Peptide & clinical-research glossary.

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21 CFR Part 11Regulatory

U.S. regulation governing electronic records and electronic signatures in FDA-regulated settings.

A

Absolute bioavailabilityPK/PD

The fraction of an administered dose that reaches systemic circulation unchanged, usually compared with intravenous administration.

AbsorptionPK/PD

The movement of a compound from the administration site into the bloodstream or target tissue. In peptides, absorption is strongly affected by route, molecular size, enzymatic degradation, formulation, and tissue permeability.

AcetylationPeptide science

A chemical modification where an acetyl group is added to a molecule. In peptides, N-terminal acetylation may improve stability or alter biological activity.

Acid-labile peptidePeptide science

A peptide that degrades or loses activity under acidic conditions, such as gastric acid.

Active comparatorClinical trials

An approved or established treatment used as the comparison group in a clinical trial instead of placebo.

Active pharmaceutical ingredient (API)APIRegulatory

The biologically active substance in a drug product.

Acute dosingPK/PD

A short-term dosing schedule, often single-dose or limited repeat dosing, used to assess immediate effects, tolerability, or pharmacokinetics.

Adaptive trial designClinical trials

A clinical-trial design that allows prespecified modifications based on interim data, such as dose adjustment, sample-size change, or dropping ineffective arms.

Additive effectPeptide science

A combined effect where two agents produce a result equal to the sum of their individual effects.

AdherenceClinical trials

How closely a participant follows the assigned intervention, dosing schedule, visit schedule, or study instructions.

AdjuvantPeptide science

A substance used to enhance an immune response or improve the effect of another therapy.

ADMEPK/PD

Absorption, distribution, metabolism, and excretion — the core pharmacokinetic processes describing what the body does to a compound.

Adverse drug reaction (ADR)ADRSafety

A harmful or unintended response to a drug where a causal relationship is suspected.

Adverse event (AE)AEPK/PD

Any unfavorable medical occurrence in a study participant after exposure to an intervention, whether or not the intervention caused it.

AffinityPeptide science

The strength with which a ligand, peptide, or drug binds to its receptor or target.

AgonistPeptide science

A compound that binds to and activates a receptor.

Albumin bindingPK/PD

A half-life extension strategy where a peptide is designed to bind serum albumin, slowing renal clearance and prolonging circulation.

Allocation concealmentClinical trials

Preventing investigators from knowing upcoming treatment assignments before enrollment.

Allosteric modulatorPeptide science

A compound that binds to a receptor at a site different from the main ligand-binding site and changes receptor activity.

Alpha helixPeptide science

A common secondary structure where the peptide backbone coils into a helical shape.

AmidationPeptide science

A chemical modification often applied to the C-terminus of peptides to improve stability, mimic natural peptides, or alter receptor activity.

Amino acidPeptide science

The building block of peptides and proteins. Peptides are chains of amino acids linked by peptide bonds.

Amino acid sequencePeptide science

The ordered arrangement of amino acids in a peptide or protein, usually written from the N-terminus to the C-terminus.

AnalyteBiomarkers

The specific substance being measured in a laboratory test, such as a peptide, metabolite, hormone, biomarker, or impurity.

Analytical method validationLab testing

The process of proving that a laboratory test method is accurate, precise, specific, sensitive, and suitable for its intended purpose.

Animal modelSafety

A non-human biological system used to study disease mechanisms, toxicity, pharmacology, or therapeutic effects before or alongside human research.

AntagonistPeptide science

A compound that binds to a receptor and blocks or reduces activation by another ligand.

Antibody-drug conjugate (ADC)ADCPeptide science

A targeted therapy made by linking an antibody to an active drug payload.

Aqueous solutionPeptide science

A water-based solution. Many peptides are reconstituted into aqueous solutions before use in research or clinical settings.

ArmClinical trials

A group in a clinical trial assigned to a specific intervention, dose, comparator, placebo, or observational condition.

AssayLab testing

A laboratory test used to detect, measure, or characterize a substance or biological effect.

AUC, area under the curveAUCPK/PD

A pharmacokinetic measure of total drug exposure over time.

Audit trailRegulatory

A record showing who changed data, what changed, and when. Essential in regulated clinical research and lab systems.

B

Bacteriostatic waterDosing & reconstitution

Sterile water containing a preservative, commonly benzyl alcohol, used in some medication reconstitution settings. Suitability depends on product labeling, patient factors, and clinical use.

BaselineClinical trials

The starting measurement collected before treatment or intervention begins.

BatchManufacturing

A defined quantity of material produced in a single manufacturing or preparation run.

