Now have full text of Probing the stability of nonglycosylated wild-type erythropoietin protein via reiterative alanine ligations here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3358843/
And here is a patent, held by SK on this method - Dr Samuel Danishefsky is one of the 11 names on the patent.
Homogeneous erythropoietin and other peptides and proteins, methods and intermediates for their preparation
EP 2010556 A2 (text from WO2007120614A2)