Regulatory and methodologic challenges to tocolytic development

Effect of Rubus idaeus L. Consumption During Pregnancy on Maternal Mice and Their Offspring

The trigger for human labor is a scientific mystery. This research examined Rubus idaeus (RI), commonly referred to as red raspberry, which is widely purported to be efficacious in promoting parturition processes and favorable birth outcomes. This randomized controlled trial sought to determine the influence of RI consumption during gestation on C57BL/6N Tac mice and their offspring. The aims of this study were to (1) determine differences in the length of gestation, gestational weight gain, and litter size where RI is consumed daily at varied strengths and (2) determine differences in offspring characteristics and behavior where maternal RI consumption occurred. Once paired, mice were randomly assigned to one of three groups: placebo (n = 10) receiving plain water, RI aqueous extract fluid of 1.78 mg/mL (n = 10), or RI aqueous extract fluid of 2.66 mg/mL (n = 10). All received the same standardized diet throughout gestation. Pregnant mice were weighed with chow intake and fluid consumption determined daily. Gestation length and litter size were recorded at the time of birth. Differences in offspring characteristics were also determined and included physical characteristics (weight, physical development) and neuromotor reflexes and behaviors (locomotive abilities, geotaxis reflex, cliff avoidance reflex, and swimming development). When compared with controls, high-dose RI ingestion resulted in shorter length of gestation and smaller litter size (P ≤ .05). There was also an increase in fluid consumption and a decrease in pup weights on postnatal day 4 and 5 with RI treatment (P ≤ .05). Altogether, results suggest that RI influences parturition and fecundity processes with transplacental exposure impacting offspring characteristics.

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..

Randomized Trials of Retosiban Versus Placebo or Atosiban in Spontaneous Preterm Labor

OBJECTIVE

The aim of this study is to assess the efficacy and safety of retosiban in spontaneous preterm labor (sPTL).

STUDY DESIGN

Two multicenter, randomized, and double-blind trials compared retosiban with placebo and retosiban with atosiban in women with a singleton pregnancy and intact membranes in sPTL at 24 to 33^6/7 weeks' gestation. Coprimary endpoints in the placebo-controlled trial were time to delivery (TTD) or treatment failure (whichever occurred first) and neonatal composite morbidity and mortality. The primary endpoint of the atosiban comparator trial was TTD.

RESULTS

The trials were terminated early because of slow recruitment. The placebo-controlled trial enrolled 23 participants (February 2016-July 2017; 2.6% of target);the atosiban-comparator trial enrolled 97 (March 2015-August 2017; 29% of target). Baseline participant characteristics were similar between treatments. In the placebo-controlled trial, mean gestational ages at randomization were 30.8 (retosiban, n = 10) and 30.5 weeks (placebo, n = 13), and mean times to delivery/treatment failure were 18.9 days (retosiban) and 11.1 days (placebo). Two and four neonates in the retosiban and placebo groups, respectively, had ≥1 component of the neonatal composite endpoint. In the atosiban-comparator trial, mean gestational age at randomization was 31.5 weeks (for both retosiban, n = 47, and atosiban, n = 50), and adjusted mean TTDs were 32.51 days (retosiban) and 33.71 days (atosiban; p > 0.05). Adverse events were no more common with retosiban than placebo or atosiban.

CONCLUSION

Despite considerable efforts to conduct two adequate and well-controlled studies in patients with sPTL, both studies were unable to recruit effectively and consequently terminated prematurely. Key factors negatively affecting participation were patient and physician resistance to use of a placebo comparator, lack of investigator consensus on diagnostic criteria and acceptance of protocol procedures, and ethics committee decisions. Meaningful cooperation between pharmaceutical companies, regulatory authorities, and the obstetric community is essential for future development of drugs to treat sPTL.

Drug discovery strategies for the identification of novel regulators of uterine contractility

Preterm birth and postpartum hemorrhage are the leading causes of neonatal and maternal morbidities worldwide, respectively. Current clinically utilized tocolytics and uterotonics to manage these obstetric conditions are limited due to their off-target effects and/or lack of efficacy. Thus, an ideal tocolytic or uterotonic would be uterine-selective with rapid onset and long-duration efficacy. Here, we discuss strategies for the discovery of new therapeutic targets and compounds that regulate uterine contractility with the aforementioned properties.

The effect of barusiban, a selective oxytocin antagonist, in threatened preterm labor at late gestational age: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

The objective of the study was to compare barusiban with placebo in threatened preterm labor.

STUDY DESIGN

This was a randomized, double-blind, placebo-controlled, multicenter study. One hundred sixty-three women at 34-35 weeks plus 6 days, and with 6 or more contractions of 30 seconds duration during 30 minutes, cervical length 15 mm or less, and cervical dilatation > 1 and < 4 cm were randomized to a single intravenous bolus of barusiban (0.3, 1, 3, or 10 mg) or placebo. The primary endpoint was percentage of women who did not deliver within 48 hours.

RESULTS

None of the barusiban doses reduced the number of uterine contractions compared with placebo. There was no significant difference in the percentage of women who did not deliver within 48 hours (72% placebo and 65-88% barusiban groups; P = .21-.84). Barusiban was not associated with an adverse safety profile in the woman, fetus, neonate, or infant.

CONCLUSION

An intravenous bolus of barusiban was no more effective than placebo in stopping preterm labor in pregnant women at late gestational age.

Emerging tocolytics: challenges in designing and testing drugs to delay preterm delivery and prolong pregnancy

The global rate of preterm delivery (before 37 completed weeks of pregnancy) is increasing and there are no effective means available to prevent this rise. Prematurity is the principal cause of neonatal mortality and a major cause of pediatric morbidity and long-term disability. Current strategies to prolong pregnancy are based on inhibiting the mechanisms that effect uterine smooth muscle (myometrium) contractions in women who are in preterm labor. Most drugs in this group were developed for other purposes. Newer strategies are designed to maintain a state of uterine quiescence and pregnancy, preventing the myometrium from initiating contractions and entering preterm labor. Again, it may be possible to use existing drugs for pregnancy maintenance. Several financial and practical barriers exist for developing completely new drugs to delay labor. Designing clinical trials to test tocolytics is complicated, as the health of two patients must be considered and the nature of preterm birth and its outcomes are different at early preterm labor (< 28 weeks) and late preterm labor (34 - 36 weeks).