Daily Doxycycline to Inform Sexually Transmitted Infection Prophylaxis Regimens

Inclusion Criteria

• Assigned male sex or female sex at birth
• In good general health
• Not currently taking doxycycline or other tetracycline-derived antibiotics and no plans to initiate during the study
• For HIV positive people, on stable antiretroviral therapy with an undetectable viral load and cluster of differentiation 4 (CD4) count> 300ul/ml
• Willing to use condoms consistently for the duration of the study
• Able to provide informed consent
• No plans for relocation in the next 4 months
• Not pregnant and does not plan on getting pregnant for the duration of the study
• Willing to undergo peripheral blood, urine, rectal or vaginal secretion collection, and a rectal or vaginal and cervical biopsy procedure
• Willing to use study products as directed

Exclusion Criteria

• Current or chronic history of liver disease
• Continued need for, or use during the 90 days prior to enrollment, of the following medications:
• Systemic immunomodulatory agents
• Supraphysiologic doses of steroids (short course steroids less than 7 days duration, allowable at the discretion of the investigators)
• Chemotherapy or radiation for treatment of malignancy
• Experimental medications, vaccines, or biologicals
• Intent to use doxycycline or other tetracycline-derived antibiotics during the course of the study, outside of the study procedures
• Any other clinical condition or prior therapy that, in the opinion of the investigator, would make the patient unsuitable for the study or unable to comply with the study requirements
• Known allergic reaction to study drugs
• Significant laboratory abnormalities at baseline visit for rectal biopsies, including but not limited to:
• Hemoglobin (Hgb) ≤ 10 g/dL
• Partial thromboplastin time (PTT) > 1.5x upper limit of normal (ULN) or international normalised ratio (INR) > 1.5x ULN
• Platelet count <100,000