Israel's Teva Pharmaceutical Industries Ltd. lost an appeal to regain four patents on its blockbuster multiple sclerosis drug Copaxone, reaffirming marketability of generics from Mylan NV and Novartis AG generics unit Sandoz.

The U.S. Court of Appeals for the Federal Circuit on Oct. 12 upheld a January 2017 decision by a District Court judge that said the patents on Copaxone's 40-milligram-per-milliliter dose were invalid.

Mylan launched the first Copaxone generic in October 2017, called Glatiramer Acetate Injection, followed by Novartis' Glatopa. Copaxone had sales of $4.2 billion in 2016, which fell to $3.8 billion in 2017, according to Teva's recent financial reports. Although the company retained an 85% market share halfway through 2018, sales have dwindled over the course of the year, and the branded drug is expected to post sales of about $1.8 billion for 2018.

The U.S. District Court for the District of Delaware, in deciding the original case, ruled that it was reasonable to believe generics makers could have created the product on their own, invalidating Teva's patents.

"Here, there was market pressure to solve a known problem — the fact that many MS patients could not tolerate daily injections," the District Court ruled. "And there were a finite number of predictable solutions that a person of ordinary skill in the art would have good reason to pursue."

Copaxone and its generics are designed to be injected three times per week, a regimen that improved upon daily injections for patients with multiple sclerosis and led to its blockbuster status.

The loss lends added importance to Teva's other prospects, including its newly U.S. Food and Drug Administration-approved migraine treatment Ajovy, which will go head-to-head against rivals Aimovig from Amgen Inc. and Emgality from Eli Lilly and Co.