Panel OKs Genentech’s Breast Cancer Drug

Herceptin, a drug that increases survival in certain breast cancer patients, won the endorsement Wednesday of a Food and Drug Administration advisory panel--a crucial step before it can be marketed in the U.S.

The genetically engineered medication, produced by Genentech Inc. of South San Francisco, is among the first of a new breed of pharmaceuticals that make use of genetic differences between normal and cancer cells. And it is the first directed against a major form of cancer.

The drug is based on the work of UCLA scientists who discovered that a specific gene, called HER2/neu, is present in normal tissue but is over-activated in about 30% of breast cancer cases.

Genentech developed a modified mouse antibody that sticks to HER2/neu-produced proteins that sit on the surface of these particularly aggressive tumor cells.

Clinical trials of Herceptin in patients with metastatic breast cancer--tumors that have spread beyond the breast--showed that the drug can delay the progress of the disease, and in a small group of patients even reverse it. The drug was tested in combination with chemotherapy in women just diagnosed with metastatic cancer, or alone in patients whose cancer had progressed after failing to respond to chemotherapy.

For Genentech, one of the oldest and most profitable biotechnology companies, final FDA approval could eventually mean from $200 million to $400 million in added revenue each year, analysts say.

Generally, the federal agency follows the advice of its advisory panels. Herceptin was reviewed on FDA’s “fast track” and could receive final approval by the end of November.

In the U.S. alone, close to 180,000 women will be diagnosed with breast cancer this year, according to the American Cancer Society, and almost 44,000 will die.

A substantial number of these patients--between 45,000 and 54,000--will have aggressive tumors that over-express the HER2/neu gene.

Testing for HER2/neu is widely available but still not standard for all breast cancer tumors, said Dr. Dennis Slamon, director of the Revlon/UCLA Women’s Cancer Research Program. Slamon led the team that first discovered the association between the gene and breast cancer and that conducted the preliminary clinical trials.

He said that Genentech is now sponsoring other trials of the drug--this time in women when they are first diagnosed, before the cancer has spread.

On the New York Stock Exchange, Genentech’s shares closed at $66.75, up $1.75, before the advisory panel reached its widely anticipated conclusion.

Analysts point out that Roche Holding Ltd. now holds about 65% of Genentech’s stock and has the option to acquire the rest by June 1999 under a complicated buyout agreement.

Under the terms of the deal, Roche will pay no more than $82.50 per share if it moves ahead.

Because of the structure of the deal, the stock will continue to trade between those two prices. Given the current limit on the appreciation of the stock, Editor Jim McCamant of the Medical Technology Stock Letter said he hasn’t tracked Genentech for years. “It has a limited upside and limited downside,” he said.

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* BREAST CANCER TREATMENT: Tamoxifen wins reluctant approval by FDA panel. A21