Testing the Safety and Effectiveness of CTH120 Compared to Placebo in Adult Men with Fragile X Syndrome

What is this study about?

This study is looking at Fragile X syndrome, a genetic condition that affects development and can cause learning disabilities and behavioral challenges. The treatment being tested is CTH120, which is given as hard capsules taken by mouth. Some participants will receive CTH120 while others will receive placebo capsules that look identical but contain no active medicine. The purpose of this study is to assess the safety and tolerability of CTH120 in people with Fragile X syndrome compared to placebo.

The study will involve adult males between 18 and 45 years old who have been diagnosed with Fragile X syndrome through genetic testing. Participants will need to have a parent or caregiver who can attend all study visits with them and help provide information throughout the study. The treatment period will last for 42 days, with the maximum daily dose being 150 milligrams of CTH120. During the study, doctors will monitor participants for any unwanted effects and will check vital signs, heart activity through an ECG (a test that records the electrical activity of the heart), and laboratory test results from blood samples.

Throughout the study, various assessments will be performed to understand how the treatment affects participants. These will include measurements of behavior, thinking abilities, anxiety levels, sleep quality, daily living skills, and overall quality of life through questionnaires completed by caregivers. The study will also use electroencephalography (a test that measures brain wave activity), eye-tracking technology to observe social attention, and activity monitors worn on the body to track movement and sleep patterns. Blood samples will be taken to measure drug levels and certain proteins including FMRP (a protein that is typically low or absent in people with Fragile X syndrome) and BDNF (a substance that supports nerve cell health).

1 Initial treatment period

Your participation in the trial begins on Day 1. At this point, you will start receiving either the study medication called CTH120 or a placebo. A placebo is an inactive substance that looks identical to the real medication but contains no active ingredient.

The medication is provided as hard capsules that are taken by mouth. The active substance in CTH120 is 2-[4-[3-(methylamino)-1-phenylpropoxy]phenyl]ethanol hydrochloride.

Your caregiver or legal representative will need to accompany you to all study visits and help ensure that you take the medication as instructed.

2 Ongoing monitoring throughout the study

During the trial, various assessments will be conducted to monitor your safety and how the medication may be affecting you. These assessments include checking your vital signs (such as blood pressure and heart rate), performing a 12-lead ECG (a test that records the electrical activity of your heart), and taking blood samples for laboratory tests.

Any new health problems or side effects that occur from Day 1 onwards will be recorded as treatment-emergent adverse events.

Blood samples will be collected at specific times to measure the levels of CTH120 and its breakdown product (called metabolite M4) in your blood. This helps determine how your body processes the medication.

3 Behavioral and functional assessments

Throughout the study, you will undergo several assessments to evaluate different aspects of your daily functioning and well-being. These include:

A Visual Analogue Scale to rate your overall functioning.

The Clinical Global Impression Scale, where a clinician rates the severity of your condition and any improvement.

The Aberrant Behaviour Checklist to assess behavioral difficulties.

The Anxiety, Depression, and Mood Scale to evaluate anxiety levels.

The Vineland Adaptive Behaviour Scale to measure your ability to perform daily activities.

Questionnaires about your cognitive functioning (thinking and memory skills) and quality of life, which will be completed by your caregiver.

The Pittsburgh Sleep Quality Index to assess how well you are sleeping.

4 Specialized testing procedures

You will undergo an Electroencephalography (EEG) test, which measures electrical activity in your brain using sensors placed on your scalp. During this test, you will listen to sounds while the device records your brain’s responses.

Eye-tracking technology will be used to observe where you look and for how long, which helps assess social attention.

You may be asked to wear an actigraphy device, which is a small wearable monitor that tracks your movement and sleep patterns over time.

Additional blood samples will be taken to measure levels of FMRP protein (a protein that is typically reduced in Fragile X syndrome) and BDNF (a substance in the blood related to brain health).

