NEW YORK (CNNMoney.com) - Genentech Inc. put a stop to a clinical trial for a potential treatment for peanut allergies after two children suffered "severe" reactions during tests, according to a news report published Monday.

Genentech (up $1.32 to $87.46, Research), the world's second-biggest biotech, was conducting clinical trials of Xolair to see if the drug could prevent reactions to peanut allergies, when two of the 150 children in the trial experienced "severe hypersensitivity reactions" to a trace amount of peanut protein, The Wall Street Journal reported Monday.

The children had not been given Xolair, the report said, but were given the protein to test their reactions.

"We are not going to do that anymore," Genentech spokeswoman Susan Desmond-Hellmann told the newspaper.

Xolair is currently on the market as a treatment for allergic asthma and totaled $320 million in U.S. sales in 2005. Drug makers often test products for additional uses after they've already been approved for the market.

Genentech, based in South San Francisco, Calif., reported $5.9 billion in total worldwide sales for 2005. The biotech's top-selling products are Rituxan, a treatment for non-Hodgkin's lymphoma that totaled $1.8 billion in U.S. sales in 2005, and Avastin, a treatment for colorectal cancer with $1.1 billion in total U.S. sales.

Genentech last week reported a 64 percent surge infourth-quarter earnings, but this failed to impress some investors.

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