US regulators are demanding more safety data from GlaxoSmithKline and partner Adolor Corp before they will consider giving the green light to the firm’s investigational bowel drug Entereg.

The companies have confirmed that the US Food and Drug Administration has requested that additional data be submitted as part of the complete response to the approvable letter it issued last November for Entereg/Entrareg (alvimopan) in postoperative ileus. The agency has placed the investigational New Drug Application for Entereg on clinical hold pending submission and analysis of the requested information, and neither GSK nor Adolor currently have any ongoing studies on the drug.

Therefore, the additional data requested by the FDA include the final results of Study 101684, an extension of the Phase IIb Study 008 of alvimopan in cancer pain patients with opioid-induced bowel dysfunction (OBD), as well as further analysis of results from Study 014 and the final study reports from the two-year carcinogenicity studies in rats and mice, which were conducted to support the OBD indication. It also wants to see safety data from one of Adolor’s studies which has been discontinued to enable final data collection and analysis.

Entereg is vital to the fortunes of Adolor and its share price collapsed in April following the suspension of trials of the drug over fears of fractures and cardiovascular risk. The firm’s chief executive, Michael Dougherty, said “we are working closely with GSK to complete analyses of these studies and satisfy all requests for data for our complete response,” and the submission is scheduled to occur in the third quarter of this year. It will be only then that GSK will update its development plans for the drug.