Batch recordManufacturing

Documentation of how a batch was produced, tested, released, stored, and labeled.

Bayesian trial designStatistics

A statistical trial design that incorporates prior probability and updates estimates as new data accumulate.

Benefit-risk assessmentSafety

A structured evaluation comparing potential therapeutic benefits against known and possible risks.

Beta sheetPeptide science

A secondary structure formed by hydrogen bonding between peptide strands.

BiasStatistics

Systematic error that can distort study results. Randomization, blinding, allocation concealment, prespecified endpoints, and proper analysis plans help reduce bias.

BioactivityPeptide science

The biological effect of a peptide or compound in a cell, tissue, animal, or human system.

Bioanalytical assayLab testing

A test used to measure drug or peptide concentrations in biological samples such as plasma, serum, urine, or tissue.

BioavailabilityPK/PD

The rate and extent to which an active compound becomes available at the site of action or in systemic circulation. AUC and Cmax are commonly used to describe exposure.

BioequivalencePK/PD

A determination that two products have no meaningful difference in rate and extent of absorption under similar conditions.

BiomarkerBiomarkers

A measurable biological indicator of normal biology, disease, exposure, response, safety, or risk.

Biomarker-guided trialBiomarkers

A trial that uses biomarkers to select participants, stratify risk, monitor response, or define endpoints.

BiopotencyLab testing

The measured strength of a biological product based on its effect in a validated assay.

BiosimilarLab testing

A biological product that is highly similar to an already approved reference biologic, with no clinically meaningful differences in safety, purity, or potency.

Black box warningSafety

The strongest FDA warning for serious or life-threatening risks associated with a drug.

Blinded endpoint adjudicationClinical trials

Independent review of endpoints by assessors unaware of treatment assignment.

BlindingStatistics

A trial method where participants, investigators, or assessors do not know which intervention was assigned. Blinding reduces expectation and assessment bias.

Bolus dosePK/PD

A dose administered quickly to produce a rapid exposure.

Bridging studyManufacturing

A study used to connect data across formulations, populations, manufacturing processes, or regions.

BufferPeptide science

A solution system that helps maintain pH. Peptide stability can be highly pH-dependent.

C

C-terminusPeptide science

The end of a peptide or protein with a free carboxyl group.

CappingManufacturing

Chemical modification of a peptide terminus, such as acetylation or amidation, often used to improve stability or alter activity.

Carryover effectClinical trials

Persistence of treatment effects after a treatment period ends, especially important in crossover studies.

Case report form (CRF)CRFClinical trials

A structured form used to collect study data from each participant.

Case-control studyPK/PD

An observational study comparing people with a condition to people without it to identify possible exposures or risk factors.

Causal inferencePK/PD

Methods used to estimate whether an intervention or exposure caused an outcome.

Cell-penetrating peptide (CPP)CPPPeptide science

A peptide capable of crossing cell membranes or helping deliver cargo into cells.

Certificate of Analysis (COA)COALab testing

A document summarizing test results for identity, purity, strength, potency, impurities, sterility, endotoxin, heavy metals, residual solvents, or other specifications.

Chain lengthPeptide science

The number of amino acids in a peptide.

Chemical modificationPK/PD

A structural change made to a peptide to alter stability, solubility, receptor activity, immunogenicity, or pharmacokinetics.

ChromatographyLab testing

A lab separation technique used to analyze purity, identity, impurities, and concentration. HPLC and UPLC are common peptide methods.

Chronic dosingDosing & reconstitution

Repeated dosing over an extended period.

CleavageManufacturing

The process of removing a peptide from resin or splitting a peptide bond.

Clinical benefitClinical trials

A meaningful positive effect on how a person feels, functions, or survives.

Clinical endpointClinical trials

A direct measure of clinical benefit or outcome in a trial, such as survival, symptom improvement, disease progression, or hospitalization.

Clinical holdManufacturing

An FDA action that delays or stops a clinical investigation because of safety, design, manufacturing, or regulatory concerns.

Clinical outcome assessment (COA)COAClinical trials

A measure describing how a patient feels, functions, or survives. Examples include patient-reported outcomes, clinician-reported outcomes, observer-reported outcomes, and performance outcomes.

Clinical protocolClinical trials

The formal plan for a clinical study, including objectives, design, population, interventions, endpoints, assessments, and analysis methods.

Clinical researchClinical trials

Research involving human participants, human biological samples, or identifiable human health data.

Clinical significanceStatistics

The practical or medical importance of a result, distinct from statistical significance.

