Kirkland & Ellis cemented a hard-fought patent victory for client C. R. Bard Inc. on Tuesday, fending off the latest appeal in a case that's already cost rival medical device maker W.L. Gore & Associates Inc. $1.25 billion—and could cost it nearly $800 million more over the next five years.

In a 19-page decision, the U.S. Court of Appeals for the Federal Circuit affirmed once again that Gore is liable for past damages and ongoing royalties stemming from the companies' bitter patent dispute over ownership of an artificial blood vessel that revolutionized vascular surgery.

“Gore raises no new facts in this appeal,” Chief Circuit Judge Sharon Prost wrote for the three-judge panel, concluding that nothing in the lower court's decision “would warrant an extraordinary review at this stage.”