Since the birth of biotechnology, hundreds of biotherapeutics have been developed and approved by the US Food and Drug Administration (FDA) for human use. These novel medicines not only bring significant benefit to patients but also represent precision tools to interrogate human disease biology. Accordingly, much has been learned from the successes and failures of hundreds of high-quality clinical trials. In this review, we discuss general and broadly applicable themes that have emerged from this collective experience. We base our discussion on insights gained from exploring some of the most important target classes, including interleukin-1 (IL-1), tumor necrosis factor α (TNF-α), IL-6, IL-12/23, IL-17, IL-4/13, IL-5, immunoglobulin E (IgE), integrins and B cells. We also describe current challenges and speculate about how emerging technological capabilities may enable the discovery and development of the next generation of biotherapeutics.

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