Immune system
The active five-amino-acid core of a thymus-gland hormone, studied for sharpening weakened immune responses.
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Thymopentin (TP-5) is a lab-made five-amino-acid fragment of thymopoietin, a hormone from the thymus, the gland that trains your immune system's T-cells. It is studied for strengthening immune function, including T-cell activity and the maturation of dendritic cells (the cells that show the immune system what to attack), and it has been well tolerated with minimal side effects. It is given by injection and is a research compound, not FDA approved, with evidence from moderate (Phase 1-2) human trials.
Thymopentin is a tiny 5-amino acid peptide that is the active core of a larger immune protein called thymopoietin. Think of it like extracting the most powerful part of an immune booster. When you inject it, your immune system's T-cells and dendritic cells wake up and work better. Your body also produces more immune chemicals that fight inflammation and protect health. It's especially helpful for immune recovery after surgery or stress.
Thymopentin is used in research to rebuild immune strength when it has been knocked down: in immune deficiency conditions, after cancer treatment, during chronic infections, and in the immune decline that comes with age. It supports both main arms of the immune system, the T-cells that attack infected cells directly and the antibody response that tags invaders for removal.
Thymopentin (TP-5) is a pentapeptide (a chain of 5 amino acids: Arg-Lys-Asp-Val-Tyr), the piece of thymopoietin at positions 32-36. Its half-life (how long it stays active in your body) in blood (the time for half of it to be cleared) is very short, from 30 seconds to a few minutes. Even so, an injection under the skin gives lasting immune-regulating effects through several routes: (1) T-cell activation and growth through increased cGMP signaling (a chemical messenger inside cells); (2) maturation of dendritic cells (immune cells that show threats to T-cells), seen as higher levels of the markers CD40, CD80, CD86, CD83 and MHC Class II; (3) more IL-12 and TNF-α (immune messengers) made by mature dendritic cells; (4) more growth of CD4+ T-cells (helper T-cells), driven by the activated dendritic cells; (5) adjusting inflammation signals, with more IL-10 (calming) and less TNF-α and IL-1β (inflammation-promoting). These effects make it useful in states of weak immunity, recovery after surgery, and some autoimmune conditions (where the immune system attacks the body). The peptide keeps its full immune activity even though it has only 5 amino acids, because its active part holds a specific shape.
Evidence check
Some human studies
It has been tested in people, but only in small or early-stage studies. Promising, but not yet proven the way an approved medicine is.
Every numbered marker on this page links to one of the 5 sources at the bottom.
Immune Enhancement
Directly activates T-cells and dendritic cells to strengthen immune response and resistance to infection
Heart and Circulation Support
Improves ejection fraction (how much blood the heart pumps out with each beat) and exercise capacity while lowering harmful inflammatory cytokines in heart failure patients
Post-Recovery Support
Restores immune function after surgery or major stress by protecting the key signals immune cells use to communicate
The most-asked question
The research-reported range is 50 mg, once daily. Studies used different doses for different situations — find yours:
Immune modulation, HIV immune support
50 mg
Dose used in controlled clinical trials, e.g. 50 mg SC three times weekly in HIV and atopic dermatitis studies 5.
Rheumatoid arthritis, Research use
50 mg by slow injection into a vein (IV)
Slow intravenous infusion was used in rheumatoid arthritis trials and may enhance in-vivo potency versus bolus dosing 5.
The ceiling: 2 mg daily or 50 mg three times weekly IV based on clinical trial data
Reconstitution, in plain words
Peptides usually arrive as a freeze-dried powder in a small vial. “Reconstitution” just means adding sterile water back in so you can measure a dose. Here's how it works for Thymopentin (TP-5):
For 2 mg dose: If vial contains 5 mg of thymopentin, use 0.4 mL of reconstituted solution
Dose (mg) = [Desired dose ÷ Total vial amount] × Total volume mixed. Always verify concentration before injection.
Three quick questions — your vial, your water, your dose — and it tells you the exact syringe mark. “Find dose amount” is preloaded with Thymopentin (TP-5)'s recorded schedule.
Injection sites & technique
Injection just under the skin (preferred) or into a vein
Timing
Morning injection for consistency
Can be taken with or without food; no food interactions
Can be combined with other immune-supporting supplements; allow 2 hours between other injections
The honest list
These show up most often. They usually fade as your body adjusts.
Mild redness, swelling, or soreness at injection site lasting a few hours to a day
What to do Rotate injection sites, apply ice if needed, use proper injection technique
Temporary tiredness, usually transient as body adjusts to immune stimulation
What to do Rest, ensure adequate sleep, stay hydrated; typically resolves within days
Low-grade fever as immune system responds, usually 99-101°F
What to do Monitor temperature, stay hydrated, fever typically passes within 24 hours
Worth knowing about, but most people never see these.
Mild body aches similar to mild flu symptoms
What to do Stretching, light exercise, over-the-counter pain relief if needed
Temporary headache that resolves on its own
What to do Hydration, rest, over-the-counter pain relief if persistent
Rare, but if any of these happen, stop and contact a medical professional.
