Avastin, Erbitux side effects probed

Researchers figured out how two different cancer drugs--Avastin and Erbitux--might lead to side effects. Made by Genentech, Avastin can cause kidney damage in some people. And Erbitux, sold by Bristol-Myers Squibb, causes severe allergic reactions in about 3 percent of patients.

Avastin works by cutting off the blood supply to tumors, inhibiting the growth of blood vessels feeding the cancer. But the medicine can also inhibit growth of tiny blood vessels in the kidney, researchers said. About 1 percent to 2 percent of patients develop serious kidney damage; 21 percent to 64 percent excrete excess protein in their urine, which can be an indicator of damage. The study's lead author said more research needs to be done into just how many patients end up with some level of kidney damage, because as of now, "we don't know."

Meanwhile, the Erbitux reactions may be preventable. The reactions appear to be caused by antibodies patients previously developed, perhaps in reaction to--of all things--tick bites. Researchers saw that the allergic reactions were most common in southeastern states such as Tennessee and North Carolina; there, they saw that patients bitten by multiple ticks developed the sort of antibodies that caused reactions to Erbitux. A test for these antibodies is under development.

- find the study abstract on Avastin in the New England Journal of Medicine
- see the article in the Washington Post
- read the Erbitux abstract in NEJM
- check out this coverage