{ "id": "epk3wj9sec", "slug": "inhibition-assay", "title": "Inhibition assay", "updated": "2026-10-21", "topic_path": [ { "id": "life", "label": "Life and health", "api_url": "https://www.edgepedia.org/api/v1/topics/life" }, { "id": "life.biology", "label": "Biological foundations", "api_url": "https://www.edgepedia.org/api/v1/topics/life.biology" }, { "id": "life.biology.biochemistry", "label": "Biochemistry and metabolism", "api_url": "https://www.edgepedia.org/api/v1/topics/life.biology.biochemistry" }, { "id": "life.biology.biochemistry.practice", "label": "Biochemistry field and methods", "api_url": "https://www.edgepedia.org/api/v1/topics/life.biology.biochemistry.practice" }, { "id": "life.biology.biochemistry.practice.methods", "label": "Biochemical methods and techniques", "api_url": "https://www.edgepedia.org/api/v1/topics/life.biology.biochemistry.practice.methods" }, { "id": "life.biology.biochemistry.practice.methods.assays", "label": "Assay techniques", "api_url": "https://www.edgepedia.org/api/v1/topics/life.biology.biochemistry.practice.methods.assays" } ], "geo": [ { "id": "geo.nongeo.t1800.life.biology", "label": "Non-geographic · 1800 to 1945: Biological foundations", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1800.life.biology", "path": [ { "id": "geo.nongeo", "label": "Non-geographic", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo" }, { "id": "geo.nongeo.t1800", "label": "Non-geographic · 1800 to 1945", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1800" }, { "id": "geo.nongeo.t1800.life", "label": "Life and health", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1800.life" }, { "id": "geo.nongeo.t1800.life.biology", "label": "Biological foundations", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1800.life.biology" } ] }, { "id": "geo.nongeo.t1946.life.biology.biochemistry.practice.methods.assays", "label": "Non-geographic · 1946 to 2000: Assay techniques", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.biology.biochemistry.practice.methods.assays", "path": [ { "id": "geo.nongeo", "label": "Non-geographic", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo" }, { "id": "geo.nongeo.t1946", "label": "Non-geographic · 1946 to 2000", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946" }, { "id": "geo.nongeo.t1946.life", "label": "Life and health", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life" }, { "id": "geo.nongeo.t1946.life.biology", "label": "Biological foundations", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.biology" }, { "id": "geo.nongeo.t1946.life.biology.biochemistry", "label": "Biochemistry and metabolism", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.biology.biochemistry" }, { "id": "geo.nongeo.t1946.life.biology.biochemistry.practice", "label": "Biochemistry field and methods", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.biology.biochemistry.practice" }, { "id": "geo.nongeo.t1946.life.biology.biochemistry.practice.methods", "label": "Biochemical methods and techniques", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.biology.biochemistry.practice.methods" }, { "id": "geo.nongeo.t1946.life.biology.biochemistry.practice.methods.assays", "label": "Assay techniques", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.biology.biochemistry.practice.methods.assays" } ] } ], "excerpt": "An inhibition assay is a bench biology method measuring how a competitor reduces a target's binding or activity, yielding percent inhibition, IC50, and an inhibition constant (Ki).", "snippet": "An inhibition assay is a bench biology method measuring how a competitor reduces a target's binding or activity, yielding percent inhibition, IC50, and an inhibition constant (Ki).", "node": "life.biology.biochemistry.practice.methods.assays", "markdown": "# Inhibition assay\n\nAn inhibition assay is a bench biology method that measures how a competitor molecule reduces the binding or activity of a target, converting the resulting dose-response curve into a percent inhibition value and often an inhibition constant (\\( K_{i} \\)) that quantifies affinity or potency. It is a standard tool of receptor pharmacology and enzyme drug discovery; in radioligand receptor-binding screens the two typical assay formats are filtration and [scintillation proximity assay](https://www.edgepedia.org/scintillation-proximity-assay).[1](https://www.ncbi.nlm.nih.gov/books/NBK91992/)\n\n| Key fact | Value or statement |\n|---|---|\n| Primary readout | Percent inhibition and \\( \\mathrm{IC_{50}} \\); \\( K_{i} \\) obtained by the Cheng–Prusoff transformation [2](https://doi.org/10.1016/0006-2952%2873%2990196-2) • [3](https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/j.1476-5381.2009.00604.x) |\n| Binding-mode conversion | \\( K_{i} = \\mathrm{IC_{50}}/(1 + [L]/K_{dL}) \\) for competitive ligand binding [3](https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/j.1476-5381.2009.00604.x) |\n| Standard curve span | 90% to 10% specific binding over an 81-fold competitor range, Hill slope −1.0 [1](https://www.ncbi.nlm.nih.gov/books/NBK91992/) |\n| Ligand depletion limit | Keep radioligand depletion below 10% (\\( [R_{T}] < 0.1\\ K_{\\mathrm{d}} \\)) [3](https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/j.1476-5381.2009.00604.x) |\n| Tight-binding onset | When Ki or Ki′ is within 10-fold of the assay active-site concentration [4](https://www.ncbi.nlm.nih.gov/books/NBK92001/) |\n| FP design window | Fraction of tracer bound \\( f_{0} \\) typically 0.5–0.8; resolvable \\( K_{i} \\) floor ≈ fluorescent ligand \\( K_{\\mathrm{d}} \\) [5](https://slas-discovery.org/article/S2472-6303%2822%2900159-5/pdf) |\n| Recent efficiency gain | 50-BOA estimates inhibition constants from one inhibitor concentration, cutting experiments by more than 75% [6](https://pmc.ncbi.nlm.nih.gov/articles/PMC12141731/) |\n\n## How it works\n\nThe assay runs a target (receptor, enzyme, or binding protein) and a measurable ligand or substrate to equilibrium, then titrates a competitor and reads how much target activity or labeled-ligand binding survives. The competitor's occupancy follows the law of mass action. In an equilibrium binding assay, a single-site competitive displacement curve reports the competitor's affinity once the tracer's concentration and \\( K_{\\mathrm{d}} \\) are known; an enzyme velocity curve additionally requires the substrate concentration and the inhibition mechanism, since the IC50 depends on both.\n\nMechanistically, inhibition modes are distinguished by where the inhibitor binds. A competitive inhibitor binds only free enzyme, usually at the active site (finite \\( K_i \\), infinite \\( K_i' \\)); a noncompetitive inhibitor binds free enzyme and the enzyme–substrate complex equally (\\( K_i'/K_i = 1 \\)); an uncompetitive inhibitor binds only the enzyme–substrate complex outside the active site (\\( K_i'/K_i = 0 \\)); and mixed inhibition has finite, unequal \\( K_i \\) and \\( K_i' \\), with \\( K_i'/K_i > 1 \\) being only one possible case (the ratio can also be below 1).[4](https://www.ncbi.nlm.nih.gov/books/NBK92001/) These modes leave kinetic signatures: competitive inhibitors raise apparent \\( K_{m} \\) with no change in \\( V_{\\mathrm{max}} \\), noncompetitive inhibitors lower \\( V_{\\mathrm{max}} \\) without affecting \\( K_{m} \\), and uncompetitive inhibitors lower both.