Evidence review: Open Peptide Project (verified against primary PubMed, ClinicalTrials.gov & FDA records) · Last checked 2026-10-27. ← Back to Evidence Library
Tuftsin (Thr-Lys-Pro-Arg): what the evidence says
At a glance
What it is: a natural four-amino-acid peptide (Thr-Lys-Pro-Arg) released from the Fc part of immunoglobulin G that stimulates phagocytic cells. R1, R2 Selank is a lengthened tuftsin analogue. UNVERIFIED Selank's sequence against a primary source in this page.
What the evidence says: lab and animal work shows it boosts macrophage functions. R2 In people, low tuftsin activity has been measured after splenectomy and in AIDS, R3 but we found no controlled trial of giving tuftsin as a treatment.
Biggest risks: unknown in people.
Rating
| Human Human evidence | None for treatment; observational deficiency data only R3 |
| Animal Animal / lab evidence | Macrophage and animal studies R2 |
| Regulatory | Not FDA-approved · not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page R4, R5, R6 · not named by WADA R7 |
| Established human dose | No |
Evidence verdict: Immune support in people: Unknown (no controlled human trials found) · Phagocyte stimulation: lab/animal only
This page reports what studies used. It is not dosing advice.
Legend: HUMAN data · ANIMAL / LAB data · UNKNOWN · UNVERIFIED: not yet confirmed against a primary source
About the evidence: the human data describe natural tuftsin levels, not treatment with injected tuftsin. Claims about immune boosting from vials go beyond the evidence.
What is it?
First described in 1970 as a phagocytosis-stimulating peptide. R1 Related pages: Selank, Thymosin alpha-1, Thymogen, Rigin.
Does it work?
- Animal Boosts phagocytosis, motility and killing activity of macrophages in lab studies. R2
- Human Tuftsin activity was lower in 21 people with AIDS and 22 splenectomy patients than in 37 healthy volunteers. R3 This is a measurement, not a treatment result.
- Unknown No controlled human treatment trials were found.
Is it safe?
- Unknown No human safety data from controlled use. Reviews describe low toxicity in animals. R2
Gray-market vials: extra risks
A gray-market vial has no quality control and no guarantee of identity, strength or sterility. We test retail vials blind under the Open Peptide Standard; see /tests/. A passing test covers one batch on one date and does not mean the compound is safe.
Is it legal?
- US: not FDA-approved; no Drugs@FDA application found (openFDA searched Oct 26, 2026).
- Compounding: not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page. R4, R5, R6
- Sport: not named on WADA's 2026 Prohibited List. R7
Study details
Study details
These are amounts researchers used, not recommendations.
| Study | People / model | Route | Amount used | Follow-up | Reported | Citation |
|---|---|---|---|---|---|---|
| Corazza 1991 | 21 AIDS, 7 ARC, 22 splenectomy, 37 controls | Observational | None given | Single measurement | Lower tuftsin activity with poor spleen function | PMID 1670648 |
Full reference list (PubMed, CT.gov, FDA and WADA checked Oct 26, 2026)
- R1 Najjar VA, et al. Nature. 1970. PMID 4097539
- R2 Fridkin M, et al. Crit Rev Biochem Mol Biol. 1989. PMID 2667894
- R3 Corazza GR, et al. Lancet. 1991. PMID 1670648
- R4 FDA, 503A bulk drug substances categories list (updated May 14, 2026). https://www.fda.gov/media/94155/download
- R5 FDA, 503B bulk drug substances categories list (updated Mar 21, 2025). https://www.fda.gov/media/94164/download
- R6 FDA, Certain bulk drug substances for use in compounding that may present significant safety risks (content current Apr 22, 2026). https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
- R7 WADA. The 2026 Prohibited List, full list checked; compound not named. https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf
Disclaimer
This page is for education and harm reduction, not medical advice or a recommendation to use Tuftsin (Thr-Lys-Pro-Arg). This compound is not FDA-approved. Any product sold under this name in the US is unregulated. Report problems to FDA MedWatch (https://www.fda.gov/safety/medwatch).