Clinical Trials

What is a Clinical Trial

Research relies on volunteers to help answer specific questions about a disease or to test a specific treatment.

Observational studies such as PREDICT–HD and ENROLL–HD (coming soon) study new ways to diagnose or observe the natural course of the disease. No drug or treatment is tested.

A clinical (or interventional) trial investigates whether supplement, currently approved drug, new experimental drugs or other treatments is safe, tolerated and effective.

Once a drug is ready to test in people, it must go through three stages of clinical trials. 

Phase One Trials

In Phase I, a small number of volunteers are given the drug and closely monitored to see whether the drug is safe and well-tolerated.

Phase Two Trials

Phase II involves more volunteers and focuses on finding the correct dose. Safety and tolerability continue to be monitored. 

Phase Three Trials

 Phase III involves a still larger group - several hundred in HD research. Volunteers are randomly assigned to either the treatment group or a control group who receives a placebo. The study is double blinded - neither the subjects nor the researchers assessing them will know who received the compound and who received a placebo until the end of the study. Phase III takes much longer since enough time must pass for differences in disease progression to emerge between the treatment group and the control group, assuming the treatment is effective.

If the results show that a compound is safe, well tolerated and effective, the FDA will be requested to approve the compound for clinical use. Because HD is a serious disease without a cure, the FDA may fast track its evaluation, taking about six months to review and make a decision.

Observational Trials

Observational trials are critical to the effort to get effective treatments to patients.  Huntington's Disease proceeds slowly; it may take two or more years for differences to be observed clinically between the treatment group and the control group.  Observational trials are underway to discover more sensitive outcomes measures such as a biomarker or cognitive test that could serve as surrogate endpoints to shorten clinical trials and make treatments available to patients more quickly.


Questions to Consider Asking Before Enrolling in a Clinical Trial

• What is the purpose of the trial?
• Does it involve a placebo or a treatment already available? What are my chances of being assigned the placebo?
• How long will the trial last; what will I be asked to do?
• What is already known about the trial intervention?
• Is there reimbursement for travel/other expenses?
• Will I be able to see my own doctor?
• Can I continue the drugs or supplements that I am currently taking?
• If the intervention works for me, can I keep taking it after the trial?
• Can anyone find out that I’m part of a clinical trial? How will my information be kept confidential?
• Will I receive follow up care afterwards?

Why Volunteer for a Trial?

As a Volunteer You Have –

• Access to new research and treatments.

• More time with clinicians familiar with HD.

• Opportunity to continue taking the drug for a specific period of time after the trial ends.

• Contribute to medical research.

• Provide HOPE for yourself and others.

The HD gene was found because hundreds of HD family members participated in research. There is a critical need for volunteers to take part in trials so the HD community can learn if treatments are safe and effective.

About Clinical Trials

Why is Rapid Recruitment Important?

The longer it takes to complete a treatment or drug trial, the longer it takes for a drug to be approved and placed on the market.

More research can be conducted if trials are completed faster because faster trials cost less money.

Phases of Clinical Trials Each phase is a different test of the drug, supplement or treatments effectiveness and ensures the safety of study participants. There are 4 phases in the drug development process:

• Phase 1: A small group of participants tests the safety of the drug, supplement or treatment.

• Phase 2: A larger group of participants tests the supplement, drug or treatment for safety and best dosage.

• Phase 3: A larger group of participants tests the effectiveness of the supplement, drug or treatment. These trials are usually longer and require more volunteers.

• Phase 4: “after marketing study.” Companies collect data on safety and effectiveness after the drug has been approved by the FDA and is on the market.

Who Can Participate?

Every trial has a specific set of criteria that is used to determine who is eligible to participate and who is not. Some aspects that may factor into eligibility are: gene status and stage of disease, age, other medications that a person may be taking, or other medical and psychiatric conditions that might affect the trial.

Why are So Many People Needed?

The number of participants required depends on the question the trial wants to answer. It is important that the trial show results that could not have occurred by chance alone. Statistics are used to find the minimum number of people needed to answer the scientific question.

What is Informed Consent?

This document explains details about the study such as its purpose, duration, procedures, risks and potential benefits, likelihood of being placed in the active treatment group vs. placebo group, reimbursement, and confidentiality. Informed Consent is not a contract; a person can withdraw from a trial at any time.

What is Trial Protocol?

Protocol is the research plan for the study. It outlines who can participate and safeguards the health of participants. It also allows researchers at multiple locations to perform the trial in exactly the same way.

Privacy and Confidentiality

Confidentiality is a prime concern. Participants’ identity and medical information is known only to the trial site personnel and NOT to anyone else involved in the study.

What Happens When the Trial Ends?

Some drug development trials allow participants to continue to take the investigational drug for a specific period of time.

As a participant, after the study is published, you can also learn whether you were assigned to the active drug or the placebo group.



Where to find information about clinical and observational trials

Sign up for confidential email notices here:

Visit these websites for detailed information:

HDSA's Ongoing Clinical Trials Section
Huntington Study Group

HDSA Clinical Trials Diplomat Program: HD family members advancing the message of research and hope


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Learn how you can participate in clinical trials - National Institutes of Health