Tuftsin
The small immune peptide freed from antibodies, why people without a working spleen lack it, and what giving it to animals has shown
Tuftsin is a four-amino-acid peptide, Thr-Lys-Pro-Arg, that sits inside the tail region of immunoglobulin G and is cut free with the help of an enzyme from the spleen. Once released it binds white blood cells such as neutrophils and macrophages and pushes them to engulf more microbes. People whose spleen is missing or failing, and patients with AIDS, cirrhosis or sickle cell disease, have less tuftsin activity in their blood, which has been linked to more infections. In animals, synthetic tuftsin protected against sepsis and eased an inflammatory brain disease model. It is a research peptide, not an approved medicine.
No established human dose Details ↓
Recommended Dosing
No established human dose
No dose can be given for tuftsin. The human studies on this page measure its activity in the blood of people with spleen loss, cirrhosis, AIDS and other conditions, or add synthetic tuftsin to their cells in the laboratory.
What is it?
Tuftsin is a short peptide, four amino acids long, that is part of the body's own antibody molecules. It sits in the Fc portion of the heavy chain of immunoglobulin G (IgG), and enzymatic processing cuts it out of the parent protein. A 1989 review by the peptide's discoverer, Victor Najjar, and Mati Fridkin describes it as a stimulant of phagocytic cells, especially macrophages: it increases their engulfing of particles, their movement, and their killing of bacteria and tumour cells, and it showed low toxicity.
The spleen matters for tuftsin. A Lancet study from 1991 describes the peptide as released from IgG by a splenic enzyme, and across people with AIDS, people whose spleen had been removed and healthy volunteers, tuftsin activity fell as spleen function fell. After elective splenectomy tuftsin activity in one study was zero, while people whose spleen had been removed after trauma kept a little, a sign that splenic tissue had regrown. The same pattern appeared in cirrhosis, in sickle cell disease, in lepromatous leprosy and in people fed intravenously for years, all conditions in which the spleen works poorly.
Low tuftsin activity has practical weight because these patients get more bacterial infections. In cirrhosis, low activity went with weaker neutrophil engulfing and with more infections over follow-up, and adding synthetic tuftsin to patients' neutrophils in the dish brought their engulfing back to normal. A liver transplant restored tuftsin activity in most cirrhotic patients. A rare inherited form of tuftsin deficiency was described in children with repeated severe infections whose blood carried a faulty peptide that blocked the normal one.
How tuftsin acts was unclear for decades. Work since 2005 shows it binds neuropilin-1, a receptor that also binds the blood-vessel growth factor VEGF, and signals through the TGF-beta pathway, shifting microglia (the brain's immune cells) toward an anti-inflammatory state. In mice with experimental autoimmune encephalomyelitis, a model of multiple sclerosis, tuftsin eased symptoms in a way that needed neuropilin-1. In other mouse studies it improved survival in sepsis and protected the spleen in severe pancreatitis.
What has not been shown is a benefit in people. Tuftsin was given to patients with cancer in early studies from the 1980s, but those PubMed records have no abstract, so this page states neither an amount nor a result for them. Most later work turned tuftsin into a building block: dozens of analogues, tuftsin-coated liposomes that steer drugs to macrophages, and tuftsin joined to phosphorylcholine as the investigational compound dazdotuftide. Selank, a longer synthetic peptide derived from tuftsin, is a different molecule with its own entry; none of its data appear on this page.
Mechanism of Action
Tuftsin is released from IgG with help from the spleen and acts on phagocytes and microglia, mainly through neuropilin-1; enzymes on the same cells switch it off quickly.
Freed from antibodies
Tuftsin is part of the IgG heavy chain and is cut free enzymatically; the spleen supplies the processing, so spleen loss lowers tuftsin activity (PMIDs 1670648, 8044558).
Stimulates phagocytes
It increases engulfing, movement and killing by neutrophils and macrophages, and restored engulfing by cirrhotic patients' neutrophils in the dish (PMIDs 2667894, 11950821).
Neuropilin-1 and TGF-beta
It binds neuropilin-1 and signals through the TGF-beta receptor and Smad3, turning microglia and macrophages toward an anti-inflammatory state (PMIDs 16371354, 24033337).
