Prader-Willi SyndromePhase 2NCT07348601
A Study of CSTI-500 in Patients With Prader-Willi Syndrome
A Phase 2 study testing CSTI-500 in people with Prader-Willi Syndrome, run by ConSynance Therapeutics at 1 site in United States.
Trial summary
This is a proof-of-concept, open-label, dose-escalation study to evaluate the safety, tolerability, pharmacokinetics, and efficacy of CSTI-500 in participants with genetically confirmed Prader-Willi Syndrome (PWS) who are 13 to 50 years of age. Read more about this study
- Who is it for?
- Ages 13 to 50 years
- Conditions the study is for
- Prader-Willi Syndrome
- What is being tested?
- CSTI-500
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 12 participants
- Where
- 1 siteUnited States
- Study dates
- 18 May 2026to Jun 2027
- 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 13 to 50 years
- All sexes
- No healthy volunteers
- Child, Adult
Who may be able to join
- Generally healthy male and female individuals between the ages of 13 and 50, inclusive
- Documented medical record history of PWS confirmed by genetic testing and PWS Nutritional Phase 3
- CGI-S score ≥4 at Screening and Baseline (behavioral)
- Screening HQ CT total scores ≥ 13
- Participants must not be taking SSRI, SNRI, DNRI (bupropion), tricyclic antidepressants, stimulants, antipsychotic medications, and MAO inhibitors within 30 days of screening and willing to not start taking these medications while on the study. Fluoxetine is exclusionary unless treatment has been discontinued >6 months prior to Screening.
- Caregiver/parent must agree to bring the subject to the site for the visits, remain with the subject during visit times when allowed and respond to any questions.
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- Caregiver/parent is willing to provide informed consent and agrees to adhere to required study procedures including telemedicine visits, visit duration requirements, and offer consistent care.
- Caregivers must agree to complete all study required assessments.
- Participants who cannot consent for themselves and are able will provide assent.
- Female participants must not be pregnant or lactating. Nonpregnancy will be confirmed for all females by a urine pregnancy test conducted at Screening and at the Baseline Visit prior to enrollment into the study. If of childbearing potential, the subject/caregiver agrees to the use of one of the accepted contraceptive regimens from Screening to the first administration of the study medication, during the study, and for at least 30 days after the last dose of the study medication. An acceptable method of contraception includes one of the following:
- Hormonal contraceptives (birth control pills, injectable/implant/insertable hormonal birth control products, transdermal patch)
- Intrauterine device (with or without hormones)
- OR agrees to use a double barrier method (e.g., condom and spermicide) during the study and for at least 30 days after the last dose of the study medication.
- The investigator can use their judgement and familiarity with the participant's preferred and usual lifestyle to understand which form of birth control would be the best and also to determine if abstinence is an option that would achieve 100% effectiveness.
- If the female is of non-childbearing potential -surgically sterile (i.e., has undergone complete hysterectomy, bilateral oophorectomy, or tubal ligation) or is postmenopausal (at least 1 year without menses) as confirmed by follicle-stimulating hormone (FSH) levels of ≥ 40 mIU/mL. No contraceptive use is required.
- Unless, sterile, a male study subject/caregiver must agree to use a double barrier method (e.g., condom and spermicide).
- For adults, supine systolic blood pressure must be ≤140 mmHg and ≥100 mmHg; diastolic blood pressure must be ≤80 mmHg and ≥60 mmHg at Screening. Heart rate must be ≥50 bpm and ≤100 bpm. Heart rate increase on standing must be within acceptable range (see exclusion criterion 10).
- For adolescents, a systolic and diastolic BP that is between the 5th and 90th percentile for age and sex.
- Two repeat measurements within 10 minutes of the first reading are permitted at the discretion of the Investigator. If this option is used, the last obtained reading will be used for determination of eligibility. Averages will not be used.
- All concomitant medications including blood pressure medications and type 2 diabetic medications must be stable for ≥3 months prior to screening (≤10% change) and there must be no medication changes (dose change, initiation, discontinuation) intentionally planned during the study. Supplements and vitamins are not considered concomitant medications for eligibility purposes.
- Stated willingness to comply with all study procedures including visits, restrictions, and availability for the duration of the study.
Who cannot join
- Participation in any clinical study with an investigational drug/device within 3 months prior to screening or during the study
- PWS diagnosis of UPD (maternal uniparental disomy).
- Current use of DCCR or if used previously, must be off at least 4 weeks before screening.
- Recent use (within 3 months) of weight loss agents including prescription, herbal medications, and weight loss supplements. Ozempic, for diabetes, would be exclusionary due to its effect on weight loss.
- History of bariatric surgery or major surgery within 6 months of screening or planned during the study.
