As well as being a clinical observational study (which is designed to study how HD happens in humans and is not testing any drugs), Enroll-HD is also a clinical research platform; this means that smaller clinical studies that are looking into certain aspects of HD in people are also connected to Enroll-HD, and these studies often use the same clinical sites and recruit people already participating in Enroll-HD. These studies might be exploring factors that influence the health of people with HD, or investigating a better way to measure the changes caused by the disease, or collecting extremely valuable research resources like cerebrospinal fluid that can give us a clearer picture of what is happening in an HD brain. When you sign up for Enroll-HD, you can choose to be contacted by your local site staff should suitable research opportunities like this become available that are looking for volunteers like you.

You may also have the chance to join a clinical trial, which usually test novel drugs to see whether they can prevent or treat a disease in people; they are sometimes called “interventional” trials, meaning that the drug being tested is a medical intervention. (These interventional trials are different from “observational” studies like Enroll-HD, which is designed to study how HD happens in humans and is not testing any drugs).

If a pharmaceutical or biotechnology company has a new HD drug that requires clinical testing in people, they usually come to Enroll-HD to help identify which clinical sites around the world are best suited to their trial. Part of this process will involve the investigators at each clinical site looking through the Enroll-HD database for people who have already said they are willing to be contacted about clinical trials. If you have agreed in your consent form to be contacted and you have the right characteristics for the trial (which will be different for each one), your neurologist or another person at the site where you get care will contact you to see if you are interested in taking part. Nobody outside your local clinical site where you go for your Enroll-HD visits will be able to see any identifying information such as your name, address or birth date.

Volunteering for any study or trial is completely up to you and is always your choice. Whatever choice you make, it won’t affect your care—you can still be part of Enroll-HD even if you don’t want to join other studies or trials.

A clinical trial is the gold-standard way to systematically test whether a new drug can provide clinical benefit to people, meaning can the new drug prevent or treat a disease in people. They are sometimes called “interventional” trials, meaning that the drug being tested is a medical intervention. (These interventional trials are different from “observational” studies like Enroll-HD, which is designed to study how HD happens in humans and is not testing any drugs). Clinical trials often test drugs, but some other kinds of treatments (such as exercise and physiotherapy regimens, or surgical procedures like deep brain stimulation) may also be tested this way.

No matter how well a new drug (or even a drug already approved for another disease) seems to work in animal models of disease, that drug needs to be tested in a large group of people to test whether it also works in humans and to find out what side effects it might cause. Since humans and animal models are very different, most potential new drugs tested in clinical trials are not approved for various reasons. However, whatever the outcome of a trial, what we learn from these human trials is often extremely important for the next round of drug development.

The major reason why clinical trials often move more slowly than patients and families would like is that safety is absolutely paramount, lots of regulations are in place to make sure everything possible is done so that research participants are not harmed. This means mountains of paperwork to check that things are being done properly and within the strictly enforced rules and regulations, for very good reasons.

Another reason is recruitment; finding enough people at the “right” stage of their disease and who are willing to volunteer for a particular clinical trial is often difficult and time-consuming, especially for rare diseases like HD.

All clinical trials conducted in the US and Europe (including trials that have clinical sites in other parts of the world) must get approval from either the US Food and Drug Administration (FDA), the European Medicines Agency (EMA), or both. Similarly, almost all clinical trials are also overseen by local Institutional Review Boards (IRBs) that include doctors and scientists as well as community members. All trials involve some level of risk, that’s the nature of research, but the IRBs review the protocol that sets out how the study will be conducted to make sure that the risks are reasonable and in proportion to the potential benefit. If you decide to volunteer for a clinical trial, the informed consent form that you sign before you begin will clearly spell out the potential risks and benefits—you should discuss these and any other questions with your doctor and other health professionals.

Not necessarily. Most trials don’t include complete medical care—you will still go to your regular doctors. Also, while sometimes the drug being tested is a real improvement over current alternatives, it may turn out not to be very effective, or it may cause side effects.

You should find out whether you will have to modify your current medications, and who will be responsible for your health care. It’s good to know at the outset how long the study is expected to last, although you always have the right to withdraw from any trial or study at any time for any reason.

You might ask why the research team thinks this treatment will be effective, or whether it’s been studied before. Another good question might be, if the experimental medicine works for you, will you be able to keep getting it after the study is completed?

The US National Institutes of Health has more comprehensive lists of questions you might consider asking (NIH Clinical Trials; NIH Clinical Trials and You). The UK Medical Research Council also provides more information about clinical trials.