Atosiban

Absorption

In women receiving 300 μg/min by infusion for 6-12 h, average steady state concentrations of 442 ng/mL were reached within 1 h . Steady state concentrations increase proportionally to dosage.

Toxicity

No systemic toxicities were found in rat and dog studies at dosages equivalent to 10 times normal human exposure . It is thought that the risk of toxicity is low due to the short duration of action and short half life of atosiban .

Description

Atosiban was introduced in the UK as an injectable inhibitor of preterm labor, a major cause of infant morbidity and mortality. This peptidic oxytocin analog is an antagonist of the vasopressin V_1a receptor and of the oxytocin receptor which is found in dramatically increased concentration in the uterine myometrium of pregnant women near term. It competitively inhibited contractions in the pregnant guinea pig uterus induced by oxytocin and vasopressin. In a multicenter, double-blind, placebo-controlled trial, treatment with atosiban caused pregnancy prolongation for up to 7 days in women with more than 28 weeks of gestation. In a comparative clinical trial, atosiban showed a comparable tocolytic action (uterine relaxant) to ritodrine but the former was significantly better tolerated, especially with regards to maternal cardiovascular side effects. In healthy volunteers, plasma levels of atosiban decreased bi-exponentially with an initial and a terminal half-life of 21 min and 1.7h respectively.

Originator

Ferring AB (Sweden)

The Uses of Atosiban

Atosiban is an oxytocin receptor blocking agent in the treatment of experimental endometriosis and was shown exhibit significant therapeutic efficiency.

The Uses of Atosiban

Premature labor

The Uses of Atosiban

Atosiban has been used:

• as an oxytocin receptor antagonist
• in the calcium mobilization assay for Z factor determination in uterine myometrium (UT-myo cells) and as a therapeutic agent to inhibit preterm labor
• to inhibit the activation of oxytocin-receptor-expressing neurons in the parabrachial nucleus of mice (Oxtr^PBN)

Background

Atosiban is an inhibitor of the hormones oxytocin and vasopressin. It is used intravenously to halt premature labor. Although initial studies suggested it could be used as a nasal spray and hence would not require hospital admission, it is not used in that form. Atobisan was developed by the Swedish company Ferring Pharmaceuticals. It was first reported in the literature in 1985. Atosiban is licensed in proprietary and generic forms for the delay of imminent pre-term birth in pregnant adult women.

Indications

Atosiban is indicated for use in delaying imminent pre-term birth in pregnant adult women with:

What are the applications of Application

Atosiban is a peptide oxytocin receptor inhibitor

Indications

Atosiban is an analogue of oxytocin that is modified at positions 1, 2, 4, and 8. It is a competitive inhibitor of oxytocin binding. Early studies have demonstrated that this drug does decrease and stop uterine contractions. Atosiban is not available for use in the United States.

Definition

ChEBI: Atosiban is an oligopeptide.

Manufacturing Process

BocGly resin (3.0 g, 3 meq) was placed in the reaction vessel of a Vega Model 50 semiautomatic peptide synthesizer. The peptide was built up by increments on the resin in accordance with Tables 1 and 2.
Activation of the amino acid was carried out by dissolving 10 meq of a suitably protected amino acid, 15 meq of hydroxy benzotriazole and 10 meq of dicyclohexylcarbodiimide in DMF (70 ml), whereupon the mixture was left at room temperature for 1 h (asparagine and glutamine were activated at 0°C for 15 min), whereupon the precipitate was filtered off, and the filtrate was treated the activated amino acid in Table 1 (step 7). The completion of the coupling step was checked by the method of Kaiser (Anal. Biochem. 34, 595 (1970)) after the cycle had been completed (step 9). If the test was positive (coupling yield below 99%), the cycle was repeated starting from step 7. If the test was negative, the termination procedure was performed according to Table 2. When the whole sequence had been coupled, the resin was placed on a filter and washed repeatedly with methanol. The dried product was placed in a glass vessel and cooled in an ethanol-dry ice bath and suspended in methanol (about 100 ml). The mixture was then saturated with sodium-dried ammonia to achieve approximately 50% concentration. Then the vessel was placed in a steel cylinder and left at room temperature for two days. After the pressure had been relieved, the product was filtered, and the residue was extracted with hot (about 100°C) DMF (2x100 ml). The filtrate and the extract were combined and evaporated. The residue was dissolved in a small amount of hot DMF, and methanol was added to the coupling point. The precipitate was collected by filtration and washed on the filter with methanol. After drying in vacuum, the purity was checked by thin-layer chromatography. Yield about 2.8 g.
100 mg of the above described protected peptide were placed in a 100 ml round-bottom flask, and dry nitrogen was flushed through for about 15 min. 50 ml of sodium-dried ammonia were distilled in, and the protective group was removed from the product by adding sodium until blue color remained in the solution for 15 sec. The excess of sodium was destroyed by adding of ammonium chloride. Ammonia was removed in a nitrogen stream, and the residue was dissolved in 1 liter of methanol. The pH of the solution was adjusted to about 4 with concentrated acetic acid, and the solution was then titrated with 0.1 mM of iodine in methanol to brownish color. The mixture was stirred with 3 g of Dowex 50x2 ion exchanger in chloride form for 10 min at room temperature. The ion exchanger was removed by filtration, and the filtrate was evaporated to dryness. The residue was dissolved in 3 ml of 20% acetic acid and purified by chromatography on Sephadex G-25 with 20% acetic acid as eluent. The final purification was achieved by reverse phase HPLC. The purity of the product was determined on a HPCL column μ- Bondapak C-18 in 45% ethanol and 55% 5 mM trifluoroacetic acid in water. The column was supplied by Water Associates, Inc., Millford, Mass., U.S.A. The purity of the product was also shown by amino acid analysis.

brand name

Tractocile, Antocin

Therapeutic Function

Oxytocin antagonist

Biochem/physiol Actions

Atosiban efficiently prevent preterm uterine contractions without any major cardiovascular, pulmonary or central nervous system side effects. It has potential to treat preterm labour.

Pharmacokinetics

Atosiban reduces the frequency of uterine contractions to delay pre-term birth in adult females and induces uterine quiescence .

Anticancer Research

The antitumor effects of the essential oil of O. falcata were tested in transplantedmurine H22 solid tumors in vivo. Growth inhibition in H22 solid tumors was moderate(Yang et al. 2013).

Metabolism

There are two metabolites of atosiban created through the cleavage of the peptide bond between ornithine and proline which is thought to be facilitated by prior cleavage of the disulfide bridge . The larger fragment remains active as an antagonist of oxytocin receptors but is 10 times less potent than the parent molecule. At a dosage of 300 μg/min the ratio of parent molecule to the main metabolite was observed to be 1.4 at the second hour and 2.8 at the end of infusion .

storage

Store at -20°C