GlaxoSmithKline faces a delay in getting approval for its investigational nausea drug Rezonic after regulators in the USA asked for more information on the treatment.

The company revealed that it has received a complete response letter from the US Food and Drug Administration regarding Rezonic (casopitant). The drug was filed with the agency in May last year for the prevention of chemotherapy-induced and post-operative nausea and vomiting for cancer or surgical patients.

GSK gave no other information, merely noting that such a letter is issued when the review of a file is completed and “questions remain that preclude the approval of the application". The firm added that it is reviewing the letter “and will engage with the FDA to determine appropriate next steps”.

GSK already markets Zofran (ondansetron) to prevent nausea and vomiting caused by surgery or cancer medicines and data was recently published showing that the addition of Rezonic to the former and dexamethasone significantly reduces chemotherapy-induced nausea and vomiting compared with Zofran and dexamethasone alone. If approved, it will compete with the likes of Merck & Co's Emend (aprepitant), Eisai's Aloxi (palonosetron) and Par Pharmaceutical's Marinol (dronabinol).