The Advantages of Continuous Assays in Kinome Profiling
Most profiling platforms stop the reaction and read a single time point.
That snapshot assumes the enzyme stayed perfectly linear — but in reality, enzyme activity is dynamic. As a result, endpoint assays can distort potency, overlook time-dependent inhibition, and hide mechanistic behaviors that influence drug discovery outcomes.
Continuous assays overcome these challenges by capturing enzyme activity in real time rather than at a single endpoint.
Instead of inferring behavior from a static value, they directly monitor reaction progress — revealing how activity changes second by second as substrates are converted and inhibitors interact.
This approach provides a full kinetic profile that exposes subtle but critical behaviors — such as time-dependent inhibition, reversibility, and off-rate effects — delivering data that truly reflect enzyme mechanism.
Continuous Assays Capture True Enzyme Behavior
A Single Timepoint Can’t Tell the Whole Story
AssayQuant’s PhosphoSens® technology continuously measures enzyme activity in real time — directly tracking substrate phosphorylation rather than relying on indirect coupling reactions.
Each well produces a complete progress curve with dozens of timepoints, revealing exactly how enzyme activity changes throughout the reaction. This allows for accurate, rate-based % inhibition values tailored to each of the 560+ kinases profiled in our KinSight™ selectivity screens.
Unlike endpoint assays that provide a single snapshot, the PhosphoSens continuous format captures the entire story — every frame of enzyme behavior. By measuring catalytic activity kinetically, it reveals true selectivity and mechanism of action, giving researchers the mechanistic clarity needed to drive drug development forward with confidence.
This approach forms the foundation of AssayQuant’s KinSight Profiling Service, which delivers kinetic insight into kinome-wide selectivity and mechanism of action (MOA) — helping discovery teams make data-driven decisions about therapeutic opportunities and off-target liabilities with greater confidence and precision.
What Continuous Profiling Reveals That Endpoints Miss
AssayQuant’s Quartet: Same Endpoint, Different Story
In a comparative example, four kinases — TTBK1, FGFR3, BTK, and HCK — each appeared to show ~60–65% inhibition in a standard endpoint assay.
Each mechanism produces similar endpoint values — yet radically different kinetics and implications for inhibitor optimization.
On paper, they look the same, but continuous progress curves tell a very different story:
| Target | % Inhibition |
| TTBK1 | 65% |
| FGFR3 | 61% |
| BTK | 61% |
| HCK | 60% |
TTBK1 — Linear, predictable kinetics
This is what you expect a clean enzymatic reaction to look like.
Continuous data confirm stable kinetics and reliable rate determination — with 60+ timepoints per replicate instead of one.
FGFR3 — Noisy data reveal solubility artifacts
The continuous trace exposes experimental noise likely caused by compound insolubility — something a single endpoint could never flag.
Detecting such issues early prevents false conclusions and wasted follow-up.
BTK — Saturation & time-dependent inhibition
The curve flattens over time, revealing possible substrate depletion, product inhibition, or slow off-rate behavior.
Early detection of time-dependent inhibition (TDI) provides key clues to mechanism of action (MOA) and compound reversibility.
HCK — Lag phase indicates mechanistic nuance
The lag before steady-state activity hints at conformational effects — for example, the inhibitor preferring an inactive or oligomeric kinase form.
These kinetic patterns are invisible to endpoint assays but critical for mechanistic discovery.
