And Development _hot_ — Pharmacology In Drug Discovery

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Pharmacology is the bridge between a chemical discovery and a medical treatment. It focuses on how a drug interacts with biological systems to ensure it is both and safe . 1. Early Discovery: Finding the "Hit"

3. Preclinical Profiling: ADME and Toxicology

Toxicokinetics (TK): PK studies conducted alongside toxicology studies to relate drug exposure to observed toxicities.

Key output: A candidate drug with an acceptable safety margin (e.g., NOAEL – No Observed Adverse Effect Level).

Affinity (Kd): How tightly does the drug bind to the receptor? High affinity is necessary but not sufficient.
Efficacy (Emax): What happens after binding? An agonist (activator) has high efficacy; an antagonist (blocker) has zero efficacy.
Potency (EC50): How much drug is needed to produce half the maximum effect? A highly potent drug works at low concentrations, reducing the risk of off-target toxicity.

In vivo pharmacology:

Quantitative Systems Toxicology (QST)

Pharmacokinetics (PK): What the body does to the drug — absorption, distribution, metabolism, elimination; key parameters: Cmax, Tmax, AUC, clearance (CL), volume of distribution (Vd), half-life (t1/2), bioavailability (F).
Pharmacodynamics (PD): What the drug does to the body — mechanism of action, receptor occupancy, downstream biomarkers, concentration–effect relationships, EC50/IC50, Emax.
Therapeutic index/window: Ratio of toxic exposure to efficacious exposure; guides dose selection.
Exposure–response (E–R) relationships: Correlate PK (exposure) with PD, efficacy, and safety endpoints.
Target engagement and translation: Measures (e.g., receptor occupancy, biochemical biomarkers) that link target modulation to clinical effect.
Off-target effects and selectivity: Profiling to reduce adverse effects and improve safety.
Biophase and target-site exposure: Consider differences between plasma concentration and active tissue/site concentrations.