Retrospective Mapping of SAR Data for TTR Protein in Chemico-Biological Space Using Ligand Efficiency Indices as a Guide to Drug Discovery Strategies.

We have previously reported the design and synthesis of ligands that stabilize Transthyretin protein (TTR) in order to obtain therapeutically active compounds for Familial Amyloid Polyneuropathy (FAP). We are hereby reporting a drug design strategy to optimize these ligands and map them in Chemico-Biological Space (CBS) using Ligand Efficiency Indices (LEIs). We use a binding efficiency index (BEI) based on the measured binding affinity related to the molecular weight (MW) of the compound combined with surface-binding efficiency index (SEI) based on Polar Surface Area (PSA). We will illustrate the use of these indices, combining three crucial variables (potency, MW and PSA) in a 2D graphical representation of chemical space, to perform a retrospective mapping of SAR data for a current TTR inhibitors database, and we propose prospective strategies to use these efficiency indices and chemico-biological space maps for optimization and drug design efforts for TTR ligands.

Kinetic assay for high-throughput screening of in vitro transthyretin amyloid fibrillogenesis inhibitors.

Stabilization of tetrameric transthyretin (TTR) by binding of small ligands is a current strategy aimed at inhibiting amyloid fibrillogenesis in transthyretin-associated pathologies, such as senile systemic amyloidosis (SSA) and familial amyloidotic polyneuropathy (FAP). A kinetic assay is developed for rapid evaluation of compounds as potential in vitro inhibitors in a high-throughput screening format. It is based on monitoring the time-dependent increase of absorbance due to turbidity occurring by acid-induced protein aggregation. The method uses the highly amyloidogenic Y78F mutant of human transthyretin (heterogously expressed in Escherichia coli cells). Initial rates of protein aggregation at different inhibitor concentrations follow a monoexponential dose-response curve from which inhibition parameters are calculated. For the assay development, thyroid hormones and nonsteroidal antiinflamatory drugs were chosen among other reference compounds. Some of them are already known to be in vitro inhibitors of TTR amyloidogenesis. Analysis time is optimized to last 1.5 h, and the method is implemented in microtiter plates for screening of libraries of potential fibrillogenesis inhibitors.