NEW YORK (AP) — Amgen said Wednesday that its version of Humira, the best-selling drug in the world, worked as well as the original medication in a late-stage clinical trial.

The study is one of two that Amgen is running to compare its generic biotech drug ABP 501 to Humira as a treatment for moderate to severe plaque psoriasis. Humira is also known as adalimumab, and it is used to treat a variety of conditions including Crohn’s disease, rheumatoid arthritis, ulcerative colitis and plaque psoriasis.