Key members of the Senate Judiciary Committee introduced legislation Wednesday that would prohibit manufacturers of brand-name prescription drugs from paying generic makers to delay introduction of competing products.

The aim of the bill is to eliminate delays in the marketing of generics and encourage competition that lowers drug prices. But such a ban could hurt valuations of big pharmaceutical companies and other drug developers that rely on several years of patent protection to recoup the enormous research and testing costs of creating new treatments for cancer, heart disease and other maladies.