DARPin drugs are engineered therapeutic protein molecules derived from naturally occurring ankyrin repeat domains, designed to function as targeted alternatives or enhancements to traditional monoclonal antibodies. These engineered molecules can be tailored to bind tightly to disease-associated targets, neutralize viruses by blocking cellular entry, or engage immune cells within tumor microenvironments. Because of their modular architecture, DARPins can be engineered into multi-specific formats that bind several different targets simultaneously, offering enhanced efficacy, resistance against viral mutations, excellent stability, and cost-effective production via microbial expression systems.