Bio-Marker Identifies Who Benefits From Targeted Drugs

[gpawelski]

Many patients are treated not only with a "targeted" therapy drug but with a combination of chemotherapy drugs. Therefore, existing DNA or RNA sequences or expression of individual proteins often examine only one component of a much larger, interactive process. The oncologist might need to administer several chemotherapy drugs at varying doses because tumor cells express survival factors with a wide degree of individual cell variability.

Findings presented at the 41st Annual Meeting of the European Society for Clinical Investigation in Uppsala, Sweden, April 18, 2007, concluded that "functional profiling" with cell culture assays is relevant for the study of both "conventional" and "targeted" anti-neoplastic drug agents (anti-tumor and anti-angiogenic activity of Iressa, Tarceva, Sutent, Nexavar, and Avastin in primary cultures of "fresh" human tumors).

Cell Culture Assays with "cell-death" endpoints can show disease-specific drug activity, are useful clinical and research tools for "conventional" and "targeted" drugs, and provide unique information complementary to that provided by "molecular" tests. There have been more than 25 peer-reviewed publications showing significant correlations between cell-death assay results and patient response and survival.

There is a tactic of using biopsied cells to predict which cancer treatments will work best for the patient, by taking pieces of live "fresh" tumor tissue, applying different chemotherapy treatments to it, and examining the results to see which drug or combination of drugs does the best job killing the tumor cells. A cell culture assay test with "functional profiling," using a cell-death endpoint, can help see what treatments will not have the best opportunity of being successful (resistant) and identify drugs that have the best opportunity of being successful (sensitive).

"Funtional profiling" measures the response of the tumor cells to drug exposure. Following this exposure, they measure both cell metabolism and cell morphology. The integrated effect of the drugs on the whole cell, resulting in a cellular response to the drug, measuring the interaction of the entire genome. No matter which genes are being affected, "functional profiling" is measuring them through the surrogate of measuring if the cell is alive or dead.

The "funtional profiling" technique makes the statistically significant association between prospectively reported test results and patient survival. It can correlate test results that are obtained in the lab and reported to physicians prior to patient treatment, with significantly longer or shorter overall patient survival depending upon whether the drug was found to be effective or ineffective at killing the patient's tumor cells in the laboratory.

This type of bio-marker testing could help solve the problem of knowing which patients can tolerate costly new treatments and their harmful side effects. These "smart" drugs are a really exciting element of cancer medicine, but do not work for everyone, and a test to determine the efficacy of these drugs in a patient could be the first crucial step in personalizing treatment to the individual.

Literature Citation: Eur J Clin Invest 37 (suppl. 1):60, 2007

[gpawelski]

The new “smart” drugs are a really exciting element of cancer medicine. One of the new molecularly-targeted cancer drugs is Sutent. It is a “multi-targeted kinase inhibitor.” A drug that inhibits several proteins involved in triggering replication in cancer cells. Basically, inhibits various kinases, a type of enzyme that transfers phosphate groups from high-energy donor molecules to specific target molecules.

Sutent (sunitinib) is an inhibitor of multiple protein kinases, platelet-derived growth factor (PDGFR), vascular endothelial growth factor receptors (VEGFR), stem cell factor receptor (KIT), FMS-like tyrosine kinase (Flt3), colony stimulating factor (CSF-1R), and the neurotrophic factor receptor (RET). Because these proteins are involved in both tumor proliferation and angiogenesis, Sutent has both anti-tumor as well as anti-angiogenic properties. In addition, because Sutent inhibits multiple kinases, it possesses activity against multiple types of tumors.

Sutent can be used as a second-line drug for tumors that are non-responsive to Gleevec. The proto-oncogene KIT, a tyrosine kinase that is inhibited by Gleevec, is overexpressed in a majority of GISTs. Some patients have suffered relapses due to acquired point mutations in KIT, which prevents Gleevec from binding to the protein. Similar mutations have been characterized in EGFR from Iressa-resistant lung cancer patients.

The largest group of kinases are Protein kinases, which act on and modify the activity of specific proteins. So people will try and get some sort of gene-based test to measure the expression-mutation of these kinases. But something more elemental is going on. Does the drug even enter the cell? Once entered, does it immediately get metabolized or pumped out, or does it accumulate?

The new EGFRx ™ Anti-Tyrosine Kinase Profile Assay measures the net effect of everthing which goes on (Functional Profiling). Are the cells ultimately killed, or aren’t they? In photomicrographs (two magnifications), it is fairly easy to see that some clones of tumor cells don’t accumulate the drug. These cells won't get killed by it. Sutent is conveniently pigmented, brilliant yellow. It is easy to see which cells have taken it up. But you wouldn’t pick this up with an assay which only measured the kinases themselves.

Normal chemotherapy kills both cancer cells and healthy normal cells (mainly rapidly-dividing cells). Oncologists try to minimize damage to normal cells and to enhance the cell-killing effect on cancer cells. Too often, this delicate balance is not achieved.

Targeted therapy drugs interfere with specific molecules (receptors and enzymes inside and outside a cancer cell). By focusing on these molecular and cellular changes, targeted cancer drugs go after the “target” in these cells, rather than just all cells. Because of this, “targeted” drugs may be more effective than current treatments, and may be less harmful to normal cells.

Functional profiling can discriminate between the activity of different “targeted” drugs and identify situations in which it is advantageous to combine the “targeted” drugs with other types of cancer drugs. Because these new “smart” drugs will work for “some” but not “all” cancer patients who receive them, whole cell profiling can accurately identify patients who would benefit from treatment with molecularly-targeted anti-cancer therapies.

Not only is this an important predictive test that is available, but it is also a unique tool that can help to identify newer and better drugs, evaluate promising drug combinations, and serve as a “gold standard” correlative model with which to develop new DNA, RNA, and protein-based tests that better predict for drug activity.

This kind of technique exists, and might be very valuable, especially when active chemoagents are limited in a particular disease; it makes more sense than ever to test the tumor first. Afterall, cutting-edge techniques can often provide superior results over tried-and-true methods that have been around for many years.

The EGFRx ™ Anti-Tyrosine Kinase Profile Assay is the only assay that involves direct “visualization” of the cancer cells at endpoint. This allows for accurate assessment of drug activity, discriminates tumor from non-tumor cells, and provides a permanent archival record, which improves quality, serves as control, and assesses dose response in vitro.

http://weisenthalcancer.com/Professiona ... ionals.htm

[mayos]

Thanks so much for this new info...Even when I've given up inside...you'll post something for hope and sanity. Thanx