Reference

The plain-English peptide & FDA glossary

Following this story means running into a lot of jargon - some of it scientific, some of it regulatory. Here's what the key terms actually mean, in plain language and without the spin.

Peptide science

Amino acid: One of the small molecular "building blocks" that link together to form peptides and proteins. Their order is what gives each peptide its identity.
Peptide: A short chain of amino acids. "Peptide" describes the structure - it says nothing about whether a substance is safe, effective, or approved.
Protein: A longer chain of amino acids. The line between a long peptide and a small protein is fuzzy, but peptides are generally the shorter ones (often up to a few dozen amino acids).
Sequence: The specific order of amino acids in a peptide, usually written as a string of letters (e.g. Ala-Glu-Asp-Gly). Change the order and you change the molecule.
Synthetic peptide: A peptide made in a lab rather than extracted from a living source. Most of the peptides in this review are synthetic.
Tripeptide / tetrapeptide / pentadecapeptide: Names based on length: a tripeptide has 3 amino acids (e.g. KPV), a tetrapeptide 4 (e.g. Epitalon), a pentadecapeptide 15 (e.g. BPC-157).
Preclinical (animal / cell) study: Research done in cells or animals, before human testing. It can suggest a direction, but it is not evidence that something works - or is safe - in people.
Clinical trial: A study in humans. The most reliable are large, randomized, double-blind, placebo-controlled trials. Most peptides in this review lack trials of that quality.
Bioavailability: How much of a substance actually reaches the bloodstream in an active form. Many peptides have low bioavailability, which complicates turning them into medicines.
Half-life: How long it takes for half of a substance to be cleared from the body. Short half-lives are a common practical hurdle for peptides.
Immunogenicity: The chance that the body's immune system reacts to a substance. It's one of the safety concerns the FDA has raised about unapproved injectable peptides.

Regulation & the FDA process

FDA: The U.S. Food and Drug Administration - the federal agency that regulates drugs, including whether a substance can be approved or compounded.¹
FDA-approved: A specific legal status meaning the FDA has reviewed a product and cleared it for a defined use. None of the peptides in this review are FDA-approved.
Compounding: The practice of a pharmacy preparing a customized medication for an individual patient. It is regulated separately from mass-manufactured, FDA-approved drugs.¹
Section 503A: The part of federal law that governs traditional pharmacy compounding for individual patients. A substance generally needs to be on the "503A bulks list" (or meet other criteria) to be compounded from bulk.¹
Section 503B: A related pathway for "outsourcing facilities" that compound at larger scale under stricter manufacturing rules.¹
Bulk drug substance: The raw active ingredient a compounder would start from. The current debate is about which peptide bulk substances may be used in 503A compounding.¹
Interim 503A bulks list - Category 1: Substances the FDA is considering that don't currently raise the concerns that would bar their use while the rulemaking is pending. Effectively the "may be used for now" bucket.²
Interim 503A bulks list - Category 2: Substances that raise significant safety concerns; the FDA's position is that they should not be compounded while under review. The peptides here were moved out of Category 2 in April 2026 - which is not the same as being approved.²
PCAC: The Pharmacy Compounding Advisory Committee - the outside panel of experts the FDA convenes to review substances and vote a recommendation. It met July 23-24, 2026 on seven peptides.³
Advisory committee: A panel that gives the FDA independent expert advice. Its votes are recommendations only - the FDA usually follows them but is not legally bound to.³
Evaluated use: The specific condition the FDA reviewed a substance for at the meeting (for example, BPC-157 was evaluated for ulcerative colitis). It is the use under discussion, not an endorsement.³
Rulemaking: The formal process by which an agency proposes and finalizes a regulation, with a required public comment period. This is the stage where public comment carries legal weight.³
Docket: The official file where an agency collects materials and public comments for a specific action. The July 2026 meeting's docket is FDA-2025-N-6895.³
Public comment: Input any member of the public can submit to an open docket. See our step-by-step guide to submitting one.⁴
Regulations.gov: The federal website where public comments are submitted and read.⁴
Dietary supplement / dietary ingredient: A separate legal category from drugs. The FDA has taken the position that these peptides don't qualify as lawful dietary ingredients, so they can't simply be sold as supplements either.¹

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References

U.S. Food and Drug Administration. "Human Drug Compounding" - overview of 503A/503B, bulk drug substances, and compounding basics. fda.gov - compounding Q&A
U.S. Food and Drug Administration. "Bulk Drug Substances Nominated for Use in Compounding Under Section 503A" - interim list and categories. fda.gov - 503A bulk drug substances
U.S. Food and Drug Administration. "July 23-24, 2026: Meeting of the Pharmacy Compounding Advisory Committee." fda.gov - PCAC July 2026 meeting
U.S. Federal Government. Regulations.gov - the federal eRulemaking portal. regulations.gov

Definitions are written for a general audience and simplified for clarity. Peppies is independent and is not affiliated with the FDA. Last verified July 4, 2026.