Rapidly inactivated
A surface enzyme on neutrophils, probably leucine aminopeptidase, breaks tuftsin down soon after it acts (PMID 6894864).
Published Research
These are studies of tuftsin itself, read from their PubMed abstracts: measurements of tuftsin in the blood of people with spleen loss and other diseases, laboratory work on human and animal immune cells, studies that gave synthetic tuftsin to animals, and three reviews. Work on tuftsin analogues, tuftsin-bearing liposomes and tuftsin conjugates is listed under References only, and Selank's studies are on its own entry.
Chemistry, biology and clinical promise
This review by Fridkin and Najjar describes tuftsin as a Thr-Lys-Pro-Arg peptide held in the Fc domain of IgG and released by enzymatic processing. It boosts phagocytosis, cell movement, and bacteria- and tumour-killing by macrophages and other phagocytes, acts through specific receptors isolated from rabbit granulocytes, has low toxicity, and can be made at scale by chemical synthesis.
Thirty years after its discovery
A survey of tuftsin research mostly from 1984 to 1997: where tuftsin and its reversed sequence occur in proteins, its synthesis and antigenic properties, its effects on phagocytes, its reported antimicrobial, antiviral, antitumour and central nervous system effects, and the search for more potent analogues.
Properties and analogues reviewed
Of 86 papers reviewed, 32 dealt with tuftsin's activity in the human body and 54 with analogues, sorted by antitumour, anti-inflammatory, antimicrobial and antiviral activity. The authors note uses of tuftsin-based peptides in vaccines, in fusion proteins against cancer and as carriers for other active molecules.
Low tuftsin activity in AIDS
Tuftsin activity and spleen function were measured in 21 patients with AIDS, 7 with AIDS-related complex, 22 after splenectomy and 37 healthy volunteers. Activity fell as spleen function fell across all subjects, and it was significantly lower in AIDS, AIDS-related complex and after splenectomy than in volunteers, which the authors link to the bacterial infection risk of symptomatic HIV.
Splenectomy and residual spleen tissue
In 23 people whose spleen had been removed at least a year earlier and 50 matched volunteers, tuftsin activity tracked the pitted red cell count, a marker of spleen function, closely (rs -0.80). Activity averaged 21.6% in controls, 4.4% after splenectomy for trauma and zero after elective splenectomy, consistent with regrown splenic tissue after trauma.
Lower serum tuftsin in sickle cell disease
By radioimmunoassay, mean serum tuftsin was 154 ng/mL in haemoglobin SS disease and 181 ng/mL in SC and CC disease, against 229 ng/mL in 12 healthy controls, both significantly lower. The authors read the deficit as a sign of poor spleen function that may add to these patients' risk of severe infection.
An inherited tuftsin deficiency
Serum tuftsin activity was normal in 20 premature infants, 20 full-term infants and 20 healthy children, but absent in 5 children with repeated severe infections of the lungs, skin and lymph nodes despite normal cellular and antibody immunity. All 5 carried a mutant peptide that strongly blocked normal tuftsin, and they responded very well to gamma-globulin.
Impaired tuftsin activity in cirrhosis
In 31 patients with cirrhosis and 31 healthy subjects, median tuftsin activity was 8% against 17%, and it fell with spleen function and with Child-Pugh severity. Weak neutrophil engulfing in 19 of 23 patients tracked tuftsin activity and returned to normal when synthetic tuftsin was added in the dish; low activity went with more bacterial infections but not with survival.
A liver transplant restores tuftsin activity
In 9 cirrhotic patients tested before and a median 39 months after a successful liver transplant, tuftsin activity rose in every case (median 8% to 20%) and returned to normal in 5 of the 7 who had been low. Neutrophil engulfing with the patient's own serum improved in all, alongside better spleen function and blood counts.
Long-term intravenous feeding lowers tuftsin activity
Twenty patients with intestinal failure on long-term intravenous nutrition had tuftsin activity of 6%, against 16.5% in 20 people with Crohn's disease and 17.8% in 50 healthy controls. Their pitted red cell counts were far higher, a sign of a poorly working spleen, and 8 of the 20 had had a serious infection in the previous year.
