GlaxoSmithKline (GSK) has initiated a Phase III programme to evaluate the efficacy and safety of retosiban, an investigational oxytocin antagonist, currently being developed to improve neonatal outcomes of babies born to women in spontaneous preterm labour by prolonging the time to delivery.

Under the Phase III programme, the first trial to be conducted is designed to show the efficacy and safety of retosiban in women with spontaneous preterm (premature) labour when compared with atosiban, an oxytocin/vasopressin antagonist.

A premature birth is when a baby is born at least three weeks before the expected due date and these babies require special care to stay alive.

These premature babies can spend months in hospital in a neonatal intensive care unit while some may suffer lifelong consequences.

The trial’s primary outcome measure is the time to delivery after the start of treatment, while the secondary endpoints will measure neonatal morbidities and mortality.

A follow-up trial will be carried out to evaluate the long-term safety and outcomes of the infants born to mothers participating in the retosiban treatment studies.

The company said that further studies in this programme are also planned.

GSK Maternal & Neonatal Health Unit head and vice-president Pauline Williams said: "Preterm birth is a leading cause of illness and death in newborns and infants worldwide.

"As part of our efforts to address this issue, we are evaluating whether retosiban can potentially stop preterm labour and whether increasing the gestational age of a newborn baby can reduce the complications of prematurity."

Currently, retosiban is not approved or licensed for use anywhere in the world.

Spontaneous preterm labour accounts for about 40-50% of preterm births and is the leading cause of worldwide morbidity and death in newborns and infants.

According to the pre-clinical data, retosiban is shown to be a potent and highly selective oxytocin receptor antagonist.

Image: GlaxoSmithKline headquaters in London, UK. Photo: courtesy of Maxwell Hamilton.