Eisai shares drop on failure of Aricept successor

Shares in Japan-based pharmaceutical company Eisai dropped 3.1 per cent to reach JPY 4,960 (USD 43.21) due to the failure of entacapone, the company's successor product to the Alzheimer's disease treatment, Aricept (donepezil).

One of three studies on entacapone, showed no advantage over a placebo, according to a company statement. As a result, the regulatory filing for the drug has been set back until 2009.

Eisai also revealed it would delay applying for FDA approval of its investigational breast cancer drug, E-7389. The company will now file in Q1 2008, instead of in the current quarter. If successful, E-7389 will be Eisai's first new product on the US market since 1998.

Sales of Aricept added to Eisai's recent posting of a 20 per cent profit rise in Q3 FY07. As a result, this is Eisai's biggest-selling product, the US patent of which will run out in  2010. Q3 FY07 sales for Aricept were JPY 73.5bn (USD 640.3m).

According to Daiwa Institute of Research analysts, the delay in developing entacapone would make it very difficult for Eisai to replace lost Aricept sales. They said they had been expecting the experimental drug to recover half of Aricept sales after its US patent expires in 2010.