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July 21 (Reuters) - Agios Pharmaceuticals AGIO.O said on Tuesday it is discontinuing development of its sickle cell disease treatment after trial results failed to show enough benefit to support further development, sending its shares down 14% in premarket trading.

This comes after the company in May stopped developing the drug for a form of blood cancer, after a separate mid-stage trial failed to show sufficient benefit.

The sickle cell disease mid-stage trial was designed to characterize the dose-response relationship of tebapivat and assess whether its profile was meaningfully differentiated from other drugs in the pyruvate kinase (PK) activator class.

Over the 12-week treatment period, improvements in hemoglobin levels and hemolysis - premature destruction of red blood cells - were observed across all tebapivat dose levels.

However, the trial did not demonstrate the level of differentiation required to support continued development, said the company.

Sickle cell disease is a painful, inherited blood disorder in which the body makes sickle-shaped hemoglobin, preventing red blood cells from properly carrying oxygen to the body's tissues.

"We remain focused on mitapivat, our foundational PK activator," Chief Medical Officer Sarah Gheuens said, adding that the company expects a U.S. approval later this year.

PK activators are designed to boost the activity of an enzyme that helps red blood cells produce energy.

The U.S. Food and Drug Administration's target action date for mitapivat in sickle cell disease is November 1.

In 2023, the FDA approved Vertex's and Genetix Biotherapeutics' gene therapies for sickle cell disease in patients 12 years and older.

Other long-term treatment options for sickle cell disease include bone marrow transplant, which requires matching donors, and the chemotherapy drug hydroxyurea.