What is the most important information that you/your child should know about ELEVIDYS?

1. Rapid serious liver injury and rapid liver failure. ELEVIDYS can increase certain liver lab test levels and cause rapid serious liver injury, rapid liver failure, and death. Complication of blood clots in the blood vessel in the abdomen that helps carry blood from the intestines to the liver has happened. Patients with preexisting liver problems may be at higher risk.
   • You/your child will receive oral corticosteroid medication before and after ELEVIDYS infusion and will need weekly blood tests to monitor liver function for 3 months or longer after treatment.
   • For at least 2 months following ELEVIDYS infusion, stay close to a healthcare facility that your/your child's doctor recommends.
   • Contact your/your child's doctor immediately if your/your child's skin and/or whites of the eyes appear yellowish or if your/your child misses a dose of corticosteroid or vomits it up.
2. Serious Infection. Because you/your child will be taking corticosteroids as part of ELEVIDYS treatment, this may lower the ability of your/your child's immune system to fight infections and make it easier to get an infection. Getting an infection (like a cold, flu, stomach flu, ear infection, chest infection) before or after ELEVIDYS infusion could lead to more serious health problems, including death. Contact your/your child's doctor right away if you notice any signs of infection such as:

   coughing wheezing sneezing

   runny nose sore throat fever

   • Vaccinations should be completed at least 4 weeks before starting the corticosteroids that are part of the ELEVIDYS treatment.
   • ELEVIDYS should not be given if you have/your child has an infection.
3. Inflammation of the heart muscle (Myocarditis). Serious and life-threatening inflammation of the heart muscle has happened following ELEVIDYS infusion. In individuals who develop inflammation of the heart muscle after receiving ELEVIDYS, they may be at a higher risk of serious complications if they already had a heart condition that has affected how well the heart pumps.
   
   You/Your child will need weekly blood tests for a heart protein that can detect damage to muscle cells in the heart (troponin-I) for the first month after ELEVIDYS infusion. Contact your/your child's doctor right away if you notice:

   chest pain

   trouble breathing or shortness of breath

4. Infusion-related reactions. Reactions from the infusion, including serious allergic reactions, may happen during or after ELEVIDYS infusion. Contact your/your child's doctor right away if you notice:

   fast heart rate fast breathing swollen lips shortness of breath nostrils widening hives

   red and blotchy skin itchy or inflamed lips rash vomiting nausea chills fever

5. Immune response affecting muscles (Immune-mediated myositis). Immune response affecting muscles, including serious and life-threatening reactions, has happened in patients about 1 month after receiving ELEVIDYS infusion. Contact your/your child's doctor right away if you notice:

   Unexplained increased muscle pain Tenderness

   Weakness, including trouble swallowing, breathing or speaking

What are the possible side effects of ELEVIDYS?

• ELEVIDYS can cause serious side effects. See “What is the most important information I should know about ELEVIDYS?”
• The most common side effects in individuals treated with ELEVIDYS include:

  vomiting nausea liver injury fever

  lower number of platelets, which is a kind of blood cell that helps you stop bleeding higher levels of heart protein that can detect damage to muscle cells in the heart (troponin-I)

• Avoid taking new medications that are known to damage the liver as this may make liver problems worse. Tell your doctor about all the medicines you/your child takes, including prescription and over-the counter medicines, vitamins, and herbal supplements.
• Discuss with your/your child's doctor before receiving a vaccine after ELEVIDYS treatment.
• Avoid missing any dose of corticosteroids. Contact your/your child's doctor immediately if this happens.