Carbopol 974POther Names: BufferGel, carbomer 974P, carbomer homopolymer type B (allyl pentaerythritol crosslinked), carbopol polymer Drug Class: Microbicides Registry Number: 151687-96-6 (CAS) Chemical Name: Carbomer 974P Chemical Class: Polymers Organization: ReProtect, Inc. Phase of Development: Phase II/IIb (discontinued).
(Compound details obtained from ChemIDplus Advanced,1 NIAID Therapeutics Database,2 Journal of Pharmaceutics article,3 and AIDS article4)
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 showed that Carbopol 974P vaginal gel was ineffective in protecting women against sexually acquired HIV infection or other sexually transmitted infections.3-5
Mechanism of Action: Microbicide; acid-buffering agent. Carbopol 974P is a negatively charged, high molecular weight, crosslinked, polyacrylic acid. It is the major nonaqueous component in BufferGel.6-9 As a buffering agent, Carbopol 974P releases hydrogen ions (the active ingredient in BufferGel), which prevents an increase in vaginal pH normally caused by the alkalinizing effects of semen. By maintaining a normally acidic vaginal pH below 5.0 in the presence of semen, Carbopol 974P is thought to potentially inactivate or inhibit a broad spectrum of pathogens, including HIV.9-11
Carbopol 974P has demonstrated virucidal and spermicidal activity in vitro.11 Formulated as BufferGel, Carbopol 974P has been studied as a microbicide for preventing the transmission of HIV infection and other sexually transmitted infections (STIs) and as a contraceptive product to be used in conjunction with a diaphragm.8,12-15 In addition, the combination of Carbopol 974P microbicide gel used with a diaphragm-like device called the Duet cervical barrier was theorized and tested as a potential strategy for preventing STIs.16
Study Identifiers: HPTN 035; NCT000744258
Study Purpose: Study to evaluate the safety and effectiveness of Carbopol 974P microbicide gel (BufferGel) and PRO2000 gel for the prevention of HIV infection in women
Study Population: HIV-uninfected women in Malawi, South Africa, Zambia, Zimbabwe, and United States
Dosing: Women assigned to a gel group were instructed to apply one applicator of gel intravaginally within 1 hour before vaginal intercourse. (Mean follow-up period was 20.4 months.) Participants were randomized to one of the following four study groups:
- Carbopol 974P microbicide gel (BufferGel)
- 0.5% PRO-2000 gel
- Hydroxyethylcellulose (HEC) placebo gel
- No intervention (no gel).4,5,8
(See references cited above for information on study results.)
Additional studies (Phase I) of Carbopol 974P microbicide gel have also been completed.
In the Phase II/IIb study of Carbopol 974P microbicide gel and PRO-2000 gel used in a coitally dependent manner for approximately 20 months by more than 3000 women, the vaginal use of both gels was determined to be safe. Adverse event rates were similar across all four study arms, with no significant differences in local and systemic events. (Study arms included a placebo gel arm and a no-gel arm.) The four study arms had similar overall incidence rates of deep epithelial disruption, infections with certain sexually transmitted organisms (Neisseria gonorrheae, Chlamydia trachomatis, Trichomonas vaginalis, and Treponema pallidum), and bacterial vaginosis.4,5
Drug interactions related to Carbopol 974P microbicide gel use are currently unknown.
- 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.
- 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.
- Mayer K, Peipert J, Fleming T, et al. BufferGel: results of the first phase I study of a novel vaginal microbicide. Abstract presented at: 12th International AIDS Conference; June 28 – July 3, 1998; Geneva, Switzerland. Available at: http://www.aegis.org/DisaplayConf/?Abstract=49901. Abstract 33158. Last accessed on February 17, 2014.
- 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.
- Mayer KH, Peipert J, Fleming T, et al. Safety and Tolerability of BufferGel, a Novel Vaginal Microbicide, in Women in the United States. Clin Infect Dis. 2001 Feb 1;32(3):476-82. Available at: http://cid.oxfordjournals.org/content/32/3/476.long. 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.
- 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.
- Montgomery ET, Woodsong C, Musara P, et al. An acceptability and safety study of the Duet® cervical barrier and gel delivery system in Zimbabwe. J Int AIDS Soc. 2010 Aug 5;13:30. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2924266/. Last accessed on April 16, 2015.
Last Reviewed: April 16, 2015