Whether a tissue product is regulated as a 361 HCT/P, needing no pre-market approval, or as a 351 biologic, needing an IND and a BLA, turns on four cumulative criteria under 21 CFR 1271.10. “Minimally manipulated” is the first of those criteria and the most frequently litigated. Getting it wrong, or relying on a supplier who classified a product incorrectly, exposes a physician to FDA enforcement, including warning letters, injunctions, and in serious cases criminal referral. What follows is what minimal manipulation means, how the FDA has defined it, and what it specifically means for adipose tissue.
TLDR: A tissue qualifies as a 361 HCT/P only if it meets all four criteria in 21 CFR 1271.10: minimal manipulation, homologous use, no combination with another article (limited exceptions), and either no systemic effect/no dependence on living-cell metabolism or an autologous, first/second-degree-relative, or reproductive use. Minimal manipulation, defined in 21 CFR 1271.3(f), means processing that does not alter the relevant biological characteristics of cells or non-structural tissue. Per FDA’s July 2020 guidance, processing that isolates or extracts cellular fractions from adipose tissue is more than minimal manipulation, pushing the product to 351 status. Banking adipose tissue does not enroll a patient in therapy and does not guarantee any future eligibility, access, or benefit.
Important Disclaimer: Save My Fat does not provide FDA-approved treatments or cures for any disease. Banking adipose tissue today does not guarantee eligibility, access, or clinical benefit from any future therapy, clinical trial, or medical program. No adipose-derived stem cell product currently holds FDA approval for the conditions discussed in this article. All content is for educational purposes only and does not constitute medical advice. Patients must consult their own licensed healthcare professionals regarding all medical decisions.
The phrase does a lot of regulatory work in a small number of words. “Minimal manipulation” is not a marketing adjective; it is a defined term whose meaning the FDA has spelled out, and whether a given processing step clears it determines which entire regulatory regime applies to the product. For a physician, the practical exposure is that a supplier’s classification is not self-proving, and using a mislabeled product transfers the regulatory problem onto the person who administered it.
Why This Matters for Every Physician in the Stem Cell Space
The classification question is binary in consequence. If all four 1271.10 criteria are met, the product is a 361 HCT/P: it needs establishment registration, donor-eligibility procedures, and CGTP compliance, but no pre-market approval. The federal rule itself is explained in 21 CFR Part 1271. Miss any one criterion and the product is a 351 biologic that requires an IND before clinical use and a BLA before commercial distribution. There is no middle tier. Because minimal manipulation is the first gate and the one most often contested, it is where a physician’s due diligence should start. The downstream consequences of misclassification are detailed in the FDA regulations overview for adipose tissue.
The Four 361 Criteria Under 21 CFR 1271.10
All four of the following must be satisfied. The HCT/P is minimally manipulated. The HCT/P is intended for homologous use only, the second criterion. Its manufacture does not involve combination with another article, except water, crystalloids, or a sterilizing, preserving, or storage agent that does not raise new clinical safety concerns. And it either does not have a systemic effect and is not dependent on the metabolic activity of living cells for its primary function, or, if it does, it is for autologous use, allogeneic use in a first- or second-degree relative, or reproductive use. Failing any single one of the four moves the product into 351 territory and triggers the IND and BLA requirements.
What “Minimally Manipulated” Means
The FDA defines minimal manipulation in 21 CFR 1271.3(f), and the definition splits by tissue type. For structural tissue, such as bone, skin, blood vessels, or heart valves, minimal manipulation means processing that does not alter the original relevant characteristics of the tissue relating to its utility for reconstruction, repair, or replacement. For cells and non-structural tissues, the category that includes adipose tissue, it means processing that does not alter the relevant biological characteristics of the cells or tissues. For adipose specifically, the operative question is therefore narrow and concrete: does the processing alter the biological characteristics of the adipose tissue? Everything turns on the answer to that single question.
How the FDA Has Applied This to Adipose Tissue
The FDA addressed adipose tissue directly in its guidance, “Regulatory Considerations for Human Cells, Tissues, and Cellular and Tissue-Based Products: Minimal Manipulation and Homologous Use,” issued November 2017 and finalized in July 2020. The agency’s position is specific: processing that isolates or extracts cellular fractions from adipose tissue constitutes more than minimal manipulation, because separating out those cells alters the biological characteristics of the tissue. Intact adipose tissue processed without that kind of isolation may remain minimally manipulated, depending on the exact steps applied. The practical takeaway is that a physician cannot assess minimal manipulation from a product name; they must know the specific processing steps. The distinction between intact tissue and isolated fractions is developed further in the explainer on intact adipose tissue.
