Testing NLS-133 as a non-hormonal, on-demand male contraceptive.
Official title: Effects of NLS-133, a Potential Non-Hormonal "On-Demand" Male Contraceptive, on Semen Volume and Sperm Count in Normal Men: A Double-Blind, Placebo-Controlled Trial
Run by Next Life Sciences · NCT07393334 · Data updated 2026-11-12
This will test whether a single oral dose of NLS-133 taken 90 or 180 minutes before ejaculation can reduce semen volume and sperm count in healthy men aged 18–55.
Quick facts
| Phase | Phase 2 |
|---|---|
| Study type | Interventional |
| Ages | 18 Years to 55 Years |
| Sex | Men only |
| Enrollment | 10 (estimated) |
| Sponsor | Next Life Sciences Industry-sponsored |
| Locations | 1 site (Seattle, Washington) |
| Status | Recruiting |
| Started | December 2, 2025 |
| Main results expected | March 2026 |
| Study ends | May 2026 |
| Registry record updated | February 6, 2026 |
| Trial ID | NCT07393334 on ClinicalTrials.gov |
Is this trial a fit for you?
✓Likely a good fit
Ideal candidates are healthy men aged 18–55 with normal baseline semen parameters who can attend clinic visits and provide supervised semen samples.
✕Probably not a fit
Men with known infertility or hypogonadism, erectile dysfunction, inability to produce clinic-collected semen samples, significant medical illness, or who require prohibited medications are unlikely to benefit from this intervention.
A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.
What this trial studies
This randomized, double-blind, placebo-controlled crossover Phase 2a trial enrolls 10 healthy men who will receive single oral doses of NLS-133, an active comparator, or placebo before producing semen samples in clinic. Each participant will complete multiple dosing cycles with at least a 72-hour washout, with semen collection by masturbation 90 or 180 minutes after dosing. Primary outcomes are semen volume and total sperm count, and secondary measures include sperm motility, morphology, timed ejaculation, and a brief questionnaire on orgasm and ejaculation quality. Safety monitoring includes adverse event reporting, laboratory tests, and vital signs.
Why it matters
Potential benefit: If successful, NLS-133 could provide men with a short-acting, non-hormonal on-demand contraceptive option that lowers semen output and the risk of conception when used appropriately.
How similar studies have gone: On-demand non-hormonal male contraception is a relatively novel approach: some early or preclinical work with related agents has suggested effects on semen parameters, but there is not yet large-scale clinical proof of effectiveness.
Who can join: the full rules
Show full inclusion / exclusion criteria
Inclusion Criteria: 1. Male, age 18-55. 2. Normal physical examination and testicular volume \>15 cc 3. No significant medical history that would impact the safety of the study. 4. No current use of drugs that comprise NLS-133 5. Normal values on baseline hematology, blood chemistry and liver function tests and serum testosterone. 6. Normal baseline sperm parameters (semen volume \>1.4 cc, sperm concentration \>15 million/ml, motility \>40% and morphology \>4%). 7. Willing and able to comply with all study requirements and procedures. Exclusion Criteria: 1. History or evidence of erectile dysfunction. 2. Inability to produce semen samples in clinic setting. 3. Significant chronic or acute medical illness. 4. Previous or current ethanol or illicit drug abuse. 5. Evidence of significant underlying disease (based on results of the physical exam and the routine labs). 6. Known infertility or hypogonadism. 7. Planned or anticipated use of any prohibited medications during participation in the study. These include use of sex hormones for treatment, testosterone, anabolic steroids, retinoic acid (e.g., Accutane®), vitamin A, other drugs known to inhibit spermatogenesis, opioids, cocaine, methamphetamine, and/or the consumption of \>4 alcoholic beverages daily. 8. Presence of moderate-to-severe pulmonary or cardiovascular disease 9. Known active hepatitis B, hepatitis C, human immunodeficiency virus (HIV), or COVID-19 infection. 10. History of malignancy within 5 years before the Screening Visit, except fully treated and resolved non-metastatic squamous or basal cell carcinoma of the skin. 11. Known active chronic or acute infection requiring treatment with systemic antibiotics, antivirals, antifungals, antiparasitics or antiprotozoals during the Screening period. 12. Any other acute or chronic medical or psychiatric condition or laboratory abnormality that could increase the risk associated with study participation in the judgment of the investigator would make the participant inappropriate for entry into the study. 13. Participation in another investigational clinical trial within the last 30 days. 14. Participants who live in detention on court order or on regulatory action. 15. Related to sponsor or staff involved in the conduct of the study.
Where it's running
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Population Center for Research in Human Reproduction and Departments of Medicine, University of Washington
Seattle, Washington, United States Recruiting
Study contacts
- Study coordinator: John K Amory, MD, MPH, MSc
- Email: jamory@uw.edu
- Phone: (206) 616-1727
Similar studies
Other studies for the same condition or treatment. Recruiting studies are listed first.
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Evaluating YCT-529 for male contraception in healthy men
This study is testing a new male contraceptive called YCT-529 to see if it is safe and how it affects healthy men who don't want to have children.
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Plan A male contraceptive system to block and restore sperm flow
This test checks whether the Plan A male contraceptive system can block sperm by occluding the vas deferens and later be reversed in men seeking vasectomy-like contraception.
How to take part
- Review the eligibility criteria above with your treating physician.
- Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
- Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.