Background
Mammalian fed-batch processes for monoclonal antibody (mAb) production rely on strategic feeding of several nutrients such as glucose, vitamins and amino acids to extend culture time and improve protein production[1].In actual processes, L-cysteine and L-tyrosine are fed separately at alkaline pH due their low stability and low solubility at neutral pH, resulting in pH peaks and precipitations[2]. To simplify next generation processes, both amino acids have been chemically modified to enhance their respective stability and solubility profiles. Previous work has demonstrated that phosphotyrosine disodium salt (PTyr2Na) is a stable L-tyrosine derivative and can be used in neutral pH feeds without having a detectable impact on the culture performance or the mAb quality attributes[3]. Here, we present results obtained using a L-cysteine derivative in a neutral pH, single-feed system.