Together we can light the way for Facioscapulohumeral Muscular Dystrophy (FSHD) research.

If you are an adult living with Facioscapulohumeral Muscular Dystrophy (FSHD), consider joining the FORTITUDE™ study to evaluate an investigational drug that treats the underlying cause of FSHD.

About the Study

The FORTITUDE™ study will evaluate the safety, tolerability, and effectiveness of a new investigational medication in eligible individuals with FSHD.

What to Expect

Participants will be enrolled in the FORTITUDE™ study for approximately 13.5 months, including screening. An Open-Label Extension study is also planned.

Study Locations

This study will take place at multiple clinical sites in several countries. Click here to view our map and find a participating site location near you.

Who Is Eligible to Participate in This Study?

You or a loved one may qualify if you or they:

  • Are 18 to 65 years old
  • Have been diagnosed with FSHD
  • Are able to walk 10 meters with or without assistive devices; if you require 2 canes or a walker to walk 10 meters, you would not be eligible
  • Have not been diagnosed with congenital or infantile FSHD
  • Are not pregnant, breastfeeding, or planning a pregnancy in the next 1-2 years

Additional requirements to participate will apply. A study representative will discuss them with you during the Screening Visit.

What is Facioscapulohumeral Muscular Dystrophy (FSHD)?

FSHD, also known as facioscapulohumeral muscular dystrophy, is a rare condition that affects the muscles. It gets worse over time and can make it hard to do daily activities like throw a ball or drink from a straw.

People with FSHD have a genetic abnormality that causes DUX4 protein to be present in their skeletal muscle when it should not be. This abnormal expression of DUX4 leads to a series of downstream events that result in muscle wasting and decreased muscle function. Researchers think that one approach to treating FSHD could be to reduce the expression of the DUX4 mRNA and the DUX4 protein. It is thought that reducing the DUX4 protein in the muscle cell could disrupt the path for muscle wasting in FSHD.

FSHD is not very common, and it progresses slowly. This means that for some people, the symptoms may not appear for a long time or may not be very severe. However, it can vary from person to person.


Common symptoms may include:

  • Facial weakness
  • Abdominal muscle weakness
  • Hip weakness
  • Lower leg muscle weakness
  • Shoulder, back, and shoulder blade weakness
  • Joint and spinal abnormalities
  • Soreness of the muscles
  • Problems with eyes
  • Unequal (nonsymmetrical) weakness

About the FORTITUDE™ Study

The FORTITUDE™ study was designed in partnership with patients, caregivers, advocates, and key physicians in the field to ensure we are best meeting the needs of the FSHD community; and is focused on finding out how safe the investigational study drug is for treating FSHD in adults. The study will also look at the effectiveness of the study drug compared with a placebo on measures of muscle strength, function, and composition.

This Phase 1/2 study is also evaluating the effect of the study drug on expression of DUX4 in muscle.

What to Expect During the FORTITUDE™ Study

To participate in this study, participants will be asked to read and sign an Informed Consent Form (ICF).

The form explains:

  • The purpose of the study
  • Required study visits and procedures
  • Potential risks and benefits of participation
  • Confidentiality
  • How participant and caregiver personally identifiable information will be used
  • Information on how to withdraw from the study

Approximately 70 FSHD patients will take part in the FORTITUDE™ study in several countries around the world. After confirming eligibility, participants enrolled in the study will be randomly assigned to the investigational drug or placebo.

Two (2) out of every three (3) participants will receive the investigational study drug while the remainder will receive the placebo, both through intravenous infusions given approximately every 3 months.

The study is blinded, meaning that neither you nor the study team will know which study treatment you are receiving.

Safety is our top priority, and that’s why study teams will keep a close eye on all participants in the study. We’ll make sure participants are doing well through various procedures and checks. Some of the required procedures include:
  • Health Questions
  • Physical Examinations
  • Vital Signs
  • Pregnancy Testing
  • Blood and Urine Sample Collections
  • Electrocardiogram (ECG)
  • MRI
  • Muscle Needle Biopsies
  • Muscle Strength Testing

Participants will be enrolled in the FORTITUDE™ study for approximately 13.5 months, including screening.

Each Participant will take part in a screening period of up to 6 weeks, followed by a study treatment period of approximately 9 months, and a 3-month Post-treatment Follow-up.

Avidity Biosciences is also planning an Open-Label Extension (OLE) study, in which all participants will receive active study medication for an ongoing period.

Participants who do not immediately take part in or decline the OLE will be followed for another 6 months in an Extended Follow-up Period.

Travel support and reimbursement for the participant and a caregiver will be provided while participating in the study.

Frequently Asked Questions

What is the purpose of a clinical trial?

The main purpose of a clinical trial is to gather information on the safety and efficacy of an investigational medication. The data collected during the trial helps to determine whether the investigational medication should be approved for general use and can also provide essential information on potential side effects and risks.

Why participate in a clinical trial?

Participation in clinical trials has greatly impacted the health and well-being of many individuals. People participate for several reasons, including the desire to be more involved in their own healthcare, the opportunity to try new and innovative therapies before they become widely available, and making a positive impact on the advancement of medical science and the health of future generations.

Will I be compensated for participating in a clinical trial?
Many clinical trials offer reimbursement for participation, which can help to cover the costs associated with the trial such as transportation and time off work. It’s important to ask about reimbursement for time and travel and what expenses will be covered before deciding to participate in a clinical trial.
What is an investigational medication?
An investigational medication has not been approved by regulatory authorities but is allowed to be administered to people for research purposes to understand if it might be a safe and effective treatment for a specific disease.
What is a placebo?
In this study, the placebo is something that looks like the investigational medication but does not contain any active ingredients.
What are my rights as a participant and what will happen if I decide not to participate?
It is your choice to take part in this research study or not. You can change your mind and stop participating at any time. If you choose to stop, you may be able to still receive care at the clinic. If you’re thinking about stopping or want more information, please talk to the study doctor.
What are my responsibilities while participating in this study?
If you decide to take part in the study, you will be expected to follow the rules and instructions given to you by the study team. If you can’t follow these rules and instructions, you may be asked to leave the study. The study will be closely monitored by the study doctor and will be carried out by trained staff. You will need to share information about your health, both now and in the past, to protect your safety.

It is also recommended that you let your regular doctor know that you’re participating in this study.

How can I learn more about the investigational medication and this study?
More information on this clinical trial can be found on

Where We Are

Study Site Locations

Current study locations are listed below and more may be added at any time. If you are interested in participating in the FORTITUDE™ study, contact the site nearest you to learn more. If you don’t see a site near you but would be willing to travel, travel assistance may be made available for participants and their caregivers.

      For interested participants or caregivers:

      For more information on this study please visit

      To share this study by email, click here.

      For physicians and healthcare providers:

      Are you a physician looking to refer a patient to the FORTITUDE™ study?

      Please contact a study representative at for more information.