Birth control: Sperm-blocking vaginal gel shows promise in animal tria

  • Although nonhormonal birth control options are available, many do not provide the same effectiveness at stopping pregnancy as hormonal methods.
  • Researchers have developed a nonhormonal gel that reinforces the cervical mucus barrier aiming to prevent pregnancy.
  • Scientists have found the gel blocks 98% of sperm from entering the uterus when used on ovulating female sheep.

A combined 225 million women around the world are estimated to use hormonal birth control either as a pill, injection, or implant to help prevent pregnancy.

However, some women prefer nonhormonal birth control methods, such as condoms and copper intrauterine devices (IUDs). This can be due to health concerns, to avoid hormones, or due to the fact that hormonal birth control can have unwanted side effects, including headaches, weight gain, nausea, and mood changes.

Now, a team led by researchers from KTH Royal Institute of Technology in Stockholm, Sweden has developed a nonhormonal gel that reinforces the cervical mucus barrier to help prevent pregnancy. So far, scientists have found it to have an average decrease of 98% of sperm passing to the uterus when used on ovulating female sheep.

The study was recently published in the journal Science Translational Medicine.

How does nonhormonal birth control work?

Hormonal birth control options such as the pill use estrogen and a synthetic form of progesterone called progestin to help prevent pregnancy.

Conversely, nonhormonal birth control uses other methods, including physical methods, to stop a man’s sperm from fertilizing a woman’s egg.

Current nonhormonal birth control options include:

  • physical barriers such as diaphragms, condoms, spermicides, and the sponge
  • nonhormonal IUDs
  • surgical sterilization options, including vasectomy for men and tubal ligation for women
  • natural family planning
  • abstinence

Some nonhormonal methods offer greater protection than others.

For example, male condoms have a 98% effectiveness rate at stopping pregnancy, and copper IUDs are 99% effective. However, a diaphragm provides between 92% to 96% effectiveness. And the withdrawal method is only about 78% successful at stopping pregnancy.

A nonhormonal prophylactic gel

According to Dr. Thomas Crouzier, a biopolymers researcher in the Division of Glycoscience at KTH Royal Institute of Technology in Stockholm, Sweden, and senior author of this study, women today wish that their contraceptives would not contain hormones.

“In large part, because they fear or experience side effects, especially mental side effects,” he told Medical News Today.

“[N]onhormonal alternatives ask women to compromise for lower efficacy than hormonal contraception or for other side effects. There is thus a consensus that more nonhormonal options are needed, and ideally, contraceptive methods that provide the same efficacy as hormonal contraceptives but without the side effects.”
— Dr. Thomas Crouzier

Crouzier is also co-founder and CSO of Cirqle Biomedical — a startup company developing a new nonhormonal contraceptive for women.

“Our idea is to propose a totally new mechanism of action for a contraceptive so that the user would have more pros than cons using it. This technology could potentially lead to high efficacies, similar to the pill, without its side effects,” he said.

How the gel works

Crouzier and his team developed a nonhormonal prophylactic gel that when applied, helps reinforce the mucus barrier of the cervix. The gel uses a combination of mucus proteins called mucin and a biopolymer called chitosan.

“Chitosan molecules are ‘muco-adhesive,’ meaning they interact with the mucus gel that is in the cervical canal. By interacting with the cervical mucus gel, the chitosan closes the pores of the gel and makes it impossible for the sperm to penetrate it,” he explained.

“The sperm, which have to travel through the cervix to enter the uterus, encounter this modified mucus, and get slowed down. The sperm which remains in the vagina is naturally deactivated over time by the vaginal environment — low pH and immune response to sperm,” Crouzier continued.

Next research steps

In this study, researchers tested the nonhormonal gel on ovulating female sheep. At the conclusion of the study, researchers found the gel provided a 98% average decrease in uterine sperm numbers compared to animals not treated with the gel.

“The contraceptive is now in late preclinical stage, and (Cirqle Biomedical) has recently announced a research collaboration and licensing agreement with Organon, a global women’s health company to finish preclinical studies with the goal to continue to clinical trials,” Crouzier said when asked about the next steps in this research.

Medical News Today also spoke with Dr. Mindy Pelz, a holistic health expert focused on women’s health and hormonal health, about this study.

“Most women who are on birth control pills, even IUDs, are manipulating their hormones and moving away from their natural hormonal flow,” she explained.

However, she expressed concern about a particular issue with where the gel is applied.

“If we had nonhormonal birth control options for women, that would be amazing because then women could be back in sync with their natural hormonal rhythms, but I’m super nervous about applying something to the cervix because the cervix is such tender tissue,” she said.

Dr. Pelz said she would like to see long-term results of how this type of birth control works for women and their cervical health.

“Of all of the tissue in the body, the cervix for a woman is the most vulnerable to (toxicity) and the most susceptible to cellular change, so if we’re going to start putting birth control on the cervix, we’ve got to really know long-term what the benefits vs. risks of that are for women,” she said.

“And that’s only going to be done through long-term research, multiple years, multiple women, (and) large sample sizes,” she added.

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