Serum tuftsin in leprosy
A competitive enzyme immunoassay found mean serum tuftsin of 134 ng/mL in 16 patients with lepromatous leprosy against 263 ng/mL in 20 healthy controls, while tuberculoid leprosy was only slightly and not significantly lower. Serum IgG, tuftsin's parent protein, was higher in both leprosy groups, pointing to a failure to release tuftsin rather than a lack of IgG.
Spleen-preserving surgery keeps tuftsin near normal
Serum tuftsin measured by HPLC in 40 patients stayed close to the level in 10 controls after splenic autotransplantation for traumatic rupture or partial splenectomy for hypersplenism. It was below the control level but above that seen after total splenectomy, supporting tuftsin as a readout of residual spleen function.
Tuftsin identified in human serum
This study separated tuftsin from trypsin-treated human serum by reverse-phase HPLC and confirmed its identity by tandem mass spectrometry, the first unambiguous identification of tuftsin in serum. Measuring the amount was not the aim, but the authors estimate it in the hundreds of nanograms per millilitre.
A test for tuftsin's effect on human neutrophils
The authors built a flow-cytometry assay of human neutrophils engulfing fluorescent beads, because tuftsin's effect had been hard to show. The best conditions were a 15-minute incubation at body temperature with 5 micrograms per millilitre of tuftsin; under them tuftsin raised the number of beads each cell swallowed more than the share of cells that swallowed any.
Tuftsin and interleukin-1
Synthetic tuftsin made blood cells from healthy donors and from people without a spleen release interleukin-1 in the dish, with a larger effect in the splenectomised group, and it did the same in human spleen cells. In mouse spleen cells it acted only together with an antigen.
Lepromatous macrophages stop responding
Blood macrophages from healthy donors and from tuberculoid leprosy patients engulfed more bacteria in response to tuftsin as they matured in culture, but those from lepromatous leprosy patients became unresponsive by 14 days and reacted only to about 100 times the usual effective concentration. The authors suspect a defect in the receptor or its signalling.
Neutrophils inactivate tuftsin at their surface
Guinea-pig neutrophils rapidly inactivated tuftsin through an enzyme on the outer cell membrane, not inside the cell. The inactivation tracked leucine aminopeptidase, a surface enzyme that tuftsin competed with for its substrate, so the authors propose it as the enzyme that switches tuftsin off.
Tuftsin binds neuropilin-1
Tuftsin and a related peptide, TKPPR, bound selectively to neuropilin-1 and blocked VEGF from binding it; multimeric forms of TKPPR bound far more tightly and reduced VEGF signalling in endothelial cells. Because tuftsin's sequence resembles part of VEGF, the authors propose that some of tuftsin's known effects run through neuropilin-1.
Signalling through neuropilin-1 and TGF-beta
In mouse microglia, a drug that stops tuftsin binding neuropilin-1 reversed tuftsin's shift of the cells toward an anti-inflammatory (M2) state, and blocking the TGF-beta receptor-1 did the same. Tuftsin raised Smad3 phosphorylation and TGF-beta release, so it signals through neuropilin-1 and the classic TGF-beta pathway.
Binding studies against SARS-CoV-2
A computer analysis found 91 genes shared between tuftsin's targets and COVID-19, and docking suggested tuftsin sits on ACE2 and neuropilin-1 where the virus spike binds. Surface plasmon resonance confirmed direct binding to both receptors and showed tuftsin reduced spike S1 binding to ACE2; no cell infection or animal test is reported.
Protection after splenectomy in mice
Splenectomised mice given pneumococcal sepsis survived significantly better when treated with synthetic tuftsin, as did mice given back splenic tissue. The authors conclude that tuftsin deficiency contributes to overwhelming infection after splenectomy.
Survival in septic mice
Sepsis induced by caecal ligation and puncture lowered serum tuftsin in mice, and giving tuftsin improved survival. In cell experiments tuftsin weakened the suppressive regulatory T cells that carry high neuropilin-1, reducing their Foxp3 and CTLA-4 expression and their TGF-beta release.
Recovery in a multiple sclerosis model needs neuropilin-1
Tuftsin had already been shown to improve experimental autoimmune encephalomyelitis in mice. Here, deleting neuropilin-1 from microglia stopped tuftsin's signalling and its anti-inflammatory shift, and deleting it from microglia or regulatory T cells reduced the contacts between them and the T cells' activation, so tuftsin's benefit depended on that receptor.
