Amgen under fire from investors over Aranesp study

The study of 500 head and neck patients, conducted in Denmark, was designed to test whether Aranesp would increase the efficacy of radiation therapy for cancer patients by increasing the oxygen supply to tumors. Instead, the study was halted for safety reasons after results showed that the patients who received Aranesp were 10% more likely to see their tumors grow.

Amgen has known about the negative results since December, when the researchers sent the Californian-based company a letter regarding the study. However, Amgen did not issue a press release or tell investors at the company's first quarter earnings call in January, despite alerting regulators of the study within 24 hours.

Although the trial results have been on the web since December, they went unnoticed until recently when The Cancer Letter reported on the study.

Other studies have also raised safety concerns over the drug, which brought in $4.1 billion for Amgen in 2006. Last month, the company disclosed that its own study of patients who had cancer and anemia but were not undergoing chemotherapy showed an increased risk of death on Aranesp.