Foscarnet is a synthetic antiviral compound chemically known as phosphonoformic acid. It is a pyrophosphate analogue that directly inhibits viral DNA polymerase and viral RNA polymerase. Foscarnet is primarily used in the treatment of certain infections caused by cytomegalovirus (CMV) and herpes simplex virus (HSV), particularly when resistance or intolerance to other antiviral therapies is a concern.
Foscarnet API is a specialized antiviral pharmaceutical ingredient. The active compound has CAS Number 4428-95-9, molecular formula CH₃O₅P, and molecular weight 126.01 g/mol. Pharmaceutical formulations commonly use the trisodium salt, Foscarnet Sodium, rather than the free acid.
Foscarnet is also known as phosphonoformic acid, phosphonoformate, or carboxyphosphonic acid. It is a small phosphorus-containing organic acid with the chemical structure C(=O)(O)P(=O)(O)O.
CAS Number: 4428-95-9
Molecular Formula: CH₃O₅P
Molecular Weight: 126.01 g/mol
IUPAC Name: Phosphonoformic acid
Drug Class: Antiviral
Chemical Class: Pyrophosphate analogue
Foscarnet Sodium is the trisodium salt of foscarnet and is the pharmaceutical salt used in marketed injectable formulations. Foscarnet Sodium has the molecular formula CNa₃O₅P, molecular weight 191.95 g/mol, and CAS Number 63585-09-1.
Foscarnet acts as a pyrophosphate analogue and directly inhibits viral DNA polymerase. It binds at the pyrophosphate-binding site of the viral polymerase and prevents cleavage of pyrophosphate from nucleoside triphosphates, thereby interfering with viral DNA chain elongation. It does not require phosphorylation by viral kinases for antiviral activity.
Foscarnet is used as an antiviral pharmaceutical ingredient in the treatment of CMV retinitis and certain serious HSV infections, particularly infections caused by strains resistant to conventional antiviral agents. Foscarnet has also demonstrated activity against other herpesviruses.
Foscarnet is an achiral compound with no defined stereocenters. It has a topological polar surface area of approximately 94.8 Ų and is highly polar because of its phosphonic acid and carboxylic acid functional groups.
Foscarnet pharmaceutical material can be characterized using appropriate analytical techniques including HPLC or ion chromatography, infrared spectroscopy, assay determination, related-substance testing, elemental impurity testing and other validated pharmaceutical quality-control methods.
The USP has a specific Foscarnet Sodium Injection monograph proposal using liquid chromatographic procedures for assay and testing of phosphate and phosphite impurities.
Foscarnet and its pharmaceutical salts should be stored according to the applicable product specification and stability data. Material should be protected from unsuitable environmental conditions and handled using appropriate pharmaceutical safety procedures.
Foscarnet is particularly relevant to antiviral drug development and pharmaceutical research involving CMV, HSV and viral polymerase inhibition. Its direct mechanism of viral polymerase inhibition distinguishes it from nucleoside analogue antivirals.
Foscarnet is a pyrophosphate analogue antiviral with CAS 4428-95-9, molecular formula CH₃O₅P, and molecular weight 126.01 g/mol. Its pharmaceutical salt, Foscarnet Sodium, has CAS 63585-09-1 and molecular weight 191.95 g/mol. Foscarnet is primarily associated with antiviral therapy targeting CMV and herpesvirus infections.
| 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) | 2.0 – 4.0 |
| Individual Impurity | NMT 0.5% |
| Total Impurities | NMT 1.0% |
| Melting Point | 150°C – 154°C |