Fomivirsen is a synthetic antisense oligonucleotide antiviral compound consisting of a 21-nucleotide phosphorothioate backbone. It was developed for local treatment of cytomegalovirus (CMV) retinitis and acts by binding to complementary sequences in CMV immediate-early 2 (IE2) mRNA, thereby inhibiting viral protein production and CMV replication.
Fomivirsen sodium is the eicosasodium salt of a phosphorothioate antisense DNA oligonucleotide. The sequence is 5′-GCG TTT GCT CTT CTT CTT GCG-3′ and contains 21 nucleotides with 20 phosphorothioate linkages.
Fomivirsen sodium is described as a white to off-white, hygroscopic, amorphous powder. The molecular formula of the sodium salt is C204H243N63Na20O114P20S20, with a molecular weight of approximately 7,122 g/mol.
Fomivirsen has antiviral activity against human cytomegalovirus and was used for the local treatment of CMV retinitis. Its antisense mechanism targets CMV IE2 mRNA and suppresses expression of proteins required for viral replication.
The former Vitravene formulation contained 6.6 mg/mL fomivirsen sodium in a sterile, aqueous, preservative-free, bicarbonate-buffered solution. The formulation had a specified pH of 8.7 and osmolality of 290 mOsm/kg.
Fomivirsen sodium is hygroscopic and should be protected from moisture. Research-grade material is commonly stored at −20°C under nitrogen; storage requirements for pharmaceutical material should follow the applicable validated product specification.
Fomivirsen is a specialized oligonucleotide API requiring controlled synthesis, purification and analytical characterization. Identity and purity assessment may involve chromatographic and mass-spectrometric techniques appropriate for antisense oligonucleotides.
| Parameter | Specification |
|---|---|
| Appearance | White to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 1.0% |
| Residue on Ignition | NMT 0.5% |
| Heavy Metals | NMT 10 ppm |
| pH (1% Solution) | 8.7 |
| Individual Impurity | NMT 0.5% |
| Total Impurities | NMT 1.0% |
| Water Content | NMT 1.0% |