- Any malignancy in the 2 years prior to screening (excluding basal cell carcinoma or squamous cell carcinoma of the skin or cervical carcinoma in situ that have been successfully treated).
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- Current liver, pulmonary, cardiac, or GI disease that would be expected to adversely affect study participation. Stable disease, e.g., asthma or controlled hypertension is not excluded. Liver disease or liver injury as indicated by abnormal liver function tests, ALT, AST, alkaline phosphatase, or serum bilirubin (≥3X ULN for any of these tests).
- Participants with impaired liver function (Child-Pugh Scores A, B, C)
- Unexplained history or presence of combination of unexplained symptoms e.g., dizziness, syncope, fatigue, palpitations/tachycardia, headaches, or exercise intolerance.
- Prohibited Medications include SSRI, SNRI, DNRI (bupropion), tricyclic antidepressants, stimulants, antipsychotics, MAO inhibitors, fluoxetine, mood stabilizers, and GLP-1 agonists
- Presence of postural orthostatic tachycardia syndrome (POTS) for any reason, defined as:
- For participants aged 19 or older, sustained heart rate increase of >30 bpm or an increase to 120 bpm or greater within 3 minutes of standing.
- For participants aged 13-19, a sustained heart rate increase of >40 bpm or an increase to 120 bpm or greater within 3 minutes of standing.
- Associated with related symptoms that are worse with upright posture and that improve with recumbence.
- A clinically significant abnormal finding on 12-lead electrocardiogram (ECG) at Screening. Note QT corrected according to Fridericia's formula (QTcF) interval of ≥450 msec will be exclusionary [QTc = QT/(RR^0.33)]. The ECG may be repeated once for confirmatory purposes if initial values obtained exceed the limits specified.
- Any clinically significant cardiac arrhythmia (e.g., atrial fibrillation, Adams-Stokes's disease, Wolff-Parkinson-White syndrome, atrioventricular block 2nd or 3rd degree).
- Heart failure classified per the New York Heart Association (NYHA) as level II or greater.
- Myocardial infarction, stroke, or confirmed TIA within the last 5 years.
- Estimated glomerular filtration rate (eGFR) ≤ 90 mL/min/1.73m² for ages 13 to <18 years of age. For adults ≥18 years of age, body-surface area corrected eGFR and exclusion with eGFR <90 mL/min.
- Uncontrolled Type 2 diabetes as defined by HbA1c ≥ 9% at Screening.
- Insulin-dependent Type 1 diabetes.
- Positive screen for hepatitis B surface antigen (HBsAg), hepatitis C virus (HCV) antibodies with detected circulating ribonucleic acid (RNA), or HIV 1 and 2 antibodies.
- Uncontrolled thyroid disease.
- Known hypersensitivity to any component of investigational product.
- History or active psychotic symptoms, or medical conditions which the investigator believes will interfere significantly with study compliance. Participants with a history of other severe psychiatric disorders, e.g., schizophrenia, major depressive disorder, bipolar disorder, or other DSM-V disorders.
- History of any suicidal behavior.
- Known alcohol or substance abuse.
- Moderate to strong inhibitors/inducers of CYP2D6, CYP3A4 and CYP2C9, including grapefruit juice. Substrates of CYP1A2 and CYP2B6.
- Any other medical, physical, or personal issues which, in the opinion of the investigator, would interfere with the subject's ability to complete the trial per protocol.
- Inability to swallow the oral capsules whole with water.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site, 1 recruiting
- Recruiting
Vanderbilt University Medical Center
Nashville, Tennessee, 37232
Elizabeth Roof, 6153433330, elizabeth.roof@vanderbilt.edu
About this study
Official title: A Proof-of-Concept Open-Label Clinical Trial to Evaluate the Safety, Tolerability, and Efficacy of CSTI-500 in Participants With Prader-Willi Syndrome
This is a proof-of-concept, open-label, dose-escalation study to evaluate the safety, tolerability, pharmacokinetics, and efficacy of CSTI-500 in participants with genetically confirmed Prader-Willi Syndrome (PWS) who are 13 to 50 years of age. Participants will receive increasing doses of CSTI-500, and blood levels will be measured to guide individualized dosing.
- Conditions
- Prader-Willi Syndrome
- Being tested
- CSTI-500
- Keywords
- PWS, Prader-Willi Syndrome, CSTI-500
- Medical subject headings
- Prader-Willi Syndrome
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
CSTI-500Drug
CSTI-500 given orally in an open-label, dose-escalation design with individualized dosing.
| Study group | Role | What they receive |
|---|---|---|
| CSTI-500 (Open-label) Low Target Exposure | Experimental | Not described Receives: Drug: CSTI-500 |
| CSTI-500 (Open-Label) Medium Target Exposure | Experimental | Not described Receives: Drug: CSTI-500 |
| CSTI-500 (Open-label) High Target Exposure | Experimental | Not described Receives: Drug: CSTI-500 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Incidence of treatment-emergent adverse events (TEAEs)
Number of participants with TEAEs, defined as an adverse event (AE) that is new or worsened in severity after the dose of study drug (coded using MedDRA).
