Monoclonal antibodies inserted directly into the vagina via a dissolvable film are being tested as a method of both contraception and protection against sexually-transmitted infections (STIs).
Nicknamed “plantibodies” as they are produced using tobacco plants, researchers aim to use them against sperm cells, HIV, and herpes. The contraceptive and STI-preventative applications of the antibodies are currently being researched separately, with the team behind them aiming to eventually combine them.
A 2021 study on Human Contraception Antibody (HCA) showed that it could immobilize sperm and even make the cells clump up within 15 seconds, remaining active in vaginal conditions for up to 24 hours.
A 2021 Phase I clinical trial by some of the same researchers tested the safety of anti-HIV and herpes antibody films in humans, finding them to be “generally safe and well tolerated, with no serious [adverse events] recorded”. The monoclonal antibodies were designed to target HIV-1, Herpes Simplex Virus-1 (HSV-1) and HSV-2. Antibody levels were shown to peak one hour after film insertion, and elevated levels were still present 24 hours later. The films were also shown to not affect vaginal pH.
“There’s a need for good on-demand nonhormonal contraceptives,” study author Professor Deborah Anderson said in a statement. “Our ultimate goal is to have a contraceptive that also protects women against sexually transmitted infections.”
The team is also looking into using the antibodies in a lubricant format. “There is an enormous gender disparity in the use of and adherence to contraception. The burden most often lands directly on people who could get pregnant,” PhD student Matt Geib said. “We should always strive to give everyone an option. I hope that the future of contraceptives will hold less invasive, more effective, and more equitable options.”
Another clinical trial on the contraceptive antibody film using real human couples is set to be published soon, according to Anderson. A webpage for a clinical trial fitting Anderson’s description sponsored by ZabBio Inc, a company working on the HCA vaginal film, indicates that the trial aimed to test the film’s efficacy, safety, and pharmacokinetics. Participants were monogamous heterosexual couples, with fertile male partners and female partners that had undergone surgical sterilization. The study tested the “number of progressively motile sperm in aspirated endocervical mucus when using ZB-06 [the film] prior to intercourse,” within a time frame of “2-3 hours after sexual intercourse.”
According to Anderson, there was pretty much no motile sperm in the mucus when the film was used – “It was about as clear-cut as you can get.” However, as mentioned previously, these results have not been officially published at the time of writing.