Jennifer Hyde

Binding of small molecules to an adaptive protein–protein interface

Understanding binding properties at protein–protein interfaces has been limited to structural and mutational analyses of natural binding partners or small peptides identified by phage display. Here, we present a high-resolution analysis of a nonpeptidyl small molecule, previously discovered by medicinal chemistry [Tilley, J. W., et al. (1997) J. Am. Chem. Soc. 119, 7589–7590], which binds to the cytokine IL-2. The small molecule binds to the same site that binds the IL-2 α receptor and buries into a groove not seen in the free structure of IL-2. Comparison of the bound and several free structures shows this site to be composed of two subsites: one is rigid, and the other is highly adaptive. Thermodynamic data suggest the energy barriers between these conformations are low. The subsites were dissected by using a site-directed screening method called tethering, in which small fragments were captured by disulfide interchange with cysteines introduced into IL-2 around these subsites. X-ray structures with the tethered fragments show that the subsite-binding interactions are similar to those observed with the original small molecule. Moreover, the adaptive subsite tethered many more compounds than did the rigid one. Thus, the adaptive nature of a protein–protein interface provides sites for small molecules to bind and underscores the challenge of applying structure-based design strategies that cannot accurately predict a dynamic protein surface.

Discovery and Development of Potent LFA-1/ICAM-1 Antagonist SAR 1118 as an Ophthalmic Solution for Treating Dry Eye

LFA-1/ICAM-1 interaction is essential in support of inflammatory and specific T-cell regulated immune responses by mediating cell adhesion, leukocyte extravasation, migration, antigen presentation, formation of immunological synapse, and augmentation of T-cell receptor signaling. The increase of ICAM-1 expression levels in conjunctival epithelial cells and acinar cells was observed in animal models and patients diagnosed with dry eye. Therefore, it has been hypothesized that small molecule LFA-1/ICAM-1 antagonists could be an effective topical treatment for dry eye. In this letter, we describe the discovery of a potent tetrahydroisoquinoline (THIQ)-derived LFA-1/ICAM-1 antagonist (SAR 1118) and its development as an ophthalmic solution for treating dry eye.

Discovery of tetrahydroisoquinoline (THIQ) derivatives as potent and orally bioavailable LFA-1/ICAM-1 antagonists.

This letter describes the discovery of a novel series of tetrahydroisoquinoline (THIQ)-derived small molecules that potently inhibit both human T-cell migration and super-antigen induced T-cell activation through disruption of the binding of integrin LFA-1 to its receptor, ICAM-1. In addition to excellent in vitro potency, 6q shows good pharmacokinetic properties and its ethyl ester (6t) demonstrates good oral bioavailability in both mouse and rat. Either intravenous administration of 6q or oral administration of its ethyl ester (6t) produced a significant reduction of neutrophil migration in a thioglycollate-induced murine peritonitis model.