If possible, you would prefer to use cytokines and growth factors manufactured following guidelines set by the United States Pharmacopeia (USP) and/or the European Pharmacopeia (Ph. Eur.). However, this is not always possible, and reagents made for research use only (RUO) may be the only material available. If this is the case, you may be able to still use these reagents in your process. First, you should have confidence in the ability of the supplier to be able to provide consistent material that will meet your needs. Also, involve regulatory authorities as early as possible to ensure that the use of the reagent is acceptable and won’t result in a stumbling block to approval. Lastly, your supplier may have the ability to start manufacturing an RUO protein using USP or Ph. Eur. guidelines. At R&D Systems, we’ve worked closely with biotech and pharmaceutical companies on many of these types of projects.