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.

The June 9 decision by the Federal Circuit stated that Merck had appealed three decisions by the Patent Trial and Appeal Board (PTAB), all of which were dated July 8, 2019. Microspherix, of Boca Raton, Fla., had entered an agreement in 2015 to treat the surfaces of its brachytherapy seeds for oncology applications in an effort to restrain the seeds, and although the company does not appear to have a website, it is listed as holding title to a number of patents in recent years, including one that describes an elastic brachytherapy strand that includes an imaging marker.

The dispute centers on three Microspherix patents, including the 9,636,401 patent (the ’401 patent), and its immediate successor in the patent index, the ’402 patent. The first claim of the ’401 patent describes a flexible, non-radioactive strand that includes a marker to allow the clinician to determine the position of the strand.

Nexplanon contained a purportedly infringing component

Merck’s Nexplanon birth control implant was the subject of an allegation of infringement of all three of the contested Microspherix patents, and Merck’s argument was that the so-called Zamora patent (6,575,888), the provisional filing for which was received by the Patent and Trademark Office in January 2000, was one of several patents that anticipated one or more claims found in the Microspherix patents (the company is also the assignee of a patent for an implant directed toward the prostate).

Twelve months later, the author of the Zamora patent filed the non-provisional application for the ’888 patent, but Microspherix had in the meantime filed a provisional for one or more of its patents, in November 2000. This leapfrog-timed series of events culminated in May 2001, when Microspherix filed its non-provisional applications, and Merck had made the case at both the IPR and at the Federal Circuit that its adversary’s patents were obvious, given the existence of the Nijs and Schopflin patents. The Federal Circuit found with the PTAB that Merck did not demonstrate that it would have been obvious to a person of ordinary skill to combine the barium sulfate in the Schopflin patent with the open-ended implant design seen in the Nijs patent.

Merck’s dispute with the PTAB findings included the argument that some of the claims in the Microspherix patent were not entitled to the date of the provisional for priority because the provisional did not “reasonably convey” that the inventor had described an implantable urinary seed or strand that exceeded 10 millimeters in length. The Microspherix provisional also came up short due to failure to disclose that the strand was comprised of a biocompatible component with a non-biodegradable polymer, Merck contended, concluding that for this and other reasons, the associated references in Zamora provisional were entitled to priority.

Writing for the unanimous, three-judge opinion, Federal Circuit Judge Alan Lourie agreed that the Microspherix patents had recited discreet strand lengths, but that Merck had not challenged those claims as unsupported by the provisional. Lourie said Merck had challenged claims without a strand length limitation, and said there is “substantial evidence that supports the Board’s decision” that claims that lack strand or seed length requirements are, indeed, supported by the provisional. The provisional is said to disclose lengths of 2 mm to 10 mm with some needles and 4 mm to 6 mm with other needles. The provisional further describes the use of “a plurality of spacers” of as long as 50 mm, a description Lourie said “adequately supports the claimed strand recited” in the Microspherix patent.

Zamora provisional omission a key point of evidence

Lourie said the Zamora patent is not well supported by the associated provisional, in part because one placement of the radiopaque element on the external surface of the tube is not described in the provisional. The provisional does describe the admixture of radiopaque material “into the complex,” Lourie wrote, stating that this language is insufficient to teach coating the external surface of the tube.

Dennis Crouch, a professor of law at the University of Missouri, said Microspherix had initially filed the patent to address cancer treatments, but that it had expanded the claims in subsequent continuations to claim administration of other agents, including prophylactic and diagnostic agents.

Crouch said the interesting element of this case is the timing of the asserted prior art, a reference to Zamora, and that prior to passage of the America Invents Act, the non-provisional counted as prior art only upon issuance of the patent. Couch said the Federal Circuit had “simply assumed” that the pre-AIA provisions for prior art held in IPR proceedings for pre-AIA patents, but that this is no longer the case inasmuch as the statute now “makes clear that it is the patent/published application is the prior art.”

The Zamora non-provisional could not be traced back to the provisional, Crouch said, because of the failure of the provisional to exhaustively refer to the three options for placement of a radiopaque medium. However, he noted that the current system does not make clear the actual priority date, but rather discloses only the claimed priority date. The actual priority date may emerge only in litigation, and the Federal Circuit did little to dispute that perception with the explanation that the written description requirement requires only that the disclosure “reasonably convey” possession of the invention, Crouch said.