Refining Pharmacologic Research to Prevent and Treat Spontaneous Preterm Birth

Vaginal Nanoformulations for the Management of Preterm Birth

Preterm birth (PTB) is a leading cause of infant morbidity and mortality in the world. In 2020, 1 in 10 infants were born prematurely in the United States. The World Health Organization estimates that a total of 15 million infants are born prematurely every year. Current therapeutic interventions for PTB have had limited replicable success. Recent advancements in the field of nanomedicine have made it possible to utilize the vaginal administration route to effectively and locally deliver drugs to the female reproductive tract. Additionally, studies using murine models have provided important insights about the cervix as a gatekeeper for pregnancy and parturition. With these recent developments, the field of reproductive biology is on the cusp of a paradigm shift in the context of treating PTB. The present review focuses on the complexities associated with treating the condition and novel therapeutics that have produced promising results in preclinical studies.

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..

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.

Intramuscular 17α-hydroxyprogesterone caproate to decrease preterm delivery in women with placenta praevia: a randomised controlled trial

We tested the hypothesis that 17α-hydroxyprogesterone caproate (17α-OHP-C) may decrease preterm delivery (PTD) in women with placenta praevia. This was a randomised controlled trial included 114 women with placenta praevia (between 24 and 28 weeks). They were randomly assigned to group I (17α-OHP-C) who received weekly injection of 17α-OHP-C (250 mg/IM) till completing 37 weeks' gestation or group II (Non 17α-OHP-C). The percentage of placenta praevia patients went into PTD in the 17α-OHP-C group was significantly less in comparison to the PTD in the Non 17α-OHP-C group (∼37% vs. 63.5%, p = .004). Furthermore, the mean gestational age was significantly longer (36.7 ± 0.7 vs. 34.9 ± 1.2 weeks, p < .000), the mean number of bleeding attacks was significantly less and the mean birth weight was significantly higher (2841 ± 159 vs. 2561 ± 168 g, p < .000). In conclusion, maintenance tocolysis with intramuscular 17α-OHP-C in placenta praevia women appears beneficial in decreasing the number of bleeding attacks, the percentage of PTD and the neonatal ICU admission.IMPACT STATEMENTWhat is already known on this subject? Over the last two decades, a large number of studies indicated that placenta praevia is a major risk factor for preterm labour and prematurity with its neonatal complications. Increasing caesarean section rates had proportionally increased the incidence of placenta praevia.What do the results of this study add? Up to now, the effective and safe tocolytic agent among these patients is not established. The results of this study (prospective, randomised and controlled with calculated sample size) added a considerable support for hydroxyprogesterone caproate as an effective, safe and cheap tocolytic agent with excellent patient compliance.What are the implications of these findings for clinical practice and/or further research? Our findings may prompt researchers to conduct a large multicentre study to evaluate the prophylactic use of hydroxyprogesterone caproate to decrease preterm labour due to placenta praevia.

Spontaneous preterm labour that leads to preterm birth: An update and personal reflection

OBJECTIVE

The objective was to provide an update of progress made over time (including personal reflection) of our attempts to reduce the mortality and morbidity associated with spontaneous preterm labour that leads to preterm birth.

METHODS

An experienced and evidence based approach was taken to provide an overview of progress made over a generation (∼40 years) in our understanding of spontaneous preterm labour.

RESULTS

It is evident that we have made significant progress in our understanding of the aetiology, the measurement of the burden, the basic science, systems biology and mechanical pathways of the preterm parturition syndrome. We have better ways of predicting, preventing and managing spontaneous preterm labour than existed a generation ago.

CONCLUSIONS

The profile of spontaneous preterm labour that leads to preterm birth, thanks to organisations such as the March of Dimes, WHO and PREBIC is much more evident than before. However, while we have come a long way, we must not be complacent, and clinicians and basic scientists must continue to work in harmony, while recruiting and encouraging young investigators to join the effort to improve survival and handicap in what is one of the Great Obstetric Syndromes.