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MTN-028 was a single-site, single-blind, two-arm, randomized Phase 1 safety and PK trial of two IVRs containing a combination of a CCR5-receptor antagonist, VCV (MK-4176), with an integrase inhibitor, MK-2048.  The two rings tested in MTN-028 were formulated with different dose strengths:

1.  Formulation A (Low dose): IVR containing 91 mg of VCV (MK-4176) and 10 mg of MK-2048

2.  Formulation B (Original dose): IVR containing 182 mg VCV (MK-4176) 30 mg MK-2048

The study enrolled 18 evaluable healthy, 18-45-year-old HIV-uninfected, non-pregnant, sexually abstinent women who were using adequate contraception. Women were randomized to one of two study regimens in a 2:1 ratio (low dose: original dose). The IVR was used continuously for approximately 28 consecutive days.

Based on in vitro, in vivo, and ex vivo studies, VCV (MK-4176) and MK-2048 show promise as topically- applied microbicides. The safety and acceptability of these agents alone and in combination were evaluated in the MTN-027 trial; however, the optimal dose of MK-4176 and MK-2048 to achieve sufficient vaginal fluid concentrations for antiviral activity is unknown. Two different formulations of the MK-2048A combination IVR were developed and evaluated in MTN-028 to inform in vitro and in vivo modeling to further optimize the drug release profiles of an IVR containing VCV and MK-2048 for use in future studies, including the potential development of a combination antiretroviral/contraceptive ring.

MTN-027 and MTN-028 were the first clinical trials to test an integrase inhibitor as a microbicide. MTN-028 completed follow-up on March 22, 2016. The primary manuscript was published in Clinical Infectious Diseases on March 19, 2019, along with the primary results manuscript for Protocol MTN-027.

Protocol Chair(s)
Liu, Albert (Protocol Chair)
Protocol Title
Phase 1 Pharmacokinetic Trial of Two Intravaginal Rings (IVRs) Containing Different Dose Strengths of Vicriviroc (MK-4176) and MK-2048
DAIDS Protocol ID
Vaginal Ring
Vicriviroc (MK‐4176)  
Study Focus/Product Administration
Study Type
Study Phase
Phase I  
United States
Women (cisgender women, non‐transgender women)
Division of AIDS, US National Institute of Allergy and Infectious Diseases
US Eunice Kennedy Shriver National Institute of Child Health and Human Development
US National Institute of Mental Health
US National Institutes of Health
Other Study Info

Phase I, single-site, two-arm, randomized (2:1), single-blind trial