Generic name: viltolarsen
Dosage form: injection, for intravenous use
Drug class: Miscellaneous uncategorized agents

Medically reviewed by Melisa Puckey, BPharm. Last updated on Apr 10, 2025.

What is Viltepso?

Viltepso is a prescription medicine for the treatment of Duchenne muscular dystrophy (DMD)  with a specific gene mutation in the DMD gene that is treatable with exon 53 skipping. Viltepso helps increase dystrophin, a key protein supporting muscle health that is reduced in DMD. 

Viltepso is administered once weekly through an intravenous infusion, which can be given at home, in a hospital, or at a treatment center.

Viltepso is from a class of medicines called antisense oligonucleotide (ASOs).

Your healthcare provider will conduct a genetic test to identify if you or your child is suitable for treatment with this medicine. 

Viltepso FDA approval

Viltepso FDA approval was received for the treatment of Duchenne muscular dystrophy (DMD) in patients who have a confirmed mutation of the DMD gene that is amenable to exon 53 skipping. The FDA approval was granted to NS Pharma, Inc. on an "accelerated" basis. This means that clinical studies showed an increase in dystrophin production in skeletal muscles. For continued approval, further studies are needed to confirm there is a clinical benefit. FDA accelerated approval was granted after results from the Phase 2, two-period clinical trial (NCT02740972).

How well does Vilepso work?

Dystrophin level Increase

Clinical Trial Results for Study 1 Viltepso (80 mg/kg/week):

• 100% (8 out of 8 patients) showed an increase in dystrophin levels after treatment.
• 88% (7 out of 8 patients) achieved dystrophin levels of 3% or greater compared to normal..

Timed function tests

Patients treated with Viltepso demonstrated improvements in timed function tests compared to a matched control group at week 25. (Phase 2, two-period clinical trial NCT02740972 ):

Time to Stand from Lying Down:

• Viltepso patients: Improved by −0.19 seconds
• Control patients: Worsened by +0.66 seconds

10-Meter Run/Walk Speed:

• Viltepso patients: Improved by +0.23 meters/second
• Control patients: Slowed down by −0.04 meters/second

6-Minute Walk Test (6MWT):

• Viltepso patients: Increased distance by +28.9 meters
• Control patients: Decreased distance by −65.3 meters

What is Duchenne Muscular Dystrophy?

Duchenne muscular dystrophy (DMD) is a genetic disorder that causes progressive muscle weakness and degeneration, primarily in boys. It results from mutations in the DMD gene, which disrupt the production of dystrophin, a protein essential for muscle stability.

What is Exon 53 Skipping?

Some DMD mutations lead to missing exons, preventing functional dystrophin protein production. Exon 53 skipping is a targeted therapy that restores part of the gene’s reading frame, allowing the body to produce a shortened but functional dystrophin protein, potentially slowing muscle degeneration.

Viltepso is designed for patients with DMD mutations amenable to exon 53 skipping. 

How does Viltepso work?

Viltepso mechanism of action is by binding to exon 53 of dystrophin pre-mRNA, so the exon 53 is skipped during mRNA processing, bypassing the genetic error. This results in the body being able to produce a shorter but functional dystrophin protein to help stabilize muscles and slow disease progression.

Viltepso is a antisense oligonucleotide 

Viltepso side effects

Common Viltepso side effects

The most common Viltepso side effects may include:

• runny or stuffy nose;
• cough;
• fever;
• bruising or swelling at the injection site;
• joint pain;
• diarrhea;
• vomiting;
• stomach pain;
• fatigue;
• shortness of breath; and
• rash.

Serious Viltepso side effects

Get emergency medical help if you have signs of an allergic reaction: hives, itching, rash, blistering, or peeling; fever; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have signs of kidney problems including:

• the inability to pass urine;
• a change in how much urine is passed;
• blood in the urine; or
• fluid retention, causing swelling in your legs, ankles, or feet.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1 800-FDA-1088.

Related/similar drugs

Warnings

Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Before taking this medicine

Tell your doctor if you have ever had kidney problems.

Tell your doctor if you are pregnant or breastfeeding.

 How is Viltepso given?

Your doctor will perform blood tests to make sure you do not have conditions that would prevent you from safely using Viltepso.

Viltepso is given as an infusion into a vein, usually once per week. A healthcare provider will give you this injection.

Viltepso must be given slowly, and the infusion can take up to 60 minutes to complete.

Your kidney function may need to be checked while you are using this medicine.

Viltepso dose information

The recommended Viltepso dosage is 80 mg/kg administered once weekly as a 60-minute intravenous infusion.

Viltepso is available as 250 mg/5 mL (50 mg/mL) in a single-dose vial.

 Viltepso NDC code 73292-0011-01: Viltepso 250 mg/5 mL [50 mg/mL] single-dose vial.

What happens if I miss a dose?

Call your doctor for instructions if you miss an appointment for your treatment.

What should I avoid while receiving Viltepso?

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

What other drugs will affect Viltepso?

Other drugs may affect Viltepso, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Viltepso J code

Viltepso J code is J1427
J codes are used for medicines that are not taken orally and include injections, inhalations, and chemotherapies. J code are important for accurate and consistent coding for billing and reimbursement purposes.

Your physician will need the Viltepso J code when filling out forms for your treatment.

Viltepso Package Insert 

HCPs and patients often use the Viltepso Package Insert (PI) for more detailed information about this medicine. The Viltepso Package Insert (prescribing information) contains more comprehensive information on Indications and Usage, Dosage and Administration, Clinical Pharmacology, Clinical Studies, Drug Interaction, and more. Discuss any medical questions you have with your HCP (health care professional). This is not all the information you need to know about this medicine for safe and effective use, and it does not take the place of talking to your doctor about your treatment.

The Package Insert is sometimes called Viltepso Prescribing Information (PI) or FDA label.

Ingredients

Active ingredients: viltolarsen

Inactive ingredients: sodium chloride, hydrochloride, hydrochloric acid, sodium hydroxide, water.

Storage 

• Store at 2°C to 8°C (36°F to 46°F). 
• Do not freeze.

Company

Viltepso NS Pharma, Inc. Paramus, NJ 07652

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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