(Reuters) – Alexion Pharmaceuticals Inc said on Monday it would start a late-stage study of its rare blood-disorder drug, Ultomiris, in COVID-19 patients hospitalized with severe pneumonia or acute respiratory distress syndrome.

The study is expected to enroll about 270 patients, starting May, across countries, Alexion said.

Alexion’s drug works by inhibiting C5 protein, which makes up a part of the immune system that can attack the body’s own healthy cells if activated in an uncontrolled manner.

Independent investigators have expressed interest in studying the potential of C5 inhibition in severe COVID-19 pneumonia, Alexion said.

Ultomiris is approved to treat patients with a blood disorder called paroxysmal nocturnal hemoglobinuria, as well as atypical hemolytic uremic syndrome (aHUS), a condition that causes abnormal blood clots in small blood vessels in kidneys.

(Reporting by Manas Mishra in Bengaluru; Editing by Shinjini Ganguli)