Johnson & Johnson agreed to buy Firefly Bio for $1 billion in cash, stepping deeper into degrader-antibody conjugates (DACs) with a KRAS-focused technology and a new linker approach aimed at more selective delivery of protein degraders to tumors. The acquisition is expected to close later this year. The deal matters because DACs are still emerging as a parallel modality to antibody-drug conjugates (ADCs), where payload release and tolerability often limit dosing. J&J is positioning the Firefly platform to diversify oncology programs while offsetting pressure on parts of its broader cancer portfolio. Firefly had previously raised close to $100 million and developed therapy concepts designed to address limitations of conventional ADC payload release. J&J said the strategy could enable highly selective protein degraders in cancer tissue while sparing healthy cells.