Merck and Addex Pharmaceuticals entered a deal to develop a drug candidate for schizophrenia, under which Merck will pay Addex up to $702 million in cash plus royalties. Geneva-based Addex will receive $22 million as an upfront payment and is eligible for up to $455 million in research, development, regulatory and sales milestones for the first product developed for two uses as well as up to $225 million in additional milestones for a second product developed for two uses.