A federal appeals court on Thursday ordered a new trial in a high-profile patent infringement dispute over Sanofi’s drug Praluent and lifted a  permanent injunction barring sales of the biologic, used to fight high cholesterol.

Judge Sharon Prost of the U.S. Court of Appeals for the Federal Circuit found that a Delaware federal judge improperly excluded evidence from Sanofi and its development partner Regeneron Pharmaceuticals Inc. in the case and relayed incorrect instructions to a jury, which last year upheld the validity of Amgen Inc.’s patents on a competing biologic, Repatha.

U.S. District Judge Sue L. Robinson of the District of Delaware ordered Praluent off the market in January. While Robinson found the injunction wasn’t in the public interest, she nevertheless ruled that consideration was outweighed by the damage Sanofi and its development partner Regeneron were doing to Amgen’s $2 billion investment in Repatha.

The U.S. Court of Appeals for the Federal Circuit stayed the injunction the following month, while it considered Sanofi’s appeal.

On Wednesday, Prost called Robinson’s ruling a “clear violation” of U.S. Supreme Court precedent in eBay v. MercExchange, which requires plaintiffs to prove the patients would not be harmed by pulling a drug off of the market.

“If a plaintiff fails to show ‘that the public interest would not be disserved by a permanent injunction,’ then the district court may not issue an injunction,” Prost wrote in a 24-page precedential opinion.

In a statement, Amgen said that it was “disappointed” with the court’s decision to reverse and remand the case “based on select pre-trial rulings,” but the company vowed to continue its fight in the district court.

“We firmly believe in the validity of our patents and we look forward to reasserting our rights in court,” Amgen said in the statement, provided to Seeking Alpha.

In a joint statement, Sanofi and Regeneron praised the ruling and welcomed the chance to bolster their attack on the validity of Amgen’s patents.

“We are pleased with the Federal Circuit’s decision to remand for a new trial that allows us to present our complete evidence to the jury,” said Karen Linehan, executive vice president and general counsel for Sanofi. “It is our long-standing position that Amgen’s asserted patent claims are invalid, and we remain confident in the long-term availability of Praluent for patients.”

On remand, Prost said the companies would be able to present a jury with evidence about specific antibodies developed after the patents’ January 2008 priority date, which had been precluded at trial.

Sanofi and Regeneron believe the evidence shows that Amgen’s patents are too broad to meet the Patent Act’s written description requirement.

The companies said they did not expect a new trial to begin before the end of the year.

On the issue of validity, Prost took aim at Robinson’s jury instructions, which directed the panel that Amgen could claim a group of antibodies that are capable of binding to a precise location on a protein called PCSK9 by fully disclosing “a newly characterized antigen.”

The instructions, Prost said, flouted the basic principles of the written description requirement by allowing Amgen to claim antibodies by describing an antigen, even though it was not the claimed invention.

On appeal, Amgen defended Robinson’s determination, saying the patents provide a “comprehensive road map” that teaches persons skilled in the art how to produce the full scope of the claimed antibodies.

But Prost resisted the argument, saying that the relationship between an antibody and antigen was less like a key in a lock and more akin to a lock and “a ring with a million keys on it.”

“Yet the instruction in this case invites just that improper equation. A jury would naturally understand the instruction to permit it to deem any antibody within the claim adequately described merely because the antibody could easily be ‘produc[ed],’” Prost wrote.

Robinson, has since stepped down from Delaware’s district course, and the case has not yet been reassigned.

Amgen is represented by Melanie K. Sharp and James L. Higgins of Young Conaway Stargatt & Taylor and William Gaede III, David L. Larson, Eric W. Hagen, Terry W. Ahearn, Bhanu K. Sadasivan, Sarah C. Columbia, K. Nicole Clouse, Lauren Martin, Esther E. Lin, Michael V. O’Shaughnessy and Rebecca Harker Duttry of McDermott Will & Emery.

Sanofi and Regeneron are represented by Steven J. Balick, Tiffany Geyer Lydon and Andrew C. Mayo of Ashby & Geddes, as well as Dianne B. Elderkin, Steven D. Maslowski, Matthew A. Pearson, Angela Verrecchio, Jenna M. Pellecchia, Matthew G. Hartman and Jonathan J. Underwood of Akin Gump Strauss Hauer & Feld and John J. Molenda, Vishal C. Gupta, Jeffrey C. Lee, Siew Yen Chong, Richard Praseuth and Robert Greenfeld of Steptoe & Johnson.


Tom McParland of Delaware Law Weekly can be contacted at 215-557-2485 or at tmcparland@alm.com. Follow him on Twitter @TMcParlandTLI.