Precocious Puberty, Gonadotropin-dependentPhase 2NCT07869732
(Z)-Endoxifen in Girls With MAS-Associated Peripheral Precocious Puberty
A Phase 2 study testing (Z)-endoxifen in people with Precocious Puberty, Gonadotropin-dependent, run by Atossa Therapeutics, Inc. at 1 site in United States.
Trial summary
The goal of this clinical trial is to evaluate the safety, tolerability, and blood levels of (Z)-endoxifen in girls with McCune-Albright Syndrome that have peripheral precocious puberty. Read more about this study
- Who is it for?
- Ages 4 to 9 years, women only
- Conditions the study is for
- Precocious Puberty, Gonadotropin-dependent
- What is being tested?
- (Z)-endoxifen
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 6 participants
- Where
- 1 siteUnited States
- Study dates
- Mar 2027to Sep 2028
- Phase
- Phase 2
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 4 to 9 years
- Women only
- No healthy volunteers
- Child
Who may be able to join
- Female child aged ≥ 4 to < 10 years at the time of informed consent.
- Body weight ≥ 16 kg.
- Clinical or molecular diagnosis of McCune-Albright syndrome (MAS), with peripheral precocious puberty and at least one additional characteristic manifestation of MAS other than café-au-lait skin macules, such as polyostotic fibrous dysplasia or another autonomous endocrine manifestation distinct from the participants PPP.
- Clinical evidence of gonadotropin-independent (peripheral) precocious puberty, including onset of vaginal bleeding before 8 years of age and recurrent vaginal bleeding documented as at least 2 episodes during the prior 6 months.
- Prepubertal or low-normal basal luteinizing hormone (LH) and follicle-stimulating hormone (FSH), consistent with predominantly gonadotropin-independent disease activity.
- Advanced bone age, defined as bone age exceeding chronological age by ≥1 year at screening, determined using the protocol-specified standardized radiographic method and central or qualified local reading procedures.
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- Active peripheral estrogen activity at study entry that, in the Investigator's judgment, is the primary driver of current clinical manifestations.
- Ability to swallow small capsules with water. Capsule-swallow training may be provided during screening using non-drug training capsules, or other age-appropriate standard site procedures.
- Adequate hepatic, renal, hematologic, and coagulation function based on protocol-defined laboratory criteria.
- Parent or legal guardian able and willing to provide written informed consent, with age-appropriate participant assent when applicable.
- Participant and parent/caregiver are willing and able to comply with study visits, daily diary completion, study treatment administration, and required procedures.
Who cannot join
- Prior bilateral oophorectomy or hysterectomy.
- Central precocious puberty (CPP).
- The need for the use of GnRH agonists during the trial.
- Use of a selective estrogen receptor modulator, aromatase inhibitor, other estrogen-modifying agent, or high-dose progestin within 1 month or 5-half-lives, whichever is longer.
- Use of any bone-directed therapies.
- Dominant central precocious puberty requiring initiation or intensification of gonadotropin-releasing hormone analog therapy at screening.
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- Clinically significant uncontrolled endocrinopathy likely to interfere with growth, safety, or interpretation of study outcomes, including uncontrolled hyperthyroidism, growth hormone excess, phosphate-wasting osteomalacia, or Cushing syndrome.
- ALT or AST >3 × upper limit of normal (ULN), total bilirubin >2 × ULN, or other clinically significant hepatic impairment at screening (post-letrozole 14 day wash-out), unless the abnormality is explained, stable, and approved by the Sponsor Medical Monitor.
- Clinically significant renal impairment, hematologic abnormality, or coagulation abnormality that may increase risk or confound interpretation.
- History of venous thromboembolism or known hereditary thrombophilia.
- Significant ophthalmic conditions, including cataracts
- Known hypersensitivity to endoxifen, tamoxifen, or any formulation excipient.
- Pregnancy or breastfeeding. Pregnancy testing applies only to post-menarche or otherwise at-risk participants as medically and ethically appropriate.
- Participation in another interventional clinical study or receipt of another investigational product within 30 days or 5 half-lives, whichever is longer, before first dose, unless approved by the Sponsor.
- Planned major surgery during the 3-month treatment period that could materially affect safety or endpoint assessment.
- Any serious concomitant medical, developmental, behavioral, or psychiatric condition that, in the Investigator's judgment, would make participation unsafe, prevent reliable completion of study procedures, or compromise study integrity.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
About this study
Official title: A Phase 2 Open-Label, Safety, Tolerability and Exposure Study of Oral (Z)-Endoxifen for the Treatment of Gonadotropin-Independent Precocious Puberty in Girls With McCune-Albright Syndrome
The goal of this clinical trial is to evaluate the safety, tolerability, and blood levels of (Z)-endoxifen in girls with McCune-Albright Syndrome that have peripheral precocious puberty. The main question it aims to answer [is/are]:
Are there any safety concerns? Is there any evidence of efficacy?
There is no comparison group.
Participants will:
- take a capsule once a day for 3 months;
- have doctor visits (tele-health and in-person);
- blood samples collected; and
- complete questionnaires
- Being tested
- (Z)-endoxifen
- Keywords
- FD/MAS, MAS, McCune-Albright, McCune Albright
- Medical subject headings
- Puberty, Precocious
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
(Z)-endoxifenDrug
(Z)-endoxifen will be administered once daily via the oral route
| Study group | Role | What they receive |
|---|---|---|
| (Z)-endoxifen arm | Experimental | Not described Receives: Drug: (Z)-endoxifen |
What is being measured
The primary outcome is the main question the study is designed to answer.