Measured: 14 weeks
Proportion achieving target CSTI-500 steady-state Cmax with PK-guided dose individualization
Proportion of participants whose observed CSTI-500 steady-state Cmax is within the protocol-defined target range for the assigned target concentration level, using plasma concentrations measured from scheduled PK sampling to guide dose adjustments.
Measured: 12 weeks
Incidence of clinically significant findings in laboratory values
Laboratory evaluations include hematology, blood chemistry, and urinalysis parameters.
Measured: 12 weeks
Incidence of clinically significant findings in 12-lead electrocardiograms (ECGs)
QT interval, corrected QT interval (QTc), PR interval, QRS duration, and heart rate will be measured by 12-lead electrocardiogram.
Measured: 12 weeks
Incidence of clinically significant findings in vital signs
Participants will be assessed for any clinically significant changes in vital parameters (systolic blood pressure, diastolic blood pressure, heart rate, respiratory rate, and body temperature).
Measured: 12 weeks
Secondary outcomes (7)
Change from baseline in Hyperphagia Questionnaire for Clinical Trials (HQ-CT) total score
Change from baseline in the Hyperphagia Questionnaire for Clinical Trials (HQ-CT) total score. The HQ-CT total score ranges from 0 to 36, with higher scores indicating greater hyperphagia.
Measured: 12 weeks
Change from baseline in Aberrant Behavior Checklist - Community (ABC-C) total score and subscale scores
Change from baseline in Aberrant Behavior Checklist - Community (ABC-C) total score and subscale scores. The ABC-C is a 58-item caregiver-reported questionnaire, with higher scores indicating more severe aberrant behavior.
Measured: 12 weeks
Clinical Global Impression-Improvement (CGI-I) score
Clinical Global Impression-Improvement (CGI-I) score assessed at Week 12. The CGI-I is a 7-point ordinal scale, with lower scores indicating greater improvement.
Measured: 12 weeks
Change from baseline in Clinical Global Impression-Severity (CGI-S) score
Change from baseline in Clinical Global Impression-Severity (CGI-S) score. The CGI-S is a 7-point ordinal scale, with lower scores indicating less severe illness (better outcome).
Measured: 12 weeks
Change from baseline in Prader-Willi Syndrome Questionnaire (PADQ) score
Change from baseline in the Prader-Willi Syndrome Questionnaire (PADQ) score. The PADQ is a caregiver-reported questionnaire, with higher scores indicating greater symptom severity (worse outcome).
Measured: 12 weeks
Change from baseline in Caregiver Global Impression-Severity (careGI-S) score
Change from baseline in Caregiver Global Impression-Severity (careGI-S) score. The careGI-S is a caregiver-reported ordinal scale, with lower scores indicating less severe symptoms (better outcome).
Measured: 12 weeks
Caregiver Global Impression-Change (careGI-C) score
Caregiver Global Impression-Change (careGI-C) score assessed at Week 12. The careGI-C is a caregiver-reported ordinal scale, with lower scores indicating greater improvement.
Measured: 12 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted16 Jan 2026
- Study start18 May 2026
- Primary completionJun 2027 (estimated)
- Study completionJun 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Prader-Willi SyndromeStudies 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
- Sequential
- Masking
- None (open label)
- Enrolment
- 12 participants (estimated)
Sponsor and investigators
- Lead sponsor
- ConSynance Therapeutics
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07348601
- Sponsor's protocol ID
- CSTI-500-005
- Status last verified
- May 2026
- First submitted
- 9 Dec 2025
- Last updated
- 21 Oct 2026
- Results posted
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 21 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Proof-of-Concept Open-Label Clinical Trial to Evaluate the Safety, Tolerability, and Efficacy of CSTI-500 in Participants With Prader-Willi Syndrome
- ClinicalTrials.gov ID
- NCT07348601
- Acronym / sponsor ID
- CSTI-500-005
- Conditions
- Prader-Willi Syndrome
- Keywords
- PWS, Prader-Willi Syndrome, CSTI-500
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 12 participants (estimated)
- Lead sponsor
- ConSynance TherapeuticsIndustry (pharma, biotech, devices)
- Study start
- 18 May 2026 (actual)
- Primary completion
- Jun 2027 (estimated)
- Study completion
- Jun 2027 (estimated)
- First posted
- 16 Jan 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.
