Cancer treatment has long been haunted by the same problem: how do you strike dangerous cells without hitting healthy ones nearby? A team at the University of Geneva has built a drug-delivery system meant to answer that question with unusual precision. Instead of relying on bulky antibodies alone, the researchers used synthetic DNA strands, small binding proteins called affibodies, and aptamers to create a kind of molecular checkpoint. The treatment activates only when the right combination of markers appears on a cell’s surface. That matters because many cancer drugs still damage healthy tissue along with tumors. Antibody-drug conjugates, or ADCs, have helped narrow that gap by linking a cancer-seeking antibody to a toxic payload. However, those therapies come with tradeoffs. Antibodies are large, which can make it harder for them to move deep into solid tumors. Most can carry only a limited number of drug molecules. The Geneva group took a different route. General design of DNA-drug conjugates (DDC) for computed delivery. (CREDIT: Nature Biotechnology) Their system uses DNA hairpins, engineered strands that remain inactive …