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Thymopentin (TP-5)

Antioxidants

a.k.a. Timunox

Thymopoietin active fragment (5-mer)

Thymopentin (TP-5) is a synthetic five-amino-acid peptide derived from thymopoietin, a naturally occurring thymic hormone involved in the maturation.

§Dosing at a glance

6 protocols · from the research
What it's forDoseHow oftenHowFor how long
Atopic Dermatitis50 mgWeeklySubcutaneousInjected just under the skin, into the fat layer.12 wks
Rheumatoid Arthritis50 mg—IntravenousInjected directly into a vein.—
Hepatitis B Vaccine Non-Responders (Dialysis Patients)50 mg—SubcutaneousInjected just under the skin, into the fat layer.—
Post-Surgical / Post-Cardiopulmonary Bypass Immunomodulation150 mg—SubcutaneousInjected just under the skin, into the fat layer.—
Chronic Heart Failure2 mg——45 days
HIV / Antiretroviral Adjunct50 mg—SubcutaneousInjected just under the skin, into the fat layer.—

Approximate values pulled from the research — double-check before dosing.

§01Summary

Thymopentin (TP-5) is a synthetic five-amino-acid peptide derived from thymopoietin, a naturally occurring thymic hormone involved in the maturation and regulation of T lymphocytes — the white blood cells that coordinate immune responses. By mimicking thymopoietin's biological activity, TP-5 helps restore and balance cellular immunity, particularly in conditions where T-cell function is impaired or dysregulated.

In clinical research, thymopentin has demonstrated several promising applications. It reduces the clinical severity of atopic dermatitis, with improvements in itching, redness, and overall skin involvement observed in placebo-controlled trials1,10. In patients whose immune systems are suppressed following cardiac surgery or cardiopulmonary bypass, thymopentin — particularly when combined with indomethacin — restores key immune parameters including T-helper cell counts and interleukin-2 production2,3,7. It has also been reported to significantly improve hepatitis B vaccine response rates in dialysis patients who previously failed to respond9. In early studies in people with HIV infection, thymopentin may delay disease progression, with particularly notable effects in higher-risk individuals12. Additional research has explored its potential in rheumatoid arthritis4 and, more recently, in chronic heart failure16. Across most studied populations, thymopentin has been well-tolerated with no serious adverse events reported.

This is the layperson summary. Mechanism, dosing, the evidence base, and the published literature are in the sections below — every claim links to its source.

§02In depth

Thymopentin (TP-5) is a synthetic pentapeptide with the sequence Arg-Lys-Asp-Val-Tyr, corresponding to amino acid residues 32–36 of thymopoietin II, a 49-amino-acid hormone produced by thymic epithelial cells. This minimal active fragment retains the full biological activity of the parent molecule and acts as a thymic hormone mimetic, influencing T-lymphocyte differentiation, activation, and cytokine production.

TP-5 exerts its immunomodulatory effects primarily by enhancing T-helper (TH1) cell function. Mechanistically, it promotes the synthesis and secretion of interleukin-2 (IL-2), a critical autocrine and paracrine cytokine that drives T-lymphocyte proliferation and activation. Clinical evidence demonstrates that thymopentin, particularly in combination with prostaglandin E2 inhibition via indomethacin, restores IL-2 production suppressed by major surgery or cardiopulmonary bypass2,3,11. The combination approach targets two parallel immunosuppressive mechanisms: PGE2-mediated monocyte-driven downregulation (addressed by indomethacin) and intrinsic T-lymphocyte dysfunction (addressed by thymopentin), highlighting that neither agent alone is sufficient for full immune restoration in the perioperative context3,11.

Thymopentin modulates T-lymphocyte subset balance, increasing CD4+ T-helper cells and CD4+/CD8+ ratios while influencing cytotoxic/suppressor T-cell populations9,16. In the atopic dermatitis context, its mechanism appears to involve reduction of histamine-releasing factor (HRF) and polymorphonuclear neutrophil respiratory burst activity rather than direct modulation of IgE synthesis or CD8+CD11b+ suppressor T cells15, suggesting a distinct anti-inflammatory downstream pathway beyond classic IgE-mediated mechanisms. It also increases NK cell activity and IL-10 levels while reducing pro-inflammatory cytokines including TNF-α and IL-1β16.

In the context of acute phase response following cardiopulmonary bypass, thymopentin selectively attenuates post-operative IL-6 synthesis when combined with indomethacin, while having minimal independent effect on IL-1 or TNF counterregulation8. This cytokine selectivity suggests a T-lymphocyte-mediated rather than monocyte-mediated primary mechanism for IL-6 modulation. In cardiac surgery models, thymopentin preserves TH1-mediated immunity — including IL-2 synthesis and delayed-type hypersensitivity — without suppressing intact TH2 responses, indicating selective rather than global immune restoration7. Formal pharmacokinetic data including half-life and bioavailability are not reported in the available clinical literature; the peptide is administered parenterally (subcutaneous or intravenous), consistent with limited oral bioavailability typical of short peptides susceptible to gastrointestinal proteolysis.

§04Evidence & efficacy

Evidence base
295Studies
124Human
69Animal

Thymopentin's most consistently supported indication is the treatment of atopic dermatitis. Multiple independent randomized controlled trials demonstrate that it reduces overall clinical severity scores, pruritus, erythema, and body surface area involvement compared to placebo1,10,14,15. Clinical improvement appears to require continued administration, as treatment discontinuation has been followed by rapid relapse15, and age may modulate response, with younger patients reporting greater benefit in at least one study14.

In the perioperative setting, thymopentin combined with indomethacin restores cell-mediated immune parameters suppressed by cardiac surgery and cardiopulmonary bypass, including CD4+ T-cell counts, IL-2 synthesis, and delayed-type hypersensitivity responses2,3,7,11. These immunological endpoints were consistently preserved across multiple trials from the same research group.

Thymopentin significantly improves hepatitis B vaccine immunization rates in dialysis patients who failed standard vaccination, achieving 86% immunization at both 1-month and 6-month follow-up compared to 36% and 27% respectively in the standard-dose control group9.

In rheumatoid arthritis, thymopentin appears to improve multiple clinical parameters — including joint tenderness, swelling, and pain — with benefits persisting at 4 weeks post-treatment4.

In HIV disease, thymopentin may delay progression to ARC, AIDS, or death when added to antiretroviral therapy, with particularly amplified effects in individuals with high viral load, low CD4 counts, or ZDV resistance mutations12. For chemotherapy-induced febrile leukopenia, thymopentin showed a non-statistically significant trend toward reduction and did not add meaningfully to G-CSF therapy5. In chronic heart failure, thymopentin has been reported to improve cardiac function markers and immune parameters, though this finding comes from a single study with limited methodological transparency16.

§05Safety

Across the body of clinical research reviewed, thymopentin has consistently demonstrated a favorable tolerability profile. No serious adverse events were reported in the randomized controlled trials evaluating thymopentin for atopic dermatitis1,10, rheumatoid arthritis4, hepatitis B vaccination augmentation9, or post-surgical immunomodulation2,3. In a comparative oncology trial, thymopentin was described as excellently tolerated with no notable adverse events, while the comparator agent G-CSF was associated with mild nausea and bone pain in fewer than 9% of treated patients5. No thymopentin-related adverse events were reported in the atopic dermatitis adjunct trial10, and no adverse experiences were noted in the 6-week atopic dermatitis RCT1. Safety data were not explicitly reported in several of the cardiac surgery studies7,8,11 or in the HIV-related trial registrations6,13,18,19,20, representing areas where the reporting record is incomplete rather than signaling identified harm. No drug interactions or contraindications were described in any reviewed study.

§06History

Thymopentin was developed in the 1970s and early 1980s following the discovery of thymopoietin, a thymic hormone identified and characterized by Gideon Goldstein and colleagues. Recognizing that only a short peptide sequence (residues 32–36) was responsible for thymopoietin's immunological activity, researchers synthesized TP-5 as a minimal active pentapeptide — one of the earliest examples of rational peptide drug design based on an endogenous hormone fragment.

Initial clinical investigations in the early 1980s focused on immunodeficiency-associated and inflammatory conditions. Among the earliest RCT evidence, a 1983 study reported improvements in atopic dermatitis clinical scores and T-cell subset modulation with TP-514. Throughout the mid-to-late 1980s and 1990s, research expanded considerably into rheumatoid arthritis4, hepatitis B vaccination augmentation in dialysis patients9, perioperative immunoprotection following cardiac surgery2,3,7,8,11, atopic dermatitis1,10,15, and HIV disease management in the pre-HAART era12. A commercially developed formulation, Timunox, was the subject of multiple registered clinical trials sponsored by the Immunobiology Research Institute6,13,18,19,20.

Despite promising early results, thymopentin did not achieve broad regulatory approval in Western markets, and several registered HIV trials did not produce published results6,13. Research activity in Western literature declined through the late 1990s as combination antiretroviral therapy transformed HIV management. Interest in TP-5 has continued in Chinese clinical research, with studies exploring applications in chronic heart failure16 and hepatocellular carcinoma recurrence prevention17, reflecting an active and evolving evidence base.

§07References