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New Drug Combinations Effective on Colon Cancer

June 02, 2003|Denise Gellene | Times Staff Writer

CHICAGO — Genentech Inc. reported Sunday that its experimental drug Avastin prolonged the survival of colon cancer patients by one-third over those on chemotherapy alone, providing the first successful clinical trial results of a new class of drugs designed to starve tumors of blood supply.

Two other studies released at a medical conference here provided more promising news for patients with colon cancers. Researchers at the Mayo Clinic in Minnesota reported that a cocktail of existing chemotherapy drugs was as effective in treating colon cancer as the combination used in the Avastin trial, a result that came as a surprise.

A third study showed that the controversial ImClone Systems drug Erbitux, which sparked insider trading investigations involving Martha Stewart and others, succeeded in shrinking tumors in patients with otherwise untreatable colon cancer.

Taken together, the studies mean cancer patients may soon have more effective treatment options. Colon cancer is the second-leading cause of cancer death in the United States, after lung cancer.

The most anticipated news at the annual meeting of the American Society of Clinical Oncology was the findings on Genentech's drug. The Avastin results were in line with what the South San Francisco company led analysts to believe two weeks ago, and were strong enough for the drug to obtain Food and Drug Administration approval, doctors and analysts said.

But the unexpected results of the cocktail of existing chemotherapy drugs stole some of the thunder from Genentech's report. In fact, some analysts predicted a sell-off in Genentech shares today by investors, who had driven the stock 65% higher on expectations that Avastin would prove a breakthrough drug in colon cancer.

Fariba Ghodsian of Castle Creek Life Sciences Partners, a hedge fund in Beverly Hills, said Wall Street's excitement about Avastin's near-term prospects would be damped, given that the new chemo combination for colon cancer patients was currently available and was likely to be cheaper than a biotech drug such as Avastin.

"This will definitely dilute enthusiasm," she said. "I can see a sell-off in Genentech shares."

Investors have added $11 billion to Genentech's market value since May 19, when the company announced that its test of Avastin in 900 newly diagnosed colon cancer patients exceeded its expectations. But Genentech did not provide results until Sunday's meeting of the American Society of Clinical Oncology.

The biotech company said that patients on Avastin along with conventional chemotherapy lived an average of 20.3 months, almost one-third longer than the 15.6 months for patients on chemotherapy alone. Avastin must be used in combination with chemotherapy drugs because it is not powerful enough to destroy tumors on its own. And in its study, Genentech used a standard combination of three drugs: 5-fluorouracil, leucovorin and irinotecan.

The study led by Mayo researchers, which involved 795 colon cancer patients, pitted the same chemotherapy combination used in the Genentech trial against 5-fluorouracil, leucovorin and oxaliplatin. Patients on the latter cocktail also lived 20 months. It was the first large trial in newly diagnosed colon cancer patients using oxaliplatin since the drug, from French firm Sanofi-Synthelabo, was approved last summer.

Researchers cautioned against using the two studies to compare treatment regimens.

"They appear to be similar," said Mace L. Rothenberg of the Vanderbilt-Ingram Cancer Center in Nashville. "But until we do head-to-head trials, we won't know the subtle differences in how they perform in patients."

Also Sunday, researchers said ImClone's drug Erbitux combined with irinotecan shrank tumors in 22.9% of patients. The FDA rejected the drug's marketing application two years ago, prompting an outcry for the medication from desperate patients. The company's stock subsequently crashed and its founder, Samuel Waksal, has pleaded guilty to insider trading.

Genentech, the nation's first biotech company, has spent 15 years developing Avastin. The drug is the first to block formation of blood vessels that feed tumors, a promising yet difficult area that until now has seen nothing but failure.

The field attracted widespread attention in 1998, when Judah Folkman of Boston's Children's Hospital discovered promising drugs that eradicated tumors in mice. Researchers have been trying for 30 years to develop a drug that could cut off the blood supply to tumors in people, but have not been successful until Avastin. The intravenous medication prunes the tangled network of blood vessels that feed tumors, opening a pathway for chemotherapy drugs to reach the cancer.

Gwen Fyfe, Genentech's vice president of oncology, said the clinical trial was designed to show that Avastin could increase a patient's chance of survival on any given day by 33%. The drug, in fact, improves patients' chances by 50%, she said.

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