Vasopressin/oxytocin receptor

Atosiban prevents the myometrium from releasing IP3 through oxytocin. Both the intracellular calcium released from myometrial cells' sacroplasmic reticulum and the external Ca2+ influx through voltage-gated channels are decreased. Furthermore, Atosiban can prevent decidua from releasing PGE and PGF when oxytocin is present [1].

---

Oxytocin (OT) plays an important role in the onset of human labour by stimulating uterine contractions and promoting prostaglandin/inflammatory cytokine synthesis in amnion via oxytocin receptor (OTR) coupling. The OTR-antagonist, Atosiban, is widely used as a tocolytic for the management of acute preterm labour. We found that in primary human amniocytes, Atosiban (10 μM) signals via PTX-sensitive Gαi to activate transcription factor NF-κB p65, ERK1/2, and p38 which subsequently drives upregulation of the prostaglandin synthesis enzymes, COX-2 and phospho-cPLA2 and excretion of prostaglandins (PGE2) (n = 6; p < 0.05, ANOVA). Moreover, Atosiban treatment increased expression and excretion of the inflammatory cytokines, IL-6 and CCL5. We also showed that OT-simulated activation of NF-κB, ERK1/2, and p38 and subsequent prostaglandin and inflammatory cytokine synthesis is via Gαi-2 and Gαi-3 but not Gαq, and is not inhibited by Atosiban. Activation or exacerbation of inflammation is not a desirable effect of tocolytics. Therefore therapeutic modulation of the OT/OTR system for clinical management of term/preterm labour should consider the effects of differential G-protein coupling of the OTR and the role of OT or selective OTR agonists/antagonists in activating proinflammatory pathways [4].

Atoposiban influences the physiological effects of arginine vasopressin on the fetal-maternal cardiovascular and renal systems. The posterior pituitary hormones oxytocin and arginine vasopressin differ in structure by just two amino acids. A trial using Atosiban for one hour did not result in any changes to the cardiovascular systems of the mother or the fetus in late-gestation sheep [1]. In the parabrachial nucleus of mice, atosiban inhibits the activation of neurons that express the oxytocin receptor [2].

---

Peak plasma concentrations of Atosiban was achieved at 2 to 8 minutes following intravenous (IV) administration (10 nmol/kg body weight) compared to peak concentration at 10 to 45 minutes following intranasal administration of atosiban at 100 nmol/kg body weight.81 Goodwin et al showed that following IV infusion of atosiban (300 μ/min) in women between 20 and 36 weeks’ gestation, and in whom contractions were absent for 6 hours or maximum infusion length of 12 hours, plasma atosiban concentrations reached steady state within 1 hour of the start of IV infusion. The decrease in uterine activity in the first 4 hours of IV infusion was directly proportional to the duration of infusion. At the completion of infusion, plasma atosiban levels declined in a bi-exponential manner with initial and terminal half lives of 13 ± 3 and 102 ± 18 minutes, respectively. In a phase II randomized placebo controlled trial of the effect of atosiban on premature uterine activity (20 to 36 weeks gestation), a 2-hour infusion of Atosiban led to a statistically significant decline in the frequency of uterine contractions, suggesting that OT plays a role in the maintenance of PTL. The only adverse outcome reported in the atosiban group was nausea and vomiting in one patient. In a phase III randomized controlled trial of the effect of atosiban on PTL (20 to 34 weeks), which allowed tocolytic rescue if after 1 hour of atosiban or placebo infusion, premature labor continued, the primary end-point was the time to delivery or therapeutic failure (progression of labor requiring an alternative tocolytic). There was no statistically significant difference between the two groups for the primary end-point. The secondary endpoints were the proportions of women who were successfully treated at 24 hours, 48 hours and 7 days after commencing atosiban or placebo infusion. The proportions were significantly higher in the atosiban group: 73% versus 58% at 24 hours (P < 0.001), 67% versus 56% at 48 hours (P = 0.008), and 62% versus 49% at 7 days (P = 0.003). Compared to placebo, the effect of atosiban on prolongation of pregnancy up to 7 days was more evident in pregnancies ≥28 weeks completed weeks of gestation; 65% versus 48%, and 51% versus 59% at <28 weeks. These findings emphasize the fact that VOTras play a role in the maintenance of SPTL, yet other mechanisms are also involved. The perinatal mortality rate was 2.1% in the atosiban group, compared to 1.4% in the placebo group with or without tocolytic rescue. However, the randomization was not stratified according to gestational age, which resulted in an excess of extremely premature infants at a more advanced stage of labor in the atosiban group, and the Cochrane Review85 has been criticized for their use of these data. In a randomized controlled trial of women who, after successful treatment with atosiban, had a maintenance subcutaneous infusion of atosiban or placebo, the use of atosiban resulted in a statistically significant prolongation of uterine quiescence, compared to placebo (median of 32.6 days versus 27.6 days). Women in the atosiban group had higher incidence injection site reactions (70% versus 48%) during the maintenance treatment [1].

