Evidence review: Open Peptide Project (verified against primary PubMed, ClinicalTrials.gov & FDA records) · Last checked 2026-10-27. ← Back to Evidence Library

Glossary of peptide, lab-testing, clinical, and regulatory terms (A–Z)

Plain-English definitions for the analytical chemistry, clinical trial, pharmacology, and regulatory jargon used across Open Peptide Project reports and guides

Evidence verdict: Plain-language reference guide to scientific, laboratory, clinical-trial, and regulatory terminology used across the Open Peptide Project library, testing standard, and observational protocol.

Last reviewed: Oct 27, 2026

In 30 seconds

• Peptide monographs and lab reports use specialized terms from four worlds: analytical chemistry (HPLC, LC-MS, Net Peptide Content, TFA), clinical research (RCT, Phase 1–3, Open-Label, PMID), pharmacology (Half-Life, Bioavailability, Agonist, ADAs), and regulation (503A/503B, RUO, USP <85>, WADA S0/S2).
• Marketing sites frequently blur these terms—for example, treating chromatographic purity (%) as if it meant net peptide weight (mg), or treating an animal study (in vivo rodent data) as if it were a human randomized controlled trial (RCT).
• Use this alphabetical A–Z reference alongside any compound monograph, Certificate of Analysis (COA), or harm-reduction guide on our site.

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A

• 503A Compounding Pharmacy: A state-licensed pharmacy that compounds patient-specific prescriptions written by a licensed clinician for an individual patient under Section 503A of the Federal Food, Drug, and Cosmetic Act. Section 503A pharmacies may only compound using bulk drug substances that meet statutory criteria (such as having an active USP/NF monograph, being part of an FDA-approved drug, or appearing on FDA's 503A Category 1 list). Regulatory
• 503B Outsourcing Facility: An FDA-registered facility under Section 503B of the FD&C Act that can compound larger batches of sterile medications under current Good Manufacturing Practice (cGMP) standards without individual patient prescriptions, provided the active ingredient appears on FDA's 503B clinical-need list. Regulatory
• A+ / Pass / Caution / Fail (Open Peptide Standard Batch Grades): The four-tier batch grading scale used on Open Peptide Project test reports (Testing Standard). A+ requires >= 98.0% RP-HPLC purity and 90.0%–110.0% labeled vial content (plus passed LC-MS identity and USP <85> endotoxin); Pass requires 96.0%–97.9% purity and 90.0%–110.0% content; Caution covers 92.0%–95.9% purity or 80.0%–89.9% / 110.1%–120.0% content; Fail applies to < 92.0% purity, < 80.0% or > 120.0% content, or any failed identity, endotoxin, or sterility test. Grades apply strictly to the tested batch number and date, never to a vendor or brand. Regulatory
• Acetate Salt (Acetate Counter-Ion): A benign counter-ion commonly paired with synthetic peptides during purification (often swapped in place of harsher trifluoroacetate, or TFA, salts) to improve solubility, stability, and tissue tolerability. Lab
• Acetylation / Amidation (N-Terminal Acetylation & C-Terminal Amidation): Chemical caps added to the ends of a synthetic peptide chain (Ac- at the start or -NH2 at the end) to mimic natural protein structure and slow down rapid breakdown by blood and gut enzymes (peptidases). Lab
• Adverse Event (AE) & Serious Adverse Event (SAE): Any undesirable medical symptom or lab change that occurs while using a compound, whether or not it is proven to be caused by the compound. An SAE is a reaction that results in hospitalization, persistent disability, life-threatening danger, birth defect, or death. Regulatory
• Agonist, Partial Agonist & Antagonist: An agonist binds to a cellular receptor and switches it on (for example, semaglutide activating the GLP-1 receptor). A partial agonist activates the receptor weakly even at full saturation. An antagonist binds to the receptor and blocks natural hormones or drugs from activating it. Lab
• Allometric Scaling: The mathematical conversion of experimental doses between species based on body surface area rather than body weight. Even when scaled properly, rodent peptide studies frequently fail to translate to humans because of species differences in receptor expression, metabolism, and immune response. See Why rodent peptide studies often fail in humans. Lab
• Amino Acid Sequence: The exact chain and order of amino acid building blocks that define a peptide's identity and molecular weight. Changing or deleting even one amino acid changes the compound. Lab
• Analog (Peptide Analog): A modified version of a natural hormone or peptide engineered to last longer in the bloodstream or bind more selectively to a target receptor (for example, CJC-1295 is a synthetic analog of a 29-amino-acid segment of human GHRH). Lab
• Anchor Lab & Referee Lab: Under the Open Peptide Testing Standard, our Anchor Lab is the primary ISO/IEC 17025 accredited analytical laboratory providing preferred nonprofit per-sample pricing (with zero referral kickbacks), while our Referee Lab is a second, unaffiliated ISO/IEC 17025 laboratory that independently re-tests at least 10% of all batches plus every disputed or related-party batch using sealed Vial B archive samples.
• ANDA (Abbreviated New Drug Application): An FDA submission for a generic version of an already approved drug. FDA's synthetic peptide ANDA guidance sets strict impurity thresholds (<= 0.5% for any new unspecified peptide-related impurity) so generic peptides do not trigger unexpected immune reactions. Regulatory
• Anti-Drug Antibodies (ADAs): Immune system antibodies that form against an injected peptide or protein—especially when the sequence is non-human or contaminated with synthesis by-products. ADAs can neutralize the drug, trigger allergic reactions, or cross-react with your body's own natural hormones. See Immunogenicity and anti-drug antibodies. Controlled study
• Archival Retention Vial (Vial B): In the Open Peptide Project Testing Standard, the second identical, unopened vial purchased during a 2-vial anonymous retail checkout. Vial B is logged into -20°C NIST-traceable freezer storage so any disputed lab result can be independently re-tested.

