Citing a lack of efficacy from adding its complement inhibitor Ultomiris (ravulizumab) to best supportive care for patients hospitalized with severe COVID-19, Alexion Pharmaceuticals Inc. paused further enrollment in a global phase III study of the drug. The move, recommended by the trial's independent data monitoring committee, suggested Ultomiris may soon join the list of other therapeutics once tested against COVID-19 but now no longer.