NAPO - Novel Approach for Oligospermia (NAPO)

December 12, 2025 updated by: Martin Blomberg Jensen

Novel Approach for Oligospermia (NAPO): A Randomized Controlled Trial

This randomized controlled trial aims to assess whether treatment with denosumab can improve semen quality in infertile men selected by serum anti-mullerian hormone (AMH) as a positive predictive biomarker, and with severely impaired semen quality (concentrations between 0.01 million/mL to 2 million/mL).

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Infertility is a common problem globally and impaired semen quality is responsible for up to 40% of all cases. Despite the high prevalence there are currently only very limited treatment options to improve semen quality for infertile men. Instead, almost all infertile couples are treated with inseminations or assisted reproductive techniques (ARTs) independently of the etiology of infertility. ARTs are very successful but expensive and associated with a significant treatment burden of the female partner due to the invasive methodology and the need for hormonal treatment often for several months.

RANKL is a ligand for the receptor activator of nuclear factor kappa beta (RANK), and their pathway plays a prominent role in the regulation of bone metabolism. The binding of RANKL to RANK on osteoclast precursors induces osteoclast maturation and activation, thereby stimulating bone resorption, and regulates cell cycle i.e., proliferation, differentiation, and apoptosis. Osteoprotegerin (OPG) is a secreted decoy receptor that controls RANKL-RANK interaction by binding RANKL and inhibits activation of RANK and preventing osteoclast differentiation and activation.

Denosumab, a drug used in millions of patients worldwide under trade names Prolia® and Xgeva®, inhibits the RANKL pathway and is used to treat osteoporosis and bone metastases. The drug's mechanism of action inhibits RANKL and thus inhibits bone resorption through reduced osteoclast activation. This reduces the loss of bone mineral density (BMD), which reduces the risk of bone loss and thereby the risk of fracture and osteoporosis. Denosumab has been shown in several clinical studies to be a safe and effective drug in both women and men and has been in clinical use in both sexes for many years. As Denosumab has a teratogenic effect, pharmacokinetic studies in both monkeys and healthy men were performed before approval of the drug as a treatment for osteoporosis in men. These studies showed that Denosumab concentration in semen does not pose a risk to the fetus during sexual intercourse with the pregnant woman and therefore is safe to use for the suggested infertility indication as there is no risk of fetal transmission.

In light of this, our research group has investigated the effect of denosumab in human testicular germ cell lines as well as in human testicular tissue ex vivo "hanging drop" cultures. Treatment with denosumab did in both cases increase the proliferation of the germinal cells, which is an indicator that denosumab treatment potential beneficial effect on sperm production by reducing apoptosis in the germ cells. This led to a pilot intervention study of 12 infertile men who were overall healthy and without comorbidities. The men were treated with a single-dose of 60 mg of denosumab subcutaneous (s.c.). The study showed that the response to RANKL inhibition was either bad or highly beneficial. This was an interesting finding and indicates that only a fraction of infertile men should be offered denosumab treatment and this fraction of beneficial responders should ideally be identified based on an easily accessible biomarker before initiation of treatment. On this knowledge, a randomized controlled trial, "First In Treating Male Infertility" (FITMI), is being conducted to explore whether treatment with denosumab can improve semen quality in infertile men who are selected by serum AMH, but already have a sperm concentration that is at least 2 million/mL. This is an important study, but unfortunately, it leaves out a solution for those with sperm concentration under 2 million/mL, who are the most vulnerable in this regard. Therefore, there is a need for a randomized controlled trial that addresses the specific concerns of individuals with sperm concentrations below 2 million/mL to provide a valuable option in an otherwise hopeless situation.

NAPO is a single-center, sponsor-investigator-initiated, placebo-controlled, double-blinded randomized trial. Following successful completion of screening procedures, subjects will be randomized in a 2:1 fashion to receive either denosumab 60 mg s.c. or a placebo. The study will be carried out at the Division of Translational Endocrinology, Copenhagen University Hospital, Herlev, Copenhagen, Denmark.

With the power to avoid a type II error set to 80% (1-β) at a two-sided 5% significance level, 42 men allocated 2:1 in each of the investigation arms are needed to detect a difference in sperm concentration of 100% between intervention and placebo group in the primary outcome. The primary analysis will be a covariance analysis in which day 80 measurements are analyzed, initially as crude values but also adjusted on baseline.