Clinical study report (CSR)CSRRegulatory

A comprehensive report of clinical study methods, results, and interpretation.

Clinical trialSafety

A research study in human participants designed to evaluate the safety, efficacy, dosing, pharmacology, or effects of an intervention.

CmaxPK/PD

The maximum observed concentration of a drug or peptide in plasma or serum after dosing.

CohortPK/PD

A group of participants sharing a common characteristic, treatment assignment, exposure, or enrollment period.

ComparatorClinical trials

The intervention used for comparison in a study, such as placebo, standard of care, or active drug.

Compassionate useRegulatory

A pathway allowing access to investigational products outside clinical trials for patients with serious or life-threatening conditions when no satisfactory alternatives exist.

Composite endpointClinical trials

An endpoint combining multiple events or outcomes into one measure.

ConcentrationPK/PD

The amount of substance per volume, such as mg/mL, mcg/mL, IU/mL, or molarity.

Concomitant medicationClinical trials

Any medication or supplement taken during a study in addition to the study intervention.

Confidence interval (CI)CIStatistics

A statistical range that expresses uncertainty around an estimate.

ContraindicationSafety

A condition or circumstance where a treatment should not be used because risk is likely to outweigh benefit.

Control groupClinical trials

The group used as a comparison against the experimental intervention.

Controlled trialClinical trials

A study that compares an intervention against a control condition.

Crossover trialClinical trials

A study where participants receive multiple interventions in sequence, separated by washout periods.

Crude peptideManufacturing

The unpurified product after synthesis before purification.

CyclePeptide science

A repeated treatment period followed by rest, monitoring, or transition. In oncology, cycles are formal protocol units; in peptide wellness language, the term is often informal and should be clearly defined.

Cyclic peptidePeptide science

A peptide whose structure forms a ring. Cyclization can improve stability, receptor selectivity, and resistance to enzymatic breakdown.

D

D-amino acidPeptide science

A mirror-image amino acid form. Incorporating D-amino acids can increase resistance to proteolytic degradation.

Data and Safety Monitoring Board (DSMB)DSMBSafety

An independent group that reviews accumulating safety and efficacy data during a trial.

Data integrityRegulatory

The completeness, consistency, accuracy, and traceability of data over its lifecycle.

DeamidationPeptide science

A degradation pathway where asparagine or glutamine residues convert to acidic forms, potentially affecting potency or stability.

Decentralized trialClinical trials

A trial using remote visits, digital tools, home health, wearables, or local labs instead of relying entirely on centralized research sites.

DegradationPeptide science

Chemical or enzymatic breakdown of a peptide.

Depot formulationDosing & reconstitution

A formulation designed to slowly release drug over time.

DeviationRegulatory

A departure from protocol or procedure.

DiluentDosing & reconstitution

Liquid used to dissolve or dilute a powder or concentrate.

Disulfide bondPeptide science

A covalent bond between two cysteine residues that stabilizes peptide or protein structure.

DosePeptide science

The amount administered at one time or over a defined period.

Dose escalationPK/PD

A study design where dose is increased stepwise to evaluate safety, tolerability, pharmacokinetics, or biological activity.

Dose findingClinical trials

Research intended to identify a suitable dose or dose range for further study.

Dose proportionalityPK/PD

A relationship where drug exposure increases in proportion to dose.

Dose-expansion cohortClinical trials

A group added after dose escalation to further study safety, activity, or biomarkers at selected dose levels.

Dose-limiting toxicity (DLT)DLTSafety

A toxicity severe enough to prevent further dose escalation or continued dosing under a protocol.

Dose-response relationshipSafety

The relationship between dose level and biological, clinical, or toxic effect.

Dosing intervalDosing & reconstitution

The time between doses, such as once daily, twice weekly, or every 4 weeks.

Double-blind trialClinical trials

A trial where both participants and investigators are unaware of assigned treatments.

Double-dummy designClinical trials

A blinding method where each group receives both active and placebo forms so treatments with different appearances or routes can remain blinded.

DropoutClinical trials

A participant who leaves a study before completion.

Drug productRegulatory

The finished dosage form containing the active ingredient and excipients.

Drug substanceRegulatory

The active ingredient before formulation into the finished product.

Drug-drug interaction (DDI)DDIPK/PD

A change in the effect, exposure, or toxicity of one drug caused by another.

Duration of actionPK/PD

How long a compound produces a measurable biological or clinical effect.

E

Early Phase 1PK/PD

Exploratory human studies conducted before traditional Phase 1, often involving limited exposure and no therapeutic intent.

