enentech Inc. said yesterday that it had defeated a patent infringement suit brought by GlaxoSmithKline P.L.C. over two oncology drugs.

Genentech said a federal jury in Delaware unanimously found that the two drugs, Herceptin and Rituxan, did not infringe patents held by GlaxoSmithKline and that as a result, Genentech did not have to pay royalties for them.

GlaxoSmithKline, which is based in London, was seeking a 12 percent royalty on the sales of each drug.

The jury also found that all the patent infringement claims that GlaxoSmithKline asserted against Genentech were invalid. Genentech's defense was that it did not infringe and that GlaxoSmithKline's patents were invalid to begin with.

GlaxoSmithKline sued in May 1999, saying Genentech infringed on four of its United States patents.

"We are very pleased with the verdict," said Arthur D. Levinson, chairman and chief executive of Genentech. "We made our case successfully that GlaxoSmithKline's technology played no role in the development of Herceptin and Rituxan and that GlaxoSmithKline patent claims are invalid because Genentech scientists and others working in the field earlier developed the very technology that GlaxoSmithKline was claiming as its own."

GlaxoSmithKline's offices in Philadelphia did not return a phone call seeking comment.

Shares of Genentech rose $2.92, or 6 percent, to $54, in trading on the New York Stock Exchange, where American shares of Glaxo- SmithKline rose 92 cents, to $53.61.