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Could a weekly pill help men with no sperm become fathers?

NCT ID NCT07571928

What the study statuses mean

This study's is highlighted.

Recruitment status, easiest to join first

Recruiting now
This trial is taking on new participants right now.
Not yet recruiting This study
Registered, but not yet taking participants.
By invitation only
Not open to general applications. Only people the study team invites can take part.
Paused
Paused for now. It may or may not start again.
Ongoing
Running, but no longer taking on new participants.
Completed
The trial has finished. Results may not be published yet.
Stopped early
Stopped early, before it reached the end. That can be for many reasons, including safety.
Cancelled
Cancelled before anyone took part.

Expanded access (not trials)

Expanded access
Not a trial. This treatment can be requested outside a study, case by case, for people who qualify.
Expanded access (paused)
Not a trial. The treatment can normally be requested outside a study, but is unavailable right now.
Expanded access (ended)
Not a trial. The treatment could once be requested outside a study, but no longer can.
Approved
The treatment has been approved, so it is available normally rather than through this programme.

When the status isn't known

Details not published
The full record has not been published yet, so there is little to show here.
Status unknown
This status has not been confirmed recently, so it may be out of date.

First seen Jun 26, 2026 · Last updated Jun 27, 2026 · Updated 1 time

Summary

This early study tests a drug called leflutrozole in 15 men who have no sperm in their semen due to a blockage-free cause. The drug is taken as a weekly capsule and aims to boost sperm production. Researchers will check if sperm appear in the semen after 12-20 weeks of treatment.

What this could mean

Our plain-language read of the trial. This is informational only, not medical advice or a prediction.

Active substance
leflutrozole (a drug that blocks estrogen production)
What this could lead to
If it works, this could point toward a new treatment for some men with infertility due to low sperm production.
What could go wrong
This is a very early, small trial with only 15 men. It may not work, and the drug could have side effects. Success is far from guaranteed.

This is an AI summary of the original study and may miss details. Read our disclaimer.

Study facts

What this study's own registry entry says, in plain language.

Phase

Phase 1/2

Runs two stages together: safety and dose first, then whether the treatment works.

Participants

About 15 people

The number the study aims to enrol. It can still change while the study runs.

Expected to start

May 2026

An estimate. Start dates often move.

Expected to finish

Aug 2027

An estimate. End dates often move.

Lead sponsor

Other sponsor

The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.

Who can take part

This study's own entry requirements. Only the study team can say for certain whether you qualify.

Ages

18 to 55 years

Sex

Male participants only

Healthy volunteers

Not accepted

This study is not open to healthy volunteers. The entry requirements below say who it is open to.

Show the full entry requirements

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Signed informed consent by participant * Signed informed consent by participant's partner (must just be obtained before the par-ticipant starts treatment at Visit 1), if applicable, regarding blood samples, data collec-tion about fertility treatment as well as pregnancy and pregnancy outcome * 18-55 years * Azoospermia verified by at least 2 semen samples, average semen volume \>= 1,0 ml with no identifiable sign of obstruction (samples taken at Visit -1 and at Visit 0 prior to confirmation of eligibility and dosing). * Serum AMH or Inhibin B level above the lower limit of quantification (LLOQ) at screening or within 6 months prior to screening * Testosterone \< 15 nmol/L at screening or within 6 months prior to screening * Serum estradiol above the lower limit of normal range (48 pmol/L) at screening or within 6 months prior to screening Exclusion Criteria: * Klinefelter or other major genetic conditions including large deletions on sex chromosomes * Average testis size \> 20 mL unless obstruction has been excluded * TESE procedure \< ½ year ago * LH concentration \> 15 IU/L at screening * Current abuse of steroids * BMI \> 45 kg/m2 * Severe chronic diseases requiring daily medication * Prior thromboembolic event within the last 24 months * Cardiovascular event within the last 6 months judged as significant by the investigator * Osteoporosis requiring medical treatment * Use of any prescription or non-prescription medication (apart from routine vitamins, occasional use of paracetamol, acetylsalicylic acid, or ibuprofen) which could interfere with pharmacokinetic or pharmacodynamic results, as judged by the investigator, such as: * Herbal products and non-routine vitamins * Insulin * Medication such as systemic corticosteroids, tricyclic antidepressants, and atypical antipsychotics * Surgery scheduled for the trial duration period, except for minor, non-gastrointestinal surgical procedures at the discretion of the investigator * Cancer (past or present, except basal cell skin cancer or squamous cell skin cancer), which in the investigator's opinion could interfere with the results of the trial * Serum prostate specific antigen (PSA) \> 3 ng/mL at screening or within 6 months prior to screening * Hematocrit \>50% at screening or within 6 months prior to screening * Mental incapacity, language barriers or unwillingness to comply with the requirements of the protocol, which may preclude adequate understanding or co-operation during the trial, as judged by the investigator

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Conditions

The condition(s) this trial relates to.

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

How to take part

Only the study team decides who joins. These are the ways to reach them.

  1. The places running it

    1 site. The list below names each one and where it is.

  2. The official record

    ClinicalTrials.gov lists the study team's own contact details, including names and phone numbers. We don't republish those.

    Open the record ↗

  3. A doctor treating you

    A doctor who knows your case can contact a study site on your behalf, and can tell you whether this study is worth pursuing at all.

Contacts and locations

Locations

  • Division of Translational Endocrinology, Department of Endocrinology and Internal Medicine, Copenhagen University Hospital Herlev., Herlev,

    Herlev, 2100, Denmark

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