In a breakthrough that could reshape the future of family planning, scientists at Cornell University have taken a significant step toward developing a safe, reversible, and non-hormonal male contraceptive—long considered the 'holy grail' in reproductive health research.
Published in Proceedings of the National Academy of Sciences, the proof-of-principle study demonstrated that temporarily interrupting a key step in sperm production can halt fertility without causing long-term damage. Conducted over six years in mice, the research focused on disrupting meiosis - the biological process responsible for producing sex cells, showing that sperm production can be stopped and later restored.
This comes at a time when contraceptive failure remains a major contributor to unintended pregnancies globally. Studies across 43 countries estimate that male condoms have a typical-use failure rate of about 5.4%, while traditional methods exceed 13%. Against this backdrop, the absence of a reliable, long-term, and reversible male contraceptive continues to represent a critical gap in global reproductive health.
The science of stopping sperm production
To achieve this, scientists used a compound called JQ1, a small-molecule inhibitor initially developed for research in cancer and inflammatory diseases. While JQ1 itself is not suitable for clinical use due to potential neurological side effects, it has a unique ability to interfere with a crucial stage of meiosis known as prophase 1.
By targeting this stage, researchers were able to demonstrate, for the first time, that directly interrupting meiosis can safely and reversibly shut down sperm production. This marks a shift from previous approaches that largely focused on hormonal pathways or later stages of sperm development.
“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,” said Paula Cohen, professor of genetics and director of the Cornell Reproductive Sciences Centre.
The study further confirmed that this interruption does not permanently damage reproductive capacity. “Our study shows that mostly we recover normal meiosis and complete sperm function, and more importantly, that the offspring are completely normal,” Cohen said.
How fertility can be switched off and restored
At the core of the study is how JQ1 works to temporarily disrupt fertility. The compound interferes with meiosis during prophase 1, causing developing sperm cells to die at that stage. It also blocks the gene activity required for later phases of sperm maturation.
In the experiment, male mice were treated with JQ1 for three weeks. During this period, sperm production stopped completely, and key processes such as chromosome pairing and recombination were disrupted.
However, the most striking finding was the reversibility of this effect. Once the treatment stopped, recovery began almost immediately. Within six weeks, normal meiotic processes resumed, and sperm production returned to healthy levels.
For your daily dose of medical news and updates, visit: HEALTH
The researchers then tested fertility by breeding the mice. The results showed that the treated males were able to reproduce successfully, and their offspring were healthy and capable of reproduction themselves.
“It shows that we recover complete meiosis, complete sperm function, and more importantly, that the offspring are completely normal,” Cohen reiterated.
If adapted for human use, such a contraceptive could potentially be delivered as a periodic injection, perhaps every three months, or through a transdermal patch to maintain effectiveness.
Importantly, the researchers deliberately chose to target meiosis rather than earlier stages of sperm development. This was to avoid damaging spermatogonial stem cells, which are essential for long-term fertility.
“We didn't want to impact the spermatogonial stem cells, because if you kill those, a man will never become fertile again,” Cohen explained. She also noted that targeting later stages could allow partially developed sperm to escape and fertilise an egg, making meiosis the most effective intervention point.
Why do we need new male contraceptives, and what’s holding them back?
Despite decades of research, male contraceptive options remain strikingly limited, restricted largely to condoms and vasectomies. While condoms are widely accessible, their typical-use failure rates remain significant. Vasectomies, on the other hand, are often perceived as permanent, even though reversal procedures exist.
This imbalance is particularly notable given the scale of unmet need globally. According to the Male Contraceptive Initiative, the world sees over 120 crore unintended pregnancies each year, while the global population continues to grow by more than 8 crore annually.
“The world grapples with ecological strain and overpopulation. Accessible contraception is crucial. Increasing access to contraception in order to meet existing unmet needs in low- and middle-income countries alone would lead to a 68 per cent reduction in unintended pregnancies,” the organisation notes.
