Bristol Myers Squibb has agreed to pay up to $11.1 billion to partner with Germany's BioNTech and develop the latter's next-generation cancer immunotherapy, which could take on rival Merck & Co's best-selling drug Keytruda.

BioNTech SE (NASDAQ:BNTX) and Bristol Myers Squibb & Co. (NYSE:BMY) entered into a co-development and co-commercialization agreement. The pact focuses on BioNTech’s investigational bispecific antibody BNT327 across numerous solid tumor types.

Bristol-Myers makes an $11 billion deal with BioNTech to join the new cancer-treatment game, nearly double the size of Pfizer’s deal announced two weeks earlier.