The U.S. Patent and Trademark Office handed Amgen a potential setback Jan. 14 when it declined to review two patent expiration dates on a competitor’s drug.

In June, Thousand Oaks-based biotech giant Amgen asked the agency to review two formulation patents for Humira, made by Chicago-based competitor AbbVie, arguing that the patents should not have been granted to begin with. The agency declined to do so Jan. 14.

On Nov. 25, Amgen submitted an application to the FDA for approval of its biosimilar drug ABP 501. The drug is designed as a lower-cost version of Humira, which is approved to treat nine conditions including rheumatoid arthritis, skin disorders and colon inflammation. Humira typically costs $20,000 per year for treatments.

Biosimilars are similar to generics but are made with living organisms and aren’t identical to the complex compounds they replicate. They carry higher costs than generics though because they still require extensive research and development.

Humira is the best-selling drug in the world. Last year, Humira sales made up $12.54 billion of AbbVie’s $19.88 billion in sales. During the third quarter, AbbVie reported $3.65 billion in Humira sales, an increase of 19.6 percent.

Because of that, at least six biotech companies including Amgen are jockeying to develop a replacement for Humira when its patent expires. Humira is protected by a web of at least 70 patents that AbbVie says protect it until 2022.

“We determine, based on the petition and the accompanying evidence, that Amgen has not shown a reasonable likelihood of prevailing on any of its challenges,” the Patent and Trademark office told Reuters.

AbbVie said this week it expects Humira sales to reach $18 billion by 2020.

Amgen told the Business Times later in a statement, it was disappointed by the decision.

”
“Although we are disappointed by the decision, we continue to question the validity of the patents,” Amgen said. “We look forward to presenting our position in court.”

This story was updated to include a statement from Amgen.