Effect sizeStatistics

The magnitude of a treatment effect.

EfficacyPeptide science

The ability of an intervention to produce a beneficial effect under study conditions.

Eligibility criteriaClinical trials

The inclusion and exclusion rules defining who can participate in a study.

EncapsulationDosing & reconstitution

Packaging a peptide into a carrier such as a nanoparticle, liposome, or polymer matrix.

EndotoxinLab testing

Bacterial toxin, usually lipopolysaccharide from gram-negative bacteria, that can cause inflammatory reactions.

EndpointStatistics

A targeted outcome measured and statistically analyzed to determine safety, efficacy, or biological effect.

Enrichment designClinical trials

A design selecting participants more likely to respond or have measurable risk based on biomarkers or clinical features.

EnrollmentClinical trials

The process of recruiting and including participants in a study.

Enzymatic degradationPeptide science

Breakdown by enzymes such as proteases or peptidases.

Enzyme-linked immunosorbent assay (ELISA)ELISABiomarkers

A plate-based immunoassay commonly used to detect or quantify proteins, peptides, antibodies, hormones, or biomarkers.

EquimolarPK/PD

Containing the same number of molecules or moles, even if mass differs.

Essential documentsRegulatory

Documents that allow evaluation of trial conduct and data quality.

EstimationStatistics

Statistical calculation of a treatment effect, exposure, risk, or association.

Event-driven trialClinical trials

A study where final analysis occurs after a required number of endpoint events.

ExcipientDosing & reconstitution

An inactive ingredient used in formulation, stabilization, buffering, preservation, or delivery.

Exclusion criteriaClinical trials

Characteristics that prevent a person from participating in a study.

Exploratory endpointClinical trials

A secondary or hypothesis-generating measure not usually used alone to establish primary efficacy.

ExposurePK/PD

The amount of drug the body experiences over time, commonly described by AUC, Cmax, trough concentration, or time above threshold.

F

Fasting statePeptide science

A condition where dosing or sampling occurs after a defined period without food.

First-in-human (FIH)FIHClinical trials

The first study of an investigational compound in humans.

First-pass metabolismPK/PD

Metabolism that occurs before a compound reaches systemic circulation, often in the gut or liver.

Fixed doseBiomarkers

A dose that does not change based on body weight, body surface area, or biomarker level.

Fmoc chemistryManufacturing

A common solid-phase peptide synthesis strategy using Fmoc protecting groups.

FormulationRegulatory

The composition and physical form of a drug product, including active ingredient, excipients, solvent, buffer, pH, and delivery system.

Freeze-dried peptideManufacturing

A lyophilized peptide powder created by removing water under low temperature and vacuum.

Full agonistPeptide science

An agonist capable of producing maximal receptor activation.

G

GlycosylationPeptide science

Attachment of sugar groups to a molecule. Common in proteins and some peptide-related biologics.

Good Clinical Practice (GCP)GCPRegulatory

An international ethical and scientific quality standard for designing, conducting, recording, and reporting clinical trials involving human participants.

Good Laboratory Practice (GLP)GLPRegulatory

Quality standards for nonclinical laboratory studies supporting regulatory submissions.

Good Manufacturing Practice (GMP)GMPManufacturing

Manufacturing quality standards intended to ensure products are consistently produced and controlled.

Gradient elutionLab testing

A chromatography method where solvent composition changes over time to separate compounds.

GRASSafety

Generally recognized as safe, a regulatory designation mainly used for certain food substances, not a blanket safety claim for research peptides.

H

Half-lifePK/PD

The time required for drug concentration to decrease by 50%. Peptide half-life is often limited by enzymatic degradation and renal clearance, which is why strategies like terminal modification, PEGylation, lipidation, albumin binding, and formulation changes are used.

Hazard ratio (HR)HRStatistics

A time-to-event measure comparing the rate of an event between groups.

Heavy metals testingLab testing

Testing for metals such as lead, arsenic, cadmium, and mercury.

HPLC, high-performance liquid chromatographyHPLCLab testing

A common analytical method used to assess peptide purity, impurities, and identity.

Human equivalent dose (HED)HEDPeptide science

A dose converted from animal studies to humans using body-surface-area or other scaling approaches.

HydrolysisPeptide science

Chemical breakdown involving water. Peptides can degrade by hydrolysis under certain pH, temperature, or storage conditions.

HydrophilicPeptide science

Water-attracting. Many peptides are hydrophilic, which can limit membrane permeability.

HydrophobicPeptide science

Water-repelling. Hydrophobic amino acids can affect folding, solubility, aggregation, and membrane interactions.

