AMPOWER evaluates efficacy of vaginal gel in preventing pregnancy

Three analyses of the phase 3 AMPOWER study evaluated the safety and efficacy of an investigational vaginal pH regulator gel in preventing pregnancy, as well as sexual satisfaction among women receiving the gel.

The results were presented during the virtual American College of Obstetrics and Gynecology Annual Clinical and Scientific Meeting.

“The recently approved vaginal pH modulator, or VPM, trademarked Phexxi, was developed as a novel, nonhormonal, woman-controlled, water-based surfactant-free vaginal gel for prevention of pregnancy,” B. Todd Chappell, MD, a physician at Adams Patterson Gynecology & Obstetrics and the Women's Care Center of Memphis in Tennessee, said during the presentation of the efficacy results. “VPM has acid-buffering properties and is able to maintain the acidic vaginal environment even in the presence of alkaline semen.”

AMPOWER was a single-arm, open-label confirmatory trial conducted at 112 clinical sites across the United States. In the study, women were asked to administer a single prefilled applicator of VPM intravaginally before intercourse.

Chappell and colleagued conducted a “perfect-use” efficacy analysis of the study. To be included in the analysis, participants must have had a 21- to 35-day cycle, no back-up or emergency contraception and conducted at least one act of intercourse. The participants also must have reported using VPM consistently and correctly with each act of intercourse in electronic diaries.

A total of 1,384 women were enrolled in the AMPOWER trial, 1,003 of whom were included in efficacy analysis.

In the perfect-use analysis, the seven-cycle cumulative pregnancy percentage was 9.99% (95% CI, 7.17-12.81) among participants, Chappell and colleagues found.

In additional analyses that included participants with 21- to 42-day cycles and excluded those without a complete washout of previous hormonal contraceptives and women who became pregnant but did not have complete diary reporting, the researchers found that the cumulative pregnancy percentage ranged from 6.67% (95% CI, 4.61-8.73%) with all evaluable cycles to 8.44% (95% CI, 5.90-10.98%) in perfect-use cycles.

Chappell said that when using analyses parameters that had fewer restrictions to better represent “real-world” contraceptive use, the perfect-use efficacy rate of VPM was 6.68% (95% CI, 4.87-8.49).

In a separate analysis evaluating the genitourinary effects of VPM, researchers reported that 20% of participants in the AMPOWER trial experienced vaginal burning and 11.2% experienced vaginal itching. However, they also found that the rate of vaginal burning decreased with time from 11.2% in cycle zero to 1.4% in cycle seven. In addition, vaginal itching decreased from 4.5% in cycle zero to 0.3% in cycle seven. Rates of these adverse events were also lower when VPM was used once per day compared with at least twice per day.

Researchers further reported that women with genitourinary infections had higher rates of vaginal burning and itching compared with the general study population, with 32.5% experiencing vaginal burning and 22.1% experiencing vaginal itching.

In another analysis that focused on the sexual satisfaction of participants, 44.5% of women who were surveyed reported “a lot” or “a little” improvement with VPM use compared with 16.9% of women who reported these improvement levels with their previous contraception method at baseline. Researchers concluded that “VMP has the potential of filling an unmet need in women’s sexual and reproductive health.”

References:

Chappell BT, et al. Abstract 301. Presented at: American College of Obstetrics and Gynecology Annual Clinical and Scientific Meeting; October 30-31, 2020; Virtual.

Maximos B, et al. Abstract 191. Presented at: American College of Obstetrics and Gynecology Annual Clinical and Scientific Meeting; October 30-31, 2020; Virtual.

Thomas MA, et al. Abstract 321. Presented at: American College of Obstetrics and Gynecology Annual Clinical and Scientific Meeting; October 30-31, 2020; Virtual.