Eisai: Aricept in for Severe Approval

Co-promoted in the US by Eisai and Pfizer, Aricept (donepezil hydrochloride) is currently only approved for the treatment of mild to moderate AD but is widely prescribed off-label for severe cases. However, Forest’s Namenda is currently the only drug approved for severe AD. The race is on between Eisai and Forest to have the first full spectrum approved AD drug.

The supplemental new drug application (sNDA) for Namenda in mild to moderate AD was filed in November 2004 and the FDA issued a non-approvable letter in July. The regulator said the non-approvable decision was reached as, although a six-month study showed statistical significance in the required primary endpoints, a further two unpublished studies did not.

The new sNDA submission for Aricept is also based on data from a six-month trial, conducted in approximately 250 patients with severe AD. In this trial, patients demonstrated a statistically significant improvement compared to those taking placebo on both of the primary efficacy measures used.

The news comes on the back of recent launches of Aricept ODT (orally disintegrating tablets) and Aricept oral liquid formulation. The expansion in patient potential resulting from these new formulations is expected to be limited, but should, nevertheless, bolster the position of Aricept as the gold standard AD treatment. An approval in severe AD would further support this position, as well as enabling more patients to remain on Aricept as their disease progresses, which could prove beneficial both for patients and for Eisai.

Despite new entrants into the market, Aricept still retains 55% of the $1.7 billion US market and Aricept sales reached $897 million in 2004. However, sales of the drug are expected to see a sharp drop resulting from the introduction of generic and pipeline products in the next few years. With this impending threat looming on the horizon, an expanded indication would be even more welcome, helping to provide some uplift in sales in the meantime.