Viltolarsen is a synthetic antisense oligonucleotide belonging to the phosphorodiamidate morpholino oligomer (PMO) class. It is designed to target exon 53 of the human DMD (dystrophin) gene and promote exon 53 skipping during pre-mRNA processing. This molecular mechanism is intended to enable production of an internally truncated form of dystrophin in patients whose specific genetic mutations are amenable to exon 53 skipping.
Viltolarsen is also known by development codes and identifiers including NS-065, NCNP-01 and NS-065/NCNP-01. It is marketed as VILTEPSO. The active substance is a sequence-defined 21-subunit PMO designed specifically for exon 53 targeting. Unlike conventional phosphodiester or phosphorothioate oligonucleotides, PMOs contain morpholino rings connected through uncharged phosphorodiamidate linkages. This structural design contributes to the characteristic chemical and enzymatic stability of the molecule.
According to FDA information, viltolarsen contains 21 linked morpholino subunits. Its molecular formula is C244H381N113O88P20, and its molecular weight is 6924.82 daltons. The sequence reported in the FDA labeling is CCTCCGGTTC TGAAGGTGTT C.
Viltolarsen functions through sequence-specific interaction with dystrophin pre-mRNA. By binding to exon 53, it alters normal pre-mRNA splicing and promotes exclusion of exon 53 from the mature transcript. In appropriate DMD mutations, exon skipping can restore the reading frame and permit synthesis of a shorter dystrophin protein.
This mechanism makes Viltolarsen a specialized genetic medicine API rather than a conventional small-molecule pharmaceutical ingredient. Its quality assessment therefore relies on analytical approaches appropriate for synthetic oligonucleotides, including identity, sequence integrity, purity, related substances, assay, and other molecular quality attributes.
Viltolarsen is an important pharmaceutical ingredient for research, development and manufacturing activities involving antisense oligonucleotide-based therapies. As an API manufacturer and supplier in India, the product can be positioned for pharmaceutical development and biopharmaceutical applications requiring controlled, sequence-defined oligonucleotide material.
The product is particularly relevant to the development of therapies directed toward Duchenne muscular dystrophy (DMD) in patients with confirmed DMD gene mutations that are amenable to exon 53 skipping. FDA records identify VILTEPSO as an approved product for this specific patient population.
Viltolarsen has the CAS Number 2055732-84-6 and FDA/GSRS-associated UNII SXA7YP6EKX. Its molecular architecture consists of morpholino subunits linked through phosphorodiamidate groups. The molecule contains the nucleobases required for sequence-specific recognition of the target RNA.
The FDA describes Viltolarsen as a sterile, preservative-free aqueous solution when formulated as VILTEPSO. The commercial formulation contains 50 mg/mL viltolarsen in 0.9% sodium chloride, with the finished product adjusted to a pH of 7.0–7.5.
Because Viltolarsen is an oligonucleotide, standard small-molecule characteristics such as a conventional melting point or specific rotation are not generally suitable as universal API release parameters. Instead, identity and purity are evaluated using analytical methods capable of distinguishing the intended oligonucleotide sequence from truncated sequences, synthesis-related impurities and other related substances.
Quality control for Viltolarsen should focus on attributes relevant to synthetic PMO oligonucleotides. These may include molecular identity, sequence-related integrity, assay, purity, related oligonucleotide impurities, residual process-related materials and other applicable quality attributes.
Analytical characterization can involve chromatographic and molecular analytical techniques appropriate for oligonucleotide products. Depending on the applicable specification, methods such as HPLC or related chromatographic techniques, mass spectrometry, sequence-specific analytical methods and other orthogonal approaches may be used to establish product identity and quality.
For CMS presentation, fields that do not have a universal scientifically appropriate numerical value should be identified as N/A rather than assigning an unsupported small-molecule specification.
The primary therapeutic application of Viltolarsen is associated with Duchenne muscular dystrophy and exon 53 skipping. DMD is a genetic disorder involving mutations in the dystrophin gene. Viltolarsen is designed for patients with mutations that are amenable to exon 53 skipping.
The FDA-approved product is administered by intravenous infusion. FDA labeling describes VILTEPSO as an aqueous solution supplied at a concentration of 50 mg/mL. The recommended dosage described in the labeling is administered once weekly according to patient body weight.
The handling and storage of Viltolarsen API or formulated material should follow the applicable product-specific quality documentation and validated storage conditions. Oligonucleotide materials can require controlled environmental conditions to maintain chemical and molecular integrity.
For commercial pharmaceutical manufacturing, storage, packaging, transportation and handling requirements should therefore be established according to the applicable quality specification, stability data and regulatory documentation associated with the material.
Viltolarsen represents a specialized class of sequence-defined genetic medicine ingredients. Its PMO structure and exon-specific mechanism distinguish it from conventional small-molecule APIs and traditional nucleic-acid therapeutics.
For pharmaceutical and biopharmaceutical development, reliable control of identity, sequence integrity, purity and related substances is particularly important. A well-defined quality profile helps support consistent manufacturing and downstream formulation activities.
Viltolarsen API can therefore be categorized as a synthetic antisense oligonucleotide API, PMO API, and genetic medicine pharmaceutical ingredient. Its specialized structure and mechanism make accurate analytical characterization an important component of product quality management.
Viltolarsen is a sequence-specific phosphorodiamidate morpholino oligomer designed to target exon 53 of dystrophin pre-mRNA. It contains 21 linked morpholino subunits and has a molecular formula of C244H381N113O88P20 with a molecular weight of 6924.82 Da. Its therapeutic application is focused on Duchenne muscular dystrophy patients with DMD gene mutations amenable to exon 53 skipping.
For pharmaceutical manufacturing and development, Viltolarsen should be evaluated using analytical and quality parameters appropriate for synthetic oligonucleotides rather than conventional small-molecule API testing alone. Product identity, sequence integrity, assay, purity and related substances are key considerations for maintaining the quality of this specialized API.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 0.5% |
| Residue on Ignition | NMT 0.1% |
| pH (1% Solution) | 7.0–7.5 |
| Water Content | NMT 0.5% |
| Solubility | Aqueous Formulation; Finished Product Concentration 50 mg/mL |