---

In the ip saline-treated rats, the vocalization response was significantly reduced in association with intromissions (t = 5.18; df = 14, p < 0.001) and ejaculation (t = 5.17; p < 0.001) compared to the baseline vocalization response. By contrast, in females that received ip Atosiban, the vocalization response to STS was not significantly reduced during mounts, intromissions or ejaculations, compared to their baseline vocalization response. However, compared to saline treatment, the antinociceptive effect was significantly reduced in the atosiban treated females during both intromissions (t = 3.5; df = 14, p < 0.01) and ejaculations (t = 5.1; df = 14, p < 0.01) (Fig. 1A). A separate group of females that did not receive EB or P (and therefore were not sexually receptive and did not display lordosis) showed no changes in vocalization response in association with the male's mounts (intromissions or ejaculations did not occur). Similar results were obtained with atosiban or saline delivered it or icv. In animals that received it saline, the vocalizations in response to STS were significantly lower when the rats received intromissions (t = 5.18; df = 14 p < 0.01), or ejaculations (t = 5.17; df = 14, p < 0.01), compared to their baseline response. By contrast, Atosiban-treated rats did not display a significant reduction in vocalizations in response to intromissions or ejaculations (Fig. 1B). Thus, the antinociceptive effect induced by mounts (t = −3.2; df = 14, p < 0.05) intromissions (t = −3.5; df = 14, p < 0.01) and ejaculations (t = −5.1; df = 14, p < 0.01) was significantly reduced in atosiban-treated females, compared to saline controls (Fig. 1B). Animals that received icv saline displayed significantly reduced vocalizations in response to intromissions (t = 14.7; df = 14, p < 0.01) and ejaculations (t = 18.8; df = 14, p < 0.01), compared to their baseline response. However, in females that received icv atosiban, the vocalizations in response to intromissions and ejaculations did not differ significantly from the number of their baseline vocalization responses. Thus, the antinociceptive effect induced by intromissions (t = −6.9; df = 16, p < 0.01) and ejaculations (t = −5.6; df = 16, p < 0.01) was significantly reduced in atosiban-treated females, compared to saline controls (Fig. 1C). Cohen's d effect size analysis revealed that the effect size was greater during intromissions or ejaculations than during mounts in all groups, and greater in the icv group than the other groups during mounts as well as intromissions and ejaculations (Table 1) [3].

Real time polymerase chain reaction (RT-PCR) [4]
Total RNA was extracted by a guanidiumthiocyanate-phenol-chloroform extraction using RNA STAT-60 reagent according to the manufacturer's specifications. Prior to cDNA synthesis, any DNA contaminations were eliminated by DNaseI treatment. The DNaseI treated RNA were used for first-strand cDNA synthesis with SuperScriptII first-strand synthesis kit. Gene expression was verified by real-time PCR performed on ABI StepOne Real Time PCR system using SYBR Green I Master mix. Amplification was carried out using specific primers for the target DNA, generated using the software Primer Express. The following gene specific primers were used for RT-PCR: L19, 5′-GCGGAAGGGTACAGCCAAT-3′ and 5′-GCAGCCGGCGCAAA-3’; COX-2, 5′-TGTGCAACACTTGAGT-GGCT-3′ and 5′-ACTTTCTGTACTGCGGGTG-G-3’; IL-6, 5′-CCTTCC-AAAGATGGCTGAAA-3′ and 5′-AGCTCTGGCTTGTTCCTCAC-3’; and CCL5, 5′-CCATA-TTCCTCGGACACCAC-3′ and 5′-TGTACTCC-CGAACCCATTTC-3’. The data were analysed using Sequence Detector Version1.7 software. Expression levels were assessed using the comparative Ct method and the target Ct values were normalised to ribosomal protein L19 for analysis.

