“These are not complex components in these polymers. They’re pretty well characterized, and we know how they behave,” Vahdat says.
But any medical procedure could cause side effects or complications. Raevti Bole, a urologist specializing in men’s health at the Cleveland Clinic who’s not involved in the trial, says an injection into the vas deferens could come with a risk of skin infection, mild discomfort, or minor bruising, she says.
And there are still unknowns about the gel itself. While hydrogels are biocompatible and generally safe, Bole says she would want to know if Contraline’s product could cause permanent scarring or changes to the vas deferens and whether repeat injections could be done safely.
One practical consideration is how doctors will monitor patients to make sure that the gel is still working. “Even if the risk of pregnancy is low, I would want to know the risk to counsel my patients and allow them to compare their options,” Bole says.
Contraline’s gel is still years from becoming commercially available. The company will need to conduct trials of hundreds of men and their female partners to test its efficacy in preventing pregnancy. Eisenfrats says the company aims to launch a larger trial in the US in the next few years.
Meanwhile, there are other forms of male birth control in the pipeline. The US National Institutes of Health and the Population Council, an international nonprofit focused on health and social sciences, are testing a hormone-based gel that men apply daily to their shoulders to block sperm production. And in December, a small trial launched in the UK to test a hormone-free contraceptive pill developed by YourChoice Therapeutics. It prevents sperm production by blocking access to vitamin A.
YourChoice and Contraline are avoiding hormones because they tend to produce unpleasant side effects. A previous trial of an injectable hormonal contraceptive for men was stopped early when a safety monitoring board found a high number of adverse events, including acne, mood disorders, increased sexual drive, and muscle pain. The rate of side effects was high compared to what women typically experience while on hormonal birth control.
There’s evidence that men are interested in trying new types of contraception. In a US survey conducted in 2017, the Male Contraceptive Initiative found that 85 percent of the 1,500 male respondents aged 18 to 44 were interested in preventing their partner from getting pregnant.
“Men want to step up. They’re realizing that their partners have all these effects from birth control,” Eisenfrats says. “They need more options to take charge of their reproduction.”