 Alexion Pharmaceuticals Inc. ALXN said late Wednesday it stopped enrolling patients in a clinical study testing a treatment for severe COVID-19 patients based on the recommendation of a data monitoring board. The independent data monitoring committee for the Phase 3 study of the drug Ultomiris said further enrollment of patients should be paused pending more data analysis as the treatment was not looking to be effective in treating COVID-19 patients on ventilators when compared with standard care, the company said. 