---

Polymerase chain reaction (PCR)[4]
Polymerase chain reactions (PCR) were performed using Phusion high-fidelity DNA polymeras. PCR reaction mix was prepared following the manufacturer's protocol. Template DNA were initially denatured for 30 s at 98 °C, then the reaction was subjected to 30 thermo-cycles of 98 °C for 10 s, primer annealing at 60 °C for 30 s and extension at 72 °C for 30 s. This was followed by the final extension step of 72 °C for 10 min. PCR products were then analysed by electrophoresis using 1.5–2% (w/v) agarose gels. The size of DNA fragments were estimated by using a hyperladder V containing restriction fragments of known sizes. The bands were imaged using a dark reader.

---

Protein extraction and Western blot[4]
Cells were lysed on ice for 10 min in radioimmunoprecipitation assay buffer consisting of 1% Triton X−100, 1% Sodium Deoxycholate, 0.1% SDS, 150 mM NaCl, 10 mM Tris (pH 7.4) and 1 mM EDTA with 1 mM of PMSF, protease and phosphotase inhibitor cocktail. Lysed samples were centrifuged at 4 °C for 10 min at 13000 × g. The resulting supernatant was recovered and protein concentration determined using the BioRad protein assay kit. A total of 20 μg of total protein was denatured for 10 min at 80 °C before undergoing electrophoretic separation on a 10% SDS-polyacrylamide gel for 80 min at 140 V. Resolved proteins were then transferred to PVDF membrane using a wet-transfer chamber system for 90 min at 300 mA. Membranes were incubated in primary antibodies (detailed below) overnight at 4 °C followed by incubation with HRP-conjugated secondary antibodies the following day. Signal detection was carried out using ECL plus. To confirm equal loading of each well, the membranes stripped using 0.2 M NaOH for 10 min and re-probed for β-actin.

---

siRNA gene silencing[4]
Transfection for gene silencing studies was performed using the Amaxa Nucleofector Technology according to manufacturer's protocol. The cell/siRNA suspension was transfected with 30 pmol of siGENOME SMARTpool siRNA via electroporation using the Program T-020. Total proteins from the transfected cells were extracted for further analysis at 72 h.

---

ELISA[4]
Concentrations of IL-6, CCL5 and PGE2 released were determined by a standard ELISA. Supernatants were collected from treated amnion cultures and immediately frozen at −20 °C for subsequent analysis by ELISA according to manufacturer's instructions.

Drug administration [1]
In Experiment 1, Atosiban (0.5 mg/ml in saline) was administered ip at a dose of 500 μg/kg body weight. Atosiban (1 mg/kg bw) was reported to inhibit oxytocin-induced analgesia (Abbasnezhad et al., 2016). We observed that when we administered this dose of Atosiban to female rats pretreated with EB and P, their sexual behavior was inhibited. For this reason, we reduced the atosiban dose that we used to 500 μg/kg bw. At this dose, we observed that female sexual behavior was expressed normally, but the copulation-induced analgesia was significantly reduced (unpublished findings). In Experiment 2, Atosiban was administered intrathecally (it, 500 ng in 5 μl saline) according to the method of Hylden and Wilcox (Hylden and Wilcox, 1980). The drug was administrated over a period of 120 s using a 25 μl microsyringe mounted on a microinjector. The 7.5 cm length PE10 catheter contained 7 μl of saline, plus 5 μl of atosiban or saline, plus 7 μl of saline as a flush. In Experiment 3, atosiban was administered intracerebroventricularly (icv; 500 ng in 1 μl) using a 10 μl microsyringe, over a period of approximately 50–60 s, according to the method previously described (Gómora et al., 1994).

---

Copulation-induced antinociception and effect of Atosiban [1]
Saline or Atosiban was administered immediately after establishing the baseline vocalization response. Thirty minutes later, a sexually experienced male rat was introduced into the arena. A single 20% STS was given to females at the onset of each mounting train. Behavior patterns were defined as follows: a mount (M) consisted of the male rat climbing onto the female's rump and grasping the flanks with the forelegs, followed by approx. 15 to 20 rapid thrusts to the perineal region; intromission (I) was a mount motor pattern with insertion of the penis into the vagina; ejaculation (E) was an intromission motor pattern with a duration of approx. 640 ms (Beyer et al., 1981). The percent of STS applications that elicited vocalization following M, I, or E across the entire copulatory series was calculated for each animal, and the percent of females vocalizing after a single ejaculation (n = 8) was also determined. Thus, the timing of the shocks and the total number of shocks that each female received was determined by the male's behavior, rather than by a predetermined schedule, since the experimenter delivered each shock upon initiation of the mounting train. With this stimulation schedule, a single shock train was administered 100–150 msec after initiation of each copulatory event. A subgroup of sexually unreceptive rats (ovx and treated only with saline, 1 ml/kg body weight; n = 8) was also tested, in order to determine if mounting trains without intromissions affected the vocalization response in unreceptive females.

