Atosiban Acetate is a synthetic cyclic nonapeptide and an antagonist of the hormones oxytocin and vasopressin. It is used as a pharmaceutical active ingredient for delaying imminent preterm birth in appropriately selected pregnant adult women. EMA identifies the active substance of Tractocile as atosiban (as acetate).
Atosiban is structurally related to oxytocin and contains a cyclic peptide structure formed through a disulfide linkage. The active substance is manufactured by peptide synthesis and purified using chromatographic processes. EMA describes atosiban as a white to off-white, very hygroscopic, freeze-dried amorphous powder.
PubChem reports the acetate salt at C₄₅H₇₁N₁₁O₁₄S₂ and approximately 1054.2 g/mol, while the parent atosiban is C₄₃H₆₇N₁₁O₁₂S₂, approximately 994.2 g/mol.
Atosiban is used in pharmaceutical formulations intended to:
EMA specifies its use in pregnant adult women from 24 to 33 completed weeks of gestation who meet the applicable clinical criteria.
Atosiban medicinal products are supplied as intravenous injection/infusion formulations. EMA's Tractocile documentation describes a 7.5 mg/mL solution for injection and a concentrate for infusion.
Atosiban Acetate is a peptide API requiring appropriate controls for:
EMA's scientific assessment reports that more than 32 impurities were observed during development and that specific impurity limits were established for selected impurities, with a maximum total impurity limit of 3% in the evaluated active-substance specification.
Atosiban Acetate is very hygroscopic and should be stored in tightly closed packaging under the conditions specified by the approved product specification. The finished Tractocile product is refrigerated and protected from light.
| Parameter | Specification |
|---|---|
| Appearance | White to off-white, very hygroscopic, freeze-dried amorphous powder |
| Identification | Conforms to Atosiban identity by validated analytical methods |
| Assay (HPLC) | As per approved peptide/API specification |
| Individual Impurity | NMT 3.0%* |
| Specific Rotation | As per approved specification |
| Solubility | Soluble in water and aqueous buffer systems; also soluble in selected organic solvents |