Shares of Paris-based Abivax SA (Paris:ABVX) fell 25.4% to €21 (US$25.07) on March 8 after the company said it would halt a phase IIb/III trial of its lead candidate, ABX-464, in high-risk COVID-19 patients for lack of efficacy. The decision was based on a data safety monitoring board analysis that Abivax said revealed a "lower than expected rate (10.1%) of progression to severe disease or death with no difference between ABX-464 and placebo groups," each of which also received standard-of-care therapy.