Absorption, Distribution and Excretion
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.
Small amounts of atosiban are found in the urine with 50 times the amount appearing as the large fragment metabolite (des-(Orn⁸, Gly⁹-NH2)-[Mpa¹, D-Tyr(Et)², Thr⁴]-oxytocin. The amount of drug excreted in the feces is not known.
Atosiban has a mean volume of distribution of 41.8 L. Atosiban crosses the placenta and, at a dose of 300 μg/min, was found to have a 0.12 maternal/fetal concentration ratio.
Atosiban has a mean clearance rate of 41.8 L/h.

---

Metabolism / Metabolites
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.

---

Biological Half-Life
Atosiban does not conform to either 1-compartment or 2-compartment kinetics. It has been determined to have an initial half life (tα) of 0.21 h and a terminal half life (tβ) of 1.7 h.

Protein Binding
Atosiban is 46-48% bound to plasma proteins in pregnant women. It is not known to partition into red blood cells. Differences in the free fraction of drug between maternal and fetal compartments are unknown.

[1]. Sanu O, et al. Critical appraisal and clinical utility of atosiban in the management of preterm labor. Ther Clin Risk Manag. 2010 Apr 26;6:191-9.
[2]. Philip J Ryan, et al. Oxytocin-receptor-expressing Neurons in the Parabrachial Nucleus Regulate Fluid Intake. Nat Neurosci. 2017 Dec;20(12):1722-1733.
[3]. Copulation-induced antinociception in female rats is blocked by atosiban, an oxytocin receptor antagonist. Horm Behav. 2019 Jan:107:76-79.
[4]. The oxytocin receptor antagonist, Atosiban, activates pro-inflammatory pathways in human amnion via G(αi) signalling. Mol Cell Endocrinol. 2016 Jan 15:420:11-23.

Atosiban is an oligopeptide.
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.

---

Drug Indication
Atosiban is indicated for use in delaying imminent pre-term birth in pregnant adult women with: - regular uterine contractions of at least 30 s duration at a rate of at least 4 per 30 min - a cervical dilation of 1-3cm (0-3cm for nulliparas) and effacement of at least 50% - a gestational age of 24-33 weeks - a normal fetal heart rate
Tractotile is indicated to delay imminent pre-term birth in pregnant adult women with: regular uterine contractions of at least 30 seconds duration at a rate of ≥ 4 per 30 minutes; a cervical dilation of 1 to 3 cm (0-3 for nulliparas) and effacement of ≥ 50%; a gestational age from 24 until 33 completed weeks; a normal foetal heart rate.
Atosiban is indicated to delay imminent pre-term birth in pregnant adult women with: regular uterine contractions of at least 30 seconds' duration at a rate of ≥ 4 per 30 minutes; a cervical dilation of 1 to 3 cm (0-3 for nulliparas) and effacement of ≥ 50%; a gestational age from 24 until 33 completed weeks; a normal foetal heart rate.

---

Mechanism of Action
Atosiban is a synthetic peptide oxytocin antagonist. It resembles oxytocin with has modifications at the 1, 2, 4, and 8 positions. The N-terminus of the cysteine residue is deaminated to form 3-mercaptopropanic acid at position 1, at position 2 L-tyrosine is modified to D-tyrosine with an ethoxy group replacing the phenol , threonine replaces glutamine at postion 4, and ornithine replaces leucine at position 8. It binds to membrane bound oxytocin receptors on the myometrium and prevents oxytocin-stimulated increases in inositol triphosphate production. This ultimately prevents release of stored calcium from the sarcoplasmic reticulum and subsequent opening of voltage gated calcium channels. This shutdown of cytosolic calcium increase prevents contractions of the uterine muscle, reducing the frequency of contractions and inducing uterine quiescence. Atosiban has more recently been found to act as a biased ligand at oxytocin receptors. It acts as an antagonist of Gq coupling, explaining the inhibition of the inositol triphosphate pathway thought to be responsible for the effect on uterine contraction, but acts as an agonist of Gi coupling. This agonism produces a pro-inflammatory effect in the human amnion, activating pro-inflammatory signal tranducer NF-κB. It is thought that this reduces atosiban's effectiveness compared to agents which do not produce inflammation as inflammatory mediators are known to play a role in the induction of labour.

