Initially, the amino acid and vitamin concentrations in this medium formulation were borrowed from their counterparts in Eagle and M199, respectively. This was followed by an increase in folic acid, vitamin B12 and peptone, and an improved formula was finally published in 1960.
The culture medium has been supplemented with L-Alanyl-L-Glutamine in place of L-Glutamine. Compared with L-Glutamine, L-Alanyl-L-Glutamine is much more stable, releases less ammonia in culture, and improves cell viability and growth.