An investigational drug is one that is under study and is not approved by the U.S. Food and Drug Administration (FDA) for sale in the United States. Medical research studies are conducted to evaluate the safety and effectiveness of an investigational drug. These research studies are also called clinical trials. Once an investigational drug has been proven safe and effective in clinical trials, FDA may approve the drug for sale in the United States.
Carbopol 974P (brand name: BufferGel) is an investigational drug that has been studied to prevent sexual transmission of HIV and other sexually transmitted infections (STIs). It is a type of drug product called a topical microbicide. Topical microbicides are products that are applied to the vagina or rectum (such as gels, films, or creams) or inserted into the vagina (such as vaginal rings) to prevent getting STIs, such as HIV infection.5
Topical microbicides can also be referred to as topical pre-exposure prophylaxis (PrEP) products.5,6 PrEP means using a medicine before possible exposure to a virus or bacteria to reduce the risk of becoming infected with the virus or bacteria. Topical microbicides to prevent HIV infection are designed to work close to where they are applied and near to where HIV might enter the body (through the vagina or rectum).6,7 They may prevent HIV transmission in a number of ways. For example, HIV topical microbicides might:
Carbopol 974P is an acid-buffering agent that may work by maintaining the natural acidic environment of the healthy vagina.3,8 During vaginal intercourse, semen causes the vagina to become less acidic, which may allow HIV and other sexually transmitted pathogens to survive. By blocking the alkalinizing action of semen in the vagina, Carbopol 974P may inactivate HIV and prevent the virus from multiplying.8,9,10
Carbopol 974P is currently in a gel form. The gel has been studied for vaginal use.11 Carbopol 974P gel has also been studied as a contraceptive product (spermicide).12,13
Clinical trials are conducted in phases. Each phase has a different purpose and helps researchers answer different questions.14
In most cases, an investigational drug must be proven safe and effective in a Phase III clinical trial to be considered for approval by FDA for sale in the United States. Some drugs go through FDA’s accelerated approval process and are approved before a Phase III clinical trial is complete. After a drug is approved by FDA and made available to the public, researchers track its safety in Phase IV trials to seek more information about the drug’s risks, benefits, and optimal use. 14
Carbopol 974P vaginal gel used for preventing HIV has been studied in Phase II clinical trials.2
Carbopol 974P vaginal gel was found to be ineffective as a topical microbicide for preventing HIV infection in a Phase II/IIb clinical study.4
In a Phase II/IIb study known as HPTN 035, the safety and effectiveness of two different investigational microbicide gels—Carbopol 974P (brand name: BufferGel) and PRO-2000—were compared to a placebo gel and to no gel. (A placebo is an inactive drug that is identical in appearance to the active drug being studied.) Participants in this study were instructed to apply the gels vaginally one hour or less before each episode of vaginal intercourse. Women used the gels for approximately 20 months.4
In the HPTN 035 study, when Carbopol 974P vaginal gel was compared to placebo gel and to no gel, Carbopol 974P was found to have no effect on preventing HIV infection. PRO-2000, the other investigational microbicide tested in the study, had a modest level of effectiveness in preventing HIV infection, but the results were not statistically significant. In terms of safety, both Carbopol 974P and PRO-2000 were determined to be safe.4,15
In the Phase II/IIb study discussed under the previous question, Carbopol 974P vaginal gel was determined to be safe when applied vaginally.4,15
Information on possible side effects of the drug is not complete. If testing of Carbopol 974P vaginal gel continues, additional information on possible side effects will be gathered.
More information about Carbopol 974P-related research studies is available from the AIDSinfo database of ClinicalTrials.gov study summaries. Click on the title of any trial in the list to see the ClinicalTrials.gov trial summary and more information about the study.
Participating in a clinical trial can provide benefits. For example, a volunteer participant can benefit from new research treatments before they are widely available. Participants also receive regular and careful medical attention from a research team that includes doctors and other health professionals. However, clinical trials may also involve risks of varying degrees, such as unpleasant, serious, or even life-threatening side effects from the treatment being studied.14
Your health care provider can help you decide whether participating in a clinical trial is right for you. For more information, visit NIH Clinical Research Trials and You.
1. United States National Library of Medicine. ChemIDplus Advanced. Last accessed on February 17, 2014.
2. National Institute of Allergy and Infectious Diseases (NIAID). NIAID ChemDB, HIV Drugs in Development. Last accessed on February 17, 2014.
3. Stone A, Jiang S. Microbicides: stopping HIV at the gate. Lancet. 2006 Aug 5;368(9534):431-3. Last accessed on February 17, 2014.
4. Abdool Karim SS, Richardson BA, Ramjee G, et al. Safety and Effectiveness of BufferGel and 0.5% PRO2000 Gel for the Prevention of HIV Infection in Women. AIDS. 2011 Apr 24;25(7):957-66. Last accessed on February 17, 2014.
5. National Institute of Allergy and Infectious Diseases (NIAID). Topical Microbicides. Last accessed on February 17, 2014.
6. Shattock RJ, Rosenberg Z. Microbicides: Topical Prevention against HIV. Cold Spring Harb Perspect Med. 2012 Feb;2(2):a007385. Last accessed on February 17, 2014.
7. Cranage M, Sharpe S, Herrera C, et al. Prevention of SIV Rectal Transmission and Priming of T cell Responses in Macaques after Local Pre-exposure Application of Tenofovir Gel. PLoS Med. 2008 Aug 5;5(8):e157; discussion e157. Last accessed on February 17, 2014.
8. National Institute of Allergy and Infectious Diseases (NIAID): News Releases, dated February 9, 2009. Anti-HIV Gel Shows Promise in Large-scale Study in Women. Last accessed on February 17, 2014.
9. Olmsted SS, Khanna KV, Ng EM, et al. Low pH immobilizes and kills human leukocytes and prevents transmission of cell-associated HIV in a mouse model. BMC Infect Dis. 2005 Sep 30;5:79. Last accessed on February 17, 2014.
10. Nutan, Gupta SK. Microbicides: a new hope for HIV prevention. Indian J Med Res. 2011 Dec;134(6):939-49. Last accessed on February 17, 2014.
11. National Institute of Allergy and Infectious Diseases (NIAID). Phase II/IIb Safety and Effectiveness Study of the Vaginal Microbicides BufferGel and 0.5% PRO 2000/5 Gel (P) for the Prevention of HIV Infection in Women. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on December 11, 2003. NLM Identifier: NCT00074425. Last accessed on February 17, 2014.
12. Barnhart KT, Rosenberg MJ, MacKay HT, et al. Contraceptive efficacy of a novel spermicidal microbicide used with a diaphragm: a randomized controlled trial. Obstet Gynecol. 2007 Sep;110(3):577-86. Last accessed on February 17, 2014.
13. Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). A Randomized, Controlled Trial of the Efficacy, Safety, and Acceptability of BufferGel. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on August 1, 2003. NLM Identifier: NCT00065858. Last accessed on February 17, 2014.
14. National Institutes of Health (NIH). NIH Clinical Research Trials and You. Last accessed on February 17, 2014.
15. Microbicide Trials Network (MTN): News Releases, dated February 9, 2009. Trial finds microbicide promising as HIV prevention method for women. Last accessed on February 17, 2014.
Last Reviewed: February 17, 2014
Last Updated: April 25, 2014