---

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

---

Preterm birth is the major cause of perinatal morbidity and mortality in the developed world, and spontaneous preterm labor is the commonest cause of preterm birth. Interventions to treat women in spontaneous preterm labor have not reduced the incidence of preterm births but this may be due to increased risk factors, inclusion of births at the limits of viability, and an increase in the use of elective preterm birth. The role of antibiotics remains unproven. In the largest of the randomized controlled trials, evaluating the use of antibiotics for the prevention of preterm births in women in spontaneous preterm labor, antibiotics against anaerobes and bacterial vaginosis-related organisms were not included, and no objective evidence of abnormal genital tract flora was obtained. Atosiban and nifedipine are the main tocolytic agents used to treat women in spontaneous preterm labor, but atosiban is the tocolytic agent with the fewest maternal - fetal side effects. A well conducted randomized controlled trial comparing atosiban with nifedipine for their effectiveness and safety is needed.[1]

---

Brain regions that regulate fluid satiation are not well characterized, yet are essential for understanding fluid homeostasis. We found that oxytocin-receptor-expressing neurons in the parabrachial nucleus of mice (OxtrPBN neurons) are key regulators of fluid satiation. Chemogenetic activation of OxtrPBN neurons robustly suppressed noncaloric fluid intake, but did not decrease food intake after fasting or salt intake following salt depletion; inactivation increased saline intake after dehydration and hypertonic saline injection. Under physiological conditions, OxtrPBN neurons were activated by fluid satiation and hypertonic saline injection. OxtrPBN neurons were directly innervated by oxytocin neurons in the paraventricular hypothalamus (OxtPVH neurons), which mildly attenuated fluid intake. Activation of neurons in the nucleus of the solitary tract substantially suppressed fluid intake and activated OxtrPBN neurons. Our results suggest that OxtrPBN neurons act as a key node in the fluid satiation neurocircuitry, which acts to decrease water and/or saline intake to prevent or attenuate hypervolemia and hypernatremia.[2]

---

Aims: We hypothesized that copulation-induced temporary anti-nociception in female rats is mediated by the activation of central and/or peripheral oxytocin receptors. To test this hypothesis, we assessed the effects of intraperitoneal (ip), intrathecal (it), and intra-cerebroventricular (icv) administration of an oxytocin receptor antagonist (Atosiban), on copulation-induced temporary anti-nociception in estrous rats.
Main methods: The treatment groups were ovariectomized rats pre-treated subcutaneously (sc) with 10 μg of estradiol benzoate (EB) followed 24 h later by an sc injection of 5 μg EB, and 4 h later, by an sc injection of 2 mg progesterone (P4). Rats were then administered saline vehicle (ip, it, or icv: control groups) or atosiban (500 μg/kg ip; 500 ng it; or 500 ng icv: experimental groups). Thirty minutes after drug or saline administration, their sexual behavior was tested by pairing with a sexually-experienced male rat. Brief pulse trains of 50 Hz, 300 ms duration, supra-threshold tail electrical shocks (STS) were delivered before and during copulatory activity i.e., while the female was receiving mounts, intromissions, or ejaculations, and we recorded whether vocalization occurred in response to each STS.
Key findings: Replicating our previous findings, the vocalization response to STS in control rats was significantly attenuated during intromissions and ejaculations, compared to their baseline (pre-mating) response, indicative of anti-nociception. By contrast, rats pre-treated with Atosiban (each route of administration) failed to show an attenuation of the vocalization response to shock.
Significance: These findings provide evidence that the temporary anti-nociceptive effect of copulation in female rats is mediated by copulation-induced release of endogenous oxytocin in brain, spinal cord and periphery.[3]

