Shares of Alexion Pharmaceuticals (ALXN - Get Report) were climbing over 2.3% in mid-morning trading on Tuesday after the biopharmaceutical firm secured FDA approval for its Soliris, a treatment for adult patients with generalized myasthenia gravis (gMG).

The treatment is approved for patients with gMG who are anti-acetylcholine receptor (AchR) antibody-positive.

Myasthenia gravis is a chronic condition that causes muscles to tire and weaken easily.

In a Phase 3 REGAIN study, Soliris proved beneficial for patients with anti-AchR antibody-positive gMG who had previously "failed immunosuppressive treatment and continued to suffer from significant unresolved disease symptoms," Alexion said. These symptoms included difficulties with talking, walking, swallowing and breathing.

"Today's approval is a significant milestone for Alexion and, more importantly, for the subset of patients with anti-AchR antibody-positive gMG who continue to suffer from significant unresolved disease symptoms despite existing treatment options," said John Orloff, M.D., Executive VP and Head of Research & Development at Alexion. 

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