Progress Toward a Safe, Reversible, and Hormone-Free Male Birth Control Pill


Right now, much of the responsibility for family planning falls on women.

But wouldn’t it be great if men had more birth control options too?

Currently, most effective and reversible birth control methods are designed for women.

There’s been a long-standing effort to develop a male contraceptive pill, and a new study has found a promising candidate that has already shown success in animal trials.

The New Approach

“Although researchers have been investigating several strategies to develop male contraceptives, we still do not have a birth control pill for men,” says Dr. Martin Matzuk of Baylor College of Medicine.

This study focused on a new method: targeting a protein called serine/threonine kinase 33 (STK33) that’s crucial for male fertility in both humans and mice.

Unlike many existing contraceptives, this method doesn’t involve altering hormone levels. Instead, it comes from genetic research.

How It Works

STK33 is essential for proper sperm development.

Mutations in the STK33 gene cause infertility in men without affecting the appearance of the testes or causing other issues.

This makes STK33 a promising target for a safe male contraceptive.

The research team screened billions of compounds to find one that could inhibit STK33. They also determined the crystal structure of the protein, which helped in their search.

After testing several candidates, they found one that stood out: compound CDD-2807.

Testing and Results

In previous studies, knocking out the Stk33 gene in mice caused infertility by affecting sperm quality, similar to what happens in humans. The team then tested CDD-2807 in mice.

The compound successfully reached the testes, reducing sperm count and motility without affecting testis size or causing toxic side effects.

Importantly, the contraceptive effect was reversible.

After stopping the treatment, the mice’s sperm count and motility returned to normal, and they were fertile again.

Next Steps

Dr. Mingxing Teng called this achievement a “tour de force,” and Dr. Matzuk explained that the next step is to test the compound in primates.

This isn’t the first hormone-free male contraceptive showing promise.

Another compound, YCT-529, is already in early clinical trials.

Other methods being explored aim to temporarily block sperm production, prevent sperm from swimming, or offer a reversible alternative to vasectomy.


Developing new contraceptives is a lengthy process, but more options for men would be beneficial.

Having a variety of birth control methods allows people to choose the one that best suits their needs.

Perhaps this time, the promise of a male contraceptive pill is closer to becoming a reality.