Johnson & Johnson agreed to buy Firefly Bio for $1 billion in cash, stepping further into the emerging degrader-antibody conjugate (DAC) space. J&J said the deal expands its cancer technology toolbox by coupling targeting antibodies with protein degraders intended to eliminate activity of disease-linked proteins, including KRAS-driven targets. Firefly’s Firelink platform includes linker technology intended to reduce free payload circulation and improve stability. The startup is advancing preclinical candidates for solid tumors and has previously reported tumor-volume reductions at low doses in preclinical work. J&J framed the acquisition as a way to address limitations seen in some ADC approaches, particularly around payload release and safe dosing capacity. The companies said the transaction is expected to close later this year.