Purification of a PEGylated single chain Fv

In this manuscript we describe the two-step purification of a mono-PEGylated anti-epidermal growth factor receptor (EGFR) single-chain Fv. A weak cation exchanger was used for capture. Elution using arginine suppressed protein aggregation and allowed a very good resolution with purity and product-recovery was above 90%. Free PEG was removed completely. The use of hydrophobic interaction chromatography (HIC) increased purity to 98%. Increasing the size of PEG from 5 to 30 kDa increased retention on HIC and reduced it on cation exchangers. Bioactivity of PEGylated scFv was confirmed by 125I based cell tests. Proteins modified with 5 kDa PEG showed higher bioactivity than proteins modified with larger PEGs. The combination of cation exchange and HIC provides a rational and effective basis for PEGylated scFv purification.