Combined with a remyelinating drug
In mouse models of multiple sclerosis, tuftsin given with benztropine, an approved drug that promotes remyelination, eased symptoms and tissue damage. Tuftsin was needed to turn the inflamed brain environment anti-inflammatory, while benztropine was needed for myelin repair in the toxin-induced cuprizone model.
Microglial clean-up and remyelination
In mice with experimental autoimmune encephalomyelitis, tuftsin-stimulated microglia lowered clinical scores, curbed severe disease and promoted remyelination. Tuftsin shifted the cytokine balance away from the inflammatory M1 response and toward the anti-inflammatory M2 response.
Spleen protection in severe pancreatitis
In a rodent model of severe acute pancreatitis, tuftsin reduced spleen damage and inflammation, eased mitochondrial dysfunction and oxidative stress, and moved spleen macrophages toward the M2 type by raising neuropilin-1. Blocking neuropilin-1 with a drug or silencing it in macrophages weakened tuftsin's protection.
No Established Human Dose
No dose can be given for tuftsin. The human studies on this page measure its activity in the blood of people with spleen loss, cirrhosis, AIDS and other conditions, or add synthetic tuftsin to their cells in the laboratory. Two early clinical studies in cancer patients are listed under References, but their PubMed records have no abstract, so no amount from them can be checked or stated. There is no approved tuftsin product.
What this rests on: PMID 1670648, PMID 11950821, PMID 8044558.
Educational information, not medical advice. The doses on this page come from approved labels, published studies and, where no study exists, amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
What a Buyer Needs to Know
What is sold, how it is mixed, stored and taken, and what is known about its safety, quality and legal status. Each part names its source. Where we have none, it says unknown.
What is sold
Unknown: we hold no label and no published test that says what forms or vial sizes Tuftsin is sold in. A vial's own label is a seller's claim, not a source.
Mixing a vial: a worked example
Unknown: no human dose of Tuftsin has been established (see No Established Human Dose below), so there is no amount to work out. The reconstitution calculator does the arithmetic for any vial, water and dose.
Storage before and after mixing
Unknown: no label or published stability study on file says how to store Tuftsin, before or after mixing. The mixing guide sets out the general rules, with their sources: keep a mixed vial in the fridge, and use it promptly, as the bacteriostatic water label says of any drug dissolved in it. The 28 days often quoted is the limit for an opened multiple-dose vial from a manufacturer, an outer limit set for sterility, not a time a mixed solution has been shown to keep. Nobody has published how long Tuftsin stays intact once mixed.
How it is taken
Unknown: with no established human dose, there is no established way of taking Tuftsin. What the human studies gave and how is set out under No Established Human Dose.
What to expect, and when
Unknown: no cited half-life and no label or trial duration on this page says how long Tuftsin lasts or how long it was given. Results reported in the studies are under Published Research.
Side effects, and when to stop or get help
From the Side Effects section: A 1989 review describes tuftsin as having low toxicity, without giving human safety data in its abstract (PMID 2667894); Tuftsin binds neuropilin-1, which also takes part in blood-vessel growth signalling; tuftsin-like peptides blocked VEGF binding in cell studies (PMID 16371354); No safety data in people from any study with a readable abstract. Full list and cautions ↓
When to stop or get help: unknown; no label or trial on file sets rules for stopping Tuftsin. Treat a severe or unexpected reaction as a reason to stop and see a doctor.
Source: the Side Effects section below (“No study read here reports side effects in people, because none of the human studies with an abstract gave tuftsin to anyone”).
Interactions
Unknown: a PubMed search for human interaction studies of Tuftsin (reviewed 2026-10-28) found none. Unknown is not the same as safe to combine.
Every peptide's record, with its source: the interaction matrix.
Checking what you bought
Unknown: no published independent test of Tuftsin products is in our lab-results database yet, so how products sold under this name measure up is not known.
To read a certificate of analysis, paste it into the COA decoder; it checks the measured mass against Tuftsin's expected mass, 500.6 Da, from this entry's molecular data. Trust & Verification explains what independent testing can and cannot show.
Legal status
US: Research Chemical (Not a medicine: a natural research peptide). Sport: Prohibited (S0 catch-all).
Country by country ↓ · Regulatory tracker
Source: this entry's approval status and the WADA Prohibited List, as in Legal Status below.
