Characterization of the PEGylated Functional Upstream Domain Peptide (PEG-FUD): a Potent Fibronectin Assembly Inhibitor with Potential as an Anti-Fibrotic Therapeutic

Purpose To develop PEGylated variants of pUR4/FUD (FUD), a fibronectin assembly inhibitor, using 10 kDa, 20 kDa, and 40 kDa PEGs to evaluate their binding affinity and inhibitory potency. Methods The FUD peptide was recombinantly expressed, purified, and PEGylated at the N-terminus using 10 kDa, 20 kDa, and 40 kDa methoxy-PEG aldehyde. The PEGylates were purified and fractionated using ion-exchange chromatography. The molecular weight and degree of PEGylation of each conjugate was verified using MALDI-TOF. The binding affinity of each PEG-FUD conjugate was studied using isothermal titration colorimetry (ITC) and their inhibitory potency was characterized by a cell-based matrix assembly in vitro assay. Results The 10 kDa, 20 kDa, and 40 kDa PEG-FUD conjugates were synthesized and isolated in good purity as determined by HPLC analysis. Their molecular weight was consistent with attachment of a single PEG molecule to one FUD peptide. The binding affinity (K-d) and the fibronectin fibrillogenesis inhibitory potency (IC50) of all PEG-FUD conjugates remained nanomolar and unaffected by the addition of PEG. Conclusions Retention of FUD fibronectin binding activity following PEGylation with three different PEG sizes suggest that PEG-FUD holds promise as an effective anti-fibrotic with therapeutic potential and a candidate for further pharmacokinetic and biodistribution studies.