I

Identity testingLab testing

Testing to confirm that the material is the intended compound.

ImmunogenicitySafety

The ability of a substance to trigger an immune response, such as anti-drug antibodies.

ImpurityLab testing

An unwanted chemical substance in a product, such as synthesis byproducts, degradation products, residual solvents, or related peptides.

Impurity profileLab testing

The pattern and quantity of impurities present in a sample.

Inclusion criteriaClinical trials

Characteristics required for participation in a study.

Informed consentRegulatory

The process of explaining a trial's purpose, procedures, risks, and potential benefits before a person decides whether to participate.

InfusionDosing & reconstitution

Administration over time, usually intravenously or subcutaneously.

Injection-site reactionSafety

Local redness, swelling, itching, pain, bruising, or irritation at the administration site.

Institutional Review Board (IRB)IRBRegulatory

An ethics committee reviewing human research to protect participant rights and welfare.

Intent-to-treat population (ITT)ITTClinical trials

Participants analyzed according to assigned treatment, regardless of adherence.

Intercurrent eventClinical trials

An event after treatment initiation that affects interpretation of the endpoint, such as rescue medication, treatment discontinuation, or death.

Interim analysisClinical trials

An analysis conducted before final study completion.

IntranasalDosing & reconstitution

Administration through the nose.

Intravenous (IV)IVDosing & reconstitution

Administration directly into a vein.

Investigational New Drug application (IND)INDRegulatory

A regulatory submission allowing an investigational drug to be studied in humans in the United States.

Investigational productRegulatory

A drug, biologic, device, or intervention being studied in a clinical trial.

Ion pairingPK/PD

A chromatography or formulation technique using counterions to improve separation, solubility, or absorption.

IsomerPeptide science

A molecule with the same formula but different arrangement. Peptide isomers can differ in activity or stability.

IU, international unitIUDosing & reconstitution

A unit based on biological activity rather than mass. IU-to-mg conversion depends on the specific compound.

K

Karl Fischer titrationLab testing

A method for measuring water content.

L

L-amino acidPeptide science

The naturally dominant amino acid form in human proteins.

Label claimRegulatory

The stated amount or strength of active ingredient on a product label.

LC-MSPK/PD

Liquid chromatography-mass spectrometry, a powerful analytical method for peptide identity, quantification, impurities, and pharmacokinetic studies.

Lead compoundPeptide science

A promising candidate selected for further optimization or development.

LigandPeptide science

A molecule that binds to a receptor, enzyme, transporter, or other target.

Linear peptidePeptide science

A peptide with an open chain structure, as opposed to a cyclic peptide.

LipidationPK/PD

Attachment of a lipid chain to a peptide to improve albumin binding, stability, absorption, or half-life.

Liposomal deliveryDosing & reconstitution

Use of lipid vesicles to carry or protect active compounds.

LOAELSafety

Lowest observed adverse effect level in toxicology studies.

LOD, limit of detectionLODLab testing

The lowest amount of analyte that can be detected but not necessarily quantified.

LOQ, limit of quantificationLOQLab testing

The lowest amount of analyte that can be reliably quantified.

LotManufacturing

A defined batch or production unit used for traceability.

LyophilizationManufacturing

Freeze-drying. A common method used to stabilize peptides by removing water and producing a dry powder.

M

MacrocyclePeptide science

A large ring-shaped molecule. Many cyclic peptides are macrocycles.

Mass spectrometry (MS)MSLab testing

An analytical technique measuring mass-to-charge ratio to identify molecules and impurities.

Maximum tolerated dose (MTD)MTDSafety

The highest dose associated with acceptable toxicity under a protocol.

mcgDosing & reconstitution

Microgram; one-millionth of a gram. 1 mg = 1,000 mcg.

Mechanism of action (MOA)MOAPeptide science

How a compound produces its biological effect.

MedDRASafety

Medical Dictionary for Regulatory Activities, a standardized terminology system for coding adverse events and medical history.

MetabolitePeptide science

A substance produced when a compound is metabolized.

mgDosing & reconstitution

Milligram; one-thousandth of a gram.

mg/mLDosing & reconstitution

Milligrams per milliliter, a concentration unit.

Microbial limits testLab testing

Testing to evaluate microbial contamination levels.

MicrodosePK/PD

A very small dose used to study pharmacokinetics or biological behavior with limited exposure.

MicrosphereDosing & reconstitution

A small polymer or matrix particle used for sustained release.

