A Study of Doxycycline to Treat Chlamydial Infection

This is a Phase 4 blinded, randomized, active-controlled, non-inferiority trial. Final evaluable population will include a minimum 596 individuals: 298 women with confirmed urogenital chlamydia (CT) and 298 men with confirmed rectal chlamydia (CT). Approximately 664 participants will be enrolled to achieve a minimum 596 participants who contribute primary outcome data. Randomization will be stratified by study site and sex: 332 women and 332 men. Participants will be randomized 1:1 to a 3-day regimen of doxycycline or a 7-day regimen of doxycycline. The study blind will be maintained by providing 7 days of identical pre-filled blister packs, one with 3 days of active treatment and 4 days of placebo, and the other with 7 days of active treatment. Participants will be asked to return 28 days after randomization (at day 29), at which time they will be re-tested for chlamydia (CT) using a laboratory-based chlamydia (CT) nucleic acid amplification test (NAAT). The primary objective is to compare the efficacy of a 3-day vs. 7-day regimen of doxycycline for treatment of urogenital chlamydia (CT) infection in women based on proportion of participants with microbiologic cure (negative nucleic acid amplification test \[NAAT\] of vaginal swab and no positive nucleic acid amplification test (NAAT) of vaginal swab between study treatment and Day 29) at Day 29. Also, to compare the efficacy of a 3-day vs. 7-day regimen of doxycycline for treatment of rectal chlamydia (CT) infection in men based on proportion of participants with microbiologic cure (negative nucleic acid amplification test (NAAT) of rectal swab and no positive nucleic acid amplification test (NAAT) of rectal swab between study treatment and Day 29) at Day 29. The secondary objectives are to compare the efficacy of a 3-day vs. 7-day regimen of doxycycline for treatment of rectal CT infection in women based on microbiologic cure. Also, to compare the efficacy of a 3-day vs. 7-day regimen of doxycycline for treatment of urethral CT infection in men based on microbiologic cure. In addition, compare the efficacy of a 3-day vs. 7-day regimen of doxycycline for treatment of total CT infection (any anatomic site) in women and men based on microbiologic cure. Lastly, to compare the efficacy of a 3-day vs. 7-day regimen of doxycycline for treatment of rectal CT infection in men based on microbiologic cure, stratified by lymphogranuloma venereum (LGV) status.