Arimidex outdoes tamoxifen in study

AstraZeneca has reported clinical trial data which indicate, for thefirst time, that its aromatase inhibitor Arimidex (anastrozole) is more effective than the gold-standard treatment tamoxifen as an adjuvant treatment in postmenopausal women with early breast cancer. The company said it plans to submit the new data to support regulatory approval of Arimidex in this new indication in the first quarter of next year.

Arimidex sales were up 19% to $156 million in 2000, but an approval in early-stage breast cancer could provide a significant boost to the product. AstraZeneca's branded version of tamoxifen, Nolvadex, achieved sales of $576 million last year but is already facing generic competition in Europe, while its US patent expires in 2002.

The results of the 9,366-patient study, called ATAC and presented at the San Antonio Breast Cancer meeting in the USA, found that, after a median 33-month follow-up, Arimidex monotherapy was significantly more effective in preventing relapse than tamoxifen, reducing this risk by 17%. There was no additional benefit compared to tamoxifen alone for a combination group receiving both drugs. In addition, treatment with the aromatase inhibitor was better-tolerated and associated with fewer reports of endometrial cancer compared to tamoxifen.