FDA Revises Bioequivalence Guidance for 17 Generic Peptide Products
TL;DR: FDA's revised guidance for 17 generic peptides, including tirzepatide, closes for public comment today, 28 Sept 2026.
What Did the FDA Just Publish?
On 28 July 2026, the US Food and Drug Administration published 17 revised draft product-specific guidances (PSGs) — its recommendations for how a generic drug maker should demonstrate that a proposed peptide product is therapeutically equivalent to a named reference drug.[1] The Federal Register notice announcing availability ran the following day, 29 July 2026, under docket number FDA-2007-D-0369.[2] Trade press has described the batch as an unusually large, cross-portfolio release rather than a fix aimed at a single drug class.[5]
The public comment window on that docket closes today, 28 September 2026. A PSG remains non-binding even once finalised — a sponsor may still propose an alternative bioequivalence approach if it satisfies the underlying statute and regulations — but departing from a published recommendation typically invites closer agency scrutiny of an Abbreviated New Drug Application (ANDA).[1]
Which Reference Drugs Are Covered?
The 17 revised PSGs map onto seven reference peptide drugs spanning diabetes and obesity, osteoporosis, and macular degeneration.[3]
| Reference drug | Indication area |
|---|---|
| Semaglutide | Type 2 diabetes / obesity (GLP-1 receptor agonist) |
| Tirzepatide | Type 2 diabetes / obesity (GIP/GLP-1 dual agonist) |
| Liraglutide | Type 2 diabetes / obesity (GLP-1 receptor agonist) |
| Teriparatide | Osteoporosis (PTH analogue) |
| Pegcetacoplan | Macular degeneration / complement disorders |
| Calcitonin salmon | Bone-metabolism disorders |
| Glucagon | Severe hypoglycaemia |
Table for research reference only; see FDA's published guidance index for the full, current list of product-specific guidances.[1]
What's Actually Changing in the Testing Recommendations?
Coverage of the revised guidances describes updated recommendations across five recurring areas: the submission pathway framing for peptides that are produced recombinantly, synthetically, or semi-synthetically; innate-immune-response testing; impurity thresholds; higher-order structure assessment; and biological-activity assessment.[4]
Analytical “sameness” characterisation
Comparative physicochemical and structural characterisation intended to support a generic sponsor's request to waive a full in vivo clinical bioequivalence study, provided the proposed product and the reference standard show sufficient analytical sameness.[3]
Immunogenicity and impurity screening
Expanded expectations for innate-immune-response testing and tighter recommended impurity thresholds, reflecting how synthetic and semi-synthetic manufacturing routes can introduce process-related impurities that a purely chemical identity test would miss.[4]
Alongside the revisions, FDA proposed withdrawing its May 2021 guidance, ANDAs for Certain Highly Purified Synthetic Peptide Drug Products That Refer to Listed Drugs of rDNA Origin, stating it no longer reflects the agency's current scientific thinking; a replacement framework is expected later in 2026.[3]
Why Is FDA Withdrawing Its 2021 Synthetic-Peptide Guidance?
The 2021 guidance set out when a synthetically manufactured peptide could rely on a reference drug originally made by recombinant DNA (rDNA) technology — treating chemical identity between the two manufacturing routes as sufficient grounds for a generic filing. Consultants who track FDA generic-drug policy describe the withdrawal, paired with the same-day PSG revisions, as the clearest signal yet that the agency's scientific view of peptide “sameness” has moved on from a chemistry-only test toward one that also weighs higher-order structure and biological activity — closer to how FDA already treats complex generics and some biosimilars.[5][6] One commentary flagged the timing of the posting itself as unusual, arriving without the advance notice FDA guidance releases more typically receive.[5]
What Does This Mean for the Race Toward Generic Incretin Therapies?
Tirzepatide and semaglutide are the two most commercially watched names on the list, given the size of the branded incretin market and the number of manufacturers understood to be preparing ANDA filings ahead of eventual patent and exclusivity expiries. We covered Sandoz's first accepted generic-tirzepatide ANDA filing in June 2026; today's revised PSG is the analytical rulebook that filing, and any that follow it, will now be measured against. A tighter, more clearly specified PSG cuts both ways for those sponsors: it narrows the analytical goalposts a generic applicant needs to hit, but it can also mean more characterisation work, and a longer runway before an ANDA is filing-ready, than the 2021 framework implied.