B

• Bacteriostatic Water (BAC Water): Sterile water for injection containing benzyl alcohol as a bacteriostatic preservative. The benzyl alcohol stops bacteria from multiplying if introduced by repeated needle punctures over a multi-dose window (typically up to 28 days), though it does not sterilize an already-contaminated vial or neutralize endotoxins. See Bacteriostatic water and sterility risks. Regulatory
• Baseline Period & Pre-Initiation Slope: In the OPPR Observational Registry, the 14-day period before a participant starts a peptide (measured at Day -14, Day -7, and Day 0). Measuring three pre-start timepoints estimates the participant's natural trajectory (pre-initiation slope), helping separate natural recovery from post-initiation changes. Observational
• Batch Tiers (Verified, Declared, Unverified): The three exposure-quality classifications in the OPPR Registry: Verified (batch tested under the Open Peptide Standard with a published lab report), Declared (vial photo and lot number logged by the participant, but lot not lab-tested), and Unverified (no lot number captured). Observational
• Bioavailability (F): The fraction (percentage) of an administered dose that reaches systemic circulation intact. Subcutaneous injections of small peptides often achieve high bioavailability (50%–95%+), whereas swallowed (oral) peptides usually have near-zero bioavailability (<1%) unless specially formulated because stomach acid and digestive enzymes break peptide bonds apart. See Oral vs. injectable vs. nasal bioavailability. Controlled study
• Biologic (BLA Product): Under FDA rules, a protein polymer longer than 40 amino acids is regulated as a biological product under a Biologics License Application (BLA), whereas chains of 40 amino acids or fewer created chemically are generally regulated as synthetic peptide drugs under a New Drug Application (NDA). Regulatory
• Bioregulator Peptide (Khavinson Short Peptides & Cytomax Extracts): Di-, tri-, and tetrapeptides (such as Epitalon, Pinealon, or Vilon) and animal organ extracts developed largely by the St. Petersburg Institute of Bioregulation and Gerontology. Most lack independent, multicenter randomized human trials outside developer-led cohorts. Observational
• Blind Retail Batch Testing: Purchasing a product anonymously through standard customer checkout—using non-affiliated payment cards and residential shipping addresses—and replacing the vendor label with a randomized alphanumeric code before shipping to the lab so neither the vendor nor the analyst can bias the result. See How blind retail batch testing works.
• Bulk Drug Substance Categories (FDA Category 1 vs. Category 2): Lists maintained by the FDA for Section 503A compounding evaluation. Category 1 substances may be compounded while FDA completes formal rulemaking; Category 2 substances have been flagged by FDA for significant safety risks (such as immunogenicity, impurity complexity, or lack of human safety data) and may not be compounded by 503A pharmacies. See Research-use-only peptides and FDA 503A/503B law. Regulatory

