high-throughput screening
Imagine you have a million keys and one lock, and you want to find every key that fits. Instead of trying them one at a time by hand, you build a robot that tests thousands of keys per hour. High-throughput screening (HTS) is that robot for drug discovery: it rapidly and automatically tests enormous collections of chemical compounds to see which ones do something useful to a biological target.
In practice, a target (such as an enzyme or receptor) is set up in a tiny well of a microplate that holds 384 or 1536 wells, each receiving a different compound. Robotic arms, liquid handlers, and plate readers measure a signal — often fluorescence or luminescence — that reports whether the compound changed the target's activity. Software then flags the wells where the signal crossed a threshold; these become the candidate hits.
HTS is powerful for sampling chemical diversity quickly, but it is shallow rather than deep: each compound is usually tested once, at a single concentration. That means many apparent hits are artifacts, and real hits are often weak and need a lot of follow-up. The quality of the result depends heavily on the quality of the assay and the library, which is why hit lists must always be confirmed before any real chemistry begins.
A team screens a 500,000-compound library against a kinase at 10 µM in 1536-well plates, reading ATP depletion by luminescence; 1,200 wells exceed the inhibition threshold and enter hit confirmation.
A primary HTS campaign turns a vast library into a short, noisy hit list that still needs validation.
Hit rates in HTS are typically low — often well under 1% — and a large fraction of those raw hits will later turn out to be false positives. HTS finds starting points, not drugs.