Modified intent-to-treat, mITTClinical trials

A modified version of ITT based on prespecified rules, such as requiring at least one dose or baseline measurement.

Molar doseDosing & reconstitution

A dose based on molecule count rather than mass.

MolarityPK/PD

Concentration expressed as moles per liter.

Molecular weightLab testing

The mass of a molecule, usually expressed as Daltons or g/mol.

Monoclonal antibodyPeptide science

A laboratory-produced antibody designed to bind a specific target.

Multicenter trialClinical trials

A study conducted at more than one research site.

MultiplicityStatistics

The increased chance of false-positive findings when multiple endpoints, analyses, doses, or subgroups are tested.

N

N-terminusPeptide science

The end of a peptide or protein with a free amino group.

Nanoparticle deliveryDosing & reconstitution

Use of nanoscale carriers to improve stability, absorption, targeting, or controlled release.

New Drug Application (NDA)NDARegulatory

A regulatory submission requesting approval to market a new drug in the United States.

NOAELSafety

No observed adverse effect level in toxicology studies.

Nonclinical studyPeptide science

Laboratory, animal, or in vitro research conducted before or alongside human studies.

Noninferiority trialClinical trials

A trial designed to show that a new intervention is not unacceptably worse than an active comparator by more than a prespecified margin.

O

Observational studyClinical trials

A study where researchers observe outcomes without assigning an intervention.

Off-label useRegulatory

Use of an approved drug for an indication, population, route, or dose not included in approved labeling.

Open-label trialClinical trials

A study where participants and investigators know which treatment is assigned.

Oral bioavailabilityPK/PD

The fraction of an orally administered compound that reaches systemic circulation. Oral peptide delivery is challenging because of enzymatic degradation, poor permeability, and gastrointestinal barriers.

Outcome measureClinical trials

A planned measurement used to evaluate an intervention's effect.

OverageDosing & reconstitution

Extra active ingredient added above label claim to compensate for degradation or manufacturing variability. In regulated settings, overage requires scientific justification and control.

OverfillDosing & reconstitution

Extra volume added to a container to ensure the labeled amount can be withdrawn.

P

Parenteral administrationPK/PD

Administration by routes other than the digestive tract, such as intravenous, subcutaneous, or intramuscular injection. Many peptide therapeutics rely on parenteral delivery because oral absorption is difficult.

Partial agonistPeptide science

A receptor agonist that activates the receptor but produces less than maximal effect even at full receptor occupancy.

Patient-reported outcome (PRO)PROClinical trials

A health outcome reported directly by the patient without interpretation by a clinician.

PEGylationDosing & reconstitution

Attachment of polyethylene glycol to a peptide or protein to increase size, improve solubility, reduce renal clearance, reduce immunogenicity, or extend half-life.

PeptidasePeptide science

An enzyme that breaks peptide bonds.

PeptidePeptide science

A chain of amino acids linked by peptide bonds. Peptides are generally shorter than proteins, though exact cutoffs vary by field.

Peptide backbonePeptide science

The repeating chain of atoms forming the main structure of a peptide.

Peptide bondPeptide science

The chemical bond connecting amino acids in peptides and proteins.

Peptide mappingLab testing

Analytical characterization of a peptide or protein by fragmenting it and identifying sequence components.

PeptidomimeticPeptide science

A molecule designed to mimic peptide structure or function while improving stability, potency, selectivity, or delivery.

Per-protocol populationClinical trials

Participants who sufficiently followed the protocol and had no major violations.

Percent purityLab testing

The proportion of the desired peptide relative to impurities, typically measured by chromatographic area percent or other validated methods.

Permeation enhancerDosing & reconstitution

A compound used to improve absorption across biological barriers.

Pharmacodynamics (PD)PDBiomarkers

What a drug does to the body: receptor activation, biomarker change, biological effect, or clinical response.

Pharmacokinetics (PK)PKPK/PD

What the body does to a drug: absorption, distribution, metabolism, and excretion.

Phase 1 trialSafety

First major human safety and tolerability stage, often involving small groups and dose escalation, commonly 20 to 80 people, to study safety and side effects.

Phase 2 trialSafety

A study phase evaluating preliminary effectiveness and further safety in a larger group, commonly involving about 100 to 300 participants.

Phase 3 trialSafety

A larger confirmatory trial designed to evaluate efficacy, monitor adverse reactions, and support approval decisions.

Phase 4 trialSafety

Post-marketing research after approval, often used to evaluate long-term safety, effectiveness, real-world outcomes, or additional uses.

PlaceboClinical trials

An inactive intervention designed to resemble the active intervention.