[4](https://www.ncbi.nlm.nih.gov/books/NBK92001/)\n\nThe general relationship between \\( \\mathrm{IC_{50}} \\) and the inhibition constants is [6](https://pmc.ncbi.nlm.nih.gov/articles/PMC12141731/)\n\n\\[ \\frac{1}{\\mathrm{IC_{50}}} = \\frac{\\alpha}{K_{ic}} + \\frac{1-\\alpha}{K_{iu}}, \\qquad \\alpha = \\frac{K_{M}}{S_{T}+K_{M}} \\]\n\nwhere \\( K_{ic} \\) and \\( K_{iu} \\) are the competitive and uncompetitive constants. \\(K_{ic} \\ll K_{iu}\\) gives competitive inhibition, \\(K_{iu} \\ll K_{ic}\\) gives uncompetitive, and comparable magnitudes give mixed inhibition.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC12141731/) In mechanism-of-action assays, running several substrate concentrations and fitting the change in IC50 versus \\( [\\mathrm{substrate}] \\) yields \\( K_i \\) and \\( K_i' \\), whose ratio \\( \\beta = K_i'/K_i \\) classifies the mode: \\( \\beta \\) statistically equal to 1.0 is noncompetitive, while for finite, positive \\( K_i \\) and \\( K_i' \\), \\( \\beta \\neq 1 \\) indicates mixed inhibition, with pure uncompetitive inhibition corresponding to \\( \\beta = 0 \\) and pure competitive inhibition to \\( \\beta \\) tending to infinity.[4](https://www.ncbi.nlm.nih.gov/books/NBK92001/) A mass-action competitive binding curve descends from 90% to 10% specific binding over an 81-fold competitor range with Hill slope −1.0; slopes deviating significantly from −1.0 indicate multiple binding site classes, solubility problems, or assay artifacts.[1](https://www.ncbi.nlm.nih.gov/books/NBK91992/)\n\n## How it is done\n\nA standard [ligand binding assay](https://www.edgepedia.org/ligand-binding-assay) has six steps: prepare a receptor-containing fraction, select a labeled ligand, incubate aliquots at defined time, temperature, and buffer, separate and measure bound versus free ligand, repeat with unlabeled competitors, and analyze the data.[3](https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/j.1476-5381.2009.00604.x) A typical filtration competition assay uses 96-well plates at 250 µL per well with 3–20 µg membrane protein from cells or 50–120 µg from tissue, incubated at 30 °C for 60 minutes, then vacuum-filtered onto 0.3% PEI-presoaked GF/C filters with four ice-cold washes.[7](https://www.giffordbioscience.com/wp-content/uploads/2024/06/Radioligand-Binding-Assay-Protocol-document-compressed.pdf) Competitor is used at a concentration below its \\( K_{\\mathrm{d}} \\) so it can still be detected but competed off, often incubated at 4 °C for several hours in cell-based formats.[8](https://pmc.ncbi.nlm.nih.gov/articles/PMC6067677/)\n\nFor enzyme mechanism-of-action work, the design requires at least 5 substrate concentrations spanning ½×\\( K_{\\mathrm{m}} \\) to 5×\\( K_{\\mathrm{m}} \\) and at least 8 inhibitor concentrations spanning the \\( K_{\\mathrm{i}} \\) at each substrate level.[4](https://www.ncbi.nlm.nih.gov/books/NBK92001/) A homologous competition (tracer competing with itself) is designed correctly if the IC50 falls between 2 and 10 times the radioligand concentration.[1](https://www.ncbi.nlm.nih.gov/books/NBK91992/) Incubation must reach equilibrium; one worked example with a dissociation \\( t_{1/2} \\) of 8.7 min concluded that 43 min suffices.[3](https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/j.1476-5381.2009.00604.x) Curves are fit to extract \\( \\mathrm{IC_{50}} \\) and Hill slope, then \\( K_{i} \\) via Cheng–Prusoff; a three-radioligand format (0.2×, 2×, 10× \\( K_{\\mathrm{d}} \\)) with global analysis distinguishes competitive from allosteric interactions, the \\( \\log(K_{\\mathrm{dLapp}}/K_{\\mathrm{dL}} - 1) \\) versus \\( \\log[A] \\) plot having slope 1.0 for strictly competitive behavior.