Glossary

The section of the U.S. Food, Drug, and Cosmetic Act covering compounding by state-licensed pharmacies and physicians for individual patients with a prescription.

FDA's list of bulk drug substances (without a USP monograph or approved-drug status) that 503A pharmacies may use in compounding; additions require rulemaking.

The section of the FD&C Act covering registered outsourcing facilities, which may compound larger batches, must follow CGMP, and are inspected by FDA.

A molecule that binds to a receptor and activates it, mimicking the natural signal. Semaglutide is a GLP-1 receptor agonist.

The building block of peptides and proteins; each has an amino group, a carboxyl group and a distinctive side chain.

A modified version of a natural molecule, altered to change properties such as stability, potency or half-life.

The formation of new blood vessels; important in healing but also in tumor growth.

A molecule that binds to a receptor and blocks it without activating it.

Antibodies the immune system makes against a drug, which can reduce its effect or cause reactions.

The fraction of an administered dose that reaches the bloodstream in active form.

FDA interim-policy groupings for nominated 503A bulk substances: under evaluation (1), significant safety risks (2), or insufficient nomination data (3).

A lot-specific document reporting a product's test results, such as identity, purity, and endotoxin.

Current Good Manufacturing Practice: FDA's quality-system requirements for making drugs.

Preparing a customized medication by combining or altering ingredients, done by pharmacies under 503A or 503B.

Linking parts of a peptide chain into a ring to increase rigidity and resistance to enzymes.

The mirror-image form of an amino acid; substituting D-forms can protect peptides from enzymatic breakdown.

A chemical linker that makes a peptide bond to blood albumin, greatly extending its half-life (e.g., CJC-1295 with DAC).

A chemical degradation in which asparagine or glutamine residues lose an amide group.

A toxic component (lipopolysaccharide) of certain bacterial cell walls that can cause fever and inflammation even when the bacteria are dead.

An FDA decision not to take action against certain activity that may technically violate the law, under stated conditions; it is not approval.

Authorization to market a drug after FDA review of evidence showing it is safe and effective for its intended use.

Growth hormone-releasing hormone, a hypothalamic peptide that signals the pituitary to release growth hormone; analogs include sermorelin and tesamorelin.

Growth hormone-releasing peptide, a synthetic class (e.g., GHRP-2, GHRP-6) that stimulates GH release through the ghrelin receptor.

Any substance that stimulates growth hormone release, including GHRPs, ipamorelin and the non-peptide MK-677.

Glucose-dependent insulinotropic polypeptide, a gut hormone that boosts insulin release; tirzepatide activates its receptor.

Glucagon-like peptide-1, a gut hormone that increases insulin release, slows stomach emptying and reduces appetite.

The time for the amount of a drug in the body to fall by half.

High-performance liquid chromatography, a technique that separates a sample's components to measure purity.

Insulin-like growth factor 1, a hormone produced mainly in the liver in response to growth hormone that drives tissue growth.

The tendency of a substance to provoke an immune response.

A drug being tested in clinical trials that is not approved for general use.

Attaching a fatty-acid chain to a peptide so it binds albumin and lasts longer, as in semaglutide.

Freeze-dried: water removed under vacuum at low temperature, producing a more stable powder.

An analytical method that measures molecular mass, used to confirm a peptide's identity.

A family of peptide hormones (such as alpha-MSH) and receptors involved in pigmentation, appetite and sexual function; Melanotan II and bremelanotide act here.

The percentage of a powder's weight that is actually peptide, excluding water, salts and counter-ions.

A chemical reaction with oxygen that can damage residues such as methionine, cysteine and tryptophan.

FDA's Pharmacy Compounding Advisory Committee, which gives non-binding advice on bulk substances for compounding.

Attaching polyethylene glycol chains to a molecule to increase its size, reduce kidney clearance, and extend half-life.

A short chain of amino acids, usually about 2-50, linked by peptide bonds.

The amide bond joining the carboxyl group of one amino acid to the amino group of the next.

How the body absorbs, distributes, metabolizes and eliminates a drug.

Sequential stages of human clinical testing: Phase 1 assesses safety and dosing in small groups, Phase 2 explores efficacy and side effects, and Phase 3 confirms benefit and risk in large populations.

Research done in cells or animals before testing in humans.

A long chain of amino acids (generally more than ~50) that folds into a functional three-dimensional structure.

A study that randomly assigns participants to treatment or control groups, the strongest standard design for testing whether a treatment works.

A protein on or in a cell that binds a specific signaling molecule and triggers a response.

Produced by genetically engineered cells (bacteria, yeast or mammalian cells) carrying the gene for the desired molecule.

A label indicating a product is intended for laboratory research, not human use; FDA treats it as no defense when other evidence shows human drug intent.

A substance that causes another substance to be secreted, for example a GH secretagogue triggering growth hormone release.

Merrifield's method of building a peptide one amino acid at a time on an insoluble resin bead.

Into the fatty tissue just under the skin; the most common injection route for peptide drugs.

A strong acid used in peptide synthesis and purification; peptides often retain it as a TFA salt counter-ion.

United States Pharmacopeia, a nonprofit that sets public quality standards (monographs) for medicines and ingredients.

The World Anti-Doping Agency, which publishes the annual Prohibited List of substances banned in sport.