Vala Sciences

A significant number of molecular targets are a focus for development of new therapies in modern drug discovery. In order to quickly and efficiently identify the best candidates for chemical intervention of the target function, scientists need to have robust and accurate technologies allowing selecting appropriate NCE (New Chemical Entities) from large chemical compound libraries.

Optical-based high throughput screening is a major tool in modern drug discovery process. HT screening allows to quickly and cost-efficiently scan huge chemical libraries against the molecular target in search for “active” chemical entities. Fluorescent-based optical screening assays can achieve a throughput of 100K well per day. They are cheap, easy to implement and amendable to miniaturization. A capability to record signals from multiple cells at the same time makes fluorescent-based assays a preferable technology for primary screening applications.

Commonly used screening methodologies for HTS/HCS screens include fluorescent, ligand binding and ion flux assays. All above-mentioned assays have substantial limitations in their performance.

Ion flux and fluorescence assays, in which signals are initiated either through cell depolarization by the addition of high potassium solution into the test well, can be configured for HTS for molecular targets that are amenable to this treatment. However, it is difficult to develop an array of technically different assays for a particular drug discovery target, and the abovementioned stimulation protocols are interfering with an expected physiological response of the test cells. For example, binding assays can be configured to generate robust high-throughput format data; however it is well known that binding assays may not reflect effects of test compounds on a target function.

HCS allows recording a physiologically relevant response from many cells in parallel. Automatic data processing software enables researcher to handle massive amount of data. In addition, HCA permits quantification of cellular responses from individual cells in a well as well as extraction of subpopulation data. For example, the CyteSeer data analysis package has a capability to collect and quantify data from selected sub-cellular components of individual cells, enabling to quantify a complex use-dependent and state-dependent cellular responses.

In many cases, the inability to control the membrane potential and interrogate excitable cells in different physiological conditions remains a major problem for optical assays.

Recently new generation of high-precision assays have been introduced to HCS process. Namely Planar Electrophysiology Assays. Where applicable, planar electrophysiology assays deliver higher quality multi-parametric data comparatively to HTS assays (for example, high throughput binding assays). The major limitation of HCS electrophysiological techniques remains seriously limited screening throughput and cost associated with this screening technology.

KIC module is a powerful new technique that can be generally applicable for the determination of the effects of test compounds on a variety of voltage-gated ion channels. Electrical field stimulation is not dependent on agonists to initiate ion channel opening, and therefore obviates possible interactions between test compounds and agonists or depolarizing high potassium solution. In its simplest application, this technique would allow the counter-screening of compounds on multiple ion channel types, using essentially the same stimulation technique.