Cornell Researchers Demonstrate Reversible, Nonhormonal Male Contraception in Mice

Cornell scientists used JQ1 to block prophase I of meiosis in male mice, stopping sperm production after three weeks of treatment. Upon withdrawal, normal meiosis resumed within six weeks and fertility was restored, producing healthy offspring.

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Men currently rely on condoms or vasectomies; hormonal approaches have raised safety concerns in women. Targeting a testicular checkpoint offers a nonhormonal route that could avoid permanent loss of spermatogonial stem cells.

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The work was led by Paula E. Cohen, professor of genetics and director of the Cornell Reproductive Sciences Center. Co-authors include Stephanie Tanis, Leah E. Simon, Adriana K. Alexander, Tegan S., Horan, Maria de las Mercedes Carro, Samantha Jane Bonnett, Audrey Xie, Roni Ben-Shlomo, Connor E. Owens, Charles G. Danko, and Jelena Lujic. The findings were published in the *Proceedings of the National Academy of Sciences* on 7 April 2026.

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JQ1 treatment for 21 days eliminated sperm in all subjects; after a 42-day washout, meiotic chromosome behavior normalized and sperm counts recovered. Breeding trials yielded offspring with normal growth and fertility.

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A reversible, long-acting male contraceptive without hormones would address the limited contraceptive choices currently available to men. Cohen envisions delivery as a quarterly injection or a transdermal patch.

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Cohen stressed that the strategy spares spermatogonial stem cells, preventing irreversible infertility, and acknowledged JQ1’s neurological toxicity makes it unsuitable for human use. The team plans to identify safer small-molecule inhibitors that replicate the meiotic blockade without adverse effects.

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The study’s results are limited to mice; translation to humans remains untested. Key next steps include screening for non-toxic inhibitors that could be used in future studies.

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• “We’re practically the only group that’s pushing the idea that contraception targets in the testis are a feasible way to stop sperm production,” — Paula Cohen, professor of genetics, Cornell Reproductive Sciences Center

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• “Our study shows that mostly we recover normal meiosis and complete sperm function, and more importantly, that the offspring are completely normal,” — Paula Cohen

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• “We didn’t want to impact the spermatogonial stem cells, because if you kill those, a man will never become fertile again,” — Paula Cohen

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• “What a Future Male Contraceptive Could Look Like If this approach is successfully developed for humans, it could lead to a new form of male birth control delivered as an injection every three months or possibly as a patch to maintain effectiveness, Cohen said.” — Paula Cohen

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