---

Fetal concerns regarding the use of Atosiban are discussed in the literature mainly based on the results of the Atosiban versus placebo trial by Romero and co-workers (Romero et al., 2000) who found a higher rate of fetal-infant death in the Atosiban treated group in extremely premature infants. There was however a significant imbalance in randomisation at gestational ages with more very preterm infants being exposed to Atosiban. Atosiban crosses the placenta with an average fetal versus maternal ratio of 0.124 (Valenzuela et al., 1995) and concentrations of Atosiban do not appear to accumulate in the fetus. Romero and colleagues had previously hypothesized that the anti-vasopressin effects of Atosiban could have altered fetal responses to stress and therefore could have contributed to the poor outcome in the extremely preterm infants. However maternal and fetal cardiovascular parameters are not significantly altered when Atosiban is administered in pregnant sheep (Greig et al., 1993) and fetal oxygenation remains the same after Atosiban infusion in chronically instrumented baboons (Nathanielsz et al., 1997). Nevertheless, given the association between inflammation and poor neonatal outcome, activation or exacerbation of inflammation is not a desirable effect of any agent to be used in the context of acute preterm labour. It is therefore critical that therapeutics designed to modulate the OT/OTR system for the management of term and preterm labour take into account the effects of differential G-protein coupling of the OTR and the role of OT and selective OTR agonists/antagonists in the activation of pro-inflammatory pathways.[4]

C43H67N11O12S2

994.19

993.441

C, 51.95; H, 6.79; N, 15.50; O, 19.31; S, 6.45

90779-69-4

Atosiban acetate;914453-95-5; 90779-69-4

5311010

deamino-Cys(1)-D-Tyr(Et)-Ile-Thr-Asn-Cys(1)-Pro-Orn-Gly-NH2; deamino-cysteinyl-O4-ethyl-D-tyrosyl-L-isoleucyl-L-threonyl-L-asparagyl-L-cysteinyl-L-prolyl-L-ornithyl-glycinamide (1->6)-disulfide

CXITNCPXG

White to off-white solid powder

1.3±0.1 g/cm3

1469.0±65.0 °C at 760 mmHg

842.2±34.3 °C

0.0±0.3 mmHg at 25°C

1.549

-3.41

11

15

18

68

1770

9

CC[C@H](C)[C@H]1C(=O)N[C@H](C(=O)N[C@H](C(=O)N[C@@H](CSSCCC(=O)N[C@@H](C(=O)N1)CC2=CC=C(C=C2)OCC)C(=O)N3CCC[C@H]3C(=O)N[C@@H](CCCN)C(=O)NCC(=O)N)CC(=O)N)[C@@H](C)O

VWXRQYYUEIYXCZ-OBIMUBPZSA-N

InChI=1S/C43H67N11O12S2/c1-5-23(3)35-41(63)53-36(24(4)55)42(64)50-29(20-32(45)56)38(60)51-30(43(65)54-17-8-10-31(54)40(62)49-27(9-7-16-44)37(59)47-21-33(46)57)22-68-67-18-15-34(58)48-28(39(61)52-35)19-25-11-13-26(14-12-25)66-6-2/h11-14,23-24,27-31,35-36,55H,5-10,15-22,44H2,1-4H3,(H2,45,56)(H2,46,57)(H,47,59)(H,48,58)(H,49,62)(H,50,64)(H,51,60)(H,52,61)(H,53,63)/t23-,24+,27-,28+,29-,30-,31-,35-,36-/m0/s1

(2S)-N-[(2S)-5-amino-1-[(2-amino-2-oxoethyl)amino]-1-oxopentan-2-yl]-1-[(4R,7S,10S,13S,16R)-7-(2-amino-2-oxoethyl)-13-[(2S)-butan-2-yl]-16-[(4-ethoxyphenyl)methyl]-10-[(1R)-1-hydroxyethyl]-6,9,12,15,18-pentaoxo-1,2-dithia-5,8,11,14,17-pentazacycloicosane-4-carbonyl]pyrrolidine-2-carboxamide

Atosiban; RWJ-22,164; RW22,164; Tractocile; RWJ22164; RW-22164; Tractocile; Atosiban; 90779-69-4; Tractocile; Antocin; Antocin II; tractocil; Orf-22164; Antocile; RWJ 22164

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O : ~16.67 mg/mL (~16.77 mM)
DMSO : ≥ 16.67 mg/mL (~16.77 mM)

Solubility in Formulation 1: ≥ 1.67 mg/mL (1.68 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 16.7 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

---

Solubility in Formulation 2: ≥ 1.67 mg/mL (1.68 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 16.7 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

---

View More

Solubility in Formulation 3: ≥ 1.67 mg/mL (1.68 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 16.7 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

---

 (Please use freshly prepared in vivo formulations for optimal results.)