Administration of Atosiban, an oxytocin receptor antagonist, ameliorates autistic-like behaviors in a female rat model of valproic acid-induced autism

Autism spectrum disorder (ASD) is a pervasive developmental disorder with gender differences. Oxytocin (OXT) is currently an important candidate drug for autism, but the lack of data on female autism is a big issue. It has been reported that the effect of OXT is likely to be different between male and female ASD patients. In the study, we specifically explored the role of the OXT signaling pathway in a VPA-induced female rat's model of autism. The data showed that there was an increase of either oxytocin or its receptor expressions in both the hippocampus and the prefrontal cortex of VPA-induced female offspring. To determine if the excess of OXT signaling contributed to autism symptoms in female rats, exogenous oxytocin and oxytocin receptor antagonists Atosiban were used in the experiment. It was found that exogenous oxytocin triggered autism-like behaviors in wild-type female rats by intranasal administration. More interestingly, several autism-like deficits including social interaction, anxiety, and repeat stereotypical sexual behavior in the VPA female offspring were significantly attenuated by oxytocin receptor antagonists Atosiban. Moreover, Atosiban also effectively improved the synaptic plasticity impairment induced by VPA in female offspring. Our results suggest that oxytocin receptor antagonists significantly improve autistic-like behaviors in a female rat model of valproic acid-induced autism.

The Current Status of Drug Discovery for the Oxytocin Receptor

The oxytocin receptor plays a significant role in peripheral regulation of parturition and lactation. Given this important role, multiple drug discovery programs have been conducted to develop agonists and antagonists for peripheral activity. The role of the oxytocin receptor in the central nervous system is also significant, promoting social interaction, trust, and empathy in humans. As such, molecules that can access the central nervous system and target the oxytocin receptor are of significant interest. Due to the role of the oxytocin receptor in regulating social function and psychological well-being, agonists of this receptor have considerable promise for the treatment of numerous neuropsychiatric conditions. The poor pharmacokinetic properties and blood-brain barrier penetration of peptide-based molecules means nonpeptide compounds have more commonly been the focus for central nervous system activity. This chapter aims to summarize the current standing of peptide and nonpeptide drug discovery for antagonists and agonists of the oxytocin receptor and focusses on centrally active nonpeptidic agonists.

Optimal Method for Disulfide Bond Closure in the Synthesis of Atosiban—Antagonist of Oxytocin Receptors

Abstract

This work is devoted to the large-scale solid-phase synthesis (SPS) of Atosiban, Mpa1-D-Tyr(OEt)-Ile-Thr-Asn-Cys6-Pro-Orn-Gly-NH2 cyclic 1,6 disulfide, the only clinically used oxytocin receptor antagonist. The conditions have been selected for the closure of the disulfide bond (S–S) in the Atosiban molecule both in the solution and solid phase with the minimal formation of by-products. A comparative assessment of the formation of the S–S bond was carried out under various conditions. The formation of by-products during the closure of the disulfide bond has been studied both in solution and on the polymer support. The developed technique allows for the synthesis of Atosiban on an enlarged scale (10–20 mmol) involving the cyclization of a protected intermediate with the formation of the S–S bond during solid-phase synthesis with the minimal formation of by-products.

Novel oxytocin receptor antagonists for tocolysis: a systematic review and meta-analysis of the available data on the efficacy, safety, and tolerability of retosiban

OBJECTIVE

To assess the efficacy, safety, and tolerability of retosiban-a novel tocolytic unavailable in the US-in the management of preterm labor.

METHODS

We searched ClinicalTrials.Gov, MEDLINE, PubMed, SCOPUS, Web of Science, and the Cochrane Library for relevant clinical trials using the terms "retosiban" and "preterm labor" through 09/2020. We included all published randomized clinical trials (three) that compared retosiban to placebo for preterm labor, excluding conferences, books, reviews, posters, case reports, and animal studies. We analyzed homogeneous data under the fixed-effects model and heterogeneous data under the random-effects model.

RESULTS

We included all randomized clinical trials addressing this topic, which ultimately resulted in three trials with a total of 116 patients. There were no significant differences between retosiban and placebo in births at term (RR = 0.41, p = .02), births ≤7 days from the first study treatment (RR = 0.59, p = .23), or administration of rescue tocolytic (RR = 0.36, p = .07); the maternal adverse events of headache, anemia, constipation, or urinary tract infection (p > .05); or neonatal outcomes of Apgar score at 1 min (p = .88) or 5 min (p = .69), weight (p = .23), head circumference (p = .55), malnutrition (p = .27), hyperbilirubinemia (RR = 0.56, p = .21), jaundice (RR = 1.21, p = .84), respiratory distress (RR = 0.53, p = .49), or tachypnea (RR = 0.40, p = .42).

