US regulators have rejected an application by Mallinckrodt to market stannsoporfin for newborns at risk of jaundice.

The UK group said it had received a complete response letter from the US Food and Drug Administration, outlining areas of further evaluation for resubmitting the drug for newborns ≥35 weeks of gestational age with indicators of haemolysis who are at risk of developing severe jaundice, or hyperbilirubinemia.

"The letter from the FDA was not unexpected following the outcome at the recent Advisory Committee meeting," said Steven Romano, executive vice president and chief scientific officer.

"We are evaluating the Agency's guidance and will request a meeting with the FDA in the coming months to discuss potential paths forward."

A decision on the future of the product in the US is unlikely to be make until this meeting has taken place, the firm noted.

Around 60 percent of babies have jaundice at birth, which normally disappears without intervention. However, in some cases the newborn is not able to clear excessive levels of bilirubin resulting, in an imbalance that leads to a condition called hyperbilirubinaemia. If severe and left untreated, this can lead to neurologic complications, including irreversible brain damage.

If approved, stannsoporfin, a heme oxygenase inhibitor, would be a first-in-class pharmacologic treatment for severe jaundice in newborns with a novel mechanism of action that inhibits bilirubin production at its source, Mallinckrodt noted.