Target specific screens and their use for discovering small organic molecular pharmacophores

A method of identifying ligands capable of binding to at least two determinants which together are required for biological activity of a pharmacological target, the method comprising:

• a) screening and isolating from an rVab library, rVab members comprising at least one VH and VL regions, and optionally comprising a constant domain attached by its amino terminus to the V region, and capable of binding to at least one of the determinants of the pharmacological target;
• b) making and expressing an rVab-peptide (rVab-PEP) library comprising the isolated rVab members coupled to at least one peptide comprised of a random sequence of amino acids;
• c) screening the rVab-PEP library for first rVab-Pep members which bind and activate the pharmacological target wherein the rVab component binds to a first determinant of the pharmacological target and the peptide component binds to a second determinant of the pharmacological target;
• d) screening the rVab-Pep library and identifying a second rVab-pep member capable of actively binding to the pharmacological target, and wherein the rVab component binds to a third determinant of the pharmacological target and the peptide component binds to fourth determinant of the pharmacological target.

A method of providing a model for a ligand capable of binding to a determinant of an active site of a pharmacological target, the method comprising:

• a) providing at least two rVab identified as binding to an active surface of a pharmacological target;
• b) identifying the regions of the rVabs that bind the biologically active site or individual inactive surface determinants of the bioactive structure;
• c) grouping the rVabs by overlapping structures which bind to common epitopes;
• d) determining the relative spatial orientation, charge and energetics of the identified binding sites
• e) determining the molecular structure necessary to bind the target and confer activity.