Placebo-controlled trialClinical trials

A study comparing an active intervention against placebo.

Plasma concentrationPK/PD

The amount of drug or peptide measured in the plasma portion of blood.

Post-translational modification (PTM)PTMPeptide science

A chemical modification after peptide or protein synthesis, such as phosphorylation, glycosylation, acetylation, amidation, or disulfide formation.

PotencyLab testing

The amount of drug needed to produce a defined effect. In lab settings, potency may refer to biological activity relative to a reference standard.

Pragmatic trialClinical trials

A trial designed to evaluate effectiveness in real-world clinical practice.

Preclinical researchSafety

Research before human trials, often including cell studies, animal pharmacology, toxicology, PK, and formulation testing.

Primary endpointClinical trials

The main outcome used to answer the central study question.

ProteasePeptide science

An enzyme that breaks down proteins or peptides.

Protecting groupManufacturing

A chemical group used to temporarily block reactive sites during synthesis.

ProteolysisPeptide science

Breakdown of peptides or proteins by proteases. Proteolytic degradation is a major limitation for many therapeutic peptides.

Protocol amendmentClinical trials

A formal change to the clinical protocol.

Protocol violationRegulatory

A significant departure from the approved protocol.

PurityLab testing

The degree to which a sample consists of the intended compound rather than impurities.

Q

Qualified biomarkerBiomarkers

A biomarker accepted by regulators for a specific context of use.

Quality assurance (QA)QARegulatory

Systems and oversight ensuring that processes comply with standards and produce reliable results.

Quality control (QC)QCLab testing

Testing activities used to confirm identity, purity, strength, potency, sterility, or other product specifications.

R

RandomizationStatistics

Assignment of participants to groups by chance to reduce selection bias and balance known and unknown confounders.

Randomized controlled trial (RCT)RCTClinical trials

A study where participants are randomly assigned to intervention or control groups.

ReceptorPeptide science

A biological target, often a protein, that binds a ligand and triggers a cellular response.

Receptor occupancyPeptide science

The proportion of receptors bound by a drug or ligand.

ReconstitutionManufacturing

The process of adding a diluent to a lyophilized powder to create a solution.

Reconstitution volumeDosing & reconstitution

The amount of diluent added to a powder.

Reference standardLab testing

A highly characterized material used to verify identity, purity, potency, or assay performance.

RegimenDosing & reconstitution

The full dosing plan, including dose amount, frequency, route, duration, and timing.

Relative bioavailabilityPK/PD

Bioavailability compared between two non-IV formulations or routes.

Renal clearancePK/PD

Removal of a compound by the kidneys.

Repeat-dose studyPeptide science

A study evaluating effects after multiple administrations.

Rescue medicationPeptide science

Medication allowed by protocol to manage symptoms or inadequate response.

Residual solventLab testing

Solvent remaining from synthesis or manufacturing.

ResinManufacturing

Solid support used in solid-phase peptide synthesis.

Retrospective studyClinical trials

A study examining existing data from the past.

Route of administrationDosing & reconstitution

How a compound is delivered, such as subcutaneous, intramuscular, intravenous, oral, intranasal, topical, or transdermal.

Run-in periodClinical trials

A pre-randomization period used to assess adherence, stabilize baseline status, or exclude ineligible participants.

S

Safety endpointSafety

A measure used to evaluate harm, tolerability, adverse events, labs, vital signs, ECG changes, or other safety concerns.

Sample sizeStatistics

The number of participants or samples included in a study.

ScreeningClinical trials

The process of determining whether a person meets eligibility criteria.

Secondary endpointClinical trials

An additional outcome that supports or expands interpretation of the primary endpoint.

Sequence homologyPeptide science

Similarity between peptide or protein sequences.

Serious adverse event (SAE)SAESafety

An adverse event considered serious if it results in death, is life-threatening, requires or prolongs hospitalization, causes significant disability, causes congenital anomaly, or meets other medically important criteria.

Serum stabilityPeptide science

How long a peptide remains intact in serum before degradation.

Shelf lifeRegulatory

The period during which a product is expected to remain within specifications under defined storage conditions.

Side chainPeptide science

The variable chemical group attached to each amino acid, responsible for many differences in charge, polarity, size, and function.

Signal peptidePeptide science

A short peptide sequence that directs a protein to a specific cellular location or secretion pathway.

Single ascending dose (SAD)SADSafety

A Phase 1 design where participants receive one dose, with subsequent cohorts receiving higher doses if safety criteria are met.