Safety and tolerability
Incidence, severity, seriousness, and relationship of TEAEs and SAEs; clinically significant changes in laboratory tests, vital signs, ECGs, physical examinations, growth, pubertal development, and other targeted safety parameters.
Measured: 3 months
Secondary outcomes (1)
Evaluate patient and family impact (Psycho-social impact) of the early onset of puberty in girls
This assessment will be determined via validated questionnaires
Measured: Prior to and during the study (4 to 5 months)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted9 Oct 2026
- Study startMar 2027 (estimated)
- Primary completionJun 2028 (estimated)
- Study completionSep 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Precocious Puberty, Gonadotropin-dependentStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Model description
- Open-Label, Safety, Tolerability and Exposure Study of (Z)-endoxifen
- Masking
- None (open label)
- Enrolment
- 6 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Atossa Therapeutics, Inc.
- Sponsor type
- Industry (pharma, biotech, devices)
- Collaborators
- National Institute of Dental and Craniofacial Research (NIDCR)
- Responsible party
- Sponsor
- Investigators
- Alison Boyce, MD, Principal investigator, Lasker Clinical Research Scholar Chief, Metabolic Bone Disorders Unit National Institute of Dental and Craniofacial Research National Institutes of Health
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07869732
- Sponsor's protocol ID
- ATOS-204-S
- Status last verified
- Oct 2026
- First submitted
- 6 Oct 2026
- Last updated
- 9 Oct 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Undecided: I am not sure
Study at a glance
From the registry record, last updated by the sponsor on 9 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Phase 2 Open-Label, Safety, Tolerability and Exposure Study of Oral (Z)-Endoxifen for the Treatment of Gonadotropin-Independent Precocious Puberty in Girls With McCune-Albright Syndrome
- ClinicalTrials.gov ID
- NCT07869732
- Acronym / sponsor ID
- ATOS-204-S
- Keywords
- FD/MAS, MAS, McCune-Albright, McCune Albright
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 6 participants (estimated)
- Lead sponsor
- Atossa Therapeutics, Inc.Industry (pharma, biotech, devices)
- Collaborators
- National Institute of Dental and Craniofacial Research (NIDCR)
- Study start
- Mar 2027 (estimated)
- Primary completion
- Jun 2028 (estimated)
- Study completion
- Sep 2028 (estimated)
- First posted
- 9 Oct 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The goal of this clinical trial is to evaluate the safety, tolerability, and blood levels of (Z)-endoxifen in girls with McCune-Albright Syndrome that have peripheral precocious puberty. The main question it aims to answer [is/are]:
Are there any safety concerns? Is there any evidence of efficacy?
There is no comparison group.
Participants will:
- take a capsule once a day for 3 months;
- have doctor visits (tele-health and in-person);
- blood samples collected; and
- complete questionnaires
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
- Model description
- Open-Label, Safety, Tolerability and Exposure Study of (Z)-endoxifen
| Arm | Type | Receives |
|---|---|---|
| (Z)-endoxifen arm | Experimental | Drug: (Z)-endoxifen |
Who may qualify
- Ages
- 4 to 9 years
- Sex
- Female only
- Healthy volunteers
- Not accepted
- Age groups
- Child
Key inclusion criteria (11 listed)
- Female child aged ≥ 4 to < 10 years at the time of informed consent.
- Body weight ≥ 16 kg.
- Clinical or molecular diagnosis of McCune-Albright syndrome (MAS), with peripheral precocious puberty and at least one additional characteristic manifestation of MAS other than café-au-lait skin macules, such as polyostotic fibrous dysplasia or another autonomous endocrine manifestation distinct from the participants PPP.
- Clinical evidence of gonadotropin-independent (peripheral) precocious puberty, including onset of vaginal bleeding before 8 years of age and recurrent vaginal bleeding documented as at least 2 episodes during the prior 6 months.
- Prepubertal or low-normal basal luteinizing hormone (LH) and follicle-stimulating hormone (FSH), consistent with predominantly gonadotropin-independent disease activity.
Key exclusion criteria (16 listed)
- Prior bilateral oophorectomy or hysterectomy.
- Central precocious puberty (CPP).
- The need for the use of GnRH agonists during the trial.
- Use of a selective estrogen receptor modulator, aromatase inhibitor, other estrogen-modifying agent, or high-dose progestin within 1 month or 5-half-lives, whichever is longer.
- Use of any bone-directed therapies.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| (Z)-endoxifen(Z)-endoxifen will be administered once daily via the oral route | Drug | (Z)-endoxifen arm |
Primary outcome
Safety and tolerability
Time frame: 3 months
Incidence, severity, seriousness, and relationship of TEAEs and SAEs; clinically significant changes in laboratory tests, vital signs, ECGs, physical examinations, growth, pubertal development, and other targeted safety parameters.
1 secondary outcome
Evaluate patient and family impact (Psycho-social impact) of the early onset of puberty in girls
Time frame: Prior to and during the study (4 to 5 months)
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 9 Oct 2026.
- Individual participant dataSharing planned: Undecided. I am not sure
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CPP
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Alison Boyce, MD principal investigator
Lasker Clinical Research Scholar Chief, Metabolic Bone Disorders Unit National Institute of Dental and Craniofacial Research National Institutes of Health
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing (Z)-endoxifen in people with Precocious Puberty, Gonadotropin-dependent, run by Atossa Therapeutics, Inc. at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 11 inclusion and 16 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 9 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Safety and tolerability (time frame: 3 months). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 9 Oct 2026.