Decoding Peptide Names: A Nomenclature Primer for New Researchers

Open any research-peptide catalog and the names read like a cipher: CJC-1295 DAC, IGF-1 LR3, HGH Fragment 176-191, GHRP-6, Ara-290. To a newcomer it looks like random letters and numbers. It isn't. Almost every token in a peptide name encodes something concrete — a sequence range, a chemical modification, a receptor target, or a salt form. Once you can parse those tokens, a name stops being a label to memorize and becomes a compact description of the molecule itself.

This is a foundations piece. It won't tell you what any compound does in a body — it will teach you to read the name on the vial so the rest of the library makes sense.

The Big Families of Peptide Names

Peptide names come from a few different naming systems layered on top of each other, which is why they look inconsistent. Broadly, you'll encounter:

• Code names — an alphanumeric tag assigned by the lab or company that first synthesized the compound. BPC-157, TB-500, SS-31, MK-677, GHRP-6, and Ara-290 are all code names. The letters often abbreviate the discovering institution, project, or peptide class; the number is a catalog or candidate index. They usually carry no pharmacological meaning on their own.
• Descriptive / sequence names — names that describe what the molecule is, like HGH Fragment 176-191 (a defined slice of human growth hormone) or IGF-1 LR3 (a modified insulin-like growth factor).
• International nonproprietary names (INNs) — the lowercase generic names assigned to drug candidates by the WHO, such as tesamorelin, semaglutide, retatrutide, and cagrilintide. These follow strict suffix rules (more below).
• Trade/brand names — capitalized proprietary names, which we generally avoid in a research context in favor of the generic.

The same molecule can have several of these at once. Knowing which system a name comes from tells you how much information to expect from it.

Suffixes Are the Biggest Tell

The most information-dense part of a modern drug-candidate name is its ending. The WHO INN system uses standardized stems and suffixes to group compounds by class, so the suffix often tells you the mechanism family before you read a single line of pharmacology.

A few you'll see constantly in this catalog:

• -relin — growth-hormone secretagogues and releasing-hormone analogs. Sermorelin, tesamorelin, ipamorelin, and gonadorelin all share it. The stem signals "releases/triggers a pituitary hormone."
• -tide — the generic stem for peptides. It shows up almost everywhere (semaglutide, cagrilintide, survodutide, liraglutide) and on its own just means "this is a peptide."
• -glutide — narrower: GLP-1-based incretin agonists. Semaglutide and survodutide sit here.
• -lintide — amylin analogs, e.g. cagrilintide.
• -relix / -relin — note the contrast: -relin agonizes a releasing-hormone pathway, while -relix (e.g. cetrorelix) antagonizes it. One letter flips the direction of action.

The suffix is a starting hypothesis, not a guarantee — naming rules have evolved over decades and exceptions exist — but it's the fastest first read you can make on an unfamiliar name.

Numbers: Fragments, Sequence Ranges, and Analog Indices

Numbers in peptide names do several different jobs, and telling them apart matters.

Fragment and sequence ranges describe which amino acids are present relative to a parent protein. HGH Fragment 176-191 is exactly that: residues 176 through 191 of the 191-amino-acid growth hormone chain — a defined C-terminal fragment, not a separate invented molecule. When you see two numbers joined by a dash and a parent-protein name, read it as "this slice of that protein." Likewise, LL-37 is the 37-residue active fragment of the cathelicidin precursor.

Single index numbers in code names (the 157 in BPC-157, the 6 in GHRP-6, the 1295 in CJC-1295) are usually just catalog or candidate identifiers. BPC-157's "157" does not mean 157 amino acids — the peptide is only 15 residues long. Don't try to extract chemistry from a code-name index; it's a filing number.

Position numbers in modifications tell you where a chemical change was made. A notation like "[D-Lys3]" or "Tyr-0" points to a specific residue position that was substituted or added. You'll mostly see these in technical sequence descriptions rather than the product title, but they follow the same logic: the number is an address on the chain.

Modification Tags: DAC, No-DAC, LR3, PEG-, and Acetate

This is where reading the name saves you the most confusion, because these tags change the molecule's behavior even when the core sequence is the same.

• DAC vs No-DAC — DAC stands for Drug Affinity Complex, a maleimido-proprionic-acid group that lets the peptide bind reversibly to serum albumin after entering circulation. CJC-1295 DAC carries this group; CJC-1295 No-DAC (often called modified GRF 1-29 or "Mod GRF") does not. Same parent GHRH-analog backbone, very different circulating profile — the DAC tag is the single most important word in that name.
• LR3 — in IGF-1 LR3, "Long R3" denotes an analog with an added N-terminal extension and an arginine substitution at position 3. The modification reduces binding to IGF-binding proteins relative to native IGF-1. The "LR3" is doing real chemical work; it is not a brand flourish.
• PEG- — a prefix meaning the peptide has been PEGylated (conjugated to polyethylene glycol), as in PEG-MGF versus plain MGF. PEGylation is a structural modification that changes a molecule's stability profile; the prefix flags it explicitly.
• Salt forms (Acetate, TFA, HCl) — many lyophilized peptides ship as a salt, most often acetate. This refers to the counterion paired with the peptide, not a different active molecule. It matters for net peptide content (the salt and bound water are part of the vial's mass but not the peptide itself), which is exactly why a certificate of analysis reports peptide content separately. Acetate is generally preferred over residual TFA (trifluoroacetic acid, a synthesis byproduct) in research-grade material.

Why Two Names Can Mean the Same Molecule — or Different Ones

Two traps catch new researchers constantly.

Synonyms: one molecule, many names. Thymosin Beta-4 and TB-500 are commonly used for closely related research material; CJC-1295 No-DAC, Mod GRF 1-29, and GRF(1-29) modified all point to the same backbone. The lab code, the descriptive name, and the INN can coexist for a single compound. When in doubt, the amino-acid sequence — not the name — is the unambiguous identity, which is why identity confirmation by mass spec matters more than any label.

False friends: names that look related but aren't the same molecule. Melanotan 1 and Melanotan 2 share a name root but differ in sequence, length, and receptor selectivity. GHRP-2 and GHRP-6 are distinct peptides in the same class, not versions of one compound. A shared prefix signals a family, not interchangeability.

The discipline that protects you here is simple: treat the name as a hypothesis and confirm identity against the sequence and the COA, never against the label alone.

A Quick Parsing Checklist

When you meet an unfamiliar peptide name, run it through these questions:

1. What system is this name from? Code name, descriptive name, INN, or trade name?
2. Is there a meaningful suffix? Does -relin / -glutide / -lintide / -tide hint at a class?
3. Do the numbers describe a sequence range, or are they a catalog index?
4. Are there modification tags — DAC, LR3, PEG-, a salt form — that change behavior?
5. Could this be a synonym for something I already know, or a same-family-but-different compound?

That five-step read turns most names from intimidating to legible in a few seconds.

FAQ

Does a higher code number mean a newer or stronger compound? No. Code-name numbers are filing or candidate indices assigned by whoever first described the molecule. They don't rank potency, recency, or quality.

Is "acetate" a different drug from the plain peptide? No — it's the same peptide paired with an acetate counterion as a salt. It affects mass and net peptide content, not the active sequence. See our note on reading a COA and the quality standards page.

Why do the same compounds have so many names? Because lab code names, WHO generic names, descriptive sequence names, and trade names all get attached to a molecule at different points in its history. They coexist; the sequence is the only truly unique identifier.

This article is educational and for the laboratory research community. Trulogic Labs products are sold for laboratory and research use only and are not for human consumption.