Last Updated: 2003-06-02 10:04:48 -0400 (Reuters Health)

NEW YORK (Reuters) - New drugs for colorectal cancer are developing apace after years in which new treatments have been few and far between, according to data released at the annual meeting of the American Society of Clinical Oncology.

Drugs from Genentech Inc., AstraZeneca and ImClone Systems Inc. showed promise in shrinking tumors, slowing the progression of disease, and potentially extending life, according to results from clinical trials.

"We've seen, at a single meeting, significant advances in more than one product," said Robert Erwin, president of the Marti Nelson Cancer Foundation, which helps patients enroll in clinical trials. "We still have a long way to go and these drugs don't suggest anything like a cure, but they certainly represent more important advances than we've seen in a number of years."

Genentech's experimental drug, Avastin, appears to confer an average of 4.7 months of additional survival on patients treated in early stages of the colon cancer.

Erbitux, a drug from ImClone Systems Inc. shrank tumors, when combined with chemotherapy, in 23 percent of patients with end-stage disease who had exhausted other options. It also slowed the course of the disease by an average of 4.1 months.

Erbitux taken alone shrank tumors in 11 percent of patients.

AstraZeneca's Iressa, which has already been approved to treat lung cancer, showed promise in treating early-stage colon cancer. In a small trial, the drug helped shrink tumors in 75 percent of patients when taken in conjunction with chemotherapy. Chemotherapy alone shrank tumors in 38 percent of patients.

ImClone's drug was turned back by the U.S. Food and Drug Administration for lack of clear data in December 2001, sparking a massive controversy that led to the company's former chief executive being charged with insider trading.

A trial by the company's European partner, Merck KGaA, now appears to confirm the results in the company's initial trial, raising the possibility that the drug could be approved by the U.S. Food and Drug Administration early next year or sooner.

"Based on the seemingly friendlier FDA that we have these days, combined with the publicity surrounding this drug, plus the fact it is obviously active and apparently very safe, it would seem it would be difficult for the FDA to not act," said Cory Kasimov, an analyst at Ryan Beck & Co.

Avastin is the most advanced in a new class of drugs that starve tumors of blood and oxygen in a process known as anti-angiogenesis.

Iressa and Erbitux belong to a new class that block a protein known as the epidermal growth factor. Iressa is a pill, while Erbitux is an antibody that is delivered by injection.

Both new classes of drug attack their target without destroying healthy cells, which is the main drawback of chemotherapy.

"As more people move toward combination therapy the idea that there are biotech drugs effective at both ends of the disease, early and late, is very exciting," said Erwin. (Additional reporting by Kim Dixon and Julie Steenhuysen in Chicago and Deena Beasley in Los Angeles)