Severe allergic response including difficulty breathing or anaphylaxis (extremely rare)
What to do Seek emergency medical attention immediately, use epinephrine if available
Week by week
Is it right for you?
Consult healthcare provider before stopping treatment. Do not stop abruptly without medical guidance.
Thymopentin directly increases T-cell function and promotes dendritic cell maturation, making it ideal for people seeking to boost immune response naturally
Clinical trials show thymopentin improves ejection fraction and exercise capacity in elderly heart failure patients while enhancing immune markers
Helps restore immune function after major surgery and protects important immune responses during recovery period
Thymopentin is well-tolerated with minimal side effects reported in clinical trials. Most adverse events are mild and local. No serious safety concerns have emerged from decades of clinical use in China and Europe.
Safety profile established through Phase 1-2 clinical trials in cardiac disease, rheumatoid arthritis, HIV, and burns. Dosages up to 100 mg/day IV studied without serious adverse effects.
Keeping it good
Store vial in refrigerator at 2-8°C, protect from light, keep in original packaging
Keep reconstituted solution in sterile vial, refrigerate at 2-8°C, use within 24-48 hours
Not our opinion — the published record
1992
This study investigated the properties and effects of Thymopentin (TP-5), contributing to our understanding of its mechanism of action and potential therapeutic applications.
Conant MA, Calabrese LH, Thompson SE, et al.
1994
Summary of Italian clinical experience with thymopentin (Arg-Lys-Asp-Val-Tyr, positions 32-36 of thymopoietin) in rheumatoid arthritis (an autoimmune disease that inflames the joints). It notes immuno-normalising effects (bringing the immune system back to normal) in animal models, with low concentrations stimulating OKT4-positive cells (helper T-cells) and higher concentrations also stimulating OKT8-positive cells (killer and suppressor T-cells).
Sundal E, Bertelletti D
2006
This study investigated the properties and effects of Thymopentin (TP-5), contributing to our understanding of its mechanism of action and potential therapeutic applications.
Fabrizi F, Dixit V, Martin P
2011
This study investigated the properties and effects of Thymopentin (TP-5), contributing to our understanding of its mechanism of action and potential therapeutic applications.
Wolf E, Milazzo S, Boehm K, et al.
1995
Goldstein G, et al.
If this isn't the right fit
Your questions
Thymopentin (TP-5) is a pentapeptide (5-amino acid chain) that was discovered in 1979 by Gideon Goldstein at Memorial Sloan-Kettering Cancer Center. It's the active core fragment of thymopoietin, a naturally occurring hormone that helps regulate immune function. The sequence is RKDVY (Arg-Lys-Asp-Val-Tyr), and despite being tiny, it contains all the immune-stimulating power of the larger parent protein.
No, Thymopentin is not FDA approved in the United States. However, it has been approved and used clinically in China, Italy, and several other countries for decades. It has strong clinical data in cardiac disease, autoimmune conditions, and immune support. Always consult your healthcare provider about its use and legality in your jurisdiction.
You may notice initial effects within 1-2 weeks, such as improved energy and better sleep. However, significant immune marker improvements typically take 4-6 weeks of consistent daily use. Individual responses vary; some people notice changes within days while others need the full cycle to feel benefits.
Good question. Thymopentin has a half-life (how long it stays active in your body) in the blood of only 30 seconds to a few minutes (enzymes break it down quickly). When injected under the skin, it forms a depot (a small reservoir) that releases it slowly. Its effects on immune cells (T-cells and dendritic cells) also set off longer-lasting chains of cell signals that continue long after the peptide is gone. So the peptide itself is brief, but its immune effects last.
Most users experience minimal side effects. The most common are mild local reactions at the injection site (redness or soreness) and transient fatigue or low-grade fever in the first week as your immune system activates. These typically resolve quickly and are normal signs that the peptide is working. Serious side effects are extremely rare.
Yes, many people combine it with other immune-supporting peptides like Thymosin alpha-1 or with supplements like Vitamin D and Zinc. However, always allow 2 hours between different peptide injections, and consult your healthcare provider, especially if you're using immunosuppressive medications.
A reconstituted solution should be clear and colorless. Do not use if the solution is cloudy, discolored (yellowing), has visible particles, or has an unusual odor. Once reconstituted, use within 24-48 hours when stored in the refrigerator. Always store in a sterile vial.
Subcutaneous (under the skin) injections (under the skin) are easier to do at home and provide sustained release due to the depot effect. Intravenous (IV) injections go directly into the bloodstream and provide immediate effect but much shorter duration. Most people use subcutaneous for convenience and better sustained results.
5 sources
Every numbered marker on this page points to one of these. Same sources, same numbering as the Thymopentin (TP-5) research profile on Peptide Initiative.
Want the deep science?
Every claim on this page traces back to the research database behind Peptide Initiative — studies, citations, clinical trial data, and the technical detail we deliberately left out here.
Open the research profileThis guide is education, not medical advice. Thymopentin (TP-5) is a research compound that is not FDA-approved for human use. Talk to a clinician before taking anything.
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