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IMPACT-FXS clinical trial

Fragile X syndrome (FXS) is a rare neurodevelopmental condition and the most common genetic cause of learning difficulties in the world, but there are currently no effective or approved therapies for the condition available.

Our IMPACT-FXS clinical trial

We are sponsoring a Phase 2 clinical trial (clinicaltrials.gov identifier NCT04823052) to explore the safety and efficacy of several potential medications for fragile X syndrome. The IMPACT-FXS study (which stands for Investigating Multiple Pathways And Combined Treatments for FXS) is the world’s first umbrella trial for the investigation of therapies for FXS, and will evaluate several compounds first as monotherapies and then as combination therapies in order to identify the best medication. Check your eligibility with our quick questionnaire.

What is the aim of the study?
This first phase of this research study will test two investigational medications (HLX-0201 and HLX-0206) in 13- to 40- year-old boys and men with fragile X syndrome (FXS). The purpose of this study is to test the safety and tolerability of the medications, and to see if they reduce symptoms of FXS.

What are the study procedures & duration?
Potential participants with FXS will be screened carefully for participation in the study. If selected, the participant will be randomly assigned to one of four groups: three treatment groups and one control group, which acts as a baseline for comparison.

This is a blinded study, which means neither the participant nor the study doctor will know which treatment the participant is receiving (although, in the event of a circumstance where a doctor needs to know which group a participant is assigned to, the study doctor will be able to find out what treatment they are receiving).

The study will take 14 weeks in total. During the study, procedures that participants will take part in will include cognitive and behavioural assessments, medical history, medication diaries, blood work and EEG (at some sites).

What are the good things that can happen from this research?
This research will examine candidate medications that could be new treatments for males with FXS to see if the medications are safe and have the intended effects.

HLX-0201 is a medication that has been approved in the US for indications other than FXS by the US Food and Drug Administration (FDA), an authority that regulates medicines. HLX-0206 is an investigational medicine that has been examined in a number of clinical trials involving children and adults for neurological conditions.

It is Healx’s hope that this study will lead to a better understanding of these study medications as potential treatments for FXS. The information gained in this study may be useful in treating other people diagnosed with FXS in the future.

What are the bad things that can happen from this research?
In a research study, not all of the risks or side effects may be known before you start the study. Everyone in the research study will be monitored continuously and carefully for side effects. Regular, biweekly visits, as well as an independent safety monitoring board will assure the close follow up of the participants.

Of note, HLX-0201 and HLX-0206 have known safety profiles: HLX-0201 has already been approved in the US and the EU for several decades, however in different indications than fragile X syndrome. Doses of HLX-0201 are confirmed as well tolerated with few adverse events reported. HLX-0206 has been tested in approximately 4500 people diagnosed with fragile X syndrome previously, where it was generally safe and well tolerated.

What are the eligibility criteria to take part in the study?

You may be eligible to take part if the following criteria apply to you:

  • Male
  • Fragile X syndrome suspected or already diagnosed
  • Between 13 and 40 years of age
  • Weight of 45kg or more
  • Willing and able to take oral tablets
  • Willing and able to travel to study sites
  • Not diagnosed with diabetes mellitus type 1 or type 2

Other criteria might prevent you from being allowed to participate in the study (e.g. diagnosis of other conditions or current use of certain medication). Take our survey to see if you're eligible.

Where is the trial taking place?

Across several sites in the United States.

Not yet recruiting
Children’s Hospital Colorado (Aurora)
Rush University
Medical Center
University of Massachusetts
Chan Medical School
Emory University School of Medicine (Atlanta)
Icahn School of Medicine (New York)
University of Miami (Miami)
Kennedy Krieger Institute (Baltimore)

Where can I learn more?

If you are interested in participating in the IMPACT-FXS trial, please click below to find out whether you qualify for the study.

Background to the trial

The science behind our FXS programme

We use artificial intelligence (AI) and machine learning algorithm methods, as well as in-house drug discovery expertise and patient group insights, to identify novel therapeutic opportunities from known compounds. This enables us to rapidly progress therapies to patients.

HLX-0201 was identified as a potential therapy for FXS by one of our proprietary drug discovery methods, Drug-Gene Expression Matching (DGEM). DGEM compares the gene expression profile for a disease with the gene expression profiles from our curated drug database to identify entirely novel connections between the two. The method works on the premise that a drug mechanism with the opposite mechanism profile to a disease would be a strong candidate for an effective treatment. HLX-0206 was identified as a potential combination partner to HLX-0201 by our proprietary combination prediction methods.

Several other compounds identified by our AI methods are currently being progressed through preclinical validation to uncover possible combinations and novel mechanisms of action. These compounds will join the umbrella study in the coming months.

Throughout the drug discovery phase we worked closely with a number of patient groups who contributed invaluable disease expertise, connections with fragile X researchers and a process for preclinical and clinical validation.


Where can I learn more?

If you are interested in participating in the IMPACT-FXS trial, please click below to find out whether you qualify for the study.

About fragile X syndrome

What is fragile X syndrome?

Fragile X syndrome is a rare neurodevelopmental condition and the most common inherited cause of learning difficulties in the world, affecting roughly 1 in 4,000 males and 1 in 8,000 females.

It is caused by a fault in the FMR1 gene, which is responsible for making a protein (FMRP) that is needed for normal brain development. In patients with fragile X syndrome, the protein isn’t made and the brain doesn’t develop as it should.


Affects 1 / 4,000 males
and 1 / 8,000 females


Caused by a DNA repeat in FMR1 gene (X chromosome) that means a protein required for normal brain development isn’t made


There are no approved treatments but there is medication to minimise certain symptoms


Common symptoms of fragile x include intellectual disabilities; attention deficit and hyperactivity; anxiety; speech delays; and sensory integration problems.


Where can I learn more?

If you are interested in participating in the IMPACT-FXS trial, please click below to find out whether you qualify for the study.


US patient groups

FRAXA Research Foundation
National Fragile X Foundation


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Where can I learn more?

If you are interested in participating in the IMPACT-FXS trial, please click below to find out whether you qualify for the study.


We are excited about the potential of HLX-0201: a proven, safe drug with a long track record of effectiveness. It never would have occurred to us to investigate the compound for fragile X without Healx’s innovative technology pointing us in the right direction, but the preclinical studies have shown remarkable effectiveness.

Dr Mike Tranfaglia
Chief Scientific Officer and Co-Founder, FRAXA Research Foundation