The FDA Regulatory Landscape: Sections 503A/503B Bulk Drug Substance Lists, Biologic Thresholds & Enforcement
In the United States, synthetic peptides are governed by intersecting statutory provisions of the Federal Food, Drug, and Cosmetic Act (FD&C Act) and the Public Health Service Act (PHS Act). Between late 2023 and 2026, regulatory updates reshaped how compounding pharmacies, API manufacturers, and analytical laboratories interact with investigational peptide sequences.
FDA previously listed several nominated peptide substances in Category 2. FDA’s page current as of April 22, 2026 lists BPC-157, TB-500, CJC-1295, Semax, Selank, AOD-9604, Epithalon, MOTS-c, KPV, and Thymosin Alpha-1 as nominated but withdrawn; this does not confer approval or compounding eligibility.
Key Statutory Provisions Governing Peptides in the United States
1. Section 503A Bulk Drug Substances: The Three Statutory Gateways
Under Section 503A(b)(1)(A)(i) of the FD&C Act, a state-licensed compounding pharmacy may only compound a drug product using a bulk drug substance (active pharmaceutical ingredient, or API) if that bulk substance satisfies at least one of three statutory conditions:
- USP or NF Monograph: The bulk drug substance complies with the standards of an applicable United States Pharmacopeia (USP) or National Formulary (NF) drug monograph (note: dietary supplement monographs do not satisfy this requirement); or
- Component of an FDA-Approved Drug: The bulk drug substance is a component of an FDA-approved drug product (such as Sermorelin acetate or Bremelanotide, subject to "essentially a copy" restrictions); or
- FDA 503A Positive Bulks List: The bulk drug substance appears on the list developed by the Secretary through regulation (21 CFR § 216.23) after evaluation by the Pharmacy Compounding Advisory Committee (PCAC).
2. The Interim Policy Categories (Categories 1, 2, and 3) & the September 2023 Reclassification
While formal notice-and-comment rulemaking for the 503A Positive Bulks List proceeds, FDA’s Center for Drug Evaluation and Research (CDER) maintains an interim guidance categorizing nominated bulk substances into three buckets:
- Category 1 (Enforcement Discretion During Evaluation): Substances nominated with sufficient supporting data that do not currently raise significant safety concerns while FDA completes formal review.
- Category 2 under the 503B interim policy includes ipamorelin acetate, GHRP-2 (injectable/nasal), and GHRP-6. FDA’s page current as of April 22, 2026 lists BPC-157, TB-500, CJC-1295, Semax, Selank, AOD-9604, Epithalon, MOTS-c, KPV, and Thymosin Alpha-1 as nominated but withdrawn. Withdrawal is not FDA approval or permission to compound.
- Category 3 (Insufficient Nomination Support): Substances nominated without adequate chemical characterization, stability data, or clinical rationale.
FDA previously listed several nominated peptide substances in Category 2. FDA’s page current as of April 22, 2026 lists BPC-157, TB-500, CJC-1295, Semax, Selank, AOD-9604, Epithalon, MOTS-c, KPV, and Thymosin Alpha-1 as nominated but withdrawn; this does not confer approval or compounding eligibility. Related references: Empower Pharmacy.
