- An investigator-initiated Phase 3 trial dubbed MinoCIS (NCT00666887) tested whether minocycline could delay or prevent the conversion to clinically definite MS in 142 adults with CIS. Patients were randomly assigned to receive twice-daily oral capsules of minocycline or a placebo for two years. While a significantly lower proportion of patients on minocycline converted to clinically definite MS after six years (43% vs. 61.5%), no significant differences were observed after two years.
- Researchers at the University of Calgary in Canada launched another Phase 3 trial, this one called MinoMS-2019 (NCT04291456), to confirm minocycline’s benefit in CIS patients. The open-label trial was expected to enroll an estimated 148 participants, but it was stopped early due to recruitment problems.
Minocycline was generally well tolerated in MS clinical trials, although more patients on the medication experienced side effects compared with those given a placebo. Discontinuations due to side effects were also more common with minocycline.
Multiple Sclerosis News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
FAQs about minocycline in MS
Minocycline is an oral antibiotic that is believed to reduce inflammation and protect nerve cells from damage, which was expected to help treat multiple sclerosis (MS). However, clinical trials involving people with clinically isolated syndrome and relapsing-remitting MS failed to show significant benefits from minocycline. It is not clear whether minocycline will continue to be tested for MS.
Minocycline has yielded mainly negative results in multiple sclerosis (MS) clinical trials, failing to meet several main and secondary goals. For this reason, it is unlikely that minocycline is ever considered for approval by the U.S. Food and Drug Administration for the treatment of MS.
Based on animal data, minocycline may cause harm to a developing fetus. People of childbearing age should use effective contraception while on this medication. Patients should talk with their healthcare team if they become pregnant or plan to become pregnant.
In clinical trials, some clinical benefits of minocycline were reported in people with clinically isolated syndrome as early as six months. However, the benefits did not persist over the long term.
Hair loss and weight gain have not been reported as side effects of minocycline in clinical trials for multiple sclerosis. However, hair loss or thinning of the hair are possible side effects of minocycline in other indications. Patients should talk with their healthcare team if such events occur.
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