NOTE: The development of Carbopol 974P (brand name: BufferGel) for preventing sexually acquired HIV infection has been discontinued.
The study of Carbopol 974P as a microbicide for preventing HIV infection was discontinued. Data from a Phase II/IIb study demonstrated that Carbopol 974P vaginal gel was ineffective in protecting women against sexually acquired HIV infection or other sexually transmitted infections.3-5
What is an investigational drug?
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.
To learn more about investigational drugs, read the AIDSinfo What is an Investigational HIV Drug? fact sheet.
What is Carbopol 974P?
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.6
Carbopol 974P is an acid-buffering agent that may work by maintaining the natural acidic environment of the healthy vagina.7,8 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.8-10
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) to be used with a diaphragm.12-15
How do topical microbicides work?
Topical microbicides can also be referred to as topical pre-exposure prophylaxis (PrEP) products.6,16 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).16,17 They may prevent HIV transmission in a number of ways. For example, HIV topical microbicides might:
- inactivate HIV or other pathogens (also called disease-causing microorganisms);
- strengthen the body’s normal defenses;
- block HIV from attaching to healthy cells susceptible to infection;
- prevent HIV infection from spreading to other cells that are healthy.6
Carbopol 974P works by strengthening the body’s normal defense (acidic vaginal environment), which may help to inactivate HIV or other pathogens.5,8
How are clinical trials of investigational drugs conducted?
Clinical trials are conducted in phases. Each phase has a different purpose and helps researchers answer different questions.18
- Phase I trials: Researchers test an investigational drug in a small group of people (20–80) for the first time. The purpose is to evaluate its safety and identify side effects.
- Phase II trials: The investigational drug is administered to a larger group of people (100–300) to determine its effectiveness and to further evaluate its safety.
- Phase III trials: The investigational drug is administered to large groups of people (1,000–3,000) to confirm its effectiveness, monitor side effects, compare it with standard or equivalent treatments, and collect information that will allow the investigational drug to be used safely.18
In most cases, an investigational drug must be proven effective and must show continued safety 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.18
In what phase of testing is Carbopol 974P?
Carbopol 974P vaginal gel used for preventing HIV has been studied in a Phase II/IIb clinical trial.2,4
The development of Carbopol 974P vaginal gel for preventing HIV infection has since been discontinued.3
What are some studies on Carbopol 974P?
Study Name: HPTN 035
Location: Africa and United States
Participants: HIV-uninfected women
Purpose: To look at the safety and effectiveness of two different investigational microbicide gels—Carbopol 974P (brand name: BufferGel) and PRO-2000—for preventing sexually acquired HIV infection in women.
Study Design: Participants were randomly assigned to use either Carbopol 974P microbicide gel, PRO-2000 gel, a placebo gel, or no gel at all. Participants who were assigned to a gel group were instructed to apply the gel vaginally 1 hour or less before each episode of vaginal intercourse. Women used the gels for approximately 20 months.
- 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 or other STIs (gonorrhea infection, chlamydia infection, and trichomoniasis).
- 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. PRO-2000 was not effective in preventing other STIs.
- In terms of safety, both Carbopol 974P and PRO-2000 were determined to be safe.4,5,11,19
What side effects might Carbopol 974P cause?
In the Phase II/IIb study discussed under the previous question, Carbopol 974P vaginal gel was determined to be safe when applied vaginally.4,5,19
If testing of Carbopol 974P vaginal gel for preventing HIV infection begins again, additional information on possible side effects will be gathered.
Where can I get more information about clinical trials studying Carbopol 974P?
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.
How can I find more information about participating in a clinical trial?
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.18
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.
- United States National Library of Medicine. ChemIDplus Advanced. Available at: http://chem.sis.nlm.nih.gov/chemidplus/rn/151687-96-6. Last accessed on April 16, 2015.
- National Institute of Allergy and Infectious Diseases (NIAID). NIAID ChemDB, HIV Drugs in Development. Available at: http://chemdb.niaid.nih.gov/DrugDevelopmentHIV.aspx. Last accessed on April 16, 2015.
- Singh O, Garg T, Rath G, Goyal AK. Microbicides for the Treatment of Sexually Transmitted HIV Infections. J Pharm. 2014 Feb 12;2014 doi:10.1155/2014/352425. Available at: http://www.hindawi.com/journals/jphar/2014/352425/. Last accessed on April 16, 2015.
- 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. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3083640/. Last accessed on April 16, 2015.
- Guffey MB, Richardson B, Husnik M, et al. HPTN 035 Phase II/IIb Randomized Safety and Effectiveness Study of the Vaginal Microbicides BufferGel and 0.5% PRO 2000 for the Prevention of Sexually Transmitted Infections in Women. Sex Transm Infect. 2014 Aug;90(5):363-9. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4278566/. Last accessed on April 16, 2015.
- National Institute of Allergy and Infectious Diseases (NIAID). Topical Microbicides. Available at: http://www.niaid.nih.gov/topics/hivaids/research/prevention/pages/topicalmicrobicides.aspx. Last accessed on April 16, 2015.
- Stone A, Jiang S. Microbicides: stopping HIV at the gate. Lancet. 2006 Aug 5;368(9534):431-3. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2785492/. Last accessed on April 16, 2015.
- National Institute of Allergy and Infectious Diseases (NIAID): News Release, dated February 9, 2009. Anti-HIV Gel Shows Promise in Large-scale Study in Women. Available at: http://www.nih.gov/news/health/feb2009/niaid-09.htm. Last accessed on April 16, 2015.
- 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. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1262719/. Last accessed on April 16, 2015.
- Nutan, Gupta SK. Microbicides: a new hope for HIV prevention. Indian J Med Res. 2011 Dec;134(6):939-49. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3284102/. Last accessed on April 16, 2015.
- 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. Available at: https://www.clinicaltrials.gov/ct2/show/NCT00074425. Last accessed on April 16, 2015.
- 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. Available at: http://www.ncbi.nlm.nih.gov/pubmed/17766603. Last accessed on April 16, 2015.
- 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. Available at: https://www.clinicaltrials.gov/ct2/show/NCT00065858. Last accessed on April 16, 2015.
- Schwartz JL, Weiner DH, Lai JJ, et al. Contraceptive efficacy, safety, fit, and acceptability of a single-size diaphragm developed with end-user input. Obstet Gynecol. 2015 Apr;125(4):895-903. Available at: http://www.ncbi.nlm.nih.gov/pubmed/25751199. Last accessed on April 16, 2015.
- CONRAD. Contraceptive Effectiveness and Safety Study of the SILCS Diaphragm: the Pivotal Study. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on December 19, 2007. NLM Identifier: NCT00578877. Available at: https://www.clinicaltrials.gov/ct2/show/NCT00578877. Last accessed on April 16, 2015.
- Shattock RJ, Rosenberg Z. Microbicides: Topical Prevention against HIV. Cold Spring Harb Perspect Med. 2012 Feb;2(2):a007385. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3281595/. Last accessed on April 16, 2015.
- 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. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2494562/. Last accessed on April 16, 2015.
- National Institutes of Health (NIH). NIH Clinical Research Trials and You. Available at: http://www.nih.gov/health-information/nih-clinical-research-trials-you. Last accessed on April 16, 2015.
- Microbicide Trials Network (MTN): News Release, dated February 9, 2009. Trial finds microbicide promising as HIV prevention method for women. Available at: http://www.mtnstopshiv.org/node/765. Last accessed on April 16, 2015.
Last Reviewed: April 16, 2015