Compass Therapeutics’ shares fell after the company reported that the FDA recommended conducting another trial before it can file a regulatory submission for tovecimig in previously treated biliary tract cancer. The developer had been pursuing a bispecific antibody path with earlier data, but the agency’s feedback pushes the program back toward additional evidence generation. The outcome highlights how, even with clinical progress, regulators may require further study design confirmation—particularly for oncology submissions where patient populations, endpoints, and benefit-risk framing can determine the filing route.