Upstream process development (USP) is the systematic design, optimization, and scaling of all cell culture or fermentation steps involved in the biological production of a drug substance — including host cell selection, expression system design, cell line development, seed train optimization, culture media screening, feeding strategy development, and bioreactor process parameter optimization — with the goal of maximizing product yield, quality, and consistency in a scalable and GMP-compliant manner. It represents the first major phase of bioprocess development, directly preceding downstream process development (DSP), and is a core service offering of CDMOs supporting sponsors from early-phase development through commercial manufacturing of biologics, viral vectors, cell and gene therapies, and other biopharmaceutical products.
