Viltepso (viltolarsen)
An approved treatment for Duchenne Muscular Dystrophy.
The same compound appears under different names depending on the context. Here is how to identify Viltolarsen wherever you encounter it, plus the key facts at a glance.
- Generic name
- Viltolarsen
- Brand name
- Viltepso
- Development codes
- NS-065, NCNP-01
- Drug class
- Antisense oligonucleotide (exon skipping)
- Manufacturer
- NS Pharma (Nippon Shinyaku)
- How it's taken
- Given as a weekly intravenous infusion over approximately 60 minutes.
An exon 53 skipping therapy for DMD. In clinical trials, 100% of treated patients showed increased dystrophin production in muscle biopsies.
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Where Viltolarsen fits
Exon 53 skipping therapy for DMD, serving the same mutation subset as golodirsen. Some data suggest higher levels of dystrophin production compared to earlier exon-skipping therapies.
How Viltolarsen works
Viltolarsen works by the same exon-skipping mechanism as golodirsen, targeting exon 53 in the dystrophin gene. It tells cells to skip the broken section and produce a shorter but partially functional dystrophin protein.
Mechanism: Antisense oligonucleotide that enables exon 53 skipping to produce shortened but functional dystrophin
Side effects and safety
Common side effects include upper respiratory tract infection, injection site reaction, cough, and fever. Kidney toxicity is a potential risk. Regular kidney function monitoring is recommended.
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Viltolarsen
Given as a weekly intravenous infusion over approximately 60 minutes. Dose is 80 mg/kg administered at infusion centers.
Availability and cost
Only available as the brand-name product.
Antisense oligonucleotide for exon 53 skipping with potentially higher exon-skipping efficiency. Ultra-orphan pricing for a subset of DMD patients.
Help paying for Viltepso
Pick your insurance to see which help fits. Drugmaker copay cards can't be used with Medicare, Medicaid or TRICARE; charity funds are the usual route there.
- Copay help
Commercially insured patients receiving Viltepso are automatically enrolled in the NS Support Co-pay Assistance Program, which helps eligible patients with deductible, co-pay and coinsurance costs for Viltepso, with re-enrollment each calendar year while they stay eligible. Restrictions apply; call NS Support for full eligibility terms.
For: private insurance · source - Free medicine program
Financial Assistance Program: eligible uninsured patients may get Viltepso at no charge for up to one year. Does not cover infusion costs.
For: no insurance · source - Insurance and case manager help
A Patient Engagement Lead and Director of Patient Access help with insurance approvals, reauthorizations, understanding out-of-pocket costs and choosing an infusion provider.
The official page does not say who qualifies. Ask the program. · source - Bridge or quick-start supply
NS Support lists a Bridge Program and a Quick Start Program; details and eligibility are not published. Call NS Support to ask.
The official page does not say who qualifies. Ask the program. · source
Good to know: Government-insured patients can't use the co-pay program. Hours Mon-Fri 8 AM-8 PM ET.
- From a charity · NORD RareCareDuchenne Muscular Dystrophy Medical Assistance fundOpen
Pays for: Medical and medication costs.
The foundation says: “Accepting new applications and re-enrollments for current year” - From a charity · NORD RareCareDuchenne Muscular Dystrophy Premium Copay Assistance fundOpen
Pays for: Insurance premiums and copays.
The foundation says: “Accepting new applications and re-enrollments for current year” - From a charity · The Assistance FundDuchenne Muscular Dystrophy fundOpen
Pays for: Copays, coinsurance, deductibles and other health-related expenses.
The foundation says: “OPEN — Accepting New Patients. TAF is currently accepting new patient enrollments for this program.” - From a charity · Muscular Dystrophy AssociationMDA Durable Medical Equipment (DME) Grant Program fundApply directly
Pays for: Medical equipment (wheelchairs, lifts, canes and other DME), up to $1,000 per year.
The foundation says: “Status not shown on page”
Clinical trial results
Approved in August 2020 under accelerated approval, based on dystrophin levels in muscle biopsies. In 8 boys on the approved dose, average dystrophin rose from 0.6% of normal to 5.9% after about 24 weeks, and every boy had some increase. The confirmatory Phase 3 RACER53 trial in 77 boys did not show a significant difference from placebo in time to stand from lying down after 48 weeks, NS Pharma reported in May 2024. Continued approval may depend on proof of clinical benefit.
Development history
Developed in Japan by Nippon Shinyaku and brought to the US market through NS Pharma. It was the second exon 53 skipping drug approved, offering an alternative to golodirsen for the same patient subgroup.
Explore Duchenne Muscular Dystrophy trials
Other Duchenne Muscular Dystrophy treatments
Common questions about Viltolarsen
▸What is Viltolarsen (Viltepso)?
An exon 53 skipping therapy for DMD. In clinical trials, 100% of treated patients showed increased dystrophin production in muscle biopsies.
▸How does Viltolarsen work?
Viltolarsen works by the same exon-skipping mechanism as golodirsen, targeting exon 53 in the dystrophin gene. It tells cells to skip the broken section and produce a shorter but partially functional dystrophin protein.
▸What are the side effects of Viltolarsen?
Common side effects include upper respiratory tract infection, injection site reaction, cough, and fever. Kidney toxicity is a potential risk. Regular kidney function monitoring is recommended.
▸How is Viltolarsen taken?
Given as a weekly intravenous infusion over approximately 60 minutes. Dose is 80 mg/kg administered at infusion centers.
▸Is Viltolarsen FDA approved?
Yes, Viltolarsen (Viltepso) is FDA approved (2020) for the treatment of Duchenne Muscular Dystrophy.
▸What makes viltolarsen's clinical data notable?
In the main study, all 8 boys on the approved dose had an increase in dystrophin on muscle biopsy, with average levels rising from 0.6% to 5.9% of normal. A later Phase 3 trial (RACER53) did not show a significant benefit over placebo on time to stand from lying down. These levels are still well below normal, and it has not been proven that they improve muscle strength or function. The FDA approval is based on the rise in dystrophin, and continued approval may depend on a trial confirming a clinical benefit. This consistently high response rate across all treated patients was considered a strong signal for the drug's biological activity.
▸How does viltolarsen compare to golodirsen?
Both target exon 53 and serve the same DMD patient population. They have similar mechanisms but different chemical modifications. Some data suggest viltolarsen may achieve higher levels of exon skipping and dystrophin production, though no head-to-head trial has been conducted. Practical differences include the specific infusion protocols and which insurance plans cover each drug. Your neuromuscular specialist can help determine which option is most appropriate.
▸Is viltolarsen from a Japanese company?
Yes. Viltolarsen was developed by Nippon Shinyaku, a Japanese pharmaceutical company, and is marketed in the US through its subsidiary NS Pharma. The drug was also studied and used in Japan, reflecting the strong Japanese research tradition in muscular dystrophy therapeutics.
▸What monitoring is needed during viltolarsen treatment?
Kidney tests are recommended because kidney damage was seen in animal studies of viltolarsen, and some similar drugs have caused serious, even fatal, kidney inflammation. The label says to check serum cystatin C, a urine dipstick, and the urine protein-to-creatinine ratio before starting, then the urine dipstick every month and cystatin C and urine protein-to-creatinine ratio every 3 months. A standard serum creatinine test may not be reliable in DMD because of low muscle mass. Urine samples should be taken before an infusion or at least 48 hours after one. Additionally, periodic assessment of motor function helps evaluate treatment benefit. Blood counts and liver function may also be monitored as part of routine care.