This article discusses these options in relation to recent trends in the area of drug discovery, including outsourcing, the availability of new technologies, and maximization of workflow within the lab.
As the field of high-throughput screening matures and the number of validated targets increases, there is a greater desire among all pharmaceutical companies to “screen smarter” within existing resource constraints. The development of more physiologically and biochemically relevant assays, the testing of smaller and more focused compound libraries, and the increase in compound selectivity and specificity profiling at an earlier stage have all been implemented within screening groups to meet these corporate goals.
Because of its complexity, compound profiling has proven to be the one area where outsourced compound testing has effectively competed with the in-house development of a profiling panel for a particular target class.
The development of an in-house profiling panel provides many benefits to a screening group and their internal therapeutic group customers. Assay target expertise, rapid compound turnaround, and the ability to work closely with medicinal chemistry groups to rapidly profile compounds shortens the discovery process, making in-house profiling very desirable. However, there are significant staff, reagent, workflow, and data analysis process costs associated with the set-up and maintenance of such a panel.
Each of the assays within the panel has to be developed and validated — this can take as much as two to three weeks depending on the tractability of the target and the assay methodology selected. Reagents for each assay have to be sourced, tested, validated, and ongoing supplies ensured. The workflow process has to be defined. Typically, screening laboratories are set up to process a large number of samples at a single concentration against a single target with the follow up of hits against the same target. The profiling workflow requires the testing of a small number of test compounds at intermittent time periods against multiple targets. To manage this process and resource requirements, many labs schedule profiling assays at defined intervals. Although this manages the workflow, some of the flexibility benefits of in-house profiling are lost. The in-house screening data analysis systems are also designed primarily to process large data sets from a single assay; again, these systems have to be upgraded to meet the profiling process that requires small data sets to be compared against multiple targets to determine compound selectivity. This burden on resources, for both reagents and technical staff, combined with the workflow changes and data analysis requirements is significant, making outsourcing a compelling alternative.
Outsourced profiling, while expensive and lacking some of the stated advantages of in-house profiling, can alleviate much of the resource burden associated with in-house programs. There are no assay development or validation costs, or ongoing assay maintenance and running costs. Compounds for testing are supplied direct to the outsourcing company and tested through the selected panel of assays. Prior to establishing an outsource profiling relationship however, the prospective customer needs to determine that the profiling services vendor meets the needs of the lab. This includes:
- Assay methodology — a full review of methodologies including detailed methods, SOPS, and kinetic and standard inhibitor data for each target should be obtained.
- Determine how compounds will be processed, including delivery requirements, storage, dissolution, test concentrations, replicate numbers, and concentration ranges if potency is to be determined.
- Agree on the format of data received from the vendor, determine how the data will be reported, and on the assay QC and pass/fail criteria.
Although this review process requires a significant investment of time by the potential customer, it is crucial to the long-term success of any partnership.
In response to the challenges associated with both outsourced and in-house profiling, a new generation of products is being developed that are costeffective, easy to implement inhouse, and faster than outsourcing.
Recently, ready-to-use kits have been introduced that provide users with the means to perform routine profiling against selected targets in a “pre-validated” homogeneous format. The need to accumulate sufficient compounds to batch outsource and the delays associated with the speed of turnaround are removed. The inhouse issues associated with developing and maintaining multiple assays have also been removed with such pre-validated kits.
These types of kits typically consist of 384-well plates containing up to 24 targets. Assay set-up is simplified such that the user need only add compound and other assay reagents to the plate, incubate, and read the plate.
It is anticipated that in the near future, the role of “ready-to-use” profiling kits will expand within screening groups, providing the best of both worlds. Improved turnaround along with the elimination of costs associated with the development and long-term maintenance of an assay panel should enable therapeutic research labs to perform more frequent profiles at lower costs and with immediate access to data.