Following the sudden death of four patients for reasons unrelated to cancer, researchers decided to stop enrolling new patients in a clinical trial involving Genentech's cancer drug Avastin.
Published reports say the unexpected fatalities are the first in clinical trials of Avastin, although it's not clear to what extent the drug was responsible.
The deaths came during a trial in which Avastin was used along with a chemotherapy regimen called Xelox, composed of capecitabine and oxaliplatin.
Overall there were seven non-cancer-related deaths in the Avastin/Xelox group, two from heart trouble. The cause of death of three remains unknown, and Genentech said it had no data on the other two patients.
Roche, which holds a majority stake in Genentech, said it has suspended enrollment while experts review additional safety data.
Avastin had 2005 sales of $1.1 billion.