[3](https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/j.1476-5381.2009.00604.x)\n\n## Origin\n\nThe quantitative bridge between \\( \\mathrm{IC_{50}} \\) and \\( K_{i} \\) comes from Yung-[Chi Cheng](https://www.edgepedia.org/chi-cheng) and William H. Prusoff, Department of Pharmacology, Yale University School of Medicine, whose paper was received 15 March 1973 and accepted 27 April 1973 in Biochemical Pharmacology.[2](https://doi.org/10.1016/0006-2952%2873%2990196-2) Cheng and Prusoff theoretically analyzed the relationship between the inhibition constant \\( K_{I} \\) and the concentration producing 50% inhibition (\\( \\mathrm{I_{50}} \\)): they differ under competitive kinetics; under pure noncompetitive kinetics \\( \\mathrm{I_{50}} \\) equals the inhibition constant; under uncompetitive kinetics \\( \\mathrm{I}_{50} = K_i'(1+K_M/[S]) \\), approaching \\( K_i' \\) at high substrate concentration and increasing without bound as substrate concentration approaches zero.[2](https://doi.org/10.1016/0006-2952%2873%2990196-2) When inhibitor affinity for free enzyme and the enzyme–substrate complex is the same (\\( K_i = K_i' \\)), the inhibitor is purely noncompetitive and the relationship simplifies so that I50 = the common constant \\( K_I \\).[2](https://doi.org/10.1016/0006-2952%2873%2990196-2) The repeated multi-concentration inhibition-experiment process that their analysis addressed has been seen in over 60,000 scientific publications.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC12141731/)\n\n## Variants\n\n**Radioligand displacement.** Screening applications use two typical formats, filtration and scintillation proximity assay (SPA), both pairing a radiolabeled ligand with a receptor source.[1](https://www.ncbi.nlm.nih.gov/books/NBK91992/) SPA avoids physical separation because the tracer's proximity to scintillant-coated beads generates signal; an SPA for human cytomegalovirus protease using phosphorus-33 was developed by Ellen Z. Baum and colleagues, published in Analytical Biochemistry in 1996.[9](https://doi.org/10.1006/abio.1996.0210)\n\n**Fluorescence polarization (FP).** FP gives a direct, nearly instantaneous readout of a tracer's bound/free ratio and supports true equilibrium analysis into the low picomolar range, with as little as 10 fmol/mL of fluorescein-labeled sample.[10](https://research.fredhutch.org/content/dam/stripe/hahn/methods/biochem/beacon_fluorescence_guide.pdf) Michael H. A. Roehrl, Julia Y. Wang, and [Gerhard Wagner](https://www.edgepedia.org/gerhard-wagner-biophysicist) published an exact analytical framework for competitive FP high-throughput screens in 2004 in [Biochemistry](https://www.edgepedia.org/biochemistry), including a four-state model of anticooperative incomplete displacement, and applied it to inhibitors of the human calcineurin–NFAT interaction.[11](https://doi.org/10.1021/bi048233g)\n\n**Single-concentration enzyme analysis.** The 50-BOA (IC50-Based Optimal Approach) shows that a single inhibitor concentration above \\( \\mathrm{IC_{50}} \\), combined with the Cheng–Prusoff harmonic-mean relationship as a regularization term, suffices for precise estimation of inhibition constants for all inhibition types including mixed, reducing the number of experiments by more than 75%; MATLAB and R packages implement it.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC12141731/) A 2025 derivation of optimal substrate concentration recommends \\( [S] = 2\\ K_{m} \\) for competitive and \\( 3\\ K_{m} \\) for linear mixed-type inhibitors (\\( \\alpha \\ge 7 \\)) over the typical \\( 0.5 \\le [I]/K_{i} \\le 4 \\) range, to maximize the \\( v_{o} - v_{i} \\) difference.[12](https://cdnsciencepub.com/doi/10.1139/bcb-2025-0264)\n\n## Applications\n\nIn screening, radioligand displacement assays in filtration or SPA format are used to rank receptor ligands.