Dan Thomas, GSK
Written by Jackie Howard Wednesday, 09 May 2012 09:24
Implementation of Digital Titration to enable high resolution dose-response generation and simplified experimental design
Drug discovery relies on in-vitro dose-response measurements as the principal means of quantifying the interaction between biological targets and drug molecules. Conventional titration is a century-old yet highly non-standardized work flow which exploits the use of serial dilution in the generation of concentration response curves for a considerable variety of applications. While this is a highly efficient and consistent process capable of accessing a broad concentration range, it also limits the absolute dose attainable, and modern alternatives fall short of eliminating the limitations of serial processes. Inkjet printing technology is now being used to dispense 20 picoliter droplets of reagents dissolved in a DMSO or aqueous solvent, enabling concentration-response-curves to be generated without the need for serial dilution. The required number of droplets are rapidly dispensed to obtain dosages from low nanomolar to high micromolar concentrations for a typical assay volume. This direct titration method simplifies discovery workflows, saving both time and materials. Using this methodology, intermediate plates can be eliminated together with a large reduction in compound/reagent usage as well as chemical waste. Direct titrations fundamentally improve the quality of dose-response data by eliminating serial dilution steps, avoiding carryover and allowing the user to digitally control the total dispense volume enabling the generation of any dose in any well. Ultimately this can be used to create high density bespoke titrations spanning regions of interest, assisting in the interrogation of target and compound mechanisms of action or drug-drug interaction studies. In summary, this digital picoliter dispense technology dramatically improves data quality while minimizing cost and time, both of which are critical aspects of lead generation and optimization that drive decision making. A number of different applications within the early drug discovery process will be presented.