The company's stock was down 3-7/8, or nearly 3 percent, to 134-3/8 on the New York Stock Exchange."This is not very important for Genentech. We had not counted on any revenues from CD18 in our models," said Matt Geller, an analyst at CIBC World Markets.

"We plan to meet with our investigators this summer to carefully analyze and evaluate the data and see if the treatment can be used for other indications," said Hal Barron, director of cardiovascular clinical research at Genentech.

The treatment is a recombinant humanized monoclonal antibody fragment (rhuMAb CD18). Antibodies are naturally-occurring proteins that selectively seek out and destroy other proteins deemed foreign invaders. They can be harvested and manipulated in the laboratory by so-called recombinant methods for use as drugs.

"It's a setback back to their clinical development pipeline, but a minor one," said Andrew Milne, analyst with Dain Rauscher Wessels, adding that the experimental treatment was just one of several antibodies the company was developing.

Milne is maintaining his buy rating on the company."This was one of Genentech's least-likely-to-succeed products. It is a difficult approach," said Geller, who also has a buy rating on the stock.The analyst said other drugs in Genentech's pipeline, such as anti-IgE, a humanized monoclonal antibody for treatment of asthma and allergy, as well as CD11a, an antibody designed to block certain immune cells as a potential treatment for psoriasis, hold more promise. "Anti-IgE is potentially a multibillion dollar drug," Geller said, adding he expects U.S. Food and Drug Administration to approve the asthma treatment within the next year.