Shares of Amgen Inc. /zigman2/quotes/209157011/composite AMGN +1.22% gained 1.2% in trading on Thursday after the drugmaker announced that it is collaborating with Adaptive Biotechnologies Corp. /zigman2/quotes/212846591/composite ADPT +2.70% to discover and develop antibodies that can be used to prevent or treat COVID-19. Adaptive's stock was down 0.9%. Financial terms of the exclusive collaboration will be finalized "in the coming weeks," the companies said. "Working with Adaptive and using their viral-neutralizing antibody platform will expedite our ability to bring a promising new medicine into clinical trials as quickly as possible," Robert Bradway, Amgen's chairman and CEO, said in a statement. Year-to-date, Amgen's stock is down, shares of Adaptive have dropped 8%, and the S&P 500 /zigman2/quotes/210599714/realtime SPX +1.01% has tumbled 23%.