Elan Corp and partner Transition Therapeutics have suffered a setback with the news that they have pulled patients from two of the three dosing regimens in a mid-stage trial of an investigational Alzheimer’s disease treatment.

The firms said that patients will be withdrawn immediately from the Phase II study of ELND005 in the two higher dose groups, 1,000mg and 2,000mg dosed twice daily. The 353-patient trial will continue unchanged for people on the 250mg dose, they added.

Elan says the decision to withdraw the patients was taken in concurrence with the independent safety monitoring committee following a review of the ongoing study. “Greater rates of serious adverse events, including nine deaths, were observed among patients receiving the two highest doses”, the Irish drugmaker confirmed, noting that “a direct relationship between ELND005 and these deaths has not been established”.

Ian Hunter, an analyst at Irish broker Goodbody, said that “this is a considerable blow for the progress of the drug”, which has received fast-track designation from the US Food and Drug Administration. He added that given ELND005 is in an 18-month Phase II trial, “we had little value attached to the drug candidate and no revenue pencilled in over the next five years”.

However, this is a setback, Mr Hunter said, in terms of pipeline development and longer-term potential “and will affect the sentiment on the stock”. Given that Johnson & Johnson recently picked up development of the Dublin-headquartered drugmaker’s Alzheimer's Immunotherapy Programme, which includes bapineuzumab and AAB-002, ELND005 is the most advanced product in Elan's remaining pipeline.