Trial of Azithromycin vs. Doxycycline for the Treatment of Rectal Chlamydia in MSM

A Phase 4, multi-center, randomized, double-blinded, placebo-controlled trial to compare the efficacy of azithromycin (Arm 1) vs. doxycycline (Arm 2) administered per CDC's STD Treatment Guidelines for rectal Chlamydia trachomatis (CT) in men who have sex with men (MSM). The effect of Lymphogranuloma Venereum (LGV) infection on microbiologic cure in MSM with rectal CT will also be assessed. Arm 1 will comprise of subjects receiving 1 gram of Azithromycin (4 capsules of 250 mg) orally as a single dose, and Doxycycline placebo (1 capsule) orally twice daily for 7 days. Arm 2 will comprise of subjects receiving 100 mg of Doxycycline (1 capsule) administered orally twice daily for 7 days, and Azithromycin placebo (4 capsules) administered orally as a single dose. Subjects will be males aged = / >18 years with a microbiologically confirmed diagnosis of rectal CT and at least one male sex partner in the past 12 months. The trial will be conducted at two sites in the US and will enroll up to 274 total subjects to achieve 246 subjects who contribute to the primary analysis. The duration of this study will be approximately 22 months with subject participation duration 29 days. The primary objective of this study is to compare the efficacy of azithromycin vs. doxycycline for treatment of rectal CT infection in MSM based on microbiologic cure (negative NAAT) at Day 29. The secondary objectives are: 1) to assess the effect of LGV infection on microbiologic cure in MSM with rectal CT at Days 15 and 29 and 2) to compare the efficacy of azithromycin vs. doxycycline for treatment of rectal CT in MSM based on microbiologic cure at Day 15.

Inclusion criteria

• Willing and able to understand and provide written informed consent before initiation of any study procedures.
• Willing and able to comply with planned study procedures for all study visits.
• Male sex at birth and aged = / > 18 years with valid contact information.
• At least one male sex partner (oral or anal) in the past 12 months.
• Untreated rectal CT diagnosed by a positive NAAT result.
• Willingness to abstain from condomless receptive anal sex during the trial.
• Willingness to complete a 7-day study drug regimen.

Exclusion criteria

• Current clinical diagnosis of acute proctitis per the CDC's 2015 STD Treatment Guidelines: symptoms of anorectal pain, tenesmus, and/or rectal discharge with anoscopy findings confirming inflammation.
• Concomitant untreated gonorrhea (rectal, pharyngeal, or urethral) or known exposure to gonorrhea in the time between CT testing and study enrollment.
• Clinical diagnosis of concomitant untreated primary or secondary syphilis.
• Known allergy to tetracyclines or macrolides.
• Received antimicrobial therapy active against C. trachomatis within 21 days of positive rectal CT NAAT result, or between the positive CT NAAT result and study enrollment*.

*This includes subjects treated empirically on the day of testing due to known exposure to gonorrhea or chlamydia, as well as enrollment in another study using antimicrobial therapy active against C. trachomatis, or planned enrollment in such a study during their time in this trial. Specifically, use of the following antibiotics is an exclusion criterion: azithromycin and other macrolides, doxycycline and related tetra- or glycylcyclines, fluoroquinolones, rifampin, quinupristin-dalfopristin, and linezolid.

• Plans to move to another location that would preclude study follow-up appointments in clinic or by mail-in in the next 30 days.
• Use of any investigational drug contraindicated to treatment with azithromycin or doxycycline within 7 days before enrollment.
• Previous enrollment in this trial.
• Any other condition that, in the opinion of the investigator, would interfere with participation in the trial.