Target: Tumors a "Smart Bomb" Against Cancer in Mice Must Still Prove Itself in Humans.

By Christine Gorman

If headlines could cure deadly diseases, then everyone would have rejoiced last week. Across the U.S., newspapers heralded the development by scientists from Bristol-Myers Squibb of a "smart bomb," or "magic bullet," against cancer. The weapon, a type of protein called a monoclonal antibody combined with an anticancer drug, has wiped out a wide variety of tumors in laboratory mice.

Before people get too excited, though, they should know that researchers have attacked cancer with many kinds of monoclonal antibodies for 15 years and that success in mice has spawned only limited benefit in people. Back in the 1980s, Wall Street briefly went wild over the stocks of companies developing antibody therapies, but repeated disappointments and unfulfilled promises taught investors to stop expecting instant miracles.

That said, the results reported last week by New Jersey-based Bristol-Myers Squibb in the journal Science were unusually promising, and they may give new momentum to this line of research. The monoclonal antibodies used against cancer are proteins designed to latch on to a specific molecule on the surface of a tumor cell, while leaving normal cells untouched. In Bristol-Myers Squibb's experiment, the antibody was linked with the common anticancer drug doxorubicin, and unlike many previous preparations, this combination enabled the drug to enter tumor cells, killing them from the inside.

The combination of the antibody, acting as a guidance system that homes in on tumor cells, and doxorubicin, as the lethal payload, knocked out many kinds of advanced cancer in mice, including colon, lung and breast tumors that had spread to other organs. In earlier animal experiments, researchers were able to cure only those cancers that had not been growing very long or that had not metastasized. "One of the problems that have held back the field for a long time is that we were never sure that well-established solid tumors could be eliminated," says Dr. David Scheinberg, chief of the leukemia service at the Memorial Sloan-Kettering Cancer Center in New York City. "Now we know that that is indeed possible."

But even the scientists from Bristol-Myers Squibb admit that any euphoria is premature. "I was surprised by the amount of press attention our study received," said Pamela Trail, who led the research team. "Obviously, we're tremendously excited by our data, but the true proof will be in the human trials." Within the next six months, the company will seek the Food and Drug Administration's permission to begin those crucial tests -- and perhaps generate more meaningful headlines.