Duchenne muscular dystrophy (DMD) is a genetic condition caused by a change, or mutation, in the DMD gene. This gene normally tells the body how to make dystrophin, a protein that helps protect muscles during everyday movement. When dystrophin is missing, muscles are more easily damaged and become weaker over time.
There is currently no cure for DMD, but medicines are available that can help manage symptoms, slow muscle damage, and support muscle function. Because of treatment advances, people with DMD are living longer and maintaining better function than in the past.
Viltepso (viltolarsen) is a prescription medicine used to treat DMD in people who have a specific type of genetic mutation. The FDA approved it in 2020. It is designed to increase dystrophin production in skeletal muscle. Keep reading to learn more about how Viltepso works for DMD.
Is Viltepso Right for Me?
Genetic testing is needed to confirm whether Viltepso is an option for you. Viltepso is approved to treat DMD in people who have a confirmed mutation in the DMD gene that can be treated by exon 53 skipping. Around 8%-10% of people with DMD have a mutation that can be treated by exon 53 skipping.
Your health care provider will also review your overall health and medical history. Before starting Viltepso, your health care provider will order blood and urine tests to check your kidney health. These tests help make sure whether it is safe to begin treatment.
How Does Viltepso Work for DMD?
Viltepso works using a treatment approach called exon skipping. The DMD gene is very large and is made up of many sections called exons. These exons act like instructions that tell the body how to build the dystrophin protein. In people with DMD, one or more of these exons are missing or damaged. Because of this, the body cannot make functional dystrophin, which leads to ongoing muscle damage.
Viltepso is meant for people with a DMD mutation that can be helped by skipping exon 53. This means the body is guided to ignore, or skip over, exon 53 when it reads the gene instructions. By skipping this section, the remaining exons can line up in a way that allows the body to make a shortened (truncated) version of dystrophin.
The dystrophin made with Viltepso is not perfect. But it can work well enough to help protect muscle cells and may slow muscle damage. Even a small increase in dystrophin can be meaningful for people with DMD.
How Is Viltepso Given?
Viltepso is a once-weekly IV infusion given by a health care professional. It can be given at a treatment center or at home, depending on what works best for you. Each infusion takes about 60 minutes.
During treatment, you will get regular blood and urine tests to monitor how well your kidneys are working. This is important because Viltepso can affect the kidneys in some people.
Urine samples are usually collected before an infusion or at least two days after the infusion. Your health care provider will review these results and let you know if any changes to monitoring or treatment are needed.
How Was Viltepso Studied for DMD?
Viltepso was studied in a clinical study to check how well it increased dystrophin levels in people with DMD who had a genetic mutation treatable by exon 53 skipping.
The study included boys who had a confirmed DMD gene mutation that was treatable with exon 53 skipping. All participants were able to walk and were between 4 and 10 years of age. Everyone had been taking a stable corticosteroid regimen for at least three months before entering the study.
The study enrolled a total of 16 boys. (There were no girls in the study because DMD mainly affects males.) The median age of boys was 7 years. Most of the boys were White, and one was Asian. Most were not Hispanic/Latino, one was Hispanic/Latino, and one participant did not report their ethnicity.
The study was conducted at multiple sites in the United States and Canada and took place in two phases:
- First four weeks: Participants were randomly assigned to receive either Viltepso or a placebo (no medicine in it). No one knew which treatment they were given during this period.
- Next 20 weeks: All participants received Viltepso once weekly. Half of the boys received a lower dose (40 milligrams [mg] per kilogram [kg] of body weight), and half received a higher dose (80 mg/kg).
The main goal of the study was to measure the change in dystrophin levels in muscle tissue. Muscle biopsies were taken from the biceps muscle before treatment began and again after 24 weeks of treatment (week 25). The tissue samples were tested to measure how much of the dystrophin protein was present. Results were reported as a percentage of normal dystrophin levels seen in people without DMD.
What Are the Main Benefits of Viltepso Based on Studies?
At the start of the study, muscle biopsies showed very little or no detectable dystrophin in all participants. After receiving Viltepso treatment for about six months, all participants showed an increase in dystrophin levels in their muscle tissue.
At week 25, when researchers compared dystrophin levels before and after treatment:
- In the lower-dose group, average dystrophin levels increased from 0.3% of normal at baseline to 5.7% of normal. This is an increase of 5.4 percentage points.
