Eisai and Pfizer received a knockback from the US Food and Drug Administration yesterday after a dossier seeking approval of their big-selling Alzheimer’s drug, Aricept (donepezil), in severe forms of the disease was found to contain formatting deficiencies.

However, Eisai – which filed the application in August - says it still hopes to resubmit by the end of the year as part of its bid to move quickly into this field and capitalise on its huge potential [[01/09/05g]]. Aricept is currently approved for the treatment of mild to moderate AD, and is the best-selling drug in its class, with sales recorded by Pfizer of $255 million dollars during the first nine months of this year, up 15%. And Pfizer and Eisai are not planning to rest on their laurels, with investigations also ongoing in the early stages of the disease – specifically in mild cognitive impairment [[20/07/04f]].

The severe AD submission was based on results from a six-month trial involving almost 250 nursing home patients with severe AD who experienced a significant improvement in both cognition and activities of daily living scores versus placebo. With sales to boost and perhaps a desire to augment perceptions of Aricept’s efficacy after a report in The Lancet suggested it has little benefit in treating the disease or delaying institutionalisation [[25/06/04a]], Eisai and Pfizer will be keen to avoid a regulatory delay.

Alzheimer’s disease affects some 4.5 million Americans, including one in 10 over the age of 65 and one in two over the age of 85. But the market for severe AD remains relatively untapped: Forest’s Namenda (memantine) is the only therapy currently available, and witnessed a sharp 54% hike in third quarter sales to $124 million [[20/10/05h]].