Pfizer is weighing up whether to continue trying to get approval for Remoxy, a move which has had a disastrous effect on the stock prices of its two partners it has worked with on the abuse-resistant painkiller.

Alan Litwack, Pfizer’s head of global commercial development, has written to Remi Barbier, chief executive at partner Pain Therapeutics, updating him about a recent meeting with the US Food and Drug Administration concerning Remoxy, an extended-release oxycodone capsule formulated to limit abuse. The path to approval has been a tortuous one.

Back in 2008, the agency rejected the drug in December 2008 and it was refiled two years later by King Pharmaceuticals, which was acquired by Pfizer. The file was submitted again but the FDA issued a second complete response letter in June 2011; a week before that, Pfizer and partner Acura Pharmaceuticals got the green light for Oxecta (immediate-release oxycodone).

In his letter, Mr Litwack said Pfizer will not respond to that second CRL before mid-2015, noting that "given the years of delay, additional cost incurred to bring the programme to this point and development work left in the programme, there will be much to consider when we seek management endorsement". He added that "we will be reaching out to you shortly to review high-level programme timelines and to have a confidential discussion relating to contractual terms in our current agreement".

Mr Litwack stressed that “it appears there is a regulatory pathway forward for Remoxy” but as yet, a "go/no go decision has not been made". He added that no timeframe can be given but investors at Pain fear the worst.

The company's shares slumped 49.6% to $2.68, while the stock of Durect Corp, on whose Oradur technology Remoxy is based, sank 34% to $1.05. Durect said "we understand from Pfizer that additional clinical studies are necessary".