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Newest cancer drugs target tumor growth

/ Source: The Associated Press

A new generation of experimental cancer drugs is poised to upstage current hotshots by attacking the multiple methods tumors use to grow and spread, instead of just one.

These drugs are like a repairman who brings an entire toolbox to a job instead of just a wrench or hammer. They go beyond current favored medicines like Herceptin, Avastin and Iressa, which have impressed scientists for their ability to precisely target cancer cells while leaving healthy cells alone.

At a cancer meeting Friday, doctors reported that one of Pfizer’s new multitasking drugs shrank tumors in 40 percent of people with advanced kidney cancer. Current treatments do that in only about 1 out of 10 cases.

Some patients have been on the experimental drug for more than a year — far longer than they’d been expected to live.

Blocking cancer's multiple pathways

Kurt Bonham is one. The California accountant was only 49 when he was diagnosed with kidney cancer that had already spread to his lungs.

Now, 13 large masses in his lungs have been reduced to specks.

“If I can have five more years, I think that they can come up with something fandangled that will either cure the cancer or manage it,” he said.

Doctors hope the new generation of cancer drugs will do just that by blocking cancer’s multiple pathways, such as cutting off the blood supply to a tumor or jamming the “switchboard” it uses to send messages to grow and spread.

New drugs on the horizon

The Pfizer drug, so new that it’s just called AG-013736 for now, attacks blood supply and one of the switchboard’s main lines. Another Pfizer drug, Sutent, also takes this approach. Eleven studies testing it against various cancers will be presented at the meeting, held by the American Society of Clinical Oncology.

Amgen, AstraZeneca and Eli Lilly have multitasking drugs in early stages of development. So does Novartis Pharmaceuticals, but its drug, called PTK/ZK, disappointed in a study involving people with advanced colon cancer, doctors reported Friday.

Farthest along of all such drugs is Sorafenib, made by Bayer Pharmaceuticals and Onyx Pharmaceuticals Inc., which the Food and Drug Administration already allows limited use of in certain kidney cancer patients.

“Just in the last year or so there are many more options. None of them are FDA-approved yet. Hopefully soon they will be,” said Dr. Brian Rini, a University of California at San Francisco researcher.

He reported results of the kidney cancer study on the Pfizer drug. Of the 52 patients in the study, 29 remain on the drug. Cancer has worsened in only 16, or 30 percent. The rest of the patients dropped out or died. Tumors have all but disappeared in several people.

'A significant advance'

“This looks to be a significant advance,” said Dr. David Johnson, a Vanderbilt University cancer doctor who is president of the oncology society and had no ties to the study or the drug maker.

It’s too soon to tell whether the drug can improve overall survival, but shrinking tumors and stopping disease progression are important first steps, Johnson said.

“If it only did that and improved symptoms, it would be a valuable drug,” he said.

About 33,000 cases of kidney cancer are diagnosed each year in the United States, and more than 10,000 of them spread to other parts of the body, a situation currently considered incurable.

Stable, chronic condition

For these and others with advanced cancers, the new multitasking drugs might at least make cancer a stable, chronic condition. So far, tumors eventually find ways to defeat even new drugs like Avastin that shut down one process.

“If you block one, it’s not that difficult for a cell to get around that blockade. The question is, how many do you really have to block to cripple that cell?” said Dr. Mace Rothenberg, a Vanderbilt doctor who has consulted with Pfizer on developing and testing such drugs.

Other scientists are trying to get the same multitasking approach by combining single-target drugs like Avastin and Erbitux.

“That regimen could easily run $40,000 to 60,000 a month,” Rothenberg said.

No pricing information has been set for the experimental multitaskers, but doctors expect the cost would be lower.

“The fact you can have it all in one drug is very good,” said Dr. Roy Herbst, a University of Texas-Southwestern doctor who also has consulted for Pfizer.