The patent lawsuit between Merck & Co. and Microspherix LLC began when the latter sued Merck for infringement of patents for brachytherapy in Merck’s implantable contraceptive device, but Merck was unable to prevail in an inter partes review (IRP) or in an appeal of the IPR at the Court of Appeals for the Federal Circuit. After wading through questions about purported prior art, Merck failed to persuade the two courts that Microspherix’s non-provisional filing had strayed too far from the written description of the related provisional, thus handing Microspherix a win against its much larger rival in the market for drug delivery with microspheres.