Alteogen Faces Royalty Shock And Investor Scrutiny

Halozyme filed a patent infringement lawsuit against Merck over Keytruda's subcutaneous formulation, which uses Alteogen's ALT-B4 platform technology. A UK court ruled in favor of Merck, but a U.S. patent invalidity review (PGR) remains unresolved as of April 2026. The ongoing patent dispute creates uncertainty over Alteogen's future royalty streams from its $4.3 billion licensing deal with Merck, contributing to investor concerns and market volatility.