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].

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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].

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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].

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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.

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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.

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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.

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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.

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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).

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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 a 300 μg/min infusion over 6–12 hours, the mean steady-state concentration reached was 442 ng/mL within 1 hour. Steady-state concentration increased proportionally with dose. Small amounts of atosiban were detectable in urine, while 50 times the amount was found as a large fragment metabolite (des-(Orn⁸, Gly⁹-NH₂)-[Mpa¹, D-Tyr(Et)², Thr⁴]-oxytocin). The amount of drug excreted in feces is unknown. The mean volume of distribution of atosiban was 41.8 L. Atosiban crosses the placenta, with a maternal/fetal concentration ratio of 0.12 at a dose of 300 μg/min. The mean clearance of atosiban was 41.8 L/h.

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Metabolism/Metabolites
Atosiban has two metabolites, which are produced by the cleavage of the peptide bond between ornithine and proline. Pre-cleavage of the disulfide bond is thought to promote its metabolism. The larger fragment retains oxytocin receptor antagonist activity, but its potency is 10-fold lower than that of the parent molecule. At a dose of 300 μg/min, the ratio of the parent molecule to the major metabolite was 1.4 at the second hour of infusion and 2.8 at the end of infusion.

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Biological Half-Life
Atosiban does not conform to single-compartment or two-compartment kinetic models. Its initial half-life (tα) is 0.21 hours, and its terminal half-life (tβ) is 1.7 hours.

Protein Binding
Atosiban has a protein binding rate of 46-48% in pregnant women's plasma. It is currently unclear whether it enters red blood cells. The difference in the proportion of free drug in maternal and fetal bodies is also 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. It is an inhibitor of oxytocin and vasopressin. It is administered intravenously to prevent preterm labor. Although initial studies suggested its use as a nasal spray, eliminating the need for hospitalization, this formulation is not currently used. Atosiban was developed by the Swedish company Ferring Pharmaceuticals. The drug was first reported in the literature in 1985. Atosiban is approved in both patented and generic form for delaying impending preterm labor in pregnant adult women.

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Indications
Atosiban is indicated for delaying impending preterm labor in pregnant adult women who meet the following criteria: - Regular uterine contractions lasting at least 30 seconds each, occurring at least 4 times every 30 minutes; - Cervical dilation of 1-3 cm (0-3 cm for primiparous women), with at least 50% cervical effusion; - Gestational age of 24-33 weeks; - Normal fetal heart rate.
Tractotile is indicated for delaying impending preterm labor in pregnant adult women who meet the following criteria: regular uterine contractions lasting at least 30 seconds each, at a frequency of at least 4 times every 30 minutes; cervical dilation of 1 to 3 cm (0 to 3 cm for primiparous women), with cervical canal annihilation ≥ 50%; gestational age of 24 to 33 weeks; and normal fetal heart rate.
Atosiban is indicated for delaying impending preterm labor in adult pregnant women who meet the following criteria: regular uterine contractions lasting at least 30 seconds each, at a frequency of ≥ 4 times/30 minutes; cervical dilation of 1 to 3 cm (0 to 3 cm for primiparous women), with cervical canal annihilation ≥ 50%; gestational age of 24 to 33 weeks; and normal fetal heart rate.
Mechanism of Action
Atosiban is a synthetic peptide oxytocin antagonist. It has a structure similar to oxytocin, but with modifications at positions 1, 2, 4, and 8.
The N-terminus of the cysteine residue undergoes deamination at position 1 to form 3-mercaptopropionic acid, the L-tyrosine at position 2 is modified to D-tyrosine, the phenolic hydroxyl group is replaced by an ethoxy group, glutamine at position 4 is replaced by threonine, and leucine at position 8 is replaced by ornithine. It binds to the membrane-bound oxytocin receptor on the myometrium, inhibiting oxytocin-stimulated increase in inositol triphosphate production. This ultimately prevents the release of calcium stored in the sarcoplasmic reticulum and the subsequent opening of voltage-gated calcium channels. The decrease in cytoplasmic calcium concentration inhibits myometrial contraction, thereby reducing the frequency of uterine contractions and inducing uterine quiescence. Recent studies have found that atosiban can act as a biased ligand for the oxytocin receptor. It functions as a Gq-coupled antagonist, explaining its inhibitory effect on the inositol triphosphate pathway (which is thought to be involved in uterine contractions), but simultaneously acts as a Gi-coupled agonist. This agonistic effect produces a pro-inflammatory effect in the human amnion, activating the pro-inflammatory signaling transduction molecule NF-κB. It is believed that this reduces the efficacy of atosiban compared to non-inflammatory drugs, as inflammatory mediators are known to play a role in labor induction. Pharmacodynamics Atosiban reduces the frequency of uterine contractions in adult women, thereby delaying preterm labor and inducing uterine quiescence. Preterm birth is a leading cause of perinatal morbidity and mortality in developed countries, with spontaneous preterm birth being the most common cause. Interventions for women with spontaneous preterm birth have not reduced the incidence of preterm birth, but this may be due to increased risk factors, the inclusion of fetuses at the survival limit, and the increased use of selective preterm birth. The role of antibiotics remains unproven. The largest randomized controlled trial evaluating antibiotics for the prevention of preterm birth in women with spontaneous preterm birth did not include antibiotics targeting anaerobic bacteria and pathogens associated with bacterial vaginosis, nor did it obtain objective evidence of abnormal reproductive tract flora. Atosiban and nifedipine are the main tocolytic agents for treating women with spontaneous preterm birth, but atosiban has the fewest maternal and fetal side effects. A well-designed randomized controlled trial is needed to compare the efficacy and safety of atosiban and nifedipine. [1] The brain regions that regulate fluid saturation have not been adequately characterized, but are crucial for understanding fluid homeostasis. We found that neurons expressing oxytocin receptors in the parabrachial nucleus of mice (OxtrPBN neurons) are key factors in regulating fluid saturation. Chemogenetic activation of OxtrPBN neurons significantly inhibited non-caloric fluid intake but did not reduce food intake after fasting or salt intake after salt depletion; while inactivation of OxtrPBN neurons increased saline intake after dehydration and hypertonic saline injection. Under physiological conditions, both fluid saturation and hypertonic saline injection can activate OxtrPBN neurons. OxtrPBN neurons are directly innervated by paraventricular hypothalamic oxytocin neurons (OxtPVH neurons), which slightly inhibit fluid intake. Activation of neurons in the nucleus tractus solitarius significantly inhibited fluid intake and activated OxtrPBN neurons. Our findings suggest that OxtrPBN neurons are key nodes in the fluid saturation neural circuit, which reduce water and/or saline intake to prevent or alleviate hypervolemia and hypernatremia. [2]