Solid-phase peptide synthesis (SPPS)SPPSManufacturing

A widely used peptide synthesis method where amino acids are sequentially added to a growing chain attached to a solid resin.

SolubilityPeptide science

The ability of a compound to dissolve in a solvent.

Source dataRegulatory

Original records where study information is first documented.

Source document verification (SDV)SDVRegulatory

Checking trial data against original source records.

SponsorRegulatory

The individual, company, institution, or organization responsible for initiating and managing a clinical trial.

StabilityLab testing

The ability of a peptide or product to maintain identity, purity, potency, and quality over time.

Stability-indicating methodLab testing

An analytical method capable of detecting degradation changes over time.

Standard deviation (SD)SDStatistics

A statistical measure of variability around a mean.

Standard error (SE)SEStatistics

A measure of uncertainty around an estimated mean or effect.

Standard of carePeptide science

The generally accepted treatment or management approach for a condition.

Statistical analysis plan (SAP)SAPStatistics

A prespecified document describing how study data will be analyzed.

Statistical significanceStatistics

A result unlikely to have occurred by chance under a specified statistical model, often based on a p-value threshold.

SterilityLab testing

Absence of viable contaminating microorganisms.

Sterility testLab testing

A test to determine whether viable microorganisms are present.

StratificationClinical trials

Randomization or analysis by key characteristics such as disease severity, biomarker status, age, or site.

Study visitClinical trials

A scheduled research appointment for assessments, dosing, sampling, or follow-up.

Subcutaneous (SC)SCDosing & reconstitution

Administration under the skin.

Subgroup analysisStatistics

Analysis of treatment effects within a subset of participants.

Superiority trialClinical trials

A trial designed to show one treatment is better than another.

Surrogate endpointClinical trials

A marker expected to predict clinical benefit but not itself a direct measure of how a patient feels, functions, or survives.

Sustained releaseDosing & reconstitution

A formulation approach designed to release drug gradually over time.

Synergistic effectPeptide science

A combined effect greater than the sum of individual effects.

T

TachyphylaxisPK/PD

A rapid decrease in response after repeated or continuous exposure.

Target engagementPeptide science

Evidence that a drug binds to or affects its intended biological target.

Therapeutic indexSafety

The relationship between effective dose and toxic dose.

TitrationSafety

Gradual adjustment of dose to improve tolerability, safety, or response.

TmaxPK/PD

The time at which maximum concentration occurs after dosing.

TolerabilitySafety

How well participants can tolerate a treatment's side effects or burden.

Topical administrationDosing & reconstitution

Application to the skin or surface tissue.

ToxicitySafety

Harmful biological effects caused by a compound.

Toxicokinetics (TK)TKPK/PD

Pharmacokinetics studied in toxicology settings, usually relating exposure to toxic effects.

Transdermal deliveryDosing & reconstitution

Delivery through the skin into systemic circulation.

Treatment-emergent adverse event (TEAE)TEAESafety

An adverse event that appears or worsens after treatment begins.

Trial master file (TMF)TMFRegulatory

The organized collection of essential trial documents.

Trial registryClinical trials

A public database where clinical trials are registered, such as ClinicalTrials.gov.

Trifluoroacetic acid (TFA)TFAManufacturing

A reagent often used in peptide cleavage and deprotection; residual TFA may be monitored or exchanged depending on product requirements.

Trough concentrationPK/PD

The lowest concentration before the next dose.

U

UnblindingClinical trials

Revealing treatment assignment before or after a study ends.

UPLC, ultra-performance liquid chromatographyUPLCLab testing

A higher-resolution chromatography method used for faster or more sensitive analysis.

Use-by dateLab testing

A date after which a preparation should not be used, based on stability, sterility, or handling limits.

V

Validated assayLab testing

A test method proven suitable for its intended use.

Visit windowClinical trials

The allowed date range for a scheduled study visit.

Volume of distribution, VdPK/PD

A pharmacokinetic parameter describing how extensively a drug distributes beyond the blood and plasma.

W

Washout periodPeptide science

A period allowing a previous treatment to clear before another treatment or assessment begins.

Weight-based dosingDosing & reconstitution

Dosing calculated by body weight, such as mg/kg or mcg/kg.

Withdrawable volumeDosing & reconstitution

The amount that can actually be removed from a vial.

X

XenobioticPeptide science

A chemical substance foreign to the body.

Y

YieldManufacturing

The amount of desired peptide or product obtained after synthesis, purification, or manufacturing.

Z

ZwitterionPeptide science

A molecule with both positive and negative charges; amino acids can exist as zwitterions depending on pH.