MIT researchers created antibody-bottlebrush prodrug conjugates (ABCs) that dramatically increase drug-to-antibody ratios, carrying hundreds of drug molecules per antibody versus the conventional limit of about eight. ABCs allow diverse payloads with targeted cancer cell selectivity and could overcome toxicity and efficacy limits of conventional antibody-drug conjugates. Their novel conjugation method enables tuning drug load and combining cytotoxic and low-potency chemotherapies, heralding a versatile platform with improved therapeutic profiles.