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Objective: We hypothesized that mating-induced transient analgesia in female rats is mediated by activation of central and/or peripheral oxytocin receptors. To test this hypothesis, we evaluated the effects of intraperitoneal (ip), intrathecal (it), and intraventricular (icv) administration of an oxytocin receptor antagonist (atosiban) on mating-induced transient analgesia in estrus rats.
Main methods: The treatment group consisted of ovariectomized rats that were pre-administered with a subcutaneous injection (sc) of 10 μg estradiol benzoate (EB), followed by a subcutaneous injection of 5 μg EB 24 hours later, and a subcutaneous injection of 2 mg progesterone (P4) 4 hours later. Subsequently, rats were injected with either saline (ip, it, or icv: control group) or atosiban (500 μg/kg ip; 500 ng it; or 500 ng icv: experimental group). Thirty minutes after administration of the drug or saline, their sexual behavior was tested by pairing them with a sexually experienced male rat. A 50 Hz, 300 ms overthreshold tail shock (STS) was applied before and during mating (i.e., when the female accepted mounting, penetration, or ejaculation), and vocalization in response to each STS was recorded.
Key Findings: Consistent with our previous findings, compared to baseline (pre-mating) response, control rats showed a significantly reduced vocalization response to STS during penetration and ejaculation, indicating the presence of a nociceptive mechanism. In contrast, rats pre-treated with atosiban (regardless of the route of administration) did not show a reduced vocalization response to the shock.
Significance: These findings suggest that the transient analgesic effect of mating in female rats is mediated by mating-induced release of endogenous oxytocin in the brain, spinal cord, and peripheral tissues. [3]

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Regarding the fetal risks of atosiban use, the literature is mainly based on the results of a placebo-controlled atosiban trial conducted by Romero et al. (Romero et al., 2000). This trial found that fetal-infant mortality was higher in the atosiban-treated group in extremely preterm infants. However, there was a significant imbalance in the randomization of gestational age in this trial, resulting in more extremely preterm infants being exposed to atosiban. The mean fetal to maternal concentration ratio of atosiban across the placenta was 0.124 (Valenzuela et al., 1995), and atosiban did not appear to accumulate in the fetus. Romero et al. had previously hypothesized that the anti-vasopressin effect of atosiban might alter the fetal response to stress, leading to poor outcomes in extremely preterm infants. However, no significant changes were observed in maternal and fetal cardiovascular parameters after administration of atosiban to pregnant sheep (Greig et al., 1993), and fetal oxygenation remained unchanged after infusion of atosiban to baboons with long-term implanted devices (Nathanielsz et al., 1997). Nevertheless, given the association between inflammation and poor neonatal outcomes, any drug used for acute preterm birth should not produce adverse effects that activate or exacerbate inflammation. Therefore, therapeutic drugs designed to modulate the OT/OTR system to control term and preterm birth must take into account the effects of G protein coupling differences in OTR and the role of OT and selective OTR agonists/antagonists in activating 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.

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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.

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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.

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