PRO 2000 is an experimental anti-HIV drug being developed by Procept Inc. It is designed to work by targeting the CD4 molecule, preventing HIV's gp120 molecule from binding onto cells and infecting them.

It is being tested as a single daily injection, at various doses, in a trial in Brussels. In earlier pilot studies of continuous intravenous infusions, some participants developed reversible changes in liver enzymes and platelet levels.

A gel containing PRO 2000 is also being studied as a topical vaginal or anal microbicide, to reduce the risk of sexual HIV transmission. It can prevent infection of human cervix cells in the test tube with HIV and herpes simplex virus-2, with 0.5 and 4% concentrations of the drug in the vagina producing levels capable of inhibiting infection one to two hours after application^[1][2]. The low-dose gel does not cause any significant increase in side-effects, such as irritation or inflammation, although some people using the 4% gel had mild inflammation after repeated application^[3][4][5].

PRO 2000 has entered a phase III trial to determine its efficacy in reducing HIV infections in humans.