| Peptide Nominated | 503A Interim Category Status | Primary FDA / PCAC Cited Rationale | Compounding Pharmacy Eligibility |
|---|---|---|---|
| BPC-157 (Body Protection Compound-157) | Nominated but withdrawn | FDA’s page current as of April 22, 2026 lists BPC-157 (Body Protection Compound-157) as nominated but withdrawn, rather than currently in Category 2. | Withdrawal is not FDA approval or permission to compound; eligibility must be assessed separately under Section 503A or 503B. |
| CJC-1295 (with or without DAC) | Nominated but withdrawn | FDA’s page current as of April 22, 2026 lists CJC-1295 (with or without DAC) as nominated but withdrawn, rather than currently in Category 2. | Withdrawal is not FDA approval or permission to compound; eligibility must be assessed separately under Section 503A or 503B. |
| Ipamorelin acetate | 503B Category 2 | Ipamorelin acetate remains in Category 2 under the 503B interim policy. Its 503A nomination is withdrawn. | Compounding eligibility must be assessed separately under Section 503A or 503B. |
| Thymosin Beta-4 & TB-500 Fragment | TB-500: nominated but withdrawn | FDA’s page current as of April 22, 2026 lists TB-500 (the thymosin beta-4 fragment) as nominated but withdrawn. Full-length thymosin beta-4 is a different 43-amino-acid substance. | Withdrawal is not FDA approval or permission to compound. |
| Thymosin Alpha-1 (Ta1) | Nominated but withdrawn | FDA’s page current as of April 22, 2026 lists Thymosin Alpha-1 (Ta1) as nominated but withdrawn, rather than currently in Category 2. | Withdrawal is not FDA approval or permission to compound; eligibility must be assessed separately under Section 503A or 503B. |
| AOD-9604, Semax, Selank, KPV, Epithalon, MOTS-c | Nominated but withdrawn | FDA’s page current as of April 22, 2026 lists AOD-9604 , Semax , Selank , KPV , Epithalon , MOTS-c as nominated but withdrawn, rather than currently in Category 2. | Withdrawal is not FDA approval or permission to compound; eligibility must be assessed separately under Section 503A or 503B. |
| GHK-Cu (Copper Tripeptide-1) | Injectable Excluded / Topical Cosmetic | Injectable routes excluded from 503A Category 1; remains permitted as a topical cosmetic ingredient (INCI) | Topical dermatological formulations only |
| Sermorelin & NAD+ | Component of Approved Drug / Category 1 | Sermorelin was previously FDA-approved (Geref, withdrawn for reasons other than safety/efficacy); NAD+ remains in active compounding review | Eligible for 503A compounding with valid prescription |
3. Section 506E Drug Shortage Resolution for GLP-1 & Dual GIP/GLP-1 Agonists
Between 2022 and 2024, surging prescription demand placed approved incretin mimetics (Semaglutide and Tirzepatide) onto the FDA Drug Shortage List under Section 506E. While a drug is listed as "Currently in Shortage," Sections 503A(b)(1)(D) and 503B(a)(2)(A) temporarily suspend the restriction against compounding "essentially a copy" of a commercially available drug—provided the compounder uses the exact active pharmaceutical ingredient (base form, not unapproved sodium or acetate salts lacking bioequivalence data) sourced from an FDA-registered facility.
As manufacturer fill-finish capacity expanded in 2024–2025, FDA formally resolved the statutory shortages for Tirzepatide and Semaglutide injection products, reinstating the statutory prohibition against routine pharmacy compounding of copies of those patented commercial products.
4. How CDER Evaluates Non-Pharmacy Vendors: Intended Use under 21 CFR § 201.128
Why do some online peptide sellers receive FDA CDER Warning Letters while institutional reagent suppliers operate lawfully? Under 21 CFR § 201.128, whether a chemical substance is regulated as an "unapproved new drug" under FD&C Act § 201(g)(1) depends on objective intended use inferred from marketing claims, product presentation, and customer targeting:
- Triggers Cited in FDA Warning Letters: Publishing human self-administration dosage charts, bundling bacteriostatic water and subcutaneous insulin syringes with lyophilized vials, making disease-treatment or weight-loss claims in blog articles or social media, or coaching retail consumers on reconstitution for personal injection.
- Analytical & Laboratory Reagent Compliance: Legitimate chemical and laboratory suppliers restrict their scope to characterized chemical reference materials accompanied by verifiable analytical documentation (reverse-phase HPLC-UV, LC-MS identity confirmation, net peptide content, and USP <85> endotoxin standards)—such as institutional manufacturer Bachem Holding AG (91/100) and our #1-ranked direct research supplier Oath Research (93/100, more than 500 batches via Freedom Diagnostics).