Nycomed (formerly ALTANA Pharma and Byk-Gulden) has carried out high-throughput screening (HTS) since 1998.

As far as HTS screening is concerned, we use three different robotic lines which are used according to our requirements. The use also depends on the robots’ strengths and the measurement devices available on the respective robotic line.
One of these robotic lines is used for standard screening, i.e. high-speed and high-throughput screening with more than 100,000 assay points per day. The second system (up to 60,000 assay points per day) is used for enzymatic assays and allows the high-throughput screening of radioactive assays. In addition, we also have a very flexible robotic line that can be used for high-throughput confocal microscopy.

The number of actual assay points per day depends, among other things, on the throughput rate of the measurement device: the recording of microscopic images and the time required to do so depends on the exposure parameters. This process is similar to that of a digital camera, with the only difference being that several hundreds of thousands of pictures have to be taken and processed in a single screening campaign. The process requires enormous computer capacities, but also a lot of time. The imaging system of our robotic line allows us to process over 65,000 assay points per day.

Our most modern screening system is equipped with a central conveyor belt that transports the microtitre plates. At the individual workstations, robotic arms take the assay plates and feed them into the transport process between the individual devices. Several stations can be served simultaneously as long as the conveyor belt has free places available. This guarantees maximum capacity utilisation and makes the robotic line extraordinarily fast. In contrast, our highly flexible robotic line is equipped with a mobile robotic arm that is mounted onto a guide rail. Since this arm has to feed the pipetting, incubation and measurement stations located on the left and right, this type of set up reduces the throughput speed.

In general, the more complex an assay, the greater the probability that the number of potential assay points decreases. For example, if the robot-assisted main screening involves primary cells, the cell culture supplying the cells might turn out to be the limiting factor in this process. The same is true for the incubation time required or the number of additions, e.g., another compound and reagents or additional buffer solutions. This is not so in standard screening processes, which means that complex assays require a much high number of robotic runs. If a pharmacologically important, but complex and time-consuming model is chosen, then a slower speed is selected. This leads to higher data quality because additional important parameters can be tested. In general, the throughput has increased considerably over the last few years through the miniaturisation of the assays to as little as five to eight microlitres per assay point.

Normally the screening focuses on the functional properties of the targets; this means, pure binding assays are unusual and are only used for drug profiling. The main screening involves all common test formats, including enzyme tests, cellular tests, including reporter gene-based as well ion channel tests. It is important that the targets that are to be screened can be transferred into a measurable detection format for which we use common methods, i.e. microtitre plate readers for measuring absorption, different fluorescence methods, luminescence, confocal microscopy up to 1536-well formats, but also radioactive screening. In general, our high-throughput screening involves 384-well or 1536-well microtitre plates.

Secondary screening, which is also fully automated, involves the dose-dependent screening of drug effects. We collect information on whether the hits of the primary screening have undesired side effects on related targets, which would make them unsuitable for further processing. Routine investigations also collect information on initial ADME category parameters such as absorption, distribution, metabolism, elimination. Hit evaluation also includes solubility and permeability screening as well as data from toxicological assays. This type of screening also assesses the metabolic stability of drugs and their interaction with cytochromes in order to guarantee the highest possible quality of lead structures and allow medical chemists to make initial prioritisations on the basis of a far more complex drug profile than was possible a few years ago. All assays are carried out under standard conditions and are highly automated. Suitable quality control measures provide information on the course of the screening and the results will only be made available upon the positive evaluation of the process.

This is the case in more complex test systems, which cannot be transferred into a microtitre plate-based, robot-suitable format and which must be carried out with far smaller amounts of reagents and test substances. The decision on whether automated or manual screening is used depends on a variety of factors.