Amgen's drug against muscle diseases reaches main goal in advanced study

(Adds background information on the company's drug Uplinza in paragraphs 7-10)

Sept 24 (Reuters) – Amgen said on Tuesday its drug helped improve everyday activities such as chewing and swallowing in patients suffering from a rare muscle weakness, meeting the main goal of a late-stage trial.

The drug inebilizumab has been tested on patients suffering from myasthenia gravis, a disease caused by an abnormal immune response that weakens the muscles that control the eyes, mouth, throat and limbs.

Inebilizumab, also known as Uplizna, belongs to a class of medicines that target a protein present on immune cells called CD19.

The Myasthenia Gravis Foundation of America estimates that approximately 36,000 to 60,000 people in the United States are affected by myasthenia gravis.

Separately, the drugmaker also said its experimental drug rocatinlimab met major and minor goals in a late-stage study testing it as a treatment for an inflammatory skin condition called atopic dermatitis.

The drugmaker's shares fell about 2% to $325 in extended trading.

Last year, the U.S. Food and Drug Administration approved the subcutaneous injection Vyvgart Hytrulo from Dutch company Argenx SE as a practical treatment option for this muscle weakness.

Argenx's drug, which uses the active ingredient efgartigimod, was first approved by the FDA as an intravenous injection in 2021.

Uplizna is unlikely to meet the high demands of Argenx's Vyvgart, but dosing every six months could be a potential differentiator if safety is impeccable, TD Cowen analyst Yaron Werber said in a note ahead of the results.

Uplizna, if approved to treat myasthenia gravis, will also compete with AstraZeneca's Soliris, another intravenous drug.

(Reporting by Mariam Sunny, Bhanvi Satija and Puyaan Singh in Bengaluru; Editing by Alan Barona and Shailesh Kuber)