Amgen already has its share of copycat drugs to fend off, but it was facing an even bigger threat—until now.

Enbrel, its top-selling product, has steered clear of a major stumbling block, thanks to a victory in patent court that kicks potential biosimilars years down the road.

The U.S. District Court for the District of New Jersey on Friday ruled for Amgen in a patent fight against Novartis' Sandoz unit and its Enbrel biosimilar, Erelzi. Sandoz said it’ll appeal the decision, but for now, an injunction will keep Erelzi off the market.

For Amgen, that's a multibillion-dollar relief; Enbrel, approved way back in 1998, delivered $4.8 billion in 2018 sales, more than a fifth of the company's top line.

For Sandoz, it's a blow to near-term sales—and an embarrassment. The company had been revving up to launch its biosim, which won FDA approval in 2016, and executives were pledging confidence in a rollout next year. Now, thanks to the court loss, it may have to hold off for almost a decade.

And the ruling is yet another setback for the still-nascent U.S. biosimilars market, which has struggled far more than expected when lawmakers first created the regulatory pathway.

Biosim makers have argued that biologic drugs are often protected by complex "patent thickets" in the U.S. that make it hard for them to launch copycats. And once biosimilars reach the U.S. market, they face contracting hurdles that have been the subject of litigation between Pfizer and Johnson & Johnson. Sandoz cited one calculation that said an Enbrel biosimilar could save the U.S. healthcare system about $1 billion per year.

In Europe, copycat biologics are faring much better. AbbVie's bestselling Humira faces numerous biosimilars in European markets, forcing prices down and driving meaningful savings.  

Under patent settlements, Humira won't face U.S. biosimilar competition until 2023, and that cheap competition could hurt Enbrel revenues down the line, Young wrote. A potential Enbrel patent loss has been Amgen investors’ top concern, Piper Jaffray analysts wrote in a note to clients. 

Cantor Fitzgerald analysts still predict Enbrel's revenues will fall in the coming years, but those calculations depend on competition from other brands—and, potentially, their biosims—rather than Enbrel biosimilars themselves. A loss in court could’ve meant even bigger declines, Cantor's Alethia Young wrote in a note to clients.

Samsung Bioepis this spring won FDA approval for its Enbrel biosimilar, Eticovo, but Amgen has sued that company as well, Big Molecule Watch reports.

From Sandoz's perspective, the outcome is a "black eye" as the generics and biosimilars company recently said it was confident about launching the biosim next year, possibly at risk, SVB Leerink analyst Geoffrey Porges wrote in a note to investors. He said that now seems "both unlikely and ill-advised."

The U.S. biosimilars market has been growing so slowly that former FDA chief Scott Gottlieb, usually an ally of pharma companies, last summer blasted drugmakers for the "anemic" market. The FDA pledged to take some action but many hurdles biosims face fall outside of the FDA's regulatory jurisdiction. Further, Gottlieb stepped down from the agency this year, so it remains to be seen how the agency will act on the issue moving forward.

Amgen has for now dodged Enbrel competition at a time when several of its other drugs—Neulasta, Epogen and Sensipar—cede ground to generics and biosimilars. Together, the drugs brought in more than $6.3 billion in the U.S. last year. 

On the flip side, the company is launching CGRP migraine prevention drug Aimovig and other new meds. During the second quarter, Amgen reported that prescriptions for Prolia, Repatha, Parsabiv and Aimovig grew by double digits or better. Prolia sales jumped 14% on the period to $698 million. Still, due to the patent losses, Amgen’s revenues sank overall.

Aside from Amgen’s branded offerings, the company’s own biosimilars business is set to make waves, Young’s team predicts. Cantor Fitzgerald analysts currently estimate $2.8 billion in 2023 sales for biosims developed by Amgen.