Table 1.

Summary of macaque trials of preexposure prophylaxis22,23,29,30,44–50

Preexposure prophylaxis regimen	Dosing regimen	Virus	Mode of viral challenge	Efficacy at preventing infection
Microbicides
TDF 1% gel 2 hours before exposure22	1 preexposure dose	SIV	Rectal (high dose)	89%*
TDF 1% gel with FTC 5% gel 30 minutes before exposure23	20 gel applications prior to exposure	SHIV	Vaginal (2 times per week for 20 challenges)	100%*
Topical CCR5 antagonist 30 minutes before exposure Other entry inhibitors 30 minutes before exposure29	1 preexposure dose	SHIV	Vaginal single challenge	66%–100%* with CCR5 antagonist and other entry inhibitors
Topical maraviroc (CCR5 antagonist) topical to vaginal 30 minutes before exposure30	1 preexposure dose	SHIV	Vaginal single challenge	75%–86%*
Systemic agents
TDF 20 mg/kg subcutaneously 48 hours before exposure44	Daily × 4 weeks	SIV	Intravenous × 1	100%*
Oral TDF 22 mg/kg 2 hours prior to exposure45	Daily TDF vs weekly TDF × 36 weeks	SHIV	Rectal (weekly × 14 weeks)	No statistically significant difference between the groups. Infection appeared to be delayed in treated macaques
Oral TDF 22 mg/kg 7 days prior to exposure46	Daily until 28 days after inoculation	SHIV	Rectal (single high-dose exposure)	40%
20 mg/kg of FTC subcutaneously Oral FTC/TDF (20 and 22 mg/kg, respectively) FTC subcutaneously (20 mg/kg) and TDF (22 mg/kg) subcutaneously ([1], [2], and [3] given 7–9 days prior to exposure) Subcutaneous FTC (20 mg/kg) and TDF (22 mg/kg) given weekly 2 hours before exposure47	Daily regimens given 7–9 days prior to exposure up 28 days after exposure Weekly regimen with weekly dosing with second dose 24 hours after exposure	SHIV	Rectal (weekly × 14 weeks)	33% and 67%* in groups 1 and 2. 100%* in groups 3 and 4
Intermittent tenofovir–emtricitabine before exposure (1, 3, or 7 days before exposure)48	1 preexposure dose and second postexposure dose 2 hours after	SHIV	Rectal (weekly × 14 weeks)	50%–83%*
Oral FTC/TDF 3 days prior to exposure49	Second postexposure dose 2 hours after	SHIV – FTC resistant isolate with M184V mutation	Rectal (weekly × 14 weeks)	100%*
Oral CCR5 antagonist either given on the day of challenge or 4 days before challenge50	Daily until 10 days after challenge	SHIV	Vaginal single challenge	45%–56%*. No statistically significant difference in infection rate between groups

^*Note: statistically significant.

Abbreviations: TDF, tenofovir; SIV, simian immunodeficiency virus; FVC, emtricitabine; SHIV, simian human immunodeficiency virus; CCF5, C–C chemokine receptor type 5.