Nov 19 (Reuters) - Agios Pharmaceuticals ( AGIO ) said

on Wednesday its sickle cell drug met one of its two main goals

in a late-stage study of patients aged 16 and older, but failed

to show a statistically significant reduction in pain crises.

Shares of the Cambridge, Massachusetts-based drugmaker were

down nearly 50% in premarket trading.

Sickle cell disease is a severe inherited blood ailment that

affects the shape of red blood cells, which carry oxygen to all

parts of the body.

Agios Pharma's drug, mitapivat, works by activating an

enzyme in red blood cells to boost energy production, helping

them survive longer and improve hemoglobin levels.

In a late-stage study testing mitapivat, 40.6% of patients

showed increased levels of hemoglobin compared with 2.9%

patients on a placebo.

During the study, the drug improved hemoglobin levels and

reduced markers of red blood cell breakdown - from week 24

through week 52.

However, it did not significantly reduce sickle cell pain

crises, which was one of the main goals to assess treatment

efficacy. A pain crisis is caused by sickled red blood cells

blocking small blood vessels, reducing oxygen delivery to

tissues and organs.

It also did not meet a secondary goal of fatigue score, the

company said. Fatigue score measures how tired patients feel,

affecting their daily life after the treatment.

The company added that three patients on mitapivat and two

on placebo died during the trial, but none of the deaths were

related to the treatment.

Mitapivat, under the brand name of Pyrukynd, is already

approved by the U.S. Food and Drug Administration in 2022 to

treat low red blood cell counts caused by the early breakdown of

red blood cells in adults with pyruvate kinase deficiency (PKD).

The company plans to submit a marketing application for

mitapivat in the U.S. for sickle cell disease after meeting with

the FDA in the first quarter of 2026.