Clinical research is medical research involving people. In summary, clinical research is carried out in order to provide scientific evidence for the safety, and efficacy of a drug or an intervention (for instance medicine, dietary supplements or other non-drug therapies). There are two different types of clinical research:

1. Interventional Trials

A clinical interventional trial tests either a new drug or a non-drug therapy (exercise or diet) to see if it can improve symptoms or stop the disease. It is set so some volunteers get the drug, others get an inactive pill (placebo). Both groups are monitored to see who does better.

2. Observational Trials

A clinical observational trial, like Enroll-HD, usually just takes measurements to explore how a disease changes over time and what affects the health of people with a particular disease. There is no drug being tested.

How are the trials and studies done?

Everyone who wants to conduct a trial or study needs approval from the authoroties and ethic committees.  Drug trials performed in Europe needs approval both from the European Medicines Agency and from the ethic committees in each country where there are participants.  These authorities are responsible for vetting the risk/benefit ratio of the trial – their approval does not mean that the therapy is ‘safe’ or effective, only that the trial may be conducted.

Depending on product type and development stage, investigators initially enroll volunteers or patients into small pilot studies and subsequently conduct progressively larger scale comparative studies. Clinical trials can vary in size and cost, and they can involve a single research center or multiple centers, in one country or in multiple countries. Clinical study design aims to ensure the data collected in the study holds high standards and measure the potential effect – positive, negative or no effect – in a scientifically sound way.  The procedures has to be publicly available to allow independent evaluation of the reported results.

Phase I

Trials aim to test the safety of a new treatment.

They look at side effects of a treatment – for example, does it make people sick, raise their blood pressure and so on. Phase I trials involve only a small number of people, who are often healthy volunteers.

Phase II

Trials test the new treatment

Trials test the new treatment, usually in people who have the condition for which the treatment is to be used. This is to make sure the treatment is safe and has some effect on that condition. Phase II trials also help to find out what is the dose of treatment might be needed to be effective.

Phase III

Trials involve larger numbers of patients

Trials involve larger numbers of patients (hundreds or sometimes thousands), who are usually randomised to receive the new treatment or the best available current treatment (or sometimes a placebo). They aim to assess how well the new treatment works, and usually take longer than Phase I or II trials to run.

Phase IV

Trials are done after a drug has been approved

Phase IV Trials are done after a drug has been approved by drug regulatory authorities. They are carried out to gather information on the drug’s effect in various populations and any side effects associated with long-term use.


To learn more about how medicines are approved by the European Medicine Agency (EMA), Please click on the button below.


Learn about the stages and types of clinical trials. Find also the frequently asked questions (FAQ) about Huntington’s studies.


Without clinical trials, there can be no better treatments, no prevention and no cure for Huntington’s Disease. Scientists work constantly to find enhanced ways to treat diseases, but improved treatments can never become a reality without testing in clinical trials with human volunteers. Individuals with HD are urgently needed to participate in the ongoing enrolling clinical trials focused on HD. In some studies, those who are at risk, caregivers and healthy volunteers are also needed. Recruiting and retaining trial participants is now the greatest obstacle, other than funding, to developing the next generation of HD’s treatments.

By participating in clinical research, you can help to accelerate progress and provide valuable insight into potential treatments and methods of prevention.

Benefits of clinical trials
Participating in clinical trials has the potential to help both the individual participant and other individuals who have HD or are at risk of developing it:

  • You can play a more active role in your own health care.
  • You can gain access to potential treatments before they are widely available.
  • You can receive expert medical care at leading healthcare facilities — often free of cost — while participating in important medical research.
  • You can help future generations by contributing to HD research.

Risks of participation
Patient safety is the most important aspect of every HD clinical trial. The procedures for each study are reviewed by an expert committee not directly involved in the trial, helping ensure that patient safety is protected.

There are risks, however, when participating in clinical trials:

  • There may be unpleasant or even serious side effects related to the potential treatment(s) being studied.
  • The experimental treatment may not be effective.

Details of risks related to participation in the clinical study are spelled out in the consent form participants (or their proxies) sign when they agree to participate.

Reasons for optimism
No new treatment advances to the clinical testing phase unless there is strong evidence indicating it will be as effective as, or more effective than, currently available therapies. Every clinical trial contributes valuable knowledge, whether or not the treatment works as hoped.

Participating in clinical studies gives us optimism for today and promise for the future. They provide many participants with access to cutting-edge treatments and expert medical care. And some day they will lead us to the end of HD.

Participants receive a high standard of care
All participants receive regular care related to the trial and opportunities to talk to clinical trial staff. Research shows that people living with the disease who are involved in clinical trials tend to do somewhat better than people in a similar stage of their disease who are not enrolled in clinical trials, regardless of whether the experimental treatment works. Scientists believe this advantage may be due to the general high quality of care provided during clinical trials.

Don't just hope for a cure. Help us find one.
Volunteer for a clinical trial.