CONCLUSION

With the limited high quality evidence available, retosiban demonstrates no clear benefit over placebo in the management of preterm labor. Nevertheless, its favorable safety profile, oral bioavailability, and novel mechanism of action and the limited number of studies available for review warrant further analysis.

Safety and Outcomes in Infants Born to Mothers Participating in Retosiban Treatment Trials: ARIOS Follow-Up Study

OBJECTIVE

 Retosiban, an oxytocin receptor antagonist, was developed for treating spontaneous preterm labor (sPTL) in women with intact membranes. This ARIOS follow-up study aimed to characterize clinical safety, morbidity, and mortality of infants exposed to retosiban or comparator over 2 years.

STUDY DESIGN

 ARIOS prospectively assessed outcomes in infants whose mothers received at least one dose of retosiban or comparator (placebo/atosiban) in two Phase 3 sPTL trials. Both trials were terminated prematurely owing to poor enrolment. Infants could be enrolled into ARIOS from 28 days after estimated due date until hospital discharge or up to 9 months (corrected age). An internally developed questionnaire detailing medical conditions, mortality and resource use (Child Health Inventory; CHI), Ages and Stages Questionnaire-3 (ASQ-3), Modified Checklist for Autism in Toddlers-Revised with Follow-Up, and Child Behavior Checklist for Ages 1.5 to 5 were completed remotely by parents or legal guardians at prespecified intervals. Serious adverse events (SAEs) were primarily captured via CHI. No comparative statistical analysis was conducted between treatment arms.

RESULTS

 A total of 49 (86%) infants who had received retosiban and 49 (78%) infants who had received a comparator were enrolled in ARIOS. No deaths occurred during the study. Nine infants experienced SAEs: 6/49 (12.2%) infants in the comparators group and 3/49 (6.1%) in the retosiban group. Of the nine SAEs, seven were due to infections, three, and four in the retosiban and comparators groups, respectively. Based on ASQ-3 score, the incidence of neurodevelopmental delay at 18 and 24 months were 0/18 (0%) and 2/25 (8%) with retosiban and 7/22 (31.8%) and 3/21 (14.3%) with comparator, respectively.

CONCLUSION

 The current study showed no unexpected adverse outcome or impairment with retosiban based on safety monitoring and neurodevelopment assessments. No further follow-up is intended owing to the discontinuation of clinical development of retosiban.

KEY POINTS

· There is a need for an effective and safe treatment for sPTL.. · ARIOS was a follow-up study of two Phase 3 trials in sPTL.. · There were no safety concerns with retosiban treatment.. · Slow recruitment led to termination of the Phase 3 trials..

Effectiveness and safety of atosiban versus conventional treatment in the management of preterm labor

OBJECTIVE

To compare the efficacy of atosiban with conventional treatment of the threatened preterm labor.

MATERIALS AND METHODS

All the data of pregnant women with threatened preterm labor from January 1 to December 31, 2017, who received atosiban were collected. Pregnant women with conventional treatment (including β-agonists, indomethacin, magnesium sulphate and calcium channel blockers, alone or in combination) were used as control.

RESULTS

The proportion of women not requiring an alternative tocolytic treatment within 48 h and remaining undelivered was significantly higher in atosiban treatment group (89.3%; n = 25/28) compared with conventional treatment (24.2%; n = 8/33) (P < 0.0001). For therapy efficacy, there was also no significant difference between atosiban groups and conventional treatment groups in the low gestational ages. However, for the high gestational ages, atosiban treatment group showed higher efficacy (84%; n = 21/25 vs. 37.5%; n = 3/8) (P < 0.05). Moreover, a significantly higher proportion of women in the atosiban treated group (89.3%; n = 25/28) was observed compared with the conventional treatment groups (51.5%; n = 17/33) who did not receive an alternative tocolytic within 48 h (P < 0.01). Maternal and fetal safety was significantly superior with atosiban treatment.

CONCLUSIONS

Our results support that atosiban would represent an advance over current tocolytic therapy especially for the high gestational ages.

Safety and Efficacy of Tocolytics for the Treatment of Spontaneous Preterm Labour

BACKGROUND

Preterm birth is the major cause of perinatal mortality and morbidity worldwide. Attempts to reduce the burden may be proactive using biochemical or biophysical prediction and preventative measures. If these efforts fail, then the approach may have to be reactive using tocolytics to inhibit spontaneous preterm labour.

OBJECTIVE

We have reviewed the evidence concerning the safety and efficacy of various classes of tocolytic agents.

