The FDA approved Amgen’s Amjevita — the first biosimilar of AbbVie’s best-selling inflammatory drug Humira. Amjevita is the fourth biosimilar approved in the U.S.

AbbVie filed a patent infringement suit against Amgen in August to block the launch of this biosimilar. The first biosimilar, Novartis’ Zarxio, was approved in March 2015 — but its launch was delayed by litigation until September of that year.

See also: With support of FDA committee, Remicade biosimilar edges closer to market

Humira brought in $8.4 billion in U.S. sales in 2015 and accounted for 61% of AbbVie’s revenue in the same year. It was the second-best selling drug in the U.S. in 2015, according to IMS Health. Humira is approved for six adult indications and in one indication for children who are at least four years old. The drug was first approved in December 2002.

It is used to treat conditions like rheumatoid arthritis, plaque psoriasis, and Crohn’s disease.

Amjevita will carry the same boxed warning as Humira, for an increased risk for serious infections.