[1](https://www.ncbi.nlm.nih.gov/books/NBK91992/) FP-based kinase assays are homogeneous, require no immobilization, and compete a fluorescent phosphopeptide tracer against kinase-generated phosphopeptides for anti-phosphotyrosine antibodies; nuclear receptor FP assays are ligand-displacement competitions.[10](https://research.fredhutch.org/content/dam/stripe/hahn/methods/biochem/beacon_fluorescence_guide.pdf) On the proteome scale, COOKIE-Pro determines \\( k_{\\mathrm{inact}} \\) and \\( K_{I} \\) for irreversible covalent inhibitors against on-target and off-target proteins using two-step incubation with TMT-based pulldown quantification; a two-point variant reduced samples from 17 to 7 while still fitting ibrutinib against BTK accurately, and revealed more than 10-fold selectivity of spebrutinib for TEC kinase.[13](https://www.nature.com/articles/s41467-025-63491-2)\n\n## Limitations and alternatives\n\n**Depletion and tight binding.** Radioligand depletion should stay below 10%, meaning \\( [R_{T}] < 0.1\\ K_{\\mathrm{d}} \\); then \\( \\mathrm{EC_{50}} \\) exceeds \\( K_{\\mathrm{d}} \\) by at most 5%, while 10–30% depletion compromises parameter reliability and above 50% may invalidate the experiment.[3](https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/j.1476-5381.2009.00604.x) Uncompensated ligand depletion right-shifts the curve and overestimates \\( K_{\\mathrm{d}} \\); it is avoided by keeping receptor concentration low or increasing reaction volume.[8](https://pmc.ncbi.nlm.nih.gov/articles/PMC6067677/) Inhibitor depletion begins once competitor activity reaches 2–3 fold below the ligand \\( K_{\\mathrm{d}} \\) and always understates true potency; comparing a tight-binding model detects it.[1](https://www.ncbi.nlm.nih.gov/books/NBK91992/) Tight-binding behavior starts when \\( K_i \\) or \\( K_i' \\) comes within 10-fold of the assay's active-site concentration, and \\( \\mathrm{IC_{50}} \\)'s dependence on enzyme concentration, measured at 5 or more enzyme levels, identifies it.[4](https://www.ncbi.nlm.nih.gov/books/NBK92001/)\n\n**Cheng–Prusoff validity.** The equation \\( K_{i} = \\mathrm{IC_{50}}/[1 + ([L]/K_{d})] \\) is valid when the Hill slope is near unity, receptor concentration is below \\( K_{\\mathrm{d}} \\), ligand is not depleted, and the assay is at equilibrium; applying it when more than 10% of tracer is bound can overestimate \\( K_{i} \\) by more than 10-fold, and Munson–Rodbard, Huang, or Kenakin corrections are recommended instead.[1](https://www.ncbi.nlm.nih.gov/books/NBK91992/) The reaction must also be at equilibrium, represent a 1:1 interaction, and contain no depleted ligand.[8](https://pmc.ncbi.nlm.nih.gov/articles/PMC6067677/)\n\n**Optical artifacts.** FP assays are susceptible to compound fluorescence interference, aggregation, and light scattering from particulates, producing false positives and false negatives; the Turconi method using total fluorescence \\( (S + 2P) \\) with anisotropy flags false positives.[1](https://www.ncbi.nlm.nih.gov/books/NBK91992/)\n\n**Direct binding alternatives.** Cell-based competition assays can measure binding affinity, including high-affinity interactions, and kinetic competition designs can measure kinetic parameters; kinetic exclusion assay (KinExA), whose <0.5 s flow kinetically excludes dissociation, and SPR are the recommended alternatives, though SPR becomes unreliable if \\( k_{\\mathrm{on}} \\) or \\( k_{\\mathrm{off}} \\) are too fast or too slow.