Vaginal pH Modulator Misses Primary Endpoint in STI Clinical Trial

Topline results were announced from a phase 3 trial evaluating EVO100 for the prevention of chlamydia and gonorrhea infection in women.

Topline results were announced from a phase 3 trial evaluating EVO100 for the prevention of urogenital Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC) infection in women.

EVO100 is a pH-modulating vaginal gel designed to reduce certain vaginal infections by balancing vaginal pH, thereby maintaining healthy vaginal flora. The double-blind, placebo-controlled EVOGUARD study ( Identifier: NCT04553068) included 1903 women 18 years of age and older who had a documented urogenital CT and/or GC infection or an undocumented self-reported CT or GC infection with risk factors, at any time over the 17 weeks preceding the enrollment visit, or who were positive at the screening visit.

Patients were randomly assigned 1:1 to receive either EVO100 or placebo intravaginally in a prefilled, single-dose applicator, immediately before or up to 1 hour prior to vaginal intercourse. The primary endpoint was the proportion of study successes vs failures in the EVO100 and placebo arms at week 16. Study success was defined as patients completing the study to visit 5 without any CT or GC infection and no usage of prohibited antibiotics during the study.

Findings demonstrated that treatment with EVO100 did not meet the study endpoint. The safety profile of EVO100 was consistent with that observed in previous studies, and 2 women (0.1%) discontinued treatment due to adverse events.

“We are disappointed that EVO100 did not achieve the desired outcome in this STI clinical trial, despite the data observed in our prior study,” said Saundra Pelletier, CEO of Evofem. “The impact of the public health response to the COVID pandemic included universal recommendations for social distancing, individual and household quarantines, and clinic visits for health emergencies only. We believe changes in clinical site operations, subject behavior and actions including deviations from following the clinical study protocol requirements related to STI acquisition, detection, and prevention contributed to this outcome.” 

Based on these findings, the Company has decided to discontinue the STI clinical program. Evofem’s pH-modulating vaginal gel is currently marketed under the brand name Phexxi® (lactic acid, citric acid and potassium bitartrate) as an on-demand method of contraception.


Evofem reports top-line results from phase 3 EVOGUARD clinical trial evaluating EVO100 for prevention of chlamydia and gonorrhea infection in women. News release. Evofem Biosciences, Inc. Accessed August 1, 2022.