Peptide Glossary

Traditional compounding pharmacies that prepare medications for individual patients with valid prescriptions, regulated primarily by states.

Outsourcing facilities registered with FDA that can compound larger quantities without individual prescriptions, subject to GMP requirements.

Any undesirable experience associated with use of a peptide or drug, whether or not considered related to the treatment.

Organic molecules that serve as the building blocks of proteins and peptides. There are 20 standard amino acids used in protein synthesis.

The growth of new blood vessels from existing vessels. It occurs in normal tissue repair and in some diseases.

Research conducted in animals to understand biological effects before human testing. Most peptide research is at this stage.

A peptide with activity against microorganisms under specified conditions. Some antimicrobial peptides are components of innate immune defense.

A sterile pharmaceutical diluent containing a preservative that limits bacterial growth. Compatibility and use depend on the exact drug and water product labels.

Brain-derived neurotrophic factor: a protein involved in the maintenance and function of nerve cells and their connections.

The strength of interaction between a peptide and its receptor. Higher affinity generally means more potent effect at lower doses.

The fraction of an administered substance that reaches systemic circulation unchanged; it is measured for a particular formulation and route.

The end of a peptide chain, containing a free carboxyl group (-COOH). The C-terminus is the conventional ending point when writing peptide sequences.

A report listing results and specifications for an identified sample or lot. Its scope depends on the tests performed; a COA does not automatically establish every aspect of identity, purity or safety.

A research study conducted in human subjects to evaluate the safety and efficacy of a medical intervention, conducted in phases I through IV.

A pharmacy that prepares a medication by combining, altering or mixing ingredients to meet a patient’s needs, subject to applicable pharmacy and drug laws.

A condition or factor that serves as a reason to withhold a certain treatment due to potential harm.

A peptide in which the amino acid sequence forms a ring structure, often increasing stability and receptor binding specificity compared to linear peptides.

The formation of a ring structure in a peptide, often used to increase stability and receptor specificity.

Protection of cells from harmful agents or stress, a property attributed to certain peptides like BPC-157.

The mirror image (enantiomer) of naturally occurring L-amino acids. Incorporating D-amino acids into peptides can increase protease resistance.

Reduced responsiveness to a drug after repeated exposure, requiring higher doses to achieve the same effect.

A peptide composed of exactly two amino acids joined by a single peptide bond. Examples include carnosine and anserine.

A graph showing the relationship between the dose of a substance and the magnitude of its effect, used to determine optimal dosing.

A study in which participants and relevant investigators do not know the assigned intervention during the blinded part of the trial.

A reaction between a peptide and another substance (drug, supplement, food) that alters the effect of one or both.

In a graded response assay, EC50 is the concentration associated with half of the measured maximum effect under that assay’s conditions.

A peptide produced within an organism, rather than supplied from an external source.

Toxic components from gram-negative bacteria that can cause fever and inflammation if present in injectable products.

Official authorization from the U.S. Food and Drug Administration to market a drug for specific uses after demonstrated safety and efficacy.

Growth Hormone Releasing Hormone, a hypothalamic peptide that stimulates the pituitary to release growth hormone.

Growth hormone-releasing peptide: a peptide secretagogue that can stimulate growth hormone release through the growth hormone secretagogue receptor pathway.

Glucose-dependent insulinotropic polypeptide, a hormone that stimulates insulin release. Combined with GLP-1 in dual-agonist drugs like tirzepatide.

Glucagon-like peptide-1, a hormone produced in the gut that stimulates insulin secretion and reduces appetite. The target of medications like semaglutide.

Good manufacturing practice: quality controls for consistently making and testing products to appropriate standards. In US drug regulation, CGMP means current good manufacturing practice.

Generally Recognized as Safe (GRAS) is a US food-law concept concerning the safety of a substance under specified conditions of intended use.

A peptide hormone produced by the pituitary gland that stimulates growth, cell reproduction, and regeneration.

The time for a measured amount or concentration to fall by half under specified conditions. In drug studies, the reported half-life depends on the elimination phase and model.

High-Performance Liquid Chromatography, an analytical technique used to separate, identify, and quantify components in a mixture.

The concentration of a substance required to inhibit a biological process by 50%. Used to compare potency of different compounds.

Insulin-like growth factor 1: a hormone involved in growth and other biological processes, whose production is influenced by growth hormone.

The ability of a substance to provoke an immune response, including the formation of antibodies against a therapeutic molecule.

Experiments performed outside a living organism, typically in test tubes or cell cultures. Latin for "in glass."

Experiments performed within a living organism, such as animal studies. Latin for "in the living."

The practice of varying injection locations to prevent lipodystrophy, scarring, and ensure consistent absorption.

Administration directly into muscle tissue, allowing for faster absorption than subcutaneous injection.

Delivery of peptides through the nasal mucosa, commonly used for Semax and Selank. Provides rapid absorption and brain access.

Administration directly into a vein, providing 100% bioavailability and immediate effect. Used for NAD+ infusions.

An Investigational New Drug application is a US regulatory submission that permits eligible clinical investigation of a drug under the IND framework; it is not marketing approval.

The dose of a substance that kills 50% of test animals. A measure of acute toxicity; higher LD50 means lower toxicity.

The chemical attachment of a lipid group to a molecule. In some peptide medicines, an attached fatty-acid group helps alter protein binding and duration of exposure.

Abnormal fat distribution, including accumulation or loss, that can occur at repeated injection sites.

A higher initial dose given to rapidly achieve therapeutic levels in the body before switching to a lower maintenance dose.