RESULTS

The evidence to support the use of magnesium sulfate or nitric oxide donors as a tocolytic is poor. Compared to placebo or no treatment, there is evidence to support the efficacy of calcium channel blockers (mainly nifedipine), prostaglandin synthetase inhibitors (mainly indomethacin and sulindac), oxytocin receptor antagonists (mainly atosiban) and β2-agonists (mainly ritodrine, terbutaline, salbutamol and fenoterol). Maternal safety concerns have reduced the use of β2-agonists. Fetal safety and gestational age restrictions have largely condemned prostaglandin synthetase inhibitors to second-line therapy. First-line therapy in Europe and other parts of the world outside the USA and Australia is limited to calcium channel blockers and oxytocin receptor antagonists. With respect to efficacy, atosiban and nifedipine are similar, but the robustness of the evidence favours atosiban. With respect to safety, atosiban is clearly the safest tocolytic as there are fetomaternal concerns with nifedipine, particularly in high daily doses.

CONCLUSION

The perfect tocolytic that is uniformly effective and safe does not exist. Cost, licensing and informed consent are considerations involved in the choice. Efforts continue to develop and introduce other or better agents, including novel compounds such as progesterone, PGF2α antagonists and statins.

Discovery of SHR1653, a Highly Potent and Selective OTR Antagonist with Improved Blood-Brain Barrier Penetration

The oxytocin receptor (OTR) plays a major role in the control of male sexual responses. Antagonists of the OTR have been reported to inhibit ejaculation in animal models and serve as a potential treatment for premature ejaculation (PE). Herein, we describe a novel scaffold featuring an aryl substituted 3-azabicyclo [3.1.0] hexane structure. The lead compound, SHR1653, was shown to be a highly potent OTR antagonist, which exhibited excellent selectivity over V_1AR, V_1BR, and V₂R. This novel molecule was shown to have a favorable pharmacokinetic profile across species, as well as robust in vivo efficacy in a rat uterine contraction model. Interestingly, SHR1653 exhibited excellent blood-brain barrier penetration, which might be beneficial for the treatment of CNS-related PE.

Perception of social interaction compresses subjective duration in an oxytocin-dependent manner

Communication through body gestures permeates our daily life. Efficient perception of the message therein reflects one’s social cognitive competency. Here we report that such competency is manifested temporally as shortened subjective duration of social interactions: motion sequences showing agents acting communicatively are perceived to be significantly shorter in duration as compared with those acting noncommunicatively. The strength of this effect is negatively correlated with one’s autistic-like tendency. Critically, intranasal oxytocin administration restores the temporal compression effect in socially less proficient individuals, whereas the administration of atosiban, a competitive antagonist of oxytocin, diminishes the effect in socially proficient individuals. These findings indicate that perceived time, rather than being a faithful representation of physical time, is highly idiosyncratic and ingrained with one’s personality trait. Moreover, they suggest that oxytocin is involved in mediating time perception of social interaction, further supporting the role of oxytocin in human social cognition.

Einstein once joked: “Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute. That’s relativity.” While it may not have helped explain the space-time continuum, his joke neatly captures how time can appear to pass at different rates. This perception depends in part on the sensory properties of the stimuli we are experiencing. Intense stimuli, such as bright and fast-moving objects, trigger stronger responses in the brain than less intense stimuli, and so we perceive them as longer lasting.

But what role do we, as the experiencers, play in how we perceive time? To find out, Liu, Yuan, Chen et al. showed volunteers pairs of movie clips, each featuring two human figures outlined by dots. In one clip, the two figures interacted socially, for example by passing an object between them. In the other, the two figures moved independently of each other. The volunteers had to decide which clip lasted longer.

The volunteers generally judged clips containing social interactions to be shorter than those without such interactions, even when this was not the case. Moreover, volunteers with better social skills tended to underestimate the length of the social interaction clips to a greater extent.

Previous studies have shown that people who are more social tend to have higher levels of a hormone called oxytocin in their blood. Oxytocin is sometimes referred to as the ‘love hormone’ because it promotes social behavior and bonding. Applying an oxytocin nasal spray to the volunteers who were less socially proficient caused them to perceive the social interaction clips as shorter than before. By contrast, socially proficient volunteers who used a nasal spray that blocks the effects of oxytocin perceived these clips as longer than they had done previously (although they still judged the clips to be shorter than videos that did not show people interacting).

The perception of time thus varies between people and may depend at least in part on personality. These results open up a new avenue for studying and manipulating how we process social situations. This could eventually benefit people who struggle with social interactions, such as those with autism spectrum disorders.