Astellas Pharma Inc. has agreed to pay Cullgen Inc. up to $1.9 billion-plus to jointly develop multiple protein degraders. Under the agreement, Tokyo-based Astellas will pay Cullgen, of San Diego, $35 million up front, and an additional $85 million if it decides, during the initial stages of development, to jointly commercialize and promote Cullgen’s lead program, a cell cycle protein degrader for the treatment of breast cancer and other solid tumors, in the U.S.