Study Type

Interventional

Enrollment (Actual)

42

Phase

  • Phase 2
  • Phase 1

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Denmark
      • Copenhagen, Denmark
        • Division of Translational Endocrinology, Department of Endocrinology and Internal Medicine

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Infertile men ≥ 18 years and < 60 years of age
  • Sperm concentration ≤ 2 million pr. mL
  • Serum AMH levels ≥28 pmol/L.
  • The participants must have appropriate Danish or English language skills and give written informed consent.

Exclusion Criteria:

  • Chronic diseases, defined as diagnosis where signs, symptoms, and treatment imply an expected long duration and lack of a cure, such as diabetes mellitus, metabolism disorders, osteoporosis, colitis, etc.
  • Sperm concentration <0.01 million pr. mL
  • Men with current or previous malignancies, or at potential risk of testicular cancer after baseline examination and ultrasound will be excluded.
  • Men with hypocalcemia at baseline, defined as albumin corrected calcium < 2,17 mmol/L or total calcium < 2.14 mmol/L
  • Serum vitamin D (25OHD) levels < 25 nmol/L
  • estimated Glomerular Filtration Rate (eGFR) < 60 mL/min/1,73 m2
  • Insufficient dental status
  • Vasectomy
  • Hypersensitivity to latex, Denosumab, or to any of the excipients (acetic acid, sodium hydroxide, Sorbitol (E420), Polysorbate 20) will be excluded.
  • Serum FSH <3 IU/L
  • Testis size > 17 mL
  • BMI ≥ 35 kg/m2

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Denosumab
Subcutaneous injection with 60 mg Denosumab once
Drug: Denosumab
Subcutaneous injection with 60 mg Denosumab once
Other Names:
  • Prolia
Placebo Comparator: Placebo
Subcutaneous injection with NaCl once
Drug: sodium chloride
Subcutaneous injection with NaCl once
Other Names:
  • sodium chloride (NaCl)

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
The difference in sperm concentration (million pr. mL) on day 80
Time Frame: Day 80 and day 83 after inclusion
Semen analysis - The average concentration of two semen samples delivered on day 80 and day 83 after inclusion is used.
Day 80 and day 83 after inclusion

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
The difference in semen quality (total sperm count, motile sperm, progressive motile sperm and morphologically normal sperm) between baseline and two semen samples delivered at day 80 and day 83 after inclusion
Time Frame: Day 80 and day 83 after inclusion
Semen analysis
Day 80 and day 83 after inclusion
The difference in the number of miscarriages throughout the trial before day 180
Time Frame: Day 450 after inclusion]
Survey
Day 450 after inclusion]
The change/difference in serum levels of follicle stimulating hormone (FSH) on day 80
Time Frame: Day 80 after inclusion
Serum sample
Day 80 after inclusion
The change/difference in serum levels of reproductive hormone luteinizing hormone (LH) on day 80
Time Frame: Day 80 after inclusion
Serum sample
Day 80 after inclusion
The change/difference in serum levels of reproductive hormone AMH on day 80
Time Frame: Day 80 after inclusion
Serum sample
Day 80 after inclusion
The change/difference in serum levels of reproductive hormone Inhibin B on day 80
Time Frame: Day 80 after inclusion
Serum sample
Day 80 after inclusion
The change/differences in number of pregnancies achieved before day 180
Time Frame: Day 180 after inclusion
Survey
Day 180 after inclusion

Other Outcome Measures

Outcome Measure
Measure Description
Time Frame
The change/difference in CatSper expression on day 80
Time Frame: Day 80 after inclusion
Seminal fluid
Day 80 after inclusion
The change/difference in RANKL expression on day 80
Time Frame: Day 80 after inclusion
Seminal fluid
Day 80 after inclusion

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Martin Blomberg Jensen

Investigators

  • Principal Investigator: Sam Kafai Yahyavi, MD, Division of Translational Endocrinology, Herlev, Copenhagen

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

March 1, 2024

Primary Completion (Actual)

January 29, 2025

Study Completion (Actual)

August 31, 2025

Study Registration Dates

First Submitted

March 2, 2024

First Submitted That Met QC Criteria

March 2, 2024

First Posted (Actual)

March 8, 2024

Study Record Updates

Last Update Posted (Actual)

December 19, 2025

Last Update Submitted That Met QC Criteria

December 12, 2025

Last Verified

December 1, 2025

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 2023-508325-27-00

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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