NCI says rethink...vaccine trials..

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CNBC video today: http://www.cnbc.com/id/15840232?video=408115546 & play=1

Press release below.

Contact: Greg Lester

lester@...

American Association for Cancer Research

From

clinical cancer research: rethinking therapeutic cancer vaccine trials

Ongoing

therapeutic cancer vaccine trials have yet to show evidence of vaccines

spurring a patient¡¯s immune system to shrink tumors -- yet patients who

receive these vaccines in trials tend to live longer and respond better to

subsequent treatment. In the July 1 issue of Clinical Cancer Research, a

journal of the American Association for Cancer Research, a team of National

Cancer Institute researchers asks a fundamental question: are we looking at

cancer vaccine trials the wrong way "

In a

review of five prostate cancer vaccine trials, NCI researchers offer evidence

that patients who receive vaccines may respond better to subsequent

chemotherapy or hormone treatment. The specific results ¨C or endpoints ¨C of

these clinical trials, however, were not the long term survival of patients,

but rather the degree to which the vaccine caused tumors to shrink. According

to the researchers, since they didn¡¯t achieve their primary endpoints, these

vaccines may be abandoned as dead-ends, despite their real therapeutic value in

terms of prolonging patient survival.

¡°Clinical data are providing evidence that patients are living longer

following vaccination, de-spite the fact that trials do not show the vaccines

can induce the immune system into shrinking tumors,¡± said Schlom,

Ph.D., chief of the Laboratory of Tumor Immunology and Biology at the National

Cancer Institute. ¡°The data suggests that the scientific community and

regulatory committees ought to rethink the design of clinical vaccine trials

and our current approach to measuring the effectiveness of a cancer vaccine.¡±

According

to the researchers, it may be more helpful to think of the effectiveness of a

vaccine in terms of the response of the patient, rather than the response of

the tumor. While the Response Criteria in Solid Tumors (RECIST) experimental

standards works well in evaluating therapies that are toxic to tumors, such as

radiation or chemotherapy, they are less capable of measuring the more subtle

systemic effects of immune response, Schlom said.

While

there is no conclusive evidence to explain why a vaccine may lead to better

patient sur-vival, Schlom believes the evidence suggests that vaccines are, in

fact, priming the immune sys-tem. ¡°Vaccines are not passive, they induce a

dynamic process of immune response that, in many cases may keep the tumor in

check and enhance the effectiveness of subsequent therapies,¡± Schlom said.

About

Therapeutic Cancer VaccinesUnlike preventative vaccines, like those that

protect against human papillomavirus or the flu, therapeutic cancer vaccines

are given in the hopes of treating an existing disease. These cancer vaccines

generally fall into two categories: cell-based, where vaccines are created

using cells from the patient¡¯s own immune system that have been activated to

the presence of cancer antigens and delivered back to the patient along with

additional proteins that facilitate immune activation; and vector-based, where

an engineered virus, or vector, is used to introduce cancer proteins and other

molecules to stimulate the immune system. Both approaches are designed to rile

the patient¡¯s immune system into attacking tumor cells.

In

their review Schlom and his colleagues looked at two cell-based vaccines,

Sipuleucel-T (Provenge) and GVAX, as well as three trials using an engineered

pox-virus vector. While this review article focuses on prostate cancer

vaccines, the researchers consider these trials as exam-ples of ongoing

progress in similar vaccine therapies for lymphoma, melanoma, pancreatic, lung

and other types of cancer.

###

¡°Cancer Vaccines: Moving Beyond Current Paradigms,¡± Schlom,

et. al., Clinical Cancer Research, July 1, 2007, Volume 13, No. 13, pages

3776-3782.