PRO 2000 is a candidate topical microbicide for the prevention of sexually transmitted infections including infection by the Human Immunodeficiency Virus (HIV), the cause of Acquired Immunodeficiency Syndrome (AIDS). The compound is believed to block the entry of sexually transmitted disease (STD) pathogens into human cells. In addition to its demonstrated activity against HIV infection in laboratory tests and animal models, PRO 2000 has been shown to be active against other STD pathogens such as herpes, chlamydia, and the bacterium that causes gonorrhea. Designed to be applied vaginally prior to sexual intercourse, PRO 2000 promises to offer a discreet "safer sex" option that can be controlled by women.

Phase I clinical trials, conducted in Europe, found that PRO 2000 was well tolerated by healthy, sexually abstinent women. Findings from an NIH-sponsored Phase I/II trial, conducted in the United States and South Africa, indicate a similarly promising safety profile in healthy, sexually active women. In June 2003, a Phase II clinical trial was initiated in Uganda to assess the safety of PRO 2000 in more than 100 African women. A Phase II/III clinical trial funded by the NIH was initiated in February 2005.This trial is designed to assess safety and protective efficacy of PRO 2000 involving approximately 3,100 women in the United States and several African countries.

On February 9, 2009 the Company announced results from the NIH-sponsored trial which found that women participating in the trial who received PRO 2000 had an approximately 30% lower risk of acquiring HIV infection than women who received placebo or no vaginal product. Approximately 33 percent effectiveness would have been considered statistically significant. The adverse event profile was similar in all arms, indicating that 0.5% PRO 2000 is safe for vaginal use. A full analysis of the trial data is underway.

In October 2005, The Microbicides Development Programme, funded by the British government, announced the initiation of a Phase III pivotal trial to assess the safety and effectiveness of PRO 2000.This trial will involve approximately 10,000 women. Results from this trial are expected in the second half of 2009.

An estimated 5 million people worldwide were newly infected with HIV in 2004, and 39 million adults and children are thought to be living with HIV infection. The virus's predominant route of transmission worldwide is through heterosexual contact, with women being more susceptible to infection than men. Nearly half of those infected with HIV are now women, and surveys indicate that 100 million women worldwide are concerned about contracting HIV/STDs. More than 400 million new cases of STDs occur worldwide each year, threatening the health and fertility of a growing number of people and increasing the risk of HIV infection. These statistics highlight the vast need for new, safe, effective, female-controlled options for HIV/STD prevention.

PRO 2000 has also demonstrated potential efficacy as a contraceptive in rabbits and is completely compatible with the use of latex condoms.

PRO 2000 has demonstrated a unique array of favorable attributes:

• Activity against a wide range of HIV isolates
• Activity against chlamydia, herpes, gonorrhea
• Not absorbed following topical application
• Greater safety than nonoxynol-9 spermicides
• Clear, odorless, water-based formulation
• Highly stable, easy to use
• Potential contraceptive activity
• Compatible with latex condoms
• Female-controlled option for disease prevention