A freeze-drying process used to preserve peptides by removing water content, resulting in a stable powder form.

The regular ongoing dose taken to maintain therapeutic levels after initial loading, typically lower than the loading dose.

An analytical technique that measures ions by mass-to-charge ratio. It can support peptide characterization; an intact-mass match is not complete sequence confirmation.

The specific biochemical interaction through which a drug or peptide produces its pharmacological effect on the body.

A member of a peptide signaling family derived from the POMC precursor, including ACTH and melanocyte-stimulating hormones, acting through melanocortin receptors.

The amino-terminal end of a peptide or protein chain. Peptide sequences are conventionally written from the N-terminus toward the C-terminus.

Peptides released by neurons that act as neurotransmitters or neuromodulators, influencing brain function. Examples include endorphins and substance P.

Mechanisms and strategies used to protect neurons from injury, degeneration, or death.

Using an FDA-approved drug for a purpose other than its approved indication. Tesamorelin for fat loss is an example.

A relatively short chain of amino-acid residues linked by peptide bonds. The boundary between an oligopeptide and a longer polypeptide is convention-dependent.

A peptide designed to be taken by mouth. Challenging due to stomach acid degradation; BPC-157 (stable form) and MK-677 are examples.

A drug developed for rare diseases affecting fewer than 200,000 Americans, eligible for special FDA incentives.

The attachment of polyethylene glycol chains to a molecule, typically to increase half-life and reduce immunogenicity.

A peptide related to a reference peptide but modified in sequence or chemical structure. Its properties must be established for the modified molecule.

A covalent chemical bond formed between two amino acids when the carboxyl group of one reacts with the amino group of another, releasing water.

An informal term for alternating periods of peptide use and non-use. It does not describe a universally validated medical schedule or guarantee receptor recovery.

A portion of a larger peptide or protein that retains specific biological activity. AOD-9604 is a fragment of human growth hormone.

A collection of peptides with systematically varied sequences used in drug discovery to identify peptides with desired biological activities.

A small molecule designed to mimic the biological activity of a peptide while having improved drug-like properties such as oral bioavailability.

The specific order of amino acids in a peptide chain, written from N-terminus to C-terminus using single or three-letter amino acid codes.

A chemical modification that constrains peptide structure using hydrocarbon bridges, improving stability and cell permeability of helical peptides.

The study of a substance’s effects on a biological system, including target interactions and the physiological responses that follow.

The study of how exposure to a substance changes over time through absorption, distribution, metabolism and elimination.

Large-scale clinical trials involving hundreds to thousands of patients to confirm efficacy, monitor side effects, and compare to existing treatments.

A study design in which a comparison group receives a placebo, allowing investigators to compare outcomes with the intervention being tested.

A longer chain of amino acids, typically more than 20 residues, but not large enough to be considered a protein.

Research conducted before human trials, typically involving laboratory experiments and animal studies to assess safety and potential efficacy.

A biological molecule built from one or more amino-acid chains that can fold and interact to carry out structural, catalytic, transport or signaling functions.

A substance that binds to and activates a receptor, triggering a biological response similar to the naturally occurring ligand.

A substance that binds to a receptor but does not activate it, blocking the action of agonists.

A reduction in the number or availability of receptors in a cell or at its surface. It is one possible mechanism of reduced responsiveness to a signal.

A peptide produced using recombinant DNA technology, where the peptide gene is inserted into host cells (bacteria, yeast) that then produce the peptide.

The preparation of a solution or suspension from a dry product using a specified diluent. In medicines, the product instructions determine compatibility and handling.

Substances sold for laboratory research purposes, not approved for human consumption but often used off-label.

Any substance that promotes secretion of another substance, commonly used to describe compounds that stimulate hormone release.

A cell that has stopped dividing but remains metabolically active, secreting inflammatory factors. FOXO4-DRI targets these cells.

An effect of a peptide other than the intended therapeutic effect. Can be beneficial, neutral, or harmful.

A short amino-acid sequence that helps direct a newly made protein to a cellular destination, often the secretory pathway.

Solid-phase peptide synthesis: a method of assembling a peptide through repeated chemical steps while the growing chain is attached to a solid support.

Combining multiple peptides simultaneously to achieve synergistic effects. The Wolverine Stack (BPC-157 + TB-500) is a popular example.

Administration of a substance into the fatty tissue layer between the skin and muscle, commonly used for peptide delivery.

A peptide manufactured through chemical synthesis rather than extracted from biological sources, allowing precise control over sequence and modifications.

Rapid decrease in response to a drug after repeated administration, requiring higher doses for same effect.

Two or more peptide sequences linked together to combine multiple biological activities or improve pharmacokinetic properties.

An enzyme that maintains telomere length in chromosomes, potentially extending cellular lifespan. Epitalon activates telomerase.

A region of repetitive DNA and associated proteins at a chromosome end that helps protect chromosome integrity.

The range of doses between the minimum effective dose and the dose that causes unacceptable side effects.

Titration has two common meanings. In medicine, it describes adjusting a dose over time in response to benefit, tolerability, and other monitored findings. In analytical chemistry, it is a measurement method using a known reacting substance. The context determines which meaning applies.

Administration through the skin using patches or creams. Limited use for peptides due to size, but GHK-Cu works topically.

A peptide made from three amino-acid residues joined by peptide bonds. The name specifies chain length, not a particular biological effect.

Peptides that affect blood vessel tone, causing vasodilation or vasoconstriction. Important in cardiovascular regulation and wound healing.

The World Anti-Doping Agency list of substances banned in competitive sports. BPC-157, TB-500, and growth hormone peptides are prohibited.