In results from a widely watched clinical trial, the drug Avastin failed to show a significant effect on preventing the recurrence of colon cancer, the drug’s maker, Genentech, said early Wednesday.

Although Avastin is already a best-selling cancer treatment, success in this trial could have paved the way to a new use of the drug, potentially increasing sales by billions of dollars a year.

Now those efforts will be set back. And it appears that the Swiss drug giant Roche may have paid more than necessary when it agreed in March to buy, for $46.8 billion, the portion of Genentech it did not already own.

Roche shares were down more than 10 percent on Wednesday, closing at $29.54.

Genentech and Roche said they would continue to try to develop Avastin for use in early-stage cancer.

“Our initial review of the data leads us to continue to believe Avastin may be active in patients with early-stage colon cancer,” Hal Barron, Genentech’s chief medical officer, said in a statement.

The companies did not release any data from the trial, saying the details would be presented at the American Society of Clinical Oncology meeting, which begins in late May. They said only that the trial did not meet its endpoint, meaning Avastin did not reduce the risk of cancer returning by the target level.

Avastin had sales of $2.7 billion in the United States alone last year. But it is currently approved only for late-stage colon, breast and lung cancers. In those uses, trials have shown the drug can prolong life up to a few months.

The new trial was an effort to use Avastin earlier in the course of the disease, right after surgery to remove the tumor. The hope of such so-called adjuvant therapy is to prevent the cancer from coming back at all, effectively curing the patient.

The trial had about 2,700 patients who received six months of the standard chemotherapy or six months of that chemotherapy plus a year of Avastin. The study, sponsored by the National Cancer Institute, measured how many patients were alive and free of cancer over time.

The existing chemotherapy already keeps about 70 percent of colon cancer patients free of the disease three years after their surgery. So a significant improvement over that level had been considered a high hurdle. Genentech had rated the chance of success in the trial at 61 percent, while Roche had forecast it at only 55 percent.

Roche has long insisted that its desire to own all of Genentech did not hinge on the results of this trial.

And yet, the trial appeared to play a prominent role in Roche’s months-long negotiations to buy the 44 percent of Genentech it did not already own. Roche, which had started those discussions last summer, wanted to get the deal done before the results of the Avastin trial were announced — on the assumption that a successful trial would have sent Genentech’s stock soaring, possibly putting the takeover price out of reach.

A failed trial, on the other hand, could have pushed down Genentech’s stock. So it now looks as if Roche could have paid less had the results come out before it completed the deal.

While fighting to remain independent or to persuade Roche to make a higher offer, Genentech, based in South San Francisco, Calif., argued that Avastin sales could quadruple, to $10 billion, by 2015 if the drug could be used for early-stage colon, lung and breast cancers. Roche, based in Basel, Switzerland, is running another trial of Avastin for early-stage colon cancer, with results expected in 2010.

1: World J Gastroenterol. 2009 Jan 28;15(4):449-56. Links

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