Feb. 27 (Bloomberg) -- Cancer patients who take anemia drugs sold by Amgen Inc. and Johnson & Johnson have a 10 percent higher risk of dying than those who didn't take the drugs, according to an analysis of 20 years of clinical trials.

About 7.5 percent of cancer patients who took Amgen's Aranesp or J&J's Procrit for anemia developed blood clots, compared with 4.9 percent who took a placebo in trials of 13,000 patients, according to the largest study linking the medicines to potential harm. The study was published in this week's Journal of the American Medical Association.

Amgen, the world's largest biotechnology company, lost 32 percent of its market value last year after its anemia drugs, Aranesp and an older version Epogen, were tied to heart attack, stroke and death at high doses. The Food and Drug Administration urged doctors to use the lowest doses possible in March. More than 4 million patients have taken Amgen's anemia medicines since Epogen was approved in 1989, the company said.

``There's a real potential risk here, and we as physicians need to do a better job of incorporating that risk into our practice,'' study co-author Samuel Silver, a hematologist and oncologist at the University of Michigan Medical Center in Ann Arbor, said in a telephone interview.

Silver stopped short of saying he would quit prescribing the medicines for cancer patients. The risk should be balanced against the danger of blood transfusions that patients might need if their anemia goes untreated, he said. The risks were mostly among patients taking high doses, he said.

51 Trials

A previous analysis of combined clinical trials didn't show the increased risk of death. The newer research found it when more trials were included, Silver said.

Amgen fell $1.22, or 2.6 percent, to $46.60 at 4 p.m. in Nasdaq Stock Market trading. Johnson & Johnson lost 68 cents, or 1.1 percent, to $63.04 on the New York Stock Exchange. Amgen is based in Thousand Oaks, California, and Johnson & Johnson in New Brunswick, New Jersey.

The increased risk of dying was seen when researchers combined 51 trials. Researchers can't say for certain why the patients died, although it's possible the drug is causing fatal clots or accelerating tumor growth, Silver said.

Best Sellers

Amgen and J&J's anemia drugs are used to treat patients whose weakness and fatigue is caused by chronic kidney disease and from the side effects of cancer chemotherapy. The medicines stimulate the production of oxygen-carrying red blood cells, which may boost patients' energy and strength, doctors say. The drugs were first approved in 1989 for kidney patients, and in 1993 for cancer.

The anemia treatments are among the world's best-selling pharmaceuticals. Epoetin alfa, marketed as J&J's Procrit and Eprex, as well as Amgen's Epogen, generated $5.37 billion in worldwide sales in 2007, a 5.6 percent drop from the previous year. Amgen's Aranesp, a longer-lasting version of the product, generated $3.61 billion in worldwide sales last year, a 12 percent decline from 2006.

Debate over the drugs' safety mainly involves how big a dose to use to raise concentrations of hemoglobin, the protein that carries the oxygen. The FDA-approved prescribing guidelines say the treatments can safely be given to boost hemoglobin as high as 12 grams a deciliter of blood. In July, Medicare said it would only pay for the anemia medications at doses up to 10 grams for cancer patients.

Defining the Risk

An FDA advisory panel of cancer experts is scheduled to meet March 13 in Gaithersburg, Maryland, to review the latest clinical trial results. The committee will consider data from a 733-patient trial of Aranesp, known as Prepare, that found in November that more patients died or had their tumors spread than those who didn't get the drug.

The risks of the anemia drugs are ``well-defined,'' and the newly published analysis ``looks exactly like what we've seen before,'' Roger Perlmutter, Amgen's head of research and development, said in a telephone interview.

Many of the trials that showed higher risk of death were originally designed to ask whether higher than recommended doses of the anemia drugs would help patients live longer, Perlmutter said, without looking at safety of the recommended dose. Amgen is working with the FDA to design a study to examine safety of the recommended doses, Perlmutter said.

Ortho Biotech, the unit of J&J that markets Procrit, said the newly published study does not ``provide an accurate reflection of the safety profile'' of the anemia drugs. The products are safe and effective when used according to product labeling, the company said in an e-mailed statement.

The analysis has its limitations, researchers said. Among the 51 trials, there were differences in the study drug, numbers of patients, how long they took the drug, and what type of cancer they had. The analysis was sponsored by the National Institutes of Health, based in Bethesda, Maryland.

To contact the reporter on this story: Luke Timmerman in San Francisco at ltimmerman@bloomberg.net

Last Updated: February 27, 2008 16:17 EST