Bristol Myers Squibb will pay Eisai $650 million to jointly develop the Tokyo-based firm’s first antibody-drug conjugate (ADC) for cancer. Eisai also could earn up to $2.45 billion in milestone payments. The antibody targets cancers expressing folate receptor α. It then delivers a small-molecule payload called eribulin, Eisai’s simplified and synthetic version of halichondrin B, a toxic microtubule dynamics inhibitor derived from sea sponges. The therapy is in Phase 1 studies as a possible treatment for endometrial, ovarian, lung, and breast cancers.