A generic approach to disrupting protein-protein interactions application to the hIgE-FceRI interface

Asthma and other allergic manifestations are the result of a complex cascade of events at the molecular level initiated by the detection of an allergen (from pollen, dust mites etc.) by a protein in the blood called IgE, which culminates in the release of toxic inflammatory agents (resulting in airway inflamation etc.). This research is aimed at the rational development of molecules that are able to prevent the docking of IgE to its receptor protein on the surface of certain cells, thereby preventing the generation of the harmful inflammatory agents following activation by allergens. The molecules identified as being effective for blocking this key protein-protein binding event are expected to constitute exciting leads for the development of anti-allergic drugs. Moreover, since related protein-protein binding events are widespread in human disease processes, an increased level of understanding of the manner in which these interactions can be disrupted is likely to be of significant therapeutic value in many areas of medicine and healthcare.

The IgE-FceRI protein-protein interaction (PPI) is central to the allergic cascade associated with asthma and all other allergic manifestations. We propose to use Solid Phase (SP) parallel synthesis to prepare a series of novel antagonists of this PPI, to kinetically characterise these molecules using a series of biophysical assays and to subject promising leads to parallel co-crystallisation with recombinant protein. The antagonists are conformationally constrained cyclic peptides, based on known peptide antagonists, but incorporating diphenylethylenes and biphenyls as backbone linking units and arrays of novel biphenyl amino acids at key positions aready identified as binding hot-spots by mutagenesis. In addition to being predisposed towards PPI binding, these compounds are expected to display high metabolic/proteolytic stability (as the result of decreased conformational mobility) and superior ADMET and crystallisation properties relative to conventional cyclic peptides (e.g. disulfide constrained). The chemistry program will be integrated closely to the medium-throughput binding assays based on ELISA, FRET, SPR and cellular secretion technologies and the most promising binders will be subject to semi-automated protein co-crystallisation using nanolitre volumes. The expected outcome will be the identification of a novel series of potent antagonists of this important interaction and associated high resolution structural/mode of action data which should provide a strong platform for subsequent drug design. Additionally, the specific data obtained for this protein-protein interface is expected to provide important insights of generic value for the understanding of the manner in which small molecules interact with large and complex protein surfaces at the molecular level. This information should be invaluable for advancing strategies for addressing the designed disruption of therapeutically significant PPIs.