Amgen Inc. (AMGN) scored FDA approval Thursday for Uplinza (inebilizumab-cdon) as a treatment for generalized myasthenia gravis, marking the drug's third approved indication.

The approval covers adult patients who test positive for anti-acetylcholine receptor (AChR) and anti-muscle-specific tyrosine kinase (MuSK) antibodies. These patients have a rare, chronic autoimmune disorder where B cells essentially sabotage the communication between nerves and muscles, leading to fluctuating muscle weakness that can significantly impact daily life.

What makes this interesting is the dosing schedule. After two initial loading doses, patients only need two doses per year. That's a pretty convenient regimen for managing a chronic condition that requires long-term disease control.

The FDA based its approval on data from the Phase 3 MINT trial, which had patients on steroids start tapering at Week 4, aiming to hit just 5 mg of prednisone daily by Week 24. The steroid reduction was successful for most patients: by Week 26, about 87.4% of Uplinza patients and 84.6% of placebo patients had gotten down to 5 mg or less per day.

More importantly, Uplinza showed meaningful improvement in daily functioning. At Week 26, patients taking the drug scored 1.9 points better on the Myasthenia Gravis Activities of Daily Living scale compared to placebo (a reduction of 4.2 points versus 2.2 points). That difference matters when you're measuring someone's ability to handle everyday tasks.

Amgen shares were up 0.26% at $318.19 in Friday trading.