C

• CAS Registry Number (CAS RN): The unique numerical identifier assigned by the Chemical Abstracts Service (CAS) to a specific chemical substance or salt form (for example, anhydrous vs. acetate salt forms of the same peptide carry different CAS numbers). Lab
• Case Report / Case Series: A published medical description of one patient (case report) or a small group of patients (case series) treated in clinical practice without a randomized control group. Useful for spotting rare side effects or generating hypotheses, but cannot prove a treatment works better than placebo. Case
• Certificate of Analysis (COA): A lab report summarizing analytical tests performed on a specific production lot of a chemical or drug (typically reporting identity, chromatographic purity, and sometimes mass fill or endotoxin). See How to read a peptide COA. Lab
• Chain of Custody: The unbroken, timestamped documentation tracking a sample from anonymous retail purchase and unsealing video through blind coding, cold-chain transit, and laboratory receipt. See Chain of Custody.
• Chromatogram: The visual graph produced by an HPLC instrument showing detector signal (peaks) over time (retention time). The main peak represents the target peptide, while smaller peaks before or after it represent peptide-related impurities, truncated sequences, or degradation products. Lab
• Co-Agonist (Dual & Triple Agonist): A single engineered peptide designed to activate two or three distinct hormone receptors simultaneously—such as GLP-1 + GIP (tirzepatide), GLP-1 + glucagon (survodutide, mazdutide, pemvidutide), or GLP-1 + GIP + glucagon (retatrutide). Controlled study
• Cohort Study (Observational Cohort): A study that follows a group of people over time to observe real-world outcomes and side effects without randomly assigning who gets the treatment. Observational
• Cold Chain: Continuous temperature-controlled storage and transport (typically 2°C to 8°C for refrigerated liquids or -20°C for frozen lyophilized powders) to prevent heat-driven peptide aggregation and degradation. See Peptide degradation, storage, and cold chain. Lab
• Common Rule (45 CFR Part 46): The federal U.S. regulation governing ethics, informed consent, and Institutional Review Board (IRB) oversight for human-subjects research. Regulatory
• Contraindication: A specific medical condition, genetic history, or concurrent medication that makes using a compound unsafe (for example, a personal or family history of medullary thyroid carcinoma is a boxed contraindication for GLP-1 receptor agonists). Regulatory
• Counter-Ion: Positively or negatively charged ions (most commonly acetate, trifluoroacetate/TFA, or chloride) bound to charged amino acid side chains in a lyophilized peptide powder. Counter-ions can account for 5% to 30% of the total powder weight in a vial. Lab
• Cyclic / Macrocyclic Peptide: A peptide whose amino-acid chain is joined into one or more closed rings (via disulfide bridges, lactam bonds, or thioether linkers). Cyclization rigidifies the molecule and blocks exopeptidase enzymes from chewing the ends, allowing several modern cyclic peptides (enlicitide, icotrokinra, zilucoplan) to achieve high receptor potency or oral absorption. Controlled study

D

• DAC (Drug Affinity Complex): A reactive linker attached to a peptide (most notably in CJC-1295 with DAC) designed to bind covalently to circulating blood albumin after injection, extending the compound's half-life to roughly a week—contrasting with CJC-1295 without DAC (Mod GRF 1-29), which clears in about 30 minutes. Lab
• Dalton (Da) / Kilodalton (kDa): The unit of molecular mass used to verify peptide identity by mass spectrometry (1 kDa = 1,000 Da). For example, BPC-157 has an exact monoisotopic mass of 1,419.5 Da. Lab
• Deamidation & Oxidation: Common chemical breakdown pathways where specific amino acids (such as asparagine, glutamine, methionine, or cysteine) react with water or oxygen over time—especially when exposed to heat or light—creating inactive or immunogenic impurities. Lab
• Deletion & Truncation Sequences (Synthesis Impurities): By-products created during Solid-Phase Peptide Synthesis (SPPS) when an amino acid fails to couple completely, leaving a peptide chain missing one or more internal amino acids (deletion sequence) or cut short (truncation sequence). Because they closely resemble the target peptide, they can trigger anti-drug antibodies. Lab
• Desensitization (Tachyphylaxis / Receptor Downregulation): A drop in biological response when a receptor is stimulated continuously or at high doses without a rest window (for example, continuous GnRH agonist exposure shuts down LH/FSH pulses rather than stimulating them). Controlled study
• Dimer / Oligomer / Aggregation: When two (dimer) or more (oligomer/aggregate) peptide chains clump or cross-link together, often due to heat, shaking, or improper pH. Aggregated peptides lose activity and dramatically increase the risk of triggering Anti-Drug Antibodies (ADAs). Lab
• Double-Blind: A clinical trial design in which neither the participants nor the doctors/researchers evaluating them know who is receiving the active compound versus the placebo until the study ends. Controlled study

