EC50
Definition
In a graded response assay, EC50 is the concentration associated with half of the measured maximum effect under that assay’s conditions.
By PurePeptideHub Editorial Team · Updated . Educational source review; independent clinical review pending.
Potency is not maximum benefit
A lower EC50 can indicate higher potency when compounds are tested using the same assay. It does not necessarily mean a larger maximum response or a better clinical treatment. The assay’s receptor system, endpoint and exposure time affect the value.
References: [1]
A worked comparison
Imagine compound A reaches its half-maximal response at 2 nM and compound B at 20 nM in the same experiment. A is more potent for that endpoint. If A’s maximum response is smaller than B’s, A can still produce a smaller effect at saturation. Potency and maximal efficacy must be read separately.
Check the meaning of 50%
Some fields use EC50 for an effect in half the organisms rather than half the maximum graded response. Read the paper’s definition. EC50 is also different from IC50, which concerns inhibition. Neither value can be converted directly into a human injection amount.