LONG®R3IGF‐1 is a human IGF‐1 analog containing a 13 amino acid N‐terminal extension and a mutation at position 3. It activates the Type 1 IGF receptor, which is responsible for increasing cell growth and protein synthesis effects in CHO cells. A common growth factor supplement used in CHO media, insulin, also acts primarily through the IGF‐R. Since LONG®R3IGF‐1 is manufactured under GMP and is used at low concentrations (10 –100 ng/mL) in cell culture it represents a regulatory‐friendly method of enhancing serum‐free cell culture performance.
Quantitation of LONG®R3IGF‐1 is important when developing cell culture processes in order to optimize the concentration of LONG®R3IGF‐1 used and feeding strategies. Quantitation is also important when developing a purification process, in order to demonstrate clearance. An ELISA has been developed for the quantitation of LONG®R3IGF‐1 in media and drug substance samples. The assay uses a sandwich ELISA format with colorimetric detection. The performance characteristics of the assay are presented including accuracy, precision, linearity, LOQ, recovery from media, and range.