E

• Endogenous vs. Exogenous: Endogenous refers to a hormone or peptide naturally produced inside the human body; exogenous refers to a substance synthesized outside the body and administered by injection, pill, spray, or cream. Many human studies measure endogenous blood levels of a peptide (such as nesfatin-1, phoenixin, spexin, or adropin) as a disease biomarker without ever testing whether giving exogenous peptide is safe or effective. Observational
• Endotoxin (Lipopolysaccharide / LPS): Heat-stable toxic fragments from the outer cell wall of Gram-negative bacteria. Even if a vial has zero living bacteria (passes a sterility test), leftover endotoxin causes fever, chills, inflammatory shock, and severe injection-site reactions when injected. Measured in Endotoxin Units (EU). See Endotoxins and TFA salts in peptides. Lab
• Endotoxin Units (EU/mg or EU/mL): The standardized potency measure for bacterial endotoxin under USP <85>. Our testing standard requires <0.5 EU/mg (and strict compliance with USP parenteral threshold limits). Regulatory
• Evidence Verdict Tiers: The five-level human-evidence rating scale used across the Open Peptide Project library:
  • Strong: Backed by large, replicated human Phase 3 randomized controlled trials (RCTs) or FDA approval for the studied indication.
  • Moderate: Backed by Phase 2 human RCTs or smaller well-controlled human clinical trials; long-term outcomes or Phase 3 confirmation may still be pending.
  • Limited: Studied in small pilot human studies, open-label cohorts, or non-randomized trials with small sample sizes.
  • Very limited: Only tiny human case series, unverified conference abstracts, or non-peer-reviewed clinic reports exist; zero randomized human trials.
  • No human data: Studied only in rodents (in vivo animal models) or petri dishes (in vitro). Zero published human clinical studies.
• Excipient / Lyoprotectant (Mannitol, Trehalose, Sucrose): Inert bulking sugars or stabilizers added to a vial before freeze-drying so a tiny milligram amount of peptide forms a visible, stable "cake" at the bottom of the vial instead of blowing away as microscopic dust. Lab

F

• Filtration (0.22 µm Sterile Syringe Filter): Passing a liquid solution through a membrane with 0.22-micron pores to trap intact bacteria and particulate matter. Important harm-reduction note: a 0.22 µm filter removes whole bacteria, but it does not remove dissolved bacterial endotoxins (LPS), viruses, or chemical impurities like TFA. Lab

G

• GCGR, GIP & GLP-1 (Incretin & Glucagon Receptors): The three primary metabolic hormone receptors targeted by modern obesity and diabetes peptides. GLP-1 slows gastric emptying, reduces appetite, and stimulates glucose-dependent insulin release; GIP enhances insulin sensitivity and adipose lipid handling; GCGR (glucagon receptor) increases hepatic energy expenditure and fat oxidation. See Incretin & GLP-1 agonist safety. Controlled study
• Gross Vial Weight vs. Net Peptide Content (NPC): Gross weight is the total weight of everything inside the vial (active peptide + acetate/TFA salt + bound water + mannitol filler). Net Peptide Content (NPC) is the actual mass of pure active peptide chains inside that powder. A vial with "99% HPLC purity" can still contain only 70% net peptide by weight if the remaining 30% is salt and moisture. See What's really in the vial: net peptide content vs. label weight. Lab

H

• Half-Life (t½ / Elimination Half-Life): The time it takes for the concentration of a peptide in your bloodstream to drop by 50%. Natural peptides often have half-lives of just a few minutes, while albumination or fatty-acid lipidation (as in semaglutide or tirzepatide) extends the half-life to 5–7 days. Controlled study
• Headspace GC (USP <467> Residual Solvents): Gas chromatography testing of the vapor space above a sample to detect toxic organic solvents (such as acetonitrile, dichloromethane, or DMF) left over from chemical synthesis. Lab
• HPLC (High-Performance Liquid Chromatography / RP-HPLC): The primary analytical method used to measure chromatographic purity (%). The dissolved sample is pumped at high pressure through a column that separates molecules by hydrophobicity, and a UV detector measures the area under each peak. See HPLC vs. LC-MS peptide testing explained. Lab
• HRMS (High-Resolution Mass Spectrometry): Mass spectrometry using Orbitrap or Time-of-Flight (Q-TOF) analyzers capable of measuring molecular mass to within a few parts per million (<= 10 ppm), resolving isotopic envelopes and distinguishing closely related modifications such as deamidation (+0.984 Da). Lab

