A Study of Two Doses of MRC375 in Moderate to Severe Rheumatoid Arthritis Patients

This is a double-blind, randomized, placebo-controlled study to assess the safety and efficacy of MRC375 at 75 mg or 150 mg with matching placebo (taken tid with meal or light snack) in patients with moderate to severe RA. Patients will be randomized to one of the following study arms for 24 weeks:

• Treatment 1, Placebo: 2 tablets taken tid
• Treatment 2, MRC375: 1 tablet of 75 mg tetracycline HCL plus 1 matching placebo tablet taken tid. Total daily dose = 225 mg.
• Treatment 3, MRC375: 2 tablets of 75 mg tetracycline HCL taken tid. Total daily dose = 450 mg.

Study medication should be taken within 30 minutes of a meal or light snack (either before or after).

At Week 12, Visit 5-B, ACR20 scores will be evaluated. Patients who have not shown improvement from screening on ACR20 evaluation will be allowed early escape medication as follows:

• If randomized to the placebo group, the patient through the Interactive Voice Response System (IVRS) will be placed in the MRC375 treatment group of 1active tablet (75 mg) and 1 matching placebo tablet tid group through Week 24, Visit 8. Total daily dose = 225 mg.
• If randomized to the MRC375 treatment group of 1active tablet (75 mg) and 1 matching placebo tablet tid group, the patient through IVRS will be placed in the group to receive 2 active (75 mg) tablets tid through Week 24, Visit 8. Total daily dose = 450 mg.
• If randomized to the MRC375 treatment group of 2 active (75 mg) tablets tid group, the patients will remain at the same dose (total daily dose to remain at 450 mg, documented through IVRS) through Week 24, Visit 8. At any time the patient can be withdrawn from the study at their request or be withdrawn from the study in the judgment of the Investigator.

The dose change based upon Week 12, Visit 5-B, ACR20 results will be made in a blinded way through IVRS.