Experimental Polar Surface Area
EPSA Analysis (Experimental Polar Surface Area) for Drug Discovery
What Is Experimental Polar Surface Area (EPSA)?
EPSA is an experimental technique used in drug discovery to measure the exposed polarity of small molecules under physiologically relevant conditions.
EPSA provides an empirical measurement of molecular polarity based on chromatographic behavior. The method uses Supercritical Fluid Chromatography (SFC) to determine how strongly a compound interacts with a polar stationary phase.
Because EPSA measures exposed polarity rather than theoretical polarity, it provides valuable insight into properties that strongly influence:
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Passive membrane permeability
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Oral absorption potential
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Intramolecular hydrogen bonding
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Molecular conformational behavior
EPSA has become a widely used tool for medicinal chemists optimizing compounds for drug-like properties.
Turnaround Time:
Our high-throughput EPSA measurements can analyze >1000 compounds per week.
Why EPSA Is Important in Drug Discovery
Balancing polarity and lipophilicity is one of the biggest challenges in medicinal chemistry. Compounds that are too polar often show poor permeability and limited oral bioavailability, while highly lipophilic molecules may suffer from solubility or toxicity issues.
Traditional metrics such as calculated polar surface area can fail to capture dynamic molecular behavior, especially when molecules adopt conformations that shield polar groups.
EPSA helps solve this problem by measuring how much polarity is actually exposed in solution.
Key Advantages of EPSA
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Rapid data generation – EPSA measurements can be obtained quickly using SFC-based methods.
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High reproducibility – The method delivers consistent and reliable experimental results.
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Direct relevance to permeability – EPSA values help assess how molecular polarity influences membrane permeability.
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Supports developability assessments – Provides insight into properties affecting drug candidate progression.
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Enables compound prioritization – Helps rank compounds during early drug discovery.
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Guides structure–property relationships – Assists medicinal chemists in understanding how structural changes affect polarity and permeability.
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Useful across discovery stages – Supports decision-making during both early discovery and lead optimization.
Read our full blog post about EPSA Here.
Instrumentation:
Agilent 1260 Infinity II SFC/MS