I

• IC (Ion Chromatography): An analytical lab method used to measure the exact weight percentage of charged counter-ions such as trifluoroacetate (TFA), acetate, or chloride in a peptide sample. Lab
• ICP-MS (USP <232> / <233> Elemental Impurities): Inductively Coupled Plasma Mass Spectrometry used to detect toxic heavy-metal catalysts or contaminants (such as arsenic, cadmium, lead, mercury, or palladium). Lab
• IGF-1 (Insulin-Like Growth Factor 1): A hormone produced primarily by the liver in response to Growth Hormone (GH) pulses. Elevated IGF-1 mediates many of the anabolic effects of GH secretagogues (ipamorelin, CJC-1295, tesamorelin, ibutamoren)—as well as their cell-proliferation and insulin-resistance risks. See GH secretagogues, IGF-1, cancer, and glucose risks. Controlled study
• Immunogenicity: The propensity of a therapeutic peptide or its synthesis impurities to provoke an unwanted immune response (such as Anti-Drug Antibodies, hives, or anaphylaxis) in humans. Controlled study
• In Vitro vs. In Vivo: In vitro ("in glass") means experiments run on isolated cells or tissues in a dish or test tube. In vivo ("in the living") means experiments run in a living organism (most often mice or rats in preclinical research, or humans in clinical trials). Lab
• INCI Name (International Nomenclature of Cosmetic Ingredients): The standardized systematic name required on cosmetic ingredient labels (for example, Palmitoyl Pentapeptide-4 for Matrixyl, Acetyl Hexapeptide-8 for Argireline, or Copper Tripeptide-1 for GHK-Cu). Regulatory
• IND (Investigational New Drug Application): The regulatory authorization filed with the U.S. FDA (including animal toxicology and manufacturing quality data) that is legally required before an unapproved drug or peptide can be administered to humans in a U.S. clinical trial. Regulatory
• Interrupted Time-Series (ITS) & Piecewise Linear Mixed Model: The primary statistical design of the OPPR Observational Registry, comparing each participant's outcome trajectory (slope) across multiple pre-initiation baseline measurements against their post-initiation trajectory. Observational
• IRB (Institutional Review Board): An independent ethics committee charged with reviewing human-subjects research protocols (such as our Observational Registry Protocol) to protect participant safety, privacy, and informed consent. Regulatory
• ISO/IEC 17025 Accreditation: The international quality standard for testing and calibration laboratories. An ISO/IEC 17025 accredited lab has had its specific analytical methods, reference standards, and quality management audited by an independent accreditation body. Regulatory

K

• Karl Fischer Titration (KF): An analytical titration method used to measure the exact percentage of residual moisture (water) trapped inside a freeze-dried peptide powder. Lab

L

• LAL Assay (Limulus Amebocyte Lysate) / Recombinant Factor C (rFC): The standard laboratory tests specified under USP <85> to detect and quantify bacterial endotoxins (LPS) in injectable products. Lab
• LC-MS / LC-MS/MS (Liquid Chromatography–Mass Spectrometry): An analytical technique that pairs liquid chromatography separation with a mass spectrometer to weigh molecules at the atomic level (m/z). While HPLC shows how pure a sample looks by UV light, LC-MS proves what the molecule actually is (catching swapped vials or wrong sequences). See HPLC vs. LC-MS peptide testing explained. Lab
• Lyophilization (Freeze-Drying): Removing water from a frozen peptide solution under vacuum (sublimation) to leave behind a dry powder cake (lyophilized cake) that is stable for shipping and freezer storage. Lab

M

• Mass Balance / Content Uniformity: Comparing the actual measured milligrams of active peptide in a vial against the milligram number printed on the label (for example, checking whether a "10 mg" vial actually holds 10.0 mg, 6.2 mg, or 13.5 mg of active peptide). Lab
• mcg (Microgram) vs. mg (Milligram): Metric units of dry mass in which one milligram equals one thousand micrograms. Confusing milligrams (mg) with micrograms (mcg) is one of the most common sources of thousand-fold calculation errors in unstandardized vials.
• MedWatch (FDA Safety Reporting Program): The U.S. FDA's public system (fda.gov/medwatch or 1-800-FDA-1088) where patients and clinicians can report serious adverse events, product quality defects, or injuries from drugs, compounded preparations, or unapproved products. Regulatory
• Minimum Clinically Important Difference (MCID): The smallest change in a validated clinical outcome score (such as >= 2 points on the 0–10 Patient-Specific Functional Scale in the OPPR Protocol) that a patient perceives as a meaningful improvement in daily life, as opposed to a tiny difference that is merely statistically significant. Controlled study
• Monograph: A structured scientific reference page summarizing a single compound's chemical identity, mechanism of action, human vs. animal evidence, safety profile, regulatory status, and primary PubMed citations.