Side Effects & Contraindications
Reported Side Effects
No study read here reports side effects in people, because none of the human studies with an abstract gave tuftsin to anyone.
Contraindications & Cautions
There is no product label. These cautions follow from the evidence.
Legal Status
Tuftsin is a research peptide; it is not approved as a medicine anywhere in the sources read.
Frequently Asked Questions
?What is tuftsin?
A natural four-amino-acid peptide, Thr-Lys-Pro-Arg, that is part of the IgG antibody molecule. Once cut free it stimulates neutrophils and macrophages to engulf and kill microbes.
?Why does the spleen matter for tuftsin?
The spleen supplies the processing that frees tuftsin from IgG. After splenectomy, and in diseases that weaken the spleen such as sickle cell disease and cirrhosis, tuftsin activity in the blood is lower, and in several studies that went with more infections.
?Has tuftsin been given to people?
Two early studies in cancer patients are indexed as clinical trials, but their PubMed records have no abstract, so their amounts and results could not be read. Every human study with a readable abstract measured tuftsin rather than giving it.
?What does tuftsin do in animals?
In mice it improved survival after sepsis, including after splenectomy, eased a multiple sclerosis model through the receptor neuropilin-1, and protected the spleen in severe pancreatitis.
?Is Selank the same as tuftsin?
No. Selank is a longer synthetic peptide derived from tuftsin and is a separate molecule with its own entry. Its studies are not counted on this page.
?How long does tuftsin last in the body?
No half-life figure was found in the sources read. Neutrophils break it down quickly through an enzyme on their surface, probably leucine aminopeptidase.
References
- [other] PubChem CID 156080, Tuftsin: formula C21H40N8O6, molecular weight 500.6. Read October 28, 2026. https://pubchem.ncbi.nlm.nih.gov/compound/156080
- [review] Fridkin M, et al. "Tuftsin: its chemistry, biology, and clinical potential." Crit Rev Biochem Mol Biol, 1989;24(1):1-40. PMID: 2667894.
- [review] Siemion IZ, et al. "Tuftsin: on the 30-year anniversary of Victor Najjar's discovery." Peptides, 1999;20(5):645-74. PMID: 10465518.
- [review] Siebert A, et al. "Tuftsin - Properties and Analogs." Curr Med Chem, 2017;24(34):3711-3727. PMID: 28745220.
- [clinical-trial] Corazza GR, et al. "Tuftsin deficiency in AIDS." Lancet, 1991;337(8732):12-3. PMID: 1670648.
- [clinical-trial] Zoli G, et al. "Splenic autotransplantation after splenectomy: tuftsin activity correlates with residual splenic function." Br J Surg, 1994;81(5):716-8. PMID: 8044558.
- [clinical-trial] Spirer Z, et al. "Decreased serum tuftsin concentrations in sickle cell disease." Arch Dis Child, 1980;55(7):566-7. PMID: 6893650.
- [clinical-trial] Constantopoulos A. "Congenital tuftsin deficiency." Ann N Y Acad Sci, 1983;419:214-9. PMID: 6201116.
- [clinical-trial] Trevisani F, et al. "Impaired tuftsin activity in cirrhosis: relationship with splenic function and clinical outcome." Gut, 2002;50(5):707-12. PMID: 11950821.
- [clinical-trial] Foschi FG, et al. "Effect of liver transplantation on tuftsin activity and phagocytic activity of neutrophil granulocytes in patients with liver cirrhosis." Int Arch Allergy Immunol, 2005;137(3):258-62. PMID: 15961955.
- [clinical-trial] Zoli G, et al. "Impaired splenic function and tuftsin deficiency in patients with intestinal failure on long term intravenous nutrition." Gut, 1998;43(6):759-62. PMID: 9824601.
- [clinical-trial] Kaur J, et al. "Enzyme immunoassay of phagocytosis stimulating tetrapeptide "tuftsin" in normal and leprosy sera." Int J Lepr Other Mycobact Dis, 1991;59(4):576-81. PMID: 1802940.
- [clinical-trial] Zhang Y, et al. "[Serum tuftsin concentration as an indicator of postoperative splenic function after spleen-preserving surgery]." Zhonghua Wai Ke Za Zhi, 1996;34(8):479-81. PMID: 9594193.
