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Male birth control: Scientists develop a non-hormonal "reversible" pill for men

The world’s population has increased over 2.6-fold in the last 60 years, reaching 8 billion in 2022 and projected to grow to 9 billion by 2037. This highlights the need for effective family planning, but advancements in contraception, particularly for men, have been limited. Currently, there are male birth control pills available in the market.

However, in a recent study led by the Baylor College of Medicine, scientists have shown that a novel, non-hormonal sperm-specific approach could offer a promising option for reversible male contraception in animal models.

Targeting STK33 for male contraception

“Although researchers have been investigating several strategies to develop male contraceptives, we still do not have a birth control pill for men,” said corresponding author Martin Matzuk, the director of the Center for Drug Discovery at Baylor.

“In this study we focused on a novel approach – identifying a small molecule that would inhibit serine/threonine kinase 33 (STK33), a protein specifically required for fertility in both men and mice.”

Previous research established that STK33 is essential for forming functional sperm. Knocking out the Stk33 gene in mice causes sterility due to abnormal sperm and poor motility, similar to effects seen in men with STK33 mutations.

Importantly, these mutations do not cause other defects, making STK33 a viable contraceptive target with minimal safety concerns.

Discovery of CDD-2807

Study first author Angela Ku used DNA-Encoded Chemistry Technology (DEC-Tec) to screen billions of compounds and identify potent STK33 inhibitors. The most effective of these, CDD-2807, was further refined for stability and selectivity.

In mouse models, CDD-2807 effectively reduced sperm motility and numbers, rendering mice infertile without signs of toxicity or alterations in testis size.

“We were pleased to see that the mice did not show signs of toxicity from CDD-2807 treatment,” said co-author Courtney M. Sutton, a postdoctoral fellow at Baylor. “Importantly, the contraceptive effect was reversible. After a period without CDD-2807, the mice recovered sperm motility and were fertile again.”

Advancing male birth control

Choel Kim, another co-author, revealed the first crystal structure for STK33, aiding in designing the final compound for better drug-like properties. This study marks a significant step in validating STK33 as a contraceptive target, both genetically and chemically.

“In the next few years, our goal is to further evaluate this STK33 inhibitor and compounds similar to CDD-2807 in primates to determine their effectiveness as reversible male contraceptives,” Matzuk said.

Potential advantages of male birth control pill

Potential benefits of a birth control pill for males may include:

Shared responsibility

Men can take an active role in contraception, promoting equality in family planning responsibilities. This shift helps alleviate the societal expectation that contraception is primarily a woman’s responsibility. By sharing this responsibility, couples can make joint decisions about their reproductive health.


Non-hormonal male birth control pills, like the one targeting STK33, avoid the side effects commonly associated with hormonal contraceptives. Hormonal methods can cause mood swings, weight gain, and other health issues. A non-hormonal pill can mitigate these risks, making it a more appealing option for many men.

Reversible effects of male birth control pills

The contraceptive effect of the male birth control pill is reversible. Once a man stops taking the pill, his fertility returns to normal. This flexibility is crucial for men who may want to delay fatherhood but still wish to have children in the future. Reversibility also provides peace of mind, knowing the decision isn’t permanent.


Oral contraceptives are easy to use and do not require medical procedures or regular visits to a healthcare provider. Compared to methods like injections, implants, or surgical procedures, a daily pill is straightforward and non-invasive, making it more likely to be consistently used.

“There are numerous forms of female contraception in clinical use, but male contraception continues to be very limited and lacks a medication-based approach,” noted the study authors.

This research, funded by the Cancer Prevention Research Institute of Texas and published in the journal Science, represents a major advance in the quest for male contraception, offering hope for new family planning methods that can help manage the world’s growing population.


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