During the last decades conventional treatment of complex diseases yields personalized medicine and biotherapeutics with persuasive clinical results and increasing approvals. Among monoclonal antibodies and enzymes innovative protein formats as fusion proteins or bispecific antibodies fill drug candidate pipelines. However, most candidates fail during pre-clinical development occasionally because of non-expressibility in mammalian cells, cost and time pressure, increasing regulatory requirements or disappointing results. Non-GMP transient gene expression is the method of choice to produce hundreds or thousands of molecules in a cost-efficient way before starting expensive and time-consuming stable cell line development. InVivo’s Expression System for transient Transfection (InVEST) is a state of the art expression platform meeting the demands of early and late stage drug discovery and development approaches. The platform allows the development of up to 240 candidates in small scale expressions (à 15 mL), up to 70 mid scale expressions (à 750 mL) or up to 6 large scale expressions (à 9 L) in less than 6 weeks after DNA delivery.