Scientists tested a new potential male contraceptive drug called WIN 18,446 in mice to see if taking it on-and-off would work as well as taking it every day. The drug stops sperm production by blocking a natural chemical the body needs to make sperm. They found that the on-and-off schedule worked just as well at preventing sperm as taking it continuously, but with a big advantage: sperm production came back much faster when men stopped taking it. This could make the drug safer and more practical for real-world use as a male birth control option.
The Quick Take
- What they studied: Whether a new male contraceptive drug works better when taken in cycles (on for 2 weeks, off for 2 weeks) compared to taking it every single day without breaks.
- Who participated: Male laboratory mice were divided into two groups: one group received the drug continuously for 15 weeks, and another group received it in a 4-week initial period followed by alternating 2-week cycles of drug and no drug for 12 more weeks.
- Key finding: Both treatment schedules stopped sperm production equally well, but the on-and-off schedule allowed sperm to return much faster after stopping the drug. Mice on the cyclic schedule recovered normal sperm production in about 8 weeks, while continuously treated mice took longer to recover.
- What it means for you: This research suggests that a future male birth control pill might not need to be taken every single day to work effectively, and stopping it could allow fertility to return more quickly. However, this is early-stage research in mice, and much more testing would be needed before any drug could be used in humans.
The Research Details
Researchers conducted an animal study comparing two different treatment schedules for a potential male contraceptive drug. Male mice were divided into two groups: one group received food containing WIN 18,446 continuously for 15 weeks, while the other group received the drug in a specific pattern—4 weeks of continuous treatment followed by 12 weeks of alternating 2-week periods with and without the drug. After treatment ended, both groups were monitored for 8-16 weeks to see how quickly their sperm production returned to normal.
The scientists examined the mice’s testicles under a microscope and counted their sperm at different time points throughout the study. This allowed them to see exactly how the drug affected sperm production and how quickly recovery happened after stopping treatment. By comparing the two schedules side-by-side, they could determine if taking breaks from the drug would be just as effective as continuous use.
This research approach is important because it tests a practical question about how a male contraceptive would actually be used in real life. If a drug only works when taken every single day without breaks, it would be inconvenient and people might forget doses. By testing whether an on-and-off schedule works equally well, researchers can develop a contraceptive that’s easier to use and potentially safer. The study also specifically looked at how quickly fertility returns, which is crucial for any contraceptive method.
This is a controlled laboratory study that carefully compared two specific treatment schedules in identical conditions. The researchers examined the actual tissue under a microscope and counted sperm, which are objective measurements rather than relying on self-reporting. The study included predetermined time points for examination, which means they planned exactly when to check the mice rather than making decisions after seeing results. However, this is animal research in mice, so results may not directly translate to humans. The sample size of mice is not specified in the available information, which makes it harder to assess statistical power.
What the Results Show
The main finding was that both treatment schedules—continuous and cyclic—were equally effective at stopping sperm production. Mice receiving the drug on-and-off had similar testis weights and sperm counts compared to mice receiving it continuously, meaning the drug worked just as well with breaks.
However, there was an important difference in what was happening inside the testicles. In continuously treated mice, the testicles contained only the earliest stage of sperm cells (spermatogonia). In contrast, mice receiving cyclic treatment had more advanced sperm cells present (spermatocytes and spermatids), suggesting their sperm production system was in a different state of suppression.
Most importantly, recovery was dramatically faster in the cyclic group. After stopping treatment, mice that had received the on-and-off schedule recovered normal sperm production much more quickly based on testis weight and tissue appearance compared to mice that had received continuous treatment. This suggests that taking breaks from the drug allows the body’s sperm-producing system to maintain some function, making it easier to bounce back when treatment stops.
The study found that the cyclic treatment approach may reduce potential damage to the testicles from long-term continuous drug exposure. While both groups had suppressed sperm production, the presence of more advanced sperm cells in the cyclic group suggests the testicles weren’t as completely shut down. Additionally, the faster recovery in the cyclic group indicates that the testicles’ ability to produce sperm wasn’t permanently damaged by the on-and-off treatment pattern.
This research builds on the researchers’ earlier work showing that continuous WIN 18,446 treatment could suppress sperm production and that the effect was reversible. This new study extends that finding by showing that the same drug doesn’t need to be taken continuously to achieve the same contraceptive effect. The faster recovery with cyclic treatment is a new and potentially important advantage that hadn’t been previously demonstrated.
This study was conducted only in laboratory mice, not humans, so we cannot be certain the results would be the same in men. The specific sample size of mice used is not provided, making it unclear how many animals were studied. The study doesn’t provide information about potential side effects or long-term safety of either treatment approach. Additionally, the drug WIN 18,446 is still experimental and has not been approved for human use, so this remains very early-stage research. The study also doesn’t examine whether the cyclic schedule might affect other aspects of male health or hormone levels.
The Bottom Line
Based on this animal research, the cyclic treatment approach appears promising for future male contraceptive development (moderate confidence level based on animal data). If this drug eventually reaches human testing, an on-and-off dosing schedule may be preferable to continuous daily use. However, extensive human clinical trials would be needed before any recommendations could be made for actual use. Current confidence is limited because this is animal research only.
This research is most relevant to men interested in contraceptive options, reproductive health researchers, and pharmaceutical companies developing male birth control. Men currently seeking contraception should not expect this drug to be available soon—it’s still in very early research stages. Women whose partners might use such a contraceptive in the future may also find this research interesting. This research is not directly applicable to anyone seeking contraception today.
In this mouse study, sperm production recovered within about 8 weeks after stopping cyclic treatment. However, human recovery timelines could be different. Even if this drug moves forward to human testing, it would likely take many years (potentially 10+ years) before it could become available as a contraceptive option, as new drugs require extensive safety and efficacy testing in humans.
Want to Apply This Research?
- For future users of a cyclic male contraceptive, an app could track: (1) medication adherence during on-weeks and off-weeks with daily reminders, (2) cycle dates to ensure proper timing of drug and non-drug periods, and (3) any side effects or health changes during each phase of treatment.
- Users could set up a calendar-based reminder system that alternates between ‘medication weeks’ and ‘break weeks,’ similar to how some birth control apps work for women. The app could provide clear visual indicators of which phase of the cycle the user is in and send notifications when transitioning between phases.
- Long-term tracking could include periodic fertility checks (such as sperm count tests ordered by a doctor), general health monitoring for any side effects, and adherence tracking to ensure the on-and-off schedule is being followed correctly. The app could generate reports for healthcare providers showing compliance with the treatment schedule.
This research is preliminary animal study data and does not represent a treatment available for human use. WIN 18,446 is an experimental drug that has not been approved by the FDA or other regulatory agencies for use in humans. This article is for educational purposes only and should not be interpreted as medical advice or a recommendation to use this drug. Anyone seeking contraceptive options should consult with a qualified healthcare provider about currently available and approved methods. This research may eventually contribute to the development of future male contraceptive options, but significant additional research and clinical testing would be required before any such product could be made available to the public.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.