Clinical studies cover any form of research involving people. This includes observational studies, to understand more about a muscle-wasting condition and how it progresses (its natural history), and clinical trials, to assess the safety and effectiveness of specific interventions. These interventions could be medical products, for example, drugs or devices; medical procedures, such as a type of surgery; or changes to a person’s lifestyle, such as an exercise regime.

As with any experiment, researchers design clinical trials to answer specific research questions. After reviewing what is already known about the drug or intervention, from preclinical studies or previous trials, researchers will develop a specific plan or protocol, outlining:

  • who can take part (eligibility criteria – often called inclusion and exclusion criteria)
  • how many people are needed at each stage to ensure robust data collection
  • how long the study will last
  • whether or not there will be a control group (to limit bias)
  • how the treatment will be administered and at what dosage
  • what will be measured (outcome measures) and when
  • how the data will be reviewed and analysed.

We’ve put together some frequently asked questions to help you understand the process of clinical trials. If you have further questions, please contact Dr Sofia Nnorom on 020 7803 4813 or email research@musculardystrophyuk.org


Clinical trials typically follow a series of stages, or phases:

  • Phase 1
    Aims to assess the safety of a treatment. Phase 1 trials involve a small number of people, who are often healthy volunteers. However, in the case of genetic therapies, these trials are carried out in people with the condition. The researchers adjust dosing schemes based on preclinical data from animals, to find out how much of a treatment the body can tolerate and what its potential side-effects are.
  • Phase 2
    Aims to assess the safety and effectiveness of a treatment. This may be the first time of testing it in people who have the condition that the treatment is intending to treat. Researchers may divide participants into groups – one of which will receive the optimal dose, the other of which will receive a different dose or a placebo (an inactive substance designed to resemble the treatment being tested).
    Phase 2 trials are sometimes divided into phase 2a and phase 2b. Phase 2a is specifically designed to determine the best dose of the drug. Phase 2b is specifically designed to study how well the drug works at the dose determined in the phase 2a study.
  • Phase 3
    Often referred to as the ‘confirmatory’ phase, phase 3 aims to prove the effectiveness of a treatment in people with the condition. Researchers will usually compare the new treatment against the current standard treatment (if one exists). These trials not only take much longer than phase 1 or 2 trials, but are also much larger, often involving people from multiple centres across the world.
  • Phase 4
    Also known as ‘post-marketing surveillance’, these studies may take place after the regulatory authorities have approved the treatment. They give information about the long-term risks and benefits of the treatment in a much larger patient population, many of whom may also be receiving treatment for other conditions. This helps to identify the risks and benefits in a ‘real world’ situation.

Some clinical trials may fall in two of these phases. For example, you may see phase 1/2 trials, which aims to identify the highest safe dose, and also how well that dose works.


People have different reasons. Some would like the opportunity to potentially benefit from new treatments before they become more widely available. However it’s important to remember that there are risks with taking part (see below). In addition, some trials are designed with a placebo arm, which means that some participants don’t actually receive the treatment being tested.

Another potential advantage is that people taking part in clinical trials are often followed up regularly and are closely monitored, even after the trial has finished. This close attention could result in better management of the condition.

Other people may feel that by taking part, they are ‘doing their bit’ to advance science and potentially help others in future. Participating in a clinical trial may not only help to accelerate the development of new treatments but could also improve our knowledge of muscle-wasting conditions.


Many people are understandably eager to take part in clinical trials. However it is very important to understand exactly what is involved in a particular trial and the potential risks associated with a new treatment. You should discuss the study in detail with the trial nurse or doctor before giving consent to take part.

A potential disadvantage is that studies often involve multiple and frequent visits to hospital. This is not always easy or practical and can have an impact on the whole family. Procedures could be painful, for example injections and biopsies and, of course, there is always the risk of an adverse reaction to the treatment.

Participants in a trial also have to keep in mind that the treatment they receive might not provide any direct benefit for them – there is a chance they might be given a very low dose of the drug, or even a placebo. In addition, participants should be aware that taking part in one clinical trial may affect their chances of taking part in a future clinical trial. This should be discussed with members of your healthcare team prior to enrollment.


All clinical trials have guidelines about who can take part. The factors that allow someone to participate in a clinical trial are called ‘inclusion criteria’ and those that disallow someone from participating are called ‘exclusion criteria’. These criteria are based on such factors as age, gender, the type and stage of a condition, previous treatment history, and other medical conditions. Before joining a clinical trial, a participant must qualify for the study.

Inclusion and exclusion criteria are not used to reject people personally, instead they:

  • Keep the participants safe, for example another underlying condition could make participation in the trial dangerous.
  • Help ensure that the researchers are able to produce reliable results and therefore get the treatment to market as quickly as possible so that the wider population can benefit.
  • Increase the reliability of the results by ensuring that everyone taking part has similar symptoms at the beginning of the trial. Otherwise it is difficult for the researchers to interpret the results because they won’t know if the reason one patient responded to treatment and another didn’t is due to the drug or differences in their condition to begin with. This is especially helpful in the early phases of a clinical trial when there are only few participants.

In most circumstances, people who wish to participate in a clinical trial will find it easier if they live relatively near the team of people who are conducting the research, because they need to be monitored frequently. Some studies provide financial support for travel costs; you can ask the clinical trial team if these resources are available.


You should know as much as possible about the clinical trial and feel comfortable asking the members of the healthcare team questions about it. Please see here for a list of questions you may like to ask members of your healthcare team prior to enrollment.


For more information about participating in a clinical trial, please visit our Taking Part page.


In partnership with Action Duchenne, Muscular Dystrophy UK is funding the UK part of the UNITE DMD project. This four-year project is an international collaboration working towards the first UK gene therapy clinical trial for Duchenne muscular dystrophy. We are also funding several observational studies, including the largest natural history study for Duchenne muscular dystrophy, named NorthStar.

In the past we have funded a clinical trial to test a new drug for people with McArdle’s disease as well as a clinical trial that looked into the long-term benefit of Vitamin C for people with Charcot-Marie-Tooth disease.

In addition to the studies funded directly through our research programme, we provide administrative and managerial support for the setting up of clinical trials. These include clinical trial co-ordinators, who help with the setting up and running of clinical studies at a particular centre. They are responsible for ensuring that the research takes place within regulatory guidelines as well as the specifications outlined in the trial protocol. Muscular Dystrophy UK currently funds two clinical trial co-ordinators at the muscle centres in Newcastle and London.

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