This is a proof-of-concept, open-label, dose-escalation study to evaluate the safety, tolerability, pharmacokinetics, and efficacy of CSTI-500 in participants with genetically confirmed Prader-Willi Syndrome (PWS) who are 13 to 50 years of age. Participants will receive increasing doses of CSTI-500, and blood levels will be measured to guide individualized dosing.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Sequential
- Masking
- None (open label)
- Number of arms
- 3
| Arm | Type | Receives |
|---|---|---|
| CSTI-500 (Open-label) Low Target Exposure | Experimental | Drug: CSTI-500 |
| CSTI-500 (Open-Label) Medium Target Exposure | Experimental | Drug: CSTI-500 |
| CSTI-500 (Open-label) High Target Exposure | Experimental | Drug: CSTI-500 |
Who may qualify
- Ages
- 13 to 50 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Child, Adult
Key inclusion criteria (21 listed)
- Generally healthy male and female individuals between the ages of 13 and 50, inclusive
- Documented medical record history of PWS confirmed by genetic testing and PWS Nutritional Phase 3
- CGI-S score ≥4 at Screening and Baseline (behavioral)
- Screening HQ CT total scores ≥ 13
- Participants must not be taking SSRI, SNRI, DNRI (bupropion), tricyclic antidepressants, stimulants, antipsychotic medications, and MAO inhibitors within 30 days of screening and willing to not start taking these medications while on the study. Fluoxetine is exclusionary unless treatment has been discontinued >6 months prior to Screening.
Key exclusion criteria (30 listed)
- Participation in any clinical study with an investigational drug/device within 3 months prior to screening or during the study
- PWS diagnosis of UPD (maternal uniparental disomy).
- Current use of DCCR or if used previously, must be off at least 4 weeks before screening.
- Recent use (within 3 months) of weight loss agents including prescription, herbal medications, and weight loss supplements. Ozempic, for diabetes, would be exclusionary due to its effect on weight loss.
- History of bariatric surgery or major surgery within 6 months of screening or planned during the study.
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 |
|---|---|---|
| CSTI-500CSTI-500 given orally in an open-label, dose-escalation design with individualized dosing. | Drug | CSTI-500 (Open-Label) Medium Target Exposure, CSTI-500 (Open-label) High Target Exposure, CSTI-500 (Open-label) Low Target Exposure |
Primary outcome
Incidence of treatment-emergent adverse events (TEAEs)
Time frame: 14 weeks
Number of participants with TEAEs, defined as an adverse event (AE) that is new or worsened in severity after the dose of study drug (coded using MedDRA).
Proportion achieving target CSTI-500 steady-state Cmax with PK-guided dose individualization
Time frame: 12 weeks
Proportion of participants whose observed CSTI-500 steady-state Cmax is within the protocol-defined target range for the assigned target concentration level, using plasma concentrations measured from scheduled PK sampling to guide dose adjustments.
Incidence of clinically significant findings in laboratory values
Time frame: 12 weeks
Laboratory evaluations include hematology, blood chemistry, and urinalysis parameters.
Incidence of clinically significant findings in 12-lead electrocardiograms (ECGs)
Time frame: 12 weeks
QT interval, corrected QT interval (QTc), PR interval, QRS duration, and heart rate will be measured by 12-lead electrocardiogram.
Incidence of clinically significant findings in vital signs
Time frame: 12 weeks
Participants will be assessed for any clinically significant changes in vital parameters (systolic blood pressure, diastolic blood pressure, heart rate, respiratory rate, and body temperature).
7 secondary outcomes
Change from baseline in Hyperphagia Questionnaire for Clinical Trials (HQ-CT) total score
Time frame: 12 weeks
Change from baseline in Aberrant Behavior Checklist - Community (ABC-C) total score and subscale scores
Time frame: 12 weeks
Clinical Global Impression-Improvement (CGI-I) score
Time frame: 12 weeks
Change from baseline in Clinical Global Impression-Severity (CGI-S) score
Time frame: 12 weeks
Change from baseline in Prader-Willi Syndrome Questionnaire (PADQ) score
Time frame: 12 weeks
Change from baseline in Caregiver Global Impression-Severity (careGI-S) score
Time frame: 12 weeks
Caregiver Global Impression-Change (careGI-C) score
Time frame: 12 weeks
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 21 Oct 2026.
- Individual participant dataSharing planned: No
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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.
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 CSTI-500 in people with Prader-Willi Syndrome, run by ConSynance Therapeutics 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 21 inclusion and 30 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: looking for participants now, as of the sponsor's last update on 21 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?
Contact Beth Mack (859-426-5035, bethmack@lbr-regulatory.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Incidence of treatment-emergent adverse events (TEAEs) (time frame: 14 weeks). The study lists 5 primary outcomes in all. 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 21 Oct 2026.