A Study of CSTI-500 in Patients With Prader-Willi Syndrome

NCT07348601 | Recruiting Phase 2 FDA Drug

• 1 other identifier: CSTI-500-005
• Study Type: interventional
• Target: 12
• Locations: 1 country
• Sites: 1

Brief 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. Participants will receive increasing doses of CSTI-500, and blood levels will be measured to guide individualized dosing.

Conditions

Prader-Willi Syndrome

Keywords

PWS; Prader-Willi Syndrome; CSTI-500

Outcome Measures

Primary Outcomes (5)

• 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).

  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.

  12 weeks

• Incidence of clinically significant findings in laboratory values

  Laboratory evaluations include hematology, blood chemistry, and urinalysis parameters.

  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.

  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).

  12 weeks

Secondary Outcomes (7)

• Change from baseline in Hyperphagia Questionnaire for Clinical Trials (HQ-CT) total score

  12 weeks

• Change from baseline in Aberrant Behavior Checklist - Community (ABC-C) total score and subscale scores

  12 weeks

• Clinical Global Impression-Improvement (CGI-I) score

  12 weeks

• Change from baseline in Clinical Global Impression-Severity (CGI-S) score

  12 weeks

• Change from baseline in Prader-Willi Syndrome Questionnaire (PADQ) score

  12 weeks

Study Arms (3)

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

Interventions

CSTI-500 DRUG

CSTI-500 given orally in an open-label, dose-escalation design with individualized dosing.

CSTI-500 (Open-Label) Medium Target Exposure; CSTI-500 (Open-label) High Target Exposure; CSTI-500 (Open-label) Low Target Exposure

Eligibility Criteria

• Age: 13 Years - 50 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Child (0-17), Adult (18-64)

You may qualify if:

• 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
• 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.
• 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).

You may not qualify if:

• 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.
• 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).
• 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).
• a. 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.
• 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.

Sponsors & Collaborators

• ConSynance Therapeutics: lead

Study Sites (1)

Vanderbilt University Medical Center

Nashville, Tennessee, 37232, United States

RECRUITING

MeSH Terms

Conditions

Prader-Willi Syndrome

Condition Hierarchy (Ancestors)

Intellectual Disability; Neurobehavioral Manifestations; Neurologic Manifestations; Nervous System Diseases; Abnormalities, Multiple; Congenital Abnormalities; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Chromosome Disorders; Genetic Diseases, Inborn; Imprinting Disorders; Obesity; Overweight; Overnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases

Central Study Contacts

Beth Mack

CONTACT

859-426-5035; bethmack@lbr-regulatory.com

Study Design

• Study Type: interventional
• Phase: phase 2
• Allocation: NA
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SEQUENTIAL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: December 9, 2025
• First Posted: January 16, 2026
• Study Start: May 1, 2026
• Primary Completion (Estimated): June 1, 2027
• Study Completion (Estimated): June 1, 2027
• Last Updated: May 15, 2026

Record last verified: 2026-05

Data Sharing

• IPD Sharing: Will not share

Locations

US (1)