5 End of study

The study will continue until the End-of-Study (EOS) visit. At this final visit, all safety assessments will be repeated, including vital signs, ECG, and laboratory tests.

All adverse events and any clinically significant abnormalities that occurred from Day 1 to the end of the study will be reviewed and documented.

Your participation in the trial will be complete after this final visit.

Who Can Join the Study?

Must be an adult male person
Must have a score of 3 or higher on a scale called CGI-S, which is a rating that measures how severe the condition is, as evaluated by a doctor who has experience with Fragile X syndrome
Must be able to move around on their own without help
Must have good enough vision and hearing to take part in the study tests
Must be able to be understood most of the time when speaking, and must not need to use sign language, picture boards, or special devices as the main way of communicating
Must be expected to complete all the tasks and appointments scheduled during the study visits
Must have a VCI scaled score greater than 4 on a test called WISC-V, which is a test that measures thinking abilities based on mental age
Must be between 18 and 45 years old
Must weigh between 50 and 100 kilograms
Must have a body mass index, which is a measure of body fat based on height and weight, between 18.5 and 32
Must have a confirmed diagnosis of Fragile X syndrome through both medical examination and genetic testing showing more than 200 CGG repeats in a specific part of the FMR1 gene, which is the genetic cause of the condition
Must have a parent or other dependable caregiver who agrees to come to all study visits, provide information about the participant as needed, and make sure all study tests are completed
Must have a legal representative, which is a person legally responsible for making decisions on behalf of the participant, who understands and accepts the study procedures
If only one parent signs the consent, that parent must confirm that the other parent does not object to the participation
The participant must agree or be willing to take part in the study
Must have a signed consent form from the legal representative before any study procedures begin

Who Cannot Join the Study?

The study only includes male patients, so females cannot participate
Patients who are outside the specified age range for this study cannot participate
Patients who do not have a confirmed diagnosis of Fragile X Syndrome cannot participate
Patients who have serious medical conditions that could interfere with the study or make it unsafe for them to participate
Patients who are allergic or have had bad reactions to similar medications in the past
Patients who are currently taking medications that might interact with the study drug in a harmful way
Patients who have participated in another clinical trial recently and are still within the required waiting period
Patients who cannot follow the study requirements, such as attending visits or taking the medication as instructed
Patients whose legal guardian or caregiver cannot provide informed consent, which means official permission to join the study

Where you can join this trial?

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Other Sites

Site Name	City	Country	Status
Consorci Mar Parc De Salut De Barcelona	Barcelona	Spain
Pjex Tdrom Hjrahtqn Ujpqsguusnbw	Sabadell	Spain

Trial status

Country	Status	Recruitment Start
Spain	Recruiting	01.12.2025

Trial locations

Investigated drugs:

2-[4-[3-(METHYLAMINO)-1-PHENYLPROPOXY]PHENYL]ETHANOL HYDROCHLORIDE

CTH120 is an investigational medication being studied for the treatment of Fragile X syndrome in adult men. This is an experimental drug that is being tested to see if it is safe, well-tolerated, and effective for people with this genetic condition. In this trial, CTH120 will be compared to a placebo to evaluate how well it works and what side effects it may cause.

Fragile X Syndrome – Fragile X Syndrome is a genetic condition that affects brain development and function. It is caused by a change in a specific gene called FMR1, which leads to reduced or absent production of a protein important for normal brain development. People with this condition often experience learning difficulties and intellectual disabilities of varying degrees. They may also have challenges with behavior, including anxiety, hyperactivity, and difficulty with social interactions. Speech and language development is frequently delayed or impaired. Physical features may include an elongated face, large ears, and flexible joints, though these characteristics become more noticeable with age.

Trial ID:

2025-522972-97-00

Protocol code:

CTH-CTH120-FXS-01

Trial Phase:

Therapeutic exploratory (Phase II)

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Testing the Safety and Effectiveness of CTH120 Compared to Placebo in Adult Men with Fragile X Syndrome

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?