What more can a patentee do? Baxter International won a patent infringement suit against rival Fresenius USA, convinced the Federal Circuit to uphold that verdict and on March 16, obtained a final judgment for more than $23.5 million dollars. Baxter’s legal battle, one might think, is over.

It’s not. Baxter is at risk of losing its hard-fought judicial victory because in an ex parte re-examination, the U.S. Patent and Trademark Office (PTO) found Baxter’s invention was obvious and voided its patent.