Vaccine shows promise in advanced melanoma -study

* Vaccine response rate 22.1 pct vs 9.7 pct

* Progression-free survival 2.9 months vs 1.6 months

By Bill Berkrot

NEW YORK, May 30 (Reuters) - An experimental vaccine
combined with the immunotherapy drug Interleukin-2 showed
promise against advanced melanoma -- one of the deadliest of
cancers, according to data from a late stage clinical trial.

The vaccine, developed by the National Cancer Institute
(NCI) and called gp 100:209-217, or gp 100, helped shrink tumors
and delay worsening of the disease in the study.

In the 185-patient trial, those who received the vaccine had
a statistically significant response rate of 22.1 percent,
meaning 22.1 percent of patients had their tumor shrink by at
least half. That compared with a 9.7 percent response rate in
those who received only Interleukin-2 (IL-2), researchers said.

Patients in the vaccine plus IL-2 arm also experienced
progression-free survival -- the time before the disease starts
to worsen -- of 2.9 months compared with 1.6 months in the
control group, according to results presented at the American
Society of Clinical Oncology (ASCO) meeting in Orlando on
Saturday.

There was also a trend toward overall survival benefit seen
in those receiving the vaccine. But the extension of life did
not reach statistical significance and so could have been by
chance, though researchers found it to be encouraging.

"The findings represent a significant step forward for
treatment of advanced melanoma," Dr. Douglas Schwartzentruber,
one of the study's lead investigators who will present the data
at the ASCO meeting, said in a statement.

Gp 100 and Provenge from Dendreon Corp (DNDN.O) are among
the first therapeutic cancer vaccines to show positive results
in late stage clinical trials after years of vaccine failures.

"While more follow-up is needed, this study serves as a
proof-of-principle for vaccines' role in melanoma and in cancer
therapy overall," said Dr. Patrick Hwu, chairman of M.D.
Anderson's Department of Melanoma Medical Oncology and a study
co-investigator.

The gp 100 vaccine activates patients' immune response
controlling T cells to recognize antigens on the surface of the
tumor. The T cells secrete enzymes that poke holes in the tumor
cell's membrane, causing it to disintegrate.

"If we can use the body's own defense system to attack tumor
cells, we provide a mechanism for ridding the body of cancer
without destroying healthy tissue," Hwu said.

Some 8,650 Americans will likely die from melanoma in 2009,
according to the American Cancer Society. Only 16 percent of
patients with metastatic melanoma survive five years and the
median survival is less than one year.

There are currently few approved treatments for advanced
melanoma, which strikes people of all ages and spreads very
quickly. They include an older chemotherapy agent that does not
work very well and IL-2.

"IL-2 has dramatic effects in some patients, but precious
few," said Hwu, highlighting the need for new therapies.

While the gp 100/IL-2 combination looks to be a promising
advance, Hwu said, "a 22 percent response means 78 percent of
our patients did not respond, and that's not OK."

Researchers said conducting the study was challenging due to
complications associated with administering IL-2, which is sold
by Swiss drugmaker Novartis (NOVN.VX), a co-sponsor of the trial
with NCI.

The immunotherapy is typically given in intensive care units
and is associated with significant side effects, such as low
blood pressure and capillary leak syndrome, which poses risks to
the heart and lungs but is reversible upon stopping therapy, Hwu
said.

He added that only about half of those with advanced
melanoma are eligible for the vaccine as it must match a
patient's tissue type.

"A major priority for us is to figure out ways to broaden
our approach and use mixtures of peptides so that more patients
are eligible," Hwu said.
(Reporting by Bill Berkrot, editing by Matthew Lewis)