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NCT Number: NCT07393334

Effects of NLS-133, a Potential Non-Hormonal "On-Demand" Male Contraceptive

NLS-133-CLIN001 is a Phase 2a study designed to assess the safety, tolerability, and effects of NLS-133 (combination of two FDA-approved agents) compared to an active control (FDA-approved pharmacologic agent) or placebo on semen volume and sperm count in 10 in healthy men. Participants will be randomized in a crossover design to receive a single dose of NLS-133, an active control or placebo either 90 or 180 minutes prior to collection of semen. Sperm parameters measured will be count, motility and morphology. A brief questionnaire will be completed by each subject during each treatment cycle that addresses orgasm and ejaculation quality. Safety monitoring will include adverse event reporting, laboratory assessments, and vital signs.

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Key information

Age range

18 year–55 year

Sex eligibility

Male

Study type

Interventional

Phase

Phase 2

Primary location

Population Center for Research in Human Reproduction and Departments of Medicine, University of Washington

Seattle, Washington, 98195, United States

Location status: Recruiting

Location contact

John K Amory, MD, MPH, MSc

CONTACT

[email protected]

(206) 616-1727

About this study

The aim of study NLS-133-CLIN001is to determine the time frame NLS-133 (combination of two FDA-approved agents) affected ejaculation, semen volume and sperm count in young, normal men. NLS-133 responses will be compared to responses observed after oral placebo and active control (FDA-approved pharmacological agent) treatments. This is a randomized, double-blind, placebo-controlled, crossover (6-way) trial of 10 men who will receive oral capsules 90 and 180 minutes prior to semen collection by masturbation. There will be at least a 72 hour washout period between dosing cycles. Semen volume, if any, and sperm count and morphology (if possible based on semen volume) will be assessed. Subjects will also answer a brief questionnaire regarding orgasm and ejaculation quality during masturbation. Lastly, time to ejaculation and orgasm will be measured by a stopwatch to determine any impact on the time to orgasm or ejaculation by the study treatments. A brief questionnaire about orgasm and ejaculation quality will be completed subjects during each treatment cycle. Safety monitoring will include adverse event reporting, laboratory assessments, and vital signs.

Statistical analyses will be as follows. Means and standard deviations will be calculated for ejaculate volumes and sperm counts at each time point after dosing, stratified by dose. The main outcome for this study is the Semen volume and total sperm count by dose at each time point. This outcome will be compared by Friedman's ANOVA with a Dunnett's post-hoc test. Secondary outcomes include time to ejaculation by dose and orgasm quality scores using the Derogatis questionnaire and other questions as well as serum silodosin and guanfacine concentrations by dose and time and will also be analyzed by Friedman's ANOVA with a Dunnett's post-hoc test. All analyses will be performed using STATA version 10, (College Park, TX). For all comparisons an alpha of <0.05 without correction for multiple comparisons will be considered significant.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Male, age 18-55.
  • Normal physical examination and testicular volume >15 cc
  • No significant medical history that would impact the safety of the study.
  • No current use of drugs that comprise NLS-133
  • Normal values on baseline hematology, blood chemistry and liver function tests and serum testosterone.
  • Normal baseline sperm parameters (semen volume >1.4 cc, sperm concentration >15 million/ml, motility >40% and morphology >4%).
  • Willing and able to comply with all study requirements and procedures.

Exclusion criteria

  • History or evidence of erectile dysfunction.
  • Inability to produce semen samples in clinic setting.
  • Significant chronic or acute medical illness.
  • Previous or current ethanol or illicit drug abuse.
  • Evidence of significant underlying disease (based on results of the physical exam and the routine labs).
  • Known infertility or hypogonadism.
  • 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.
  • Presence of moderate-to-severe pulmonary or cardiovascular disease
  • Known active hepatitis B, hepatitis C, human immunodeficiency virus (HIV), or COVID-19 infection.
  • 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.
  • Known active chronic or acute infection requiring treatment with systemic antibiotics, antivirals, antifungals, antiparasitics or antiprotozoals during the Screening period.
  • 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.
  • Participation in another investigational clinical trial within the last 30 days.
  • Participants who live in detention on court order or on regulatory action.
  • Related to sponsor or staff involved in the conduct of the study.

Treatment and study plan

NLS-133

Drug

NLS-133 is the primary experimental arm of the study

Placebo

Drug

Double placebo arm of the study

Active Comparator #1

Drug

Active control arm of study

Other names: Active control

Primary outcomes

  1. Semen volume (mL)

    Time frame: 90 and 180 minutes for each treatment cycle

  2. Sperm count (millions/mL)

    Time frame: 90 and 180 minutes for each treatment cycle

    Measurement of sperm count

Secondary outcomes

  1. Sperm motility

    Time frame: 90 and 180 after placebo, active-control or NLS-133 administration

    Total percentage of sperm that are actively swimming

Study contacts

Contact information is provided by the study sponsor or research team.

John K Amory, MD, MPH, MSc

CONTACT

[email protected]

(206) 616-1727

Sponsors and collaborators

Lead sponsor

Next Life Sciences

Industry

Registry information

Official study 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

Important dates

Study start
2025
Primary completion
2026
Study completion
2026
First posted
Feb 6, 2026
Registry last updated
Feb 6, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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