- In the higher-dose group, average dystrophin levels increased from 0.6% of normal at baseline to 5.9% of normal. This is an increase of 5.3 percentage points.
These increases were statistically significant in both groups, meaning they were unlikely to be due to chance
Overall, the study showed that Viltepso increased dystrophin production in skeletal muscle in patients with DMD who had a mutation treatable by exon 53 skipping. Individual results may vary.
Does Viltepso Offer Other Benefits Based on Studies?
Besides measuring dystrophin levels, researchers also looked at how treatment affected the participants’ movement and muscle function. They took measurements by testing the boys on various physical tasks, such as:
- How long it takes to stand up from lying on the floor
- How long it takes to run or walk a short distance or climb stairs
- How far a person can walk in six minutes
- Other tests to measure muscle strength
These results were compared with a similar group of boys with DMD who did not receive the treatment. The comparison data came from a large, long-term study that tracks how the disease typically progresses over time. The groups were matched by age and steroid use to make the comparison as fair as possible.
Over the 25-week study period, boys treated with Viltepso generally maintained or improved their physical abilities, while the comparison group showed worsening performance on most movement tests.
Key findings included:
- Running or walking 10 meters: Participants who received Viltepso moved faster at weeks 13 and 25, while the comparison group became slower over time.
- Six-minute walk test: Treated participants walked farther at week 25, while the comparison group walked much shorter distances than they had at the start.
- Standing up from the floor: Treated participants were able to stand slightly faster, while the comparison group took longer over time.
Other movement tests, including stair climbing and a standardized walking and movement assessment, showed improvement or stability in participants treated with Viltepso. However, the differences between the treated group and the comparison group were not large enough to be considered statistically significant for those measures. And tests that measured muscle strength directly did not show clear differences between treated participants and the comparison group during the study period.
Overall, these results suggest that treatment with Viltepso was linked to better movement and muscle function, compared with what is typically seen in people with DMD. However, these muscle tests were not the main goal, and the study was not designed to prove improvement in physical function. Still, the results help show how treatment may affect muscle function.
What Should I Know About the Long-Term Effectiveness of Viltepso?
The FDA approved Viltepso through a pathway called accelerated approval. This means approval was based on study results showing that Viltepso increased dystrophin production in skeletal muscle in people with DMD who have a mutation treatable by exon 53 skipping.
The accelerated approval pathway allows earlier access to medicines for serious conditions when early study results show a treatment is affecting an important biological marker, even if the full clinical benefit has not yet been confirmed.
Ongoing studies are being done to confirm whether the increase in dystrophin seen with Viltepso leads to meaningful long-term benefits for people with DMD.
What Can I Do to Prevent or Manage Side Effects of Viltepso?
Like other medicines, Viltepso can cause side effects. Not everyone will have the same effects, and many are mild or manageable. A health care provider can help monitor for side effects and suggest ways to reduce them.
In studies, the most common side effects reported with Viltepso included upper respiratory infections, reactions at the infusion site, cough, and fever. Some people also experienced bruising, diarrhea, vomiting, abdominal pain, or joint pain.
Infections and fever. Upper respiratory infections, such as infections of the nose and throat, were the most common side effects in Viltepso studies. You can manage these risks by washing your hands often, avoiding close contact with people who are sick, and reporting cold symptoms such as fever, cough, or congestion to a health care provider.
Infusion site reactions. Some people had reactions where the IV was given, such as redness, pain, or swelling. Let your health care provider know if this happens and bothers you. They may suggest an over-the-counter pain reliever or other comfort measures, such as using a cool compress.
Stomach-related side effects. Diarrhea, vomiting, or stomach pain were reported in some people. Encourage your child to drink plenty of fluids to stay hydrated. It’s important to let a health care provider know if symptoms persist or interfere with eating or drinking.
Serious side effects were also reported, including heart and kidney problems. A decrease in heart-pumping function was reported in a small number of people. Viltepso can also affect the kidneys. Your care team will monitor heart and kidney health with regular testing before and during treatment.
This is not a complete list of possible side effects. Tell a health care provider about any symptoms that are new, ongoing, or concerning so they can help manage them safely.
Is There Any Cost Assistance Available?
A copay savings program is available from NS Pharma, the manufacturer of Viltepso. It may help lower the cost of Viltepso. A patient assistance program is also available for those who qualify. Visit this website for more information. You can also call 833-677-8778 to speak with a representative about financial support options.