Data Analysis and Informatics
A comparison of High Throughput Screening and Virtual Screening Approaches in a Biochemical Coupled-Enzyme Inhibition Assay Program
Tuesday, February 6
12:00 PM - 12:30 PM
High throughput screening (HTS) and virtual screening (VS) are distinct strategies employed in lead discovery programs to identify potential drug candidates. In an effort to discover novel inhibitors of a Type 2 diabetes target, we employed a multi-pronged strategy using both experimental (HTS) and theoretical (VS) approaches.
An in-house compound library was screened in a well characterized biochemical, coupled-enzyme assay that has been miniaturized to 1536-format and optimized for HTS. Both enzymes are potential targets on the same pathway.
Virtual screen characterization against each of the two enzymes broadens the likelihood of garnering hits. The in silico approach for each target enzyme was unique, given their different crystal structures. The first enzyme, with a particularly large binding pocket, required a sub-pocket system to be employed. To date there is no known inhibitor for this target. On the other hand, the second target has a known inhibitor and proved to be less challenging. The virtual screens were performed on the same set of compounds as the HTS, along with another 6.5 million molecules- curated based on availability and favorable structural properties- from the eMolecule database. Molecular dynamic simulations followed by ensemble docking on Phase filtered data set and mmGBSA based postprocessing calculations were carried out. A proprietary feature matching method was employed to select a small but diverse set of hit compounds.
Results from a preliminary set of 253 VS hits tested in the biochemical assay resulted in a 24% confirmation rate, demonstrating the effectiveness of the VS approach. Further characterization of the confirmed hits established that half of them act at the first enzyme and half at the second.
A head-to-head comparison of the outcome of both approaches was performed. Multiple parameters were evaluated, including hit quality and true/false positive and negative rates. Evaluation of these factors, along with overlap between the compound sets identified from- and the relative merits of- each approach are discussed. The combination of HTS and VS methods proved to be complementary tactics to address molecular targets and to identify unique chemical matter, with VS playing a critical role by tapping into the very large chemical space of commercial collections, which are not readily available for HTS and are expensive to acquire.