The gap is even more pronounced for men. “There are currently only two methods of contraception available to sperm-producers: condoms and vasectomy, despite demonstrated demand for more methods,” the initiative adds, pointing out that millions of men globally have unmet family planning needs.
However, developing male contraceptives has proven far more complex than anticipated. A 2021 review of hormonal male contraceptive trials highlights several challenges, including side effects such as acne, weight gain, mood changes, and depression. In one large trial involving testosterone and progestin injections, the study was terminated early following an external safety review due to concerns over depression, including one reported suicide.
The review further notes that while some side effects are comparable to those experienced by women using hormonal contraception, the psychological impact, particularly mood-related changes, remains a significant concern in male trials.
Another key limitation is biological. Hormonal contraceptives for men often take two to three months to suppress sperm production and an equally long time for recovery after discontinuation. Additionally, around 5–10 per cent of men in clinical trials do not achieve full sperm suppression, while a small proportion experience 'sperm rebound', where sperm levels temporarily rise despite continued treatment.
Regulatory challenges further complicate development. A 2024 study points out that unlike female contraceptives, which have well-established approval pathways, there are no clear regulatory guidelines for male contraceptives.
“The development of a male contraceptive is complicated by the fact that the clinical treatment effect, prevention of pregnancy, is not measured in the patient receiving the intervention,” the study explains.
Instead, researchers often rely on surrogate markers such as sperm count, particularly thresholds like ≤1 million sperm per millilitre, which are associated with low pregnancy risk. However, regulatory agencies have yet to formally establish whether such markers are sufficient for approval.
The study also highlights the need for extensive safety data, noting that male contraceptives would likely require long-term monitoring, as they are intended for use by healthy individuals over extended periods.
Beyond science and regulation, cost remains another barrier. Developing a new drug can cost close to $1 billion, and unlike other pharmaceuticals, contraceptive research is often driven by public funding or non-profit organisations rather than large pharmaceutical companies.
What experts say?
Dr Rajeev Sood, Chairman – Urology & Renal Transplantation at Marengo Asia Hospitals, called the findings a ''promising proof-of-concept' for a nonhormonal male contraceptive, while cautioning that translating it to humans remains a key challenge.
“There is a clear need for more male contraceptive options because current choices for men are extremely limited - primarily condoms, which are user-dependent, and vasectomy, which is considered permanent,” he said.
He added that if successful, such a method could be “transformative, offering men a ‘switch on–switch off’ approach to fertility without systemic side effects, and enabling more flexible, partner-driven decisions around contraception.”
Dr Aswati Nair, Clinical Director and Fertility Specialist at Nova IVF Fertility, said that while the concept behind the study is scientifically sound, its application in humans remains uncertain. She pointed out that the findings are still based on animal models, making real-world translation a key concern.
“So, if we talk about science, scientifically, this theory could be correct. But since now it is in the mice model, how easily can we extrapolate it to human beings? That we don't know,” she said, adding that “the concept is correct,” but whether it will mark a true breakthrough is still unclear.
Dr Nair also highlighted the long and complex process of drug development in humans, noting that any potential contraceptive would need to pass through multiple stages of clinical trials before it can reach the market. She explained that “for any drug to come into the market, it has to go through four phases of clinical trials,” making the process both time-consuming and uncertain.
She also drew attention to the imbalance in contraceptive responsibility, noting that it largely falls on women. “The whole contraceptive scenario becomes the headache of a female,” she said. “Ultimately, the female has to take medication or undergo procedures; she is the one who is bearing it.”
Highlighting this lack of parity, Dr Nair added that “there is no evenness,” and that nearly all responsibility for effective contraception rests with women. This, she said, is precisely why research into male contraceptives is gaining momentum.
“If developed successfully, such options could be more efficacious,” she noted.
This story is done in collaboration with First Check, which is the health journalism vertical of DataLEADS