Maybe this is the reason:
biz.yahoo.com
Monday May 31, 5:03 pm Eastern Time
Study points to danger of new cancer drugs
By Maggie Fox, Health and Science Correspondent
WASHINGTON, May 31 (Reuters) - A new class of cancer drugs that shows great
promise in experimental trials might be too dangerous to use in children because they may
block bone growth, researchers said on Monday.
The drugs literally starve out tumors by stopping them from growing blood vessels to supply
themselves, a process known as angiogenesis.
There about 20 different such drugs in development and they achieve their purpose in several different ways.
Because the growth of blood vessels is so important in the development of embyros and in children, scientists have worried that
such drugs might be harmful. A study published in the journal Nature Medicine gives them one more reason to worry.
Hans-Peter Gerber and colleagues at the University of California San Francisco and at nearby Genentech (NYSE:GNE -
news) found that one of the targets of some of the drugs, known as vascular endothelial growth factor (VEGF), is important for
bone growth.
During development, cartilage is replaced by bone during a process known as ossification. This requires the formation of new
blood vessels.
Gerber's team tested 24-day-old mice, treating them with a compound that blocks VEGF activity. The leg bones of the mice
stopped growing, but started growing again when the treatment was stopped.
This showed that VEGF was key to this step in bone development, they wrote. ''These findings strengthen the hypothesis that
VEGF is a principle regulator of angiogenesis.''
They also ''emphasize an important potential side-effect of anti-VEGF treatment and, possibly, other anti-angiogenic therapies
in patients of pediatric age, when the growth plate undergoes active remodeling.''
But the findings could also shed light on diseases such as rickets, a vitamin deficiency that affects the bones, they said.
Other experts also noted that drugs that interfere with VEGF might have unintended side-effects.
''VEGF has other important physiological functions in processes such as female reproduction and wound healing,'' Jay Harper
and Michael Klagsbrun of Harvard Medical School wrote in a commentary.
''Thus, there may be certain populations who are at risk for undergoing anti-VEGF therapy.'' These would include pregnant
women and young children.
The side-effects could be terrible. Thalidomide was a drug used in the 1950s and 1960s to treat morning sickness in pregnant
women, but it caused horrific birth defects in the children.
Those who survived have missing and truncated limbs, and many doctors believe thalidomide interferes with angiogenesis and
causes the defects. The drug is now being tested against cancer but women who have any potential of becoming pregnant are
banned from the trials.
Several companies have drugs or antibodies in the clinical pipeline that work against VEGF, including Genentech, Agouron,
ImClone Systems Incorporated (Nasdaq:IMCL - news) and Sugen Inc (Nasdaq:SUGN - news).
Other anti-angiogenesis drugs being developed attack angiogenesis in different ways.
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