What Changes If a Criterion Is Not Met
| Scenario | Classification | What is required |
|---|---|---|
| All four 361 criteria met | 361 HCT/P | Establishment registration, donor eligibility, CGTP. No pre-market approval. |
| Minimal manipulation not met | 351 biologic | IND before clinical use; BLA before commercial distribution. |
| Homologous use not met | 351 biologic | IND before clinical use; BLA before distribution. |
| Combination criterion not met | 351 biologic or combination product | IND/BLA or device pathway depending on primary mode of action. |
| Systemic-effect criterion not met (and not autologous/first or second-degree relative/reproductive) | 351 biologic | IND before clinical use. |
Adipose Processing: What Alters Biological Characteristics
The table reflects the FDA’s published guidance positions. It is a starting point, not a substitute for a written regulatory assessment from the processing partner.
| Processing step | FDA position on minimal manipulation | Notes |
|---|---|---|
| Washing | Generally does not alter biological characteristics | Verify against the partner’s regulatory assessment |
| Density-gradient separation isolating a cellular fraction | Alters biological characteristics | Cellular-fraction isolation is more than minimal manipulation per the July 2020 guidance |
| Enzymatic digestion to isolate cells | Alters biological characteristics | Enzymatically isolated cells are a 351 biologic |
| Mechanical disruption without cell isolation | May qualify; depends on degree of disruption | Verify with the processing partner |
| Cryopreservation of intact adipose tissue | Generally does not alter biological characteristics | Cryoprotectant must meet the combination criterion; verify |
| Mincing | Generally acceptable if original tissue structure is maintained | Verify |
What Physicians Must Ask Their Tissue Processing Partner
Before relying on any supplier’s 361 classification, a physician should put the questions in writing. What is your regulatory classification determination for the specific product I am purchasing? Has the FDA reviewed or commented on that classification? Do you have a written regulatory assessment or legal memo supporting the 361 determination? What specific processing steps are applied, and on what basis do you conclude each step does not alter biological characteristics? Have you received any FDA warning letters or Form 483 observations related to your classification? A partner who cannot answer these in writing is a partner whose classification a physician cannot safely adopt as their own.
Frequently Asked Questions
Does isolating a cellular fraction from adipose tissue keep a product in the 361 category?
No. Per the FDA’s July 2020 guidance, isolating or extracting a cellular fraction from adipose tissue is more than minimal manipulation, which moves the product to 351 status and triggers the IND requirement before clinical use.
Can a physician rely on a supplier’s claim that a product is 361?
Not without verification. A supplier’s classification does not transfer to the physician as a defense. Obtain the written regulatory assessment and confirm the specific processing steps; the physician who administers the product carries the exposure if the classification is wrong.
Is intact adipose tissue automatically minimally manipulated?
Not automatically. Intact tissue processed without fraction isolation may qualify, but it depends on the exact steps. Minimal manipulation is assessed against the processing, not the product label.
Key Takeaways
Minimal manipulation is the first of four cumulative gates under 21 CFR 1271.10, and it is decided by a single question for adipose tissue: does the processing alter the tissue’s biological characteristics? The FDA’s July 2020 guidance answers that isolating or extracting cellular fractions does, which pushes such a product out of the 361 exemption and into 351 territory with its IND and BLA requirements. Intact adipose processed without that kind of isolation may remain minimally manipulated, but only the specific processing steps decide it, which is why a product name tells a physician nothing and a written regulatory assessment from the processing partner tells them everything. The exposure for getting this wrong sits with the physician who administers the product, not only the supplier who classified it. None of this bears on banking itself, which is a preservation decision separate from any therapeutic use and carries no guarantee of future benefit.
Save My Fat operates as a tissue preservation service, not a medical practice or treatment provider. Stem cell and regenerative medicine regulations vary by state, including specific informed-consent and disclosure requirements in Florida, Utah, and Nevada governing tissue and stem cell services. Banking adipose tissue does not connect patients to any treatment pathway, and any future use depends on FDA regulatory status, physician guidance, and the availability of approved or investigational pathways at that time.
Physicians evaluating a supplier’s regulatory classification can contact Save My Fat to discuss how tissue preservation works. Service and processing details are available at https://savemyfat.com/pricing/.
Save My Fat partners with L2 Bio for laboratory processing and storage.
This article is for educational purposes only and does not constitute medical or legal advice. Legal and medical review including neurology and neurosurgery input is required before publication. Please consult your neurologist or neurosurgeon before making any decisions about neurologic treatment or research participation.