- [clinical-trial] Naim JO, et al. "The identification of serum tuftsin by reverse-phase high-performance liquid chromatography and mass spectrometry." Anal Biochem, 1987;164(1):221-6. PMID: 3674369.
- [pubmed] Nishioka K, et al. "Studies of human granulocyte phagocytosis stimulation by tuftsin." J Surg Res, 1994;56(1):94-101. PMID: 8277776.
- [pubmed] Spirer Z, et al. "Tuftsin stimulates IL-1 production by human mononuclear cells, human spleen cells and mouse spleen cells in vitro." J Clin Lab Immunol, 1989;28(1):27-31. PMID: 2786082.
- [pubmed] Iyer RR, et al. "Modulation of human lepromatous monocyte-macrophage functions in vitro by tuftsin." Int J Immunopharmacol, 1990;12(8):847-58. PMID: 2292463.
- [pubmed] Nagaoka I, et al. "Inactivation of phagocytosis-stimulating activity of tuftsin by polymorphonuclear neutrophils. A possible role of leucine aminopeptidase as an ecto-enzyme." Biochim Biophys Acta, 1981;675(1):85-93. PMID: 6894864.
- [pubmed] von Wronski MA, et al. "Tuftsin binds neuropilin-1 through a sequence similar to that encoded by exon 8 of vascular endothelial growth factor." J Biol Chem, 2006;281(9):5702-10. PMID: 16371354.
- [pubmed] Nissen JC, et al. "Tuftsin signals through its receptor neuropilin-1 via the transforming growth factor beta pathway." J Neurochem, 2013;127(3):394-402. PMID: 24033337.
- [pubmed] Huang J, et al. "Tuftsin: A Natural Molecule Against SARS-CoV-2 Infection." Front Mol Biosci, 2022;9:859162. PMID: 35402510.
- [pubmed] Chu DZ, et al. "Effects of tuftsin on postsplenectomy sepsis." Surgery, 1985;97(6):701-6. PMID: 4002117.
- [pubmed] Gao YL, et al. "Tuftsin prevents the negative immunoregulation of neuropilin-1highCD4+CD25+Regulatory T cells and improves survival rate in septic mice." Oncotarget, 2016;7(49):81791-81805. PMID: 27835904.
- [pubmed] Nissen JC, et al. "Tuftsin-driven experimental autoimmune encephalomyelitis recovery requires neuropilin-1." Glia, 2016;64(6):923-36. PMID: 26880314.
- [pubmed] Thompson KK, et al. "Tuftsin Combines With Remyelinating Therapy and Improves Outcomes in Models of CNS Demyelinating Disease." Front Immunol, 2018;9:2784. PMID: 30555470.
- [pubmed] Bao Z, et al. "Promotion of microglial phagocytosis by tuftsin stimulates remyelination in experimental autoimmune encephalomyelitis." Mol Med Rep, 2019;20(6):5190-5196. PMID: 31702807.
- [pubmed] Wen E, et al. "Tuftsin ameliorates splenic inflammatory injury by promoting neuropilin-1 in severe acute pancreatitis." Biochem Pharmacol, 2022;199:115030. PMID: 35381211.
- [pubmed] Khan MA. "Targeted Drug Delivery Using Tuftsin-bearing Liposomes: Implications in the Treatment of Infectious Diseases and Tumors." Curr Drug Targets, 2021;22(7):770-778. PMID: 33243117.
- [pubmed] Segal Y, et al. "Tuftsin phosphorylcholine-a novel compound harnessing helminths to fight autoimmunity." Immunol Res, 2018;66(6):637-641. PMID: 30554380.
- [pubmed] Catane R, et al. "Toxicology and antitumor activity of tuftsin." Ann N Y Acad Sci, 1983;419:251-60. PMID: 6370073.
- [pubmed] Warner E, et al. "Combined immunotherapy and chemotherapy with tuftsin plus cyclophosphamide in the treatment of non-small-cell carcinoma of the lung." Chemioterapia, 1987;6(2 Suppl):706-8. PMID: 2855624.
Sources & Citations
Every study on this page was read from its PubMed record on October 29, 2026. Status comes from Drugs@FDA (openFDA), the EMA medicines list and ClinicalTrials.gov, searched October 28, 2026. Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.