Onyx, Bayer face Pfizer in cancer drug wars

By Toni Clarke

ATLANTA (Reuters) – A kidney cancer drug made by Bayer AG
and Onyx Pharmaceuticals Inc. showed promise in a small lung
cancer trial, according to data released on Sunday, further
fueling competition with a drug from Pfizer Inc.

Results presented at the annual meeting of the American
Society of Clinical Oncology showed that in a trial of 52
patients with advanced non-small cell lung cancer who had
failed previous treatment, 59 percent of patients who took the
drug, Nexavar, saw their disease stabilize.

The results come one day after Pfizer released data from a
trial of its kidney cancer drug Sutent showing it too showed
promise with lung cancer, adding fire to an already growing
battle between the two drugs in kidney cancer.

Both drugs attack multiple targets, including the vascular
endothelial growth factor, or VEGF, a protein that is
responsible for blood vessel growth. By blocking VEGF, tumors
are starved of much needed oxygen and nutrients.

Both drugs also target several other proteins, helping
differentiate them from other drugs that block VEGF such as
Genentech Inc’s Avastin.

In the Nexavar trial, some patients saw their tumors
shrink, but not by more than 30 percent, which would be called
a partial response, said Dr. Ulrich Gatzemeier, head of
thoracic oncology at Grosshansdorf Hospital in Hamburg and one
of the lead authors on the trial.

In Pfizer’s trial of 63 patients whose disease had
progressed despite chemotherapy, tumors shrank at least 50
percent in six, or 9.5 percent of patients. They stopped
growing in another 27, or 43 percent of patients.

In the Nexavar trial, the median period before the disease
began to progress again was 5.5 months, about the same as would
be expected with chemotherapy, Gatzemeier said.

The advantage of targeted therapies such as Nexavar and
Sutent, however, is that they have fewer toxic side effects
than chemotherapy.

Nonetheless, in the Nexavar trial, one patient died from
fatal bleeding in the lung, compared with two patients who died
from lung bleeding in the Pfizer trial. Another patient in the
Pfizer trial died from bleeding in the brain.

While it was not clear that all the deaths were
treatment-related, bleeding is a potential problem with all
drugs that block VEGF, experts say.

When the blood supply to a tumor is cut off, and it begins
to die, it can leave a hole in the wall of the lung leaving
blood vessels to bleed, Gatzemeier said.