BOSTON (The Boston Globe) - Millennium Pharmaceuticals' most important cancer-fighting drug, LDP-341, appears effective in fighting an often deadly blood-borne form of the disease in patients who failed to respond to other treatments, according to preliminary study results presented at a national cancer meeting.

The drug is the most advanced in the Cambridge, Mass. company's pipeline and has emerged as a cornerstone of its oncology program. Millennium has been under some pressure to transform itself from a research outfit into a company with products and profits. The news about LDP-341 follows less than a week after the company announced the $2 billion acquisition of a California biotech firm that gives Millennium an approved heart drug.

Despite the news, which analysts called "stunning" and "impressive," shares in the company fell 18 cents to $28.23 on the Nasdaq Stock Market as trading was down across the biotechnology sector.

LDP-341 is the first of an new class of medications aimed at preventing cells from getting rid of excess or unwanted proteins - a phenomenon that seems to trigger cancer cells to self-destruct while leaving healthy cells essentially unharmed.

Like the efforts of Harvard University researcher Dr. Judah Folkman to starve cancer cells, LDP-341 is part of a new wave of drugs designed to attack the biological processes on which tumors depend for survival without causing the devastating, and sometimes deadly, side effects of conventional therapies.

Although the clinical trials results are preliminary, doctors, researchers and analysts alike said the presentation at the annual meeting of the American Society for Hematology in Florida illustrated the promise of LDP-341 in treating multiple myeloma, a form of cancer that kills 11,000 people each year in the United States.

"This could develop into an important new treatment," said Dr. Brian Durie, director of the Myeloma Study Group at Cedar-Sinai Cancer Center in Los Angeles. "One of the patients had undergone 14 previous treatments, including two bone-marrow transplants, and with this drug, he has gone into full remission. It's just amazing."

The drug, which analysts expect to reach the market in 2004, was acquired as part of a merger with another Cambridge biotech firm. If the preliminary data holds up in further trials, analysts said, there would be little to stand in the way of a regulatory approval.

"I don't think there's anyone who could characterize the data as anything other than extremely positive," said Carolyn Pratt, an analyst with Needham & Co. in Boston.

Researchers analyzed data from the first 54 patients enrolled in the clinical trial, the second of three phases of human testing generally required for regulatory approval. They found the drug stopped the progress of the disease in 33 percent of patients and that another 52 percent of patients improved after two rounds of treatment. In two patients, the disease went into complete remission.

Physicians, researchers and investment analysts crowded into the conference room for the presentation and applauded at its conclusion. The results were particularly impressive, they said, because the patients in the study were extremely ill. They had exhausted their options - undergoing an average of five different treatments only to have the disease return and continue to progress.

Myeloma prevents the body's bone marrow from forming normal plasma and white blood cells to fight infection. And with each treatment, the cancer builds additional defenses, becoming even more difficult to stave off. One in four of the more than 40,000 Americans with the disease die within five years of diagnosis despite existing treatments.

"We're very encouraged," said Dr. Paul Richardson, the lead investigator on the clinical trial and a physician at the Dana-Farber Cancer Institute in Boston. "The drug shows considerable promise in treating patients for whom options are very limited."

LDP-341 seems to mount a four-pronged attack on myeloma cells, triggering them to commit suicide, preventing them from attaching to the bone marrow, dismantling their defenses against the onslaught of drugs, and starving them of food and blood supplies they need to survive. Meanwhile, healthy cells seem to overcome the action of the drug, quickly bouncing back.

An analysis of the first 93 patients enrolled in the study showed that some experienced mild to moderate nausea, diarrhea, and fatigue.

Millennium is testing the drug in patients with earlier-stage myeloma. The company also hopes the drug eventually will prove effective, either alone or in combination with conventional chemotherapies, in treating a variety of other cancers, including leukemia and non-Hodgkin's lymphoma and prostate, breast, colon, and lung cancers.

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