A different track from compounding enforcement. This PSG revision governs the ANDA generic-drug pathway under Hatch-Waxman — a separate legal track from the Section 503A/503B pharmacy-compounding framework we've covered elsewhere, including FDA's move to exclude tirzepatide and semaglutide from the 503B bulks list and its warning letter to Empower Pharmacy over compounded GLP-1 co-formulations. A generic ANDA product is a full copy of an approved drug sold under its own marketing authorisation; a compounded product is prepared by a licensed pharmacy for an individual patient. Today's docket closure affects only the former.
Does This Affect UK Research-Reagent Supply?
No. The ANDA pathway is a US statutory mechanism for approving generic copies of already-approved medicines for human patients; it has no equivalent in the UK's Human Medicines Regulations 2012, under which research reagents supplied strictly for in vitro laboratory use are assessed — see our guide on whether research peptides are legal in the UK. It is also, by definition, a pathway that can only exist once a reference drug is approved, so it has no bearing on an investigational compound such as retatrutide, which has no approved reference product to be a generic copy of.
Velox Peptides does not sell tirzepatide, semaglutide, or any FDA-approved medicine in generic, branded or compounded form. Every compound Velox stocks is supplied as an HPLC-verified in vitro research reagent only. Not a medicine. Not for human or veterinary use. See our Research Use Policy and MHRA Statement.
References
- U.S. Food and Drug Administration. FDA Publishes Revised Draft Product-Specific Guidances for Certain Generic Peptide Products. 28 July 2026. fda.gov
- Federal Register. Product-Specific Guidances; Revised Draft Guidances for Industry; Availability. 29 July 2026 (Docket FDA-2007-D-0369). federalregister.gov
- Pharmaceutical Technology. Seventeen Peptide Guidance Revised: What Developers Need to Know. 2026. pharmtech.com
- Regulatory Affairs Professionals Society (RAPS). FDA updates product-specific guidelines for injectable peptides. 2026. raps.org
- Lachman Consultants. Newly Revised Product Specific Guidances Issued in an Unusual Posting. July 2026. lachmanconsultants.com
- MFLRC. FDA's 17 Revised Peptide Guidances: What Generic Developers Must Change. 2026. mflrc.com
Frequently Asked Questions
What did the FDA publish on 28 July 2026?
FDA published 17 revised draft product-specific guidances (PSGs) setting out its current recommendations for how a generic drug maker can demonstrate that a proposed peptide product is therapeutically equivalent to a named reference drug. The batch covers reference products including semaglutide, tirzepatide, liraglutide, teriparatide, pegcetacoplan, calcitonin salmon and glucagon, spanning diabetes, obesity, osteoporosis and macular-degeneration indications.
What is a product-specific guidance (PSG)?
A PSG is FDA's non-binding recommendation, issued for an individual reference listed drug, on the analytical, in vitro and (where still required) in vivo studies a generic applicant should run to support an Abbreviated New Drug Application (ANDA). Sponsors are free to propose an alternative approach if it still satisfies the underlying statute and regulations, but deviating from a published PSG typically invites additional agency scrutiny.
Why does the comment deadline matter?
The docket for this batch, FDA-2007-D-0369, closes to public comment on 28 September 2026. Comments do not have to be filed by the deadline to be read, but FDA states it can only guarantee consideration before finalisation for input received while the docket is open. Generic sponsors with ANDAs already in development have a narrow, defined window to flag analytical or clinical concerns before the recommendations are locked in as final guidance.
Does this guidance apply to compounded or research-use peptides?
No. Product-specific guidances sit inside the Hatch-Waxman ANDA pathway, which exists only for a generic copy of an already FDA-approved reference drug. It has no bearing on Section 503A/503B pharmacy compounding of those same drugs, which we cover separately, and no bearing on an investigational compound with no approved reference product, such as retatrutide, for which no generic pathway can exist yet.
Does this affect UK research-reagent supply or Velox Peptides?
No. The ANDA generic-drug framework is a US statutory mechanism with no equivalent in the UK's Human Medicines Regulations 2012, and it governs finished pharmaceutical products for human patients, not laboratory research reagents. Velox Peptides does not sell tirzepatide, semaglutide, or any other FDA-approved medicine in generic, branded or compounded form. It supplies retatrutide as an HPLC-verified in vitro research reagent only, with no dosing or human-use claims. Order for research →