• Incidence of adverse events. [ Time Frame: The DSMB will review safety data at 3 months following 200 subjects enrolled, 3 months following 400 subject enrolled, as well as additional meetings as needed. ] [ Designated as safety issue: Yes ]
• Safety of C31G vaginal gel over 12 months (minimum of 12 cycles and 365 days) of use. [ Time Frame: The DSMB will review safety data at 3 months following 200 subjects enrolled, 3 months following 400 subject enrolled, as well as additional meetings as needed. ] [ Designated as safety issue: Yes ]

• Secondary
• • Incidence of adverse events.
• • Safety of C31G vaginal gel over 12 months (minimum of 12 cycles and 365 days) of use.

This is a multicenter, randomized, double-masked, controlled, phase III study of repeated use of C31G vaginal gel compared to Conceptrol® Vaginal Gel as the primary method of contraception over six months (183 days) and at least six cycles of use. In addition, there is an opportunity for subjects to continue with study treatment for up to twelve months (365 days) and twelve cycles of treatment upon completion of the first six months of treatment.

Approximately 85% of American women (52 million) between the ages of 15 and 44 are sexually active . Approximately two-thirds or 38 million women use some form of birth control and/or STD prevention. With growing awareness of the risk of STDs, increasing numbers of women will require contraceptive methods that provide protection against STDs in addition to providing the basic contraceptive function. Currently there is no single, reasonably effective method to achieve both ends. Condoms, both male and female, present problems of acceptability for the partners of many at-risk women and, thus, cannot be considered an effective contraceptive and STD preventive for many people. A spermicide that also has the ability to prevent transmission of STDs would be a major advance, and of tremendous value to women worldwide.

C31G is an effective spermicide with in vitro activity equal to that of N-9 . C31G has been found to be a broad-spectrum antibacterial agent in vitro or in animals, active against both gram-positive and gram-negative organisms, including chlamydia, and a range of antibiotic resistant strains. It is also active against enveloped viruses including HIV and HSV. Thus, the primary objective of the study is to determine the contraceptive efficacy of C31G vaginal gel compared to Conceptrol® Vaginal Gel. The secondary objectives are to determine the safety and acceptability of the compounds with use over a period of six months or twelve months. Additional evaluations include the incidence of urinary tract infections (UTI), bacterial vaginosis (BV) and yeast vaginitis following the use of C31G vaginal gel compared to Conceptrol® Vaginal Gel.

• Drug: C31G
• Drug: nonoxynol-9 (N-9)

• Experimental: C31G vaginal gel contains 35mg (1% concentration) of C31G in 3.5 mL volume of gel
• Active Comparator: Conceptrol® Vaginal gel contains 100mg (4% concentration) of nonoxynol-9 (N-9) in 2.5mL volume of gel.

Inclusion Criteria:

Potential subjects must:

• Be healthy women, who are sexually active, at risk for pregnancy and desiring contraception.
• Be within the age range of 18 through 40 years inclusive.
• Be at low-risk for human immunodeficiency virus (HIV) or sexually transmitted disease (STD) infection and currently have a single sex partner (minimum 4 months) who is also at low-risk for HIV or STD.
• Have a negative urine pregnancy test prior to enrollment.
• Have normal cyclic menses with a usual length of 24 to 35 days over the last 2 cycles or at least one spontaneous, normal menstrual cycle (2 menses) since delivery, abortion, or after discontinuing hormonal contraception/hormonal therapy.
• Be willing to accept a risk of pregnancy.
• Be willing to engage in at least 4 acts of heterosexual vaginal intercourse per month for a period of 6 months.
• Be willing to be randomized to either study treatment.
• Be willing to only use the study product as the primary method of contraception over the course of the study with the exception of emergency contraception (EC), when indicated.
• Be capable of using the study product properly and agree to observe all study directions and requirements.
• Be willing to keep a diary to record coital information, product use information, information about the use of other vaginal products, and sign and symptom data of subject and partner.
• Agree not to participate in any other clinical trials during the course of the study.
• Be willing to give written informed consent to participate in the trial.

Exclusion Criteria:

Potential subjects must not:

• Have a history of allergy or sensitivity to spermicides or products containing N-9.
• Have had 3 or more urinary tract infections (UTI) in the past year.
• Have UTI by urine culture or symptomatic yeast vaginitis or symptomatic bacterial vaginosis diagnosed by wet mount unless treated and proof of cure is documented.
• Be pregnant, have a suspected pregnancy or desire to become pregnant during the course of the study.
• Have a history of infertility or of conditions that may lead to infertility, without subsequent intrauterine pregnancy.
• Have any contraindications to pregnancy (medical condition) or chronic use of category D or X medications.
• Have had more than one sexual partner in the last 4 months.
• Have shared injection drug needles within the past 12 months.
• Have or have been suspected to have HIV infection.
• Have been diagnosed with genital herpes simplex virus (HSV), with the first occurrence (initial episode) within three months prior to screening.
• Have 3 or more outbreaks of HSV within the last year.
• Have been diagnosed with any other STDs (including trichomonas) in the 6 months prior to the screening visit (with the exception of Human Papilloma Virus [HPV]).
• Be lactating or breastfeeding.
• Have any clinically significant abnormal vaginal bleeding or spotting within the month prior to screening.
• Have any clinically significant abnormal finding on pelvic examination or baseline labs, which in the view of the investigator, precludes her from participating in the trial.
• Have clinically significant signs of vaginal or cervical irritation on pelvic examination.
• Have had vaginal or cervical biopsy or vaginal surgery within 3 months prior to screening.
• Have used vaginal or systemic antibiotics or antifungals within 14 days prior to screening or randomization.
• Have had a Depo-Provera® injection in the 10 months prior to enrollment.
• Have an abnormal Pap smear with high grade squamous intraepithelial lesion (HSIL), atypical glandular cells (AGC) or ASC-H (atypical squamous cells, cannot exclude HSIL) within the last 12 months.
• Have an abnormal Pap smear with low-grade squamous intraepithelial lesion (LSIL) or ASCUS-HPV HR positive unless resolved by colposcopy.
• Have a Cervical Intraepithelial Neoplasia (CIN) diagnosis by biopsy within the last 12 months.
• Have a history or a current diagnosis of cervical cancer.
• Consume (on average) greater than three drinks of an alcoholic beverage per day.
• Have a past history (within twelve months) or current history of drug abuse [recreational, prescription or over-the-counter (OTC)].
• Have taken an investigational drug or used an investigational device within the past 30 days.
• Have previously participated in or completed this study or any other phase III study of C31G.
• Have issues or concerns (in the judgment of the investigator) that may compromise the safety of the subject or confound the reliability of compliance and information acquired in this study.