[8](https://pmc.ncbi.nlm.nih.gov/articles/PMC6067677/) • [14](https://www.ncbi.nlm.nih.gov/books/NBK569501/)\n\n## References\n\n1. [Receptor Binding Assays for HTS and Drug Discovery (Assay Guidance Manual)](https://www.ncbi.nlm.nih.gov/books/NBK91992/)\n2. [Relationship between the inhibition constant (KI) and the concentration of inhibitor which causes 50 per cent inhibition (I50) of an enzymatic reaction (Biochemical Pharmacology, 1973)](https://doi.org/10.1016/0006-2952%2873%2990196-2)\n3. [Ligand binding assays at equilibrium: validation and interpretation](https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/j.1476-5381.2009.00604.x)\n4. [Mechanism of Action Assays for Enzymes, Assay Guidance Manual (NCBI Bookshelf)](https://www.ncbi.nlm.nih.gov/books/NBK92001/)\n5. [pdf (slas-discovery.org)](https://slas-discovery.org/article/S2472-6303%2822%2900159-5/pdf)\n6. [Optimizing enzyme inhibition analysis: precise estimation with a single inhibitor concentration (50-BOA)](https://pmc.ncbi.nlm.nih.gov/articles/PMC12141731/)\n7. [Radioligand Binding Assay Protocols (data sheet)](https://www.giffordbioscience.com/wp-content/uploads/2024/06/Radioligand-Binding-Assay-Protocol-document-compressed.pdf)\n8. [Cell-Binding Assays for Determining the Affinity of Protein–Protein Interactions: Technologies and Considerations](https://pmc.ncbi.nlm.nih.gov/articles/PMC6067677/)\n9. [Ellen Z. Baum and colleagues (1996). Development of a Scintillation Proximity Assay for Human Cytomegalovirus Protease Using33Phosphorous. Analytical Biochemistry.](https://doi.org/10.1006/abio.1996.0210)\n10. [Fluorescence Polarization Applications Guide (Invitrogen/BioProbes)](https://research.fredhutch.org/content/dam/stripe/hahn/methods/biochem/beacon_fluorescence_guide.pdf)\n11. [Michael H. A. Roehrl, Julia Y. Wang, Gerhard Wagner (2004). A General Framework for Development and Data Analysis of Competitive High-Throughput Screens for Small-Molecule Inhibitors of Protein−Protein Interactions by Fluorescence Polarization. Biochemistry.](https://doi.org/10.1021/bi048233g)\n12. [A practical consideration for the substrate concentration when determining IC50 values for enzyme inhibition](https://cdnsciencepub.com/doi/10.1139/bcb-2025-0264)\n13. [COOKIE-Pro: covalent inhibitor binding kinetics profiling on the proteome scale | Nature Communications](https://www.nature.com/articles/s41467-025-63491-2)\n14. [ncbi.nlm.nih.gov](https://www.ncbi.nlm.nih.gov/books/NBK569501/)\n\n---\n*Topic: Encyclopedia › Life and health › Biological foundations › Biochemistry and metabolism › Biochemistry field and methods › Biochemical methods and techniques › Assay techniques*\n\n*Initially written Sep 29, 2026 · Edited: Oct 15, 2026; Oct 21, 2026*\n\n*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*\n\nLicense: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license\n", "same_as": [], "url": "https://www.edgepedia.org/inhibition-assay", "markdown_url": "https://www.edgepedia.org/inhibition-assay.md", "license": { "name": "Edgepedia Community License 1.0", "url": "https://www.edgepedia.org/edgepedia/license", "summary": "Free with credit, commercial use included. AI training is open to everyone. For other uses, organizations over USD 100M in revenue or 100M monthly users license separately.", "spdx": "LicenseRef-Edgepedia-Community-1.0" }, "credit": "\"Inhibition assay\", Edgepedia (EdgeChat), https://www.edgepedia.org/inhibition-assay. Edgepedia Community License 1.0.", "credit_md": "\"[Inhibition assay](https://www.edgepedia.org/inhibition-assay)\", Edgepedia (EdgeChat), [https://www.edgepedia.org/inhibition-assay](https://www.edgepedia.org/inhibition-assay). [Edgepedia Community License 1.0](https://www.edgepedia.org/edgepedia/license).", "credit_html": "\"Inhibition assay\", Edgepedia (EdgeChat), https://www.edgepedia.org/inhibition-assay. Edgepedia Community License 1.0.", "speakable": "An inhibition assay is a bench biology method measuring how a competitor reduces a target's binding or activity, yielding percent inhibition, IC50, and an inhibition constant." }