Cubist Pharmaceuticals has signed an agreement to acquire fellow US firm Adolor Corp and get access to the latter's bowel drug Entereg and a potential treatment for constipation.

Under the terms of the deal, Cubist will pay $4.25 per share in cash, or $190 million upfront. In addition, each Adolor stockholder will pocket up to $4.50 for each share they own if various milestones for ADL5945, an investigational treatment of chronic opioid induced constipation (OIC), are achieved. The total transaction is valued at up to $415 million and is expected to be accretive in 2012.

Adolor currently markets Entereg (alvimopan), the only therapy approved by the US Food and Drug Administration to help patients regain gastrointestinal function (post-operative ileus) earlier following bowel resection surgery. The treatment was licensed to GlaxoSmithKline but last month Adolor bought back the rights from the drugs giant for $25 million, plus royalties.

Launched in 2008, Entereg had US sales of over $25 million in 2010 and $15.7 million for the first half of this year. Cubist chief executive Michael Bonney believes the therapy has great "and we believe our experienced sales force and strong commercial platform will realise the potential of this important hospital product". Peak Entereg sales could top$100 million annually, Cubist believes.

The company also has high hopes for ADL5945, saying that OIC is "a growing, multi-billion dollar, currently underserved market". Adolor announced positive Phase II data in August 2011 and Phase III trials are expected to be initiated in 2012. Cubist plans to retain certain US and specialty rights, "while seeking a partner to assist with ex-US and primary care commercialisation".

Last week, Cubist, which itself has been seen as a takeover target, posted a 24% rise in revenues to $201.7 million for the third quarter, driven by sales of Cubicin (daptomycin), for the treatment of complicated skin infections and bacteremia caused by MRSA, which were up 21% to $186.4 million. However, net income fell 22.4% to $24.2  million.