Amgen said that its anemia drug Aranesp showed no difference in the risk of death compared with a placebo in a closely watched study of the medicine in small-cell lung cancer patients, sending its shares as much as 7%.
Aranesp and similar anemia drugs have been under fire amid concerns that they have been used too aggressively and could be harming patients.
Industry analysts have called results of this study critical to future use of Amgen's most important product. Aranesp had sales of about $4.1 billion last year, and along with its predecessor Epogen accounted for roughly half of Amgen's sales.
Had study 145 -- the first involving this class of drugs to specifically have survival as a primary goal -- shown that Aranesp increased the risk of death in cancer patients undergoing chemotherapy, it would likely have wiped out the lion's share of Aranesp sales. Chemotherapy-induced anemia is by far the most important indication for Aranesp.
"These results contribute to the growing body of evidence on (Aranesp) safety, reinforcing the neutral impact on survival in cancer patients suffering from chemotherapy-induced anemia," Amgen's research and development chief Roger Perlmutter said in a statement.
Aranesp, Epogen and Johnson & Johnson's Procrit are all forms of the natural protein erythropoietin, or Epo, used to treat anemia by stimulating the body's production of hemoglobin, the protein in red blood cells that carries oxygen.
The U.S. Food and Drug Administration last month slapped a strong new warning on the anemia drugs, calling on doctors to use the lowest dose that can effectively avoid the need for blood transfusions.
Amgen, the world's largest biotechnology company, said patients who received Aranesp in study 145 had a significantly lower risk of blood transfusions as the drug significantly boosted hemoglobin levels.
Following a wave of concerning news on the anemia drugs, including increased death seen in an Aranesp study of cancer patients who were not on chemotherapy, Wall Street had been bracing for moderately negative findings from study 145.