Phase 3 Trial to Assess the Efficacy of Long-term (6 Months) Combination Antibiotics as a Treatment for Chlamydia-induced Reactive Arthritis

The initial infection that causes reactive arthritis is caused by one of two bacteria: Chlamydia trachomatis, which is usually acquired through sexual contact, or Chlamydia pneumoniae, which can cause respiratory infections. Most people recover fully from the initial flare of arthritis symptoms. However, about 20% of people with reactive arthritis experience long-lasting symptoms. In these individuals, the Chlamydia bacteria exist in a persistent metabolically active state within the joint tissue, even years after the initial exposure. The bacteria produce heat shock proteins (HSPs), which are thought to play a key role in the chronic persistent state of Chlamydia and which may stimulate the immune inflammatory response seen in reactive arthritis. This indicates the need for antimicrobial therapy that can reduce Chlamydia's HSP production and block its metabolism. The purpose of this study is to determine the effectiveness of long-term combination antibiotic therapy in treating people with chronic reactive arthritis. The study will use two different combinations of common antibiotics: doxycycline paired with rifampin and azithromycin paired with rifampin.

This study will entail 6 months of treatment followed by 3 months of follow-up. After screening, eligible participants will be randomly assigned to one of three treatment groups: rifampin once a day plus doxycycline twice a day; rifampin once a day plus azithromycin once a day for 5 days, then twice weekly; or placebo. Study visits will occur at baseline and Months 1, 3, 6, and 9. At all visits, participants will undergo an interview, a physical examination, and blood collection. They will also complete a questionnaire related to their symptoms and functional status. At screening and Month 6, a synovial biopsy may be performed. This will involve taking a sample of the tissue that lines the joints.