Structural Guided Scaffold Phage Display Libraries as a Source of Bio-Therapeutics

We have developed a structurally-guided scaffold phage display strategy for identification of ligand mimetic biotherapeutics.

As a proof of concept we used the ligand of integrin avb6, a tumour cell surface receptor and a major new

target for imaging and therapy of many types of solid cancer. NMR structure analysis showed that RGD-helix structures are

optimal for avb6 ligand-interaction, so we designed novel algorithms to generate human single chain fragment variable

(scFv) libraries with synthetic VH-CDR3 encoding RGD-helix hairpins with helices of differing pitch, length and amino acid

composition. Study of the lead scFv clones D25scFv and D34scFv and their corresponding VH-CDR3 derived peptides, D25p

and D34p, demonstrated: specific binding to recombinant and cellular avb6; inhibition of avb6-dependent cell and ligand

adhesion, avb6-dependent cell internalisation; and selective retention by avb6-expressing, but not avb6-negative, human

xenografts. NMR analysis established that both the D25p and D34p retained RGD-helix structures confirming the success of

the algorithm. In conclusion, scFv libraries can be engineered based on ligand structural motifs to increase the likelihood of

developing powerful bio-therapeutics.