In recent decades, mAbs have been used increasingly as targeted therapeutics for various diseases. However, the selective nature of antibodies can often lead to mAbs that do not recognize the target antigen in a preclinical model species used in studies of in vivo efficacy and safety. This feature review article focuses on the use of alternative animal models and surrogate antibodies for studies of efficacy for cases in which the primary therapeutic antibody does not recognize the antigen in a relevant species. In addition, the use of rodent and non-human primate models for preclinical safety studies with mAbs is discussed.