Causes and Significance of Increased Compound Potency in Cellular or Physiological Contexts.

Compound potency is a key metric that is often used to drive medicinal chemistry programs. Compound potency is also taken into account when identifying the mechanism of action of compounds whose pharmacological target is unknown, particularly when these compounds are identified in phenotypic screens. Often compound potency is determined from assays using recombinantly generated, purified protein. It is well understood in the medicinal chemistry community that potency measured with recombinant enzyme and potency measured in cell may not entirely coincide. Decreases in cellular vs recombinant potency are often anticipated or explainable. What is less often realized is that compound potency can increase in a cellular environment due to several factors including cellular metabolism of compounds, protein-protein interactions, post-translational modifications, and asymmetric intracellular localization of compound. Here we discuss these factors and highlight examples where increases in cellular compound potency were critical to the development of probes or drugs.