In a precedent-setting decision Thursday, the U.S. Court of Appeals for the Federal Circuit granted Sanofi SA and Regeneron Pharmaceuticals Inc. a do-over of sorts on whether their cholesterol drug Praluent infringes Amgen Inc.'s patent claims for antibodies targeting PCSK9.

The three-judge panel sent the case back to the district court in Delaware for a retrial, saying the lower court erred when it improperly instructed the jury on the written description and when it refused to allow Sanofi and Regeneron to submit post-priority-date evidence to show that the two patents in question didn't provide an adequate written description.

Perhaps more importantly, the Federal Circuit vacated the lower court's permanent injunction against the U.S. marketing of Praluent (alirocumab). "The injunction decision was a little alarming to some . . . because it proposed to take an FDA-approved product off the market" with little explanation, Joshua Whitehill, a patent attorney with Goodwin Procter LLP, told BioWorld.

While the Federal Circuit vacated the injunction in light of the retrial, it took the lower court to task for its improper analysis of what is considered a "disservice to the public interest" when granting an injunction in the biopharma space.

"Eliminating a choice of drugs is not, by itself, sufficient to disserve the public interest. . . . Just as a patent owner does not automatically receive an injunction merely by proving infringement . . . an accused infringer cannot escape an injunction merely by producing infringing drugs. Accordingly, a reduction in choice of drugs cannot be the sole reason for a district court to deny an injunction," Chief Judge Sharon Prost wrote in the unanimous opinion.

However, the court made it clear that the plaintiff, in this case Amgen, has the burden to show "that the public interest would not be disserved by a permanent injunction." That can set a high bar for some plaintiffs to get an injunction, Whitehill said.

Although the injunction wasn't enforced – the appellate court had granted a stay while the appeal was pending – it was one of the most closely watched, and emotional, aspects of Amgen v. Sanofi. Whatever the Federal Circuit decided about the injunction was expected to be explosive. On one hand, some people saw a permanent injunction as overkill and were upset that it could be used to remove an approved drug from the market, reducing patient choice. But others questioned the purpose of drug patents if they're not able to protect biopharmaceutical innovation from infringement. (See BioWorld Today, June 7, 2017.)

Despite the injunction being vacated and the new trial, Thursday's decision didn't leave Amgen empty-handed. The appellate judges upheld the lower court's determination that the patents, which are part of the intellectual property fence protecting Amgen's Repatha (evolocumab), were not obvious. However, the possibility remains that the patents could be invalidated in the new trial based on the written description and enablement.

Competition continues

Amgen officials said they were disappointed that the case was remanded, but they welcomed the obviousness ruling, saying it was a main argument brought by Sanofi and Regeneron in seeking to overturn the injunction. "We firmly believe in the validity of our patents and we look forward to reasserting our rights in court," the Thousand Oaks, Calif.-based company said.

Sanofi and Regeneron downplayed the obviousness ruling, noting that it was one of several challenges they made to 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.

The new trial isn't likely to start until next year. In the meantime, Paris-based Sanofi and Regeneron, of Tarrytown, N.Y., will continue marketing, selling and manufacturing Praluent in the U.S. in competition with Amgen's Repatha as an adjunct treatment for adults with heterozygous familial hypercholesterolemia or clinical atherosclerotic cardiovascular disease who require additional lowering of LDL cholesterol.

The two drugs are rooted in a race that's more than a decade old. In 2005, Amgen began studying development of proportion convertase subtilisin/kexin type 9 (PCSK9) inhibitors, according to court documents. Sanofi/Regeneron started exploring antibodies targeting PCSK9 in September 2007.

In 2014, the two patents were issued to Amgen with a 2008 priority date, and the company filed suit to keep Praluent out of the game.

At that time, Amgen's Repatha looked to be first to market in the U.S. But in 2015, Regeneron and Sanofi leapfrogged over their competitor by using a priority review voucher bought for $67.5 million. That gave Praluent a one-month head start in the market over Repatha. (See BioWorld Today, Aug. 1, 2014, and Oct. 20, 2014.)

That lead wasn't enough to claim the PCSK9 market, as Praluent has consistently trailed Repatha in sales and the gap is widening. Praluent generated $117 million in sales last year and is expected to generate $244 million this year, according to Cortellis.

The consensus forecast is that it will reach blockbuster status in 2020 with $1.07 billion in sales. In contrast, Repatha generated $141 million in sales in 2016 and should bring in $368 million this year. It's expected to join the blockbuster club in 2019 with nearly $1.66 billion in sales.

Looking further into the future, the Cortellis consensus forecast continues to give Repatha the edge, predicting nearly $3.27 billion in sales in 2023, while Praluent is forecast to produce about $2.53 billion that year.

Thursday's decision had little impact on Wall Street. Amgen shares (NASDAQ:AMGN) closed the day at $186.85, down $1.74. Regeneron (NASDAQ:REGN) closed at $463.40, up $7.35. And Sanofi (NYSE:SNY) gained 58 cents, closing the day at $50.61.