N

• N-of-1 Self-Tracking & Observational Registry: Structured self-tracking where an individual logs baseline metrics, batch/source identifiers, dosing schedules, and standardized symptom or lab outcomes over time. See N-of-1 self-tracking and observational registry methods. Observational
• NCT Number (NCT########): The unique 8-digit identifier assigned to a registered human clinical study on ClinicalTrials.gov (for example, NCT04881760).
• NDA (New Drug Application): The formal application through which the U.S. FDA reviews and approves a synthetic drug (including synthetic peptides of 40 amino acids or fewer) for sale in the United States. Regulatory
• NIST-Traceable: Temperature loggers, weights, or analytical reference standards whose calibration is linked through an unbroken chain of comparisons to standards held by the National Institute of Standards and Technology (NIST).

O

• Off-Label Use: When a licensed physician prescribes an FDA-approved drug for a condition, dose, or patient group outside its official FDA-approved label. (Note: selling or using an unapproved "Research Use Only" chemical in humans is not off-label prescribing—it is distributing or using an unapproved new drug.) Regulatory
• Open-Label Study: A clinical study in which both the researchers and the participants know exactly what compound and dose everyone is taking (no placebo disguise). Open-label studies are prone to placebo effects in subjective outcomes like pain, energy, or mood. Observational
• OSF (Open Science Framework) Preregistration & DOI: Publicly locking and timestamping a study's protocol, primary endpoint, and statistical analysis plan on the Open Science Framework with a permanent Digital Object Identifier (DOI) before data collection or analysis begins, preventing selective reporting. Observational

P

• Parenteral: Administered by a route that bypasses the digestive tract—most commonly subcutaneous (SubQ), intramuscular (IM), or intravenous (IV) injection. Parenteral products require strict sterility and endotoxin limits because they bypass the gut's natural barrier. Regulatory
• PEGylation: Attaching polyethylene glycol (PEG) polymer chains to a peptide (such as in PEG-MGF or pegozafermin) to increase molecular size, slow kidney clearance, and shield the molecule from proteolytic enzymes. Lab
• Peptide vs. Small Molecule: A peptide is a short chain of amino acids linked by peptide bonds (typically 2 to 40 amino acids under FDA's chemistry definition). A small molecule (such as 5-Amino-1MQ or Ibutamoren / MK-677) is a non-peptide organic chemical that is often sold alongside peptides on gray-market sites even though it is chemically not a peptide. Lab
• Pharma-Comparable Impurity Flag: An informational flag added to an A+ batch report under the Open Peptide Standard when RP-HPLC purity is >= 98.0% and no single unidentified impurity exceeds 0.5% (referencing the analytical threshold in FDA's synthetic peptide ANDA guidance). It means comparable on that single chromatographic measure only—never "pharmaceutical grade," FDA-approved, or safe. Lab
• Pharmacokinetics (PK) & Pharmacodynamics (PD): PK is what the body does to the compound (absorption, distribution, metabolism, and excretion over time). PD is what the compound does to the body (receptor activation, hormone release, or downstream biomarker changes). Controlled study
• Phase 1, Phase 2, Phase 3 & Phase 4 Clinical Trials:
  • Phase 1: Small first-in-human safety and dosing studies (typically 20–80 healthy volunteers or patients) testing tolerability and pharmacokinetics (PK).
  • Phase 2: Mid-sized controlled trials (typically 100–300 patients) testing whether the compound shows biological efficacy for a specific condition and identifying optimal doses.
  • Phase 3: Large, multi-center randomized controlled trials (often 500 to several thousand patients) comparing the compound against placebo or standard of care to confirm efficacy and detect less-common side effects prior to FDA approval.
  • Phase 4: Post-marketing surveillance trials conducted after FDA approval to monitor long-term real-world safety. Controlled study
• Placebo-Controlled: A clinical study in which the active treatment group is compared directly against a group receiving an identical-looking inactive substance (placebo) so researchers can separate true drug effects from expectation and natural recovery. Controlled study
• PMID (PubMed Identifier): The unique reference number assigned to a peer-reviewed biomedical journal article indexed in the U.S. National Library of Medicine's PubMed database (pubmed.ncbi.nlm.nih.gov/<PMID>/).
• Preclinical Study: Laboratory research conducted in cell cultures (in vitro) or animals (in vivo, usually mice or rats) before any human testing begins. Preclinical success does not establish human safety or efficacy. Lab
• PROMIS & PSFS (Validated Patient-Reported Outcome Measures): Standardized clinical questionnaires used in the OPPR Observational Registry: PROMIS (NIH Patient-Reported Outcomes Measurement Information System) tracks global health and sleep, while PSFS (Patient-Specific Functional Scale) tracks a participant's ability to perform three self-selected daily activities on a 0–10 scale. Observational
• Purity (Chromatographic Purity %): The percentage of the total HPLC UV-peak area that belongs to the target peptide versus other UV-absorbing peptide impurities. Crucial distinction: 99% HPLC purity means 99% of the peptide material detected by UV is the target sequence—it does not mean 99% of the powder weight in the vial is peptide. Lab

Q

• qNMR (Quantitative Nuclear Magnetic Resonance) / AAA (Amino Acid Analysis) / Nitrogen Analysis (CHN): Orthogonal laboratory methods used to measure true Net Peptide Content (NPC) and detect non-UV-absorbing fillers (such as undeclared mannitol or sugars) that standard HPLC cannot see. Lab

R

• RCT (Randomized Controlled Trial): The gold standard of clinical evidence, in which human participants are randomly assigned by computer to receive either the active intervention or a control (placebo or standard therapy). Controlled study
• Reconstitution: Dissolving a dry, freeze-dried (lyophilized) peptide powder cake with a measured volume of sterile liquid diluent (typically bacteriostatic water) prior to use.
• Regression to the Mean: The statistical phenomenon where extreme symptoms naturally drift back toward a person's average over time. Because people usually start a new peptide when pain or symptoms are at their worst, natural regression to the mean is frequently mistaken for a treatment effect in unblinded self-reports. Observational
• Related-Party Firewall: The Open Peptide Project's permanent governance rule (Disclosure) barring any person with a financial interest in peptide sales (including the founder's brother, who owns a separate retail business, Peptide Hall) from board seats, editorial decisions, batch selection, lab routing, and sponsorship, and requiring any tested batch from a related party to be labeled as such and confirmed by a second unaffiliated referee lab. Regulatory
• Research Use Only (RUO): A regulatory labeling designation for laboratory reagents intended strictly for in vitro laboratory or animal experimentation—never for human clinical or personal use. Under U.S. law, slapping a "For Research Use Only — Not for Human Consumption" disclaimer on a vial does not make selling it for human injection legal if the seller markets or intends it for human use. See Research-use-only peptides and FDA 503A/503B law. Regulatory
• Retraction & Expression of Concern: Formal notices issued by a scientific journal when published data are found to be fabricated, manipulated, or unreliable (Retraction), or are under active institutional investigation for data-integrity problems (Expression of Concern). Retracted papers are never counted as positive evidence in the Open Peptide Project Library. Controlled study

S

• SARM (Selective Androgen Receptor Modulator): A class of synthetic non-steroidal small molecules (enobosarm, LGD-4033, RAD-140, andarine S-4, YK-11) frequently sold by gray-market peptide vendors. None are FDA-approved, all are prohibited at all times under WADA Class S1, and human studies document testosterone suppression, HDL cholesterol drops, and drug-induced liver injury (DILI). Controlled study
• Secretagogue (Growth Hormone Secretagogue / GHRH / GHRP): A substance that signals the pituitary gland to secrete more of the body's own endogenous hormone (such as Growth Hormone), rather than supplying synthetic hormone directly. Includes GHRH analogs (Sermorelin, Tesamorelin, CJC-1295) and ghrelin-mimetic GHRPs (Ipamorelin, GHRP-2, GHRP-6, Hexarelin, Ibutamoren). Controlled study
• Solid-Phase Peptide Synthesis (SPPS): The standard chemical manufacturing method in which a peptide chain is assembled one amino acid at a time on insoluble polymer resin beads, cleaved from the resin with trifluoroacetic acid (TFA), and purified by preparative RP-HPLC. Lab
• Sterile Water for Injection (SWFI): Single-use sterile purified water with no antimicrobial preservative (0% benzyl alcohol). Unlike bacteriostatic water, SWFI is intended for single-dose immediate use because bacteria introduced during needle puncture can multiply in unpreserved water. Lab
• Sterility Testing (USP <71>): The pharmacopeial culture test that incubates a sample in growth media for 14 days to verify that no viable bacteria, yeast, or mold grow. Regulatory
• Subcutaneous (SubQ), Intramuscular (IM) & Intranasal: Common administration routes. SubQ injects into the fatty layer just beneath the skin using a short, fine needle; IM injects deeper into muscle tissue; Intranasal sprays solution across the nasal mucosa. Controlled study
• Surrogate Endpoint vs. Clinical Outcome: A surrogate endpoint is a laboratory biomarker or imaging measurement (such as serum IGF-1, fasting insulin, or bone mineral density) used as a stand-in for a clinical outcome (how a patient feels, functions, or survives—such as fracture rate, cardiovascular events, or validated pain/function scores). Improving a lab biomarker does not automatically prove clinical benefit or safety. Controlled study
• Systematic Review & Meta-Analysis: A study that systematically gathers all published clinical trials on a research question (systematic review) and statistically pools their data together (meta-analysis) to estimate overall effect size and certainty. Controlled study

T

• TFA (Trifluoroacetic Acid / Trifluoroacetate Salt): A strong acid routinely used to cleave synthetic peptides from solid-phase resin and run RP-HPLC purification. Unless an extra ion-exchange step is paid for to swap TFA for acetate, residual TFA remains bound to the peptide powder. High TFA levels are cytotoxic to cells in culture and cause stinging, tissue irritation, and inflammation when injected. See Endotoxins and TFA salts in peptides. Lab

U

• U-100 Insulin Syringe ("Units"): A liquid-volume syringe graduated in U-100 markings rather than dry weight. "Units" on a syringe measure liquid volume, not milligram or microgram mass—the amount of compound in any given volume depends entirely on the concentration after reconstitution.
• USP <85> Bacterial Endotoxins Test: The official United States Pharmacopeia standard for measuring bacterial endotoxin (LPS) levels in injectable drugs using LAL or recombinant reagents. Regulatory

V

• Vendor Firewall: The Open Peptide Project's foundational governance rule (Disclosure and How We Make Money): zero compound sales, zero affiliate codes or referral kickbacks, zero acceptance of vendor-submitted samples, and strict separation between funding and editorial or laboratory verdicts. All tested vials are purchased anonymously at retail checkout.

W

• WADA Prohibited List (S0, S2): The World Anti-Doping Agency's international list of substances banned in tested sports:
  • Category S0 (Non-Approved Substances): Any pharmacological substance not currently approved by any governmental regulatory health authority for human therapeutic use (which automatically bans most experimental and preclinical research peptides in tested athletes at all times).
  • Category S2 (Peptide Hormones, Growth Factors, Related Substances, and Mimetics): Explicitly bans growth hormone (GH), IGF-1, GH secretagogues (GHRH analogs, GHRPs, Ibutamoren), TB-500 / Thymosin beta-4, and BPC-157 in and out of competition. See WADA Prohibited List and peptides in tested sports. Regulatory
• Washout Period: A scheduled compound-free interval (at least 4 weeks prior to enrollment for the target compound in the OPPR Protocol) allowing a previously taken substance and its downstream biological effects to clear before recording a new baseline. Observational

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Evidence levels used on this page

• [Regulatory] FDA, USP, HHS, or WADA primary document. [Controlled study] randomized trial or systematic review of trials. [Observational] market surveillance, pharmacovigilance, or cohort data. [Lab] cell, analytical chemistry, or animal work. [Case] single case report.

Related

How to read a peptide COA, HPLC vs. LC-MS peptide testing explained, What's really in the vial: net peptide content vs. label weight, Endotoxins and TFA salts in peptides, Research-use-only peptides and FDA 503A/503B law, WADA Prohibited List and peptides in tested sports

References

1. US Pharmacopeia (USP) General Chapters <71> Sterility Tests and <85> Bacterial Endotoxins Test.
2. Choules MP, et al. NMR reveals an undeclared constituent in custom synthetic peptides. J Pharm Biomed Anal. 2020. PMID 31671336.
3. Mrozik W, et al. Determination of counter-ions in synthetic peptides by ion chromatography, capillary isotachophoresis and capillary electrophoresis. J Pept Sci. 2012. PMID 22252914.
4. De Groot AS, et al. Immunogenicity risk assessment of synthetic peptide drugs and their impurities. Drug Discov Today. 2023. PMID 37467878.
5. US FDA. Bulk Drug Substances Used in Compounding Under Section 503A and Section 503B of the Federal Food, Drug, and Cosmetic Act.
6. World Anti-Doping Agency (WADA). The World Anti-Doping Code International Standard Prohibited List (Categories S0 and S2).

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