Thymostimulin
A partly purified peptide extract of calf thymus, given by injection in trials for immune defects, infections and cancer from the 1980s to 2010
Thymostimulin, also called TP-1, is a peptide fraction extracted from calf thymus rather than a single molecule. Through the 1980s and 1990s it was injected in small trials as an immune booster: in recurrent infections, chronic hepatitis B, HIV, eczema, surgery and alongside chemotherapy. Results were mixed, many trials were small and unblinded, and its largest trial, a 2010 phase III study in advanced liver cancer, found no survival benefit. It is not approved in the US or the EU.
Used in human trials: 75 mg, Five times a week, Subcutaneous (Study: advanced liver cancer, phase III (135 patients) and phase II...) Details ↓
Recommended Dosing
Used in human trials
No manufacturer dose exists for this use: these are amounts given in published trials, not recommendations.
Work out syringe units → · New to syringes? · All dosing data ↓
What is it?
Thymostimulin is a peptide extract of calf thymus, the gland in which T cells mature. It is one of several thymus preparations tested as a way to restore weak cellular immunity. It is a mixture: a 1991 case report describes it as a group of polypeptides with a combined molecular weight of about 12,000 daltons, and no single active molecule has been named. Trials called it thymostimulin, TS or TP-1, and many gave it by intramuscular injection at 1 mg per kilogram.
The early trials were in people whose immunity was thought to be weak. In a double-blind crossover trial of 20 patients with chronic purulent sinusitis and measurable defects in cell-mediated immunity, two months of injections improved symptoms and nasal cultures and restored the movement of blood monocytes, with no change on placebo. A randomised trial in 78 people with long-standing COPD found fewer flare-ups and hospital stays over a year, though lung function and immune tests did not change. In 37 melanoma patients after surgery, more of those given thymostimulin were free of disease at a year. Smaller studies reported fewer recurrences of herpes keratitis, a better antibody response to tetanus vaccine in older people, and better outcomes in hepatitis B-related liver disease.
Other trials found nothing. In 50 people with advanced HIV-related illness, six months of thymostimulin did not slow progression to AIDS or change CD4 counts. In 30 people withdrawing from treatment for autoimmune hepatitis, relapse was just as common with it. In severe atopic eczema, a gain at three months faded by the later follow-up.
The most persistent use was alongside cancer treatment, where it was meant to reduce infections and blood count damage from chemotherapy. Randomised trials in breast cancer, small cell lung cancer and lymphoma reported fewer infections, less marrow toxicity or higher remission rates, and a colorectal cancer trial in 211 patients found more tumour responses. A large trial in 859 colorectal surgery patients found fewer wound and abdominal infections when thymostimulin was added to an antibiotic. A 2011 Cochrane review pooled thymus extracts, thymostimulin among them, given with chemotherapy or radiotherapy and found no effect on overall survival, disease-free survival or tumour response.
The final test came in liver cancer. After two phase II studies suggested benefit, a placebo-controlled, double-blind phase III trial randomised 135 people with advanced hepatocellular carcinoma to 75 mg under the skin five times a week. Survival at 12 months was 28% with thymostimulin and 32% with placebo, and median survival was about five months in both groups. The authors concluded there was no reason to use it as a single agent.
Thymostimulin was not reported to be toxic in animal studies at many times the human dose, and most trials reported few side effects. It is still a foreign protein: a 1991 case report describes a severe anaphylactic reaction to the first injection in a person sensitised to bovine proteins. It has no US or EU approval, and any product sold under the name today is outside a regulated supply.
Mechanism of Action
Thymostimulin was given to strengthen cell-mediated immunity; the studies measured changes in T cells, monocytes and natural killer cells, but because it is a mixture no single receptor or molecule is credited.
T-cell numbers
In Hodgkin's disease survivors with low T cells, five weeks of daily injections raised the proportions and numbers of all T-cell fractions measured.
Monocyte movement
In chronic sinusitis it restored the chemotactic polarisation of blood monocytes and lowered a suppressive serum factor.
Natural killer and Kupffer cells
In the lab it raised natural killer activity of blood cells from breast cancer patients and made human liver Kupffer cells release TNF-alpha and kill a liver cancer line.
Published Research
These are studies of thymostimulin (TP-1) itself, read from their PubMed abstracts: randomised and controlled trials in immune defects, infections, liver disease and cancer, a phase II and a phase III liver cancer trial, a Cochrane review, laboratory work on human cells, animal toxicology and two older reviews. Other thymus preparations, such as thymomodulin, thymalin and thymosin fraction 5, have their own entries or are not carded here.
Phase III in advanced liver cancer: no benefit
In a double-blind, placebo-controlled phase III trial, 135 people with locally advanced or metastatic hepatocellular carcinoma received 75 mg under the skin five times a week or placebo. Twelve-month survival was 28% against 32%, median survival 5.0 against 5.2 months and time to progression did not differ. Fewer treated patients developed worsening ascites and kidney failure.
Phase II in advanced liver cancer
Forty-four patients unsuitable for or refractory to standard therapy received 75 mg subcutaneously five times a week for a median of eight months. Median survival was 11.5 months; of 39 evaluable, two had complete and five partial responses and 24 stable disease, and response predicted survival along with tumour stage and cirrhosis.
Chronic sinusitis with immune defects
In a double-blind crossover trial, 20 patients with chronic purulent rhinosinusitis and defects in cell-mediated immunity had 1 mg/kg intramuscularly daily for 14 days and then twice weekly for six weeks. Most felt better, mucopus disappeared in 13 and positive nasal cultures fell from 14 of 16 to 5 of 15, alongside better monocyte polarisation; placebo had no effect.
No effect on HIV progression
In a multicentre, double-blind trial, 50 evaluable people with advanced HIV disease short of AIDS had injections twice weekly for six months after two weeks of daily doses. Progression to AIDS at a year occurred in 9 on thymostimulin and 11 on placebo, CD4 counts did not change, and no toxicity was seen.
Atopic eczema: a gain that did not last
Twenty-nine people with severe atopic eczema were randomised to ten weeks of thymostimulin or placebo. Clinical scores were better with thymostimulin at three months, but the difference disