Asthma is a chronic inflammatory disease of the airways long known for phenotypic heterogeneity. Phenotyping studies in asthma have led to a better characterization of disease pathogenesis, yet further work is needed to pair available treatments with disease endotypes. In this review, the biology of targeted pathways is discussed along with the efficacy of biologic therapies targeting those pathways. Results of asthma clinical trials are included, as well as results of trials in related diseases. This review then analyzes how biologics help to inform the complex immunobiology of asthma and further guide their use while identifying areas for future research.