Evaluation and optimization of compound solubilization and delivery methods in a two-tiered ion channel lead optimization triage

Assay Drug Dev Technol. 2012 Apr;10(2):202-11. doi: 10.1089/adt.2011.0385. Epub 2011 Nov 15.

Abstract

Low-volume dispensing of neat dimethyl sulfoxide (DMSO) into plate-based assays conserves compound, assay reagents, and intermediate dilution plate cost and, as we demonstrate here, significantly improves structure-activity relationship resolution. Acoustic dispensing of DMSO solutions into standard volume 384W plates yielded inconsistent results in studies with 2 cell lines because of apparent effects on the integrity of the cell monolayer (increased intracellular Ca⁺⁺ levels as indicated by elevated basal dye fluorescence after acoustic transfer). PocketTip-mediated transfer was successful at increasing apparent potency on a more consistent basis. Notably, the correlation coefficient among fluorescence imaging plate reader (FLIPR):electrophysiology (EP) across a representative ~125 compound collection was increased ~5× via conversion to a PocketTip direct dispensation, indicating a triage assay more predictive of activity in the decisional patch-clamp assay. Very importantly, the EP-benchmarked false-negative rate as measured by compounds with FLIPR EC₅₀ more than the highest concentration tested fell from >11% to 5% assay-wide, and the relative FLIPR:EP rank-order fidelity increased from 55% to 78%. Elimination of the aqueous intermediate step provided additional benefits, including reduced assay cost, decreased cycle time, and reduced wet compound consumption rate. Direct DMSO dispensing has broad applicability to cell-based functional assays of multiple varieties, especially in cases where limit solubility in assay buffer is a recognized impediment to maximizing interassay connectivity.

MeSH terms

  • Acoustics
  • Buffers
  • Calcium / analysis
  • Calcium / chemistry
  • Centrifugation
  • Dimethyl Sulfoxide / chemistry
  • False Negative Reactions
  • Fluorometry
  • HEK293 Cells
  • High-Throughput Screening Assays / instrumentation*
  • High-Throughput Screening Assays / methods*
  • Humans
  • Image Processing, Computer-Assisted
  • Indicator Dilution Techniques
  • Ion Channels / drug effects*
  • Patch-Clamp Techniques
  • Solubility
  • Solutions
  • Water

Substances

  • Buffers
  • Ion Channels
  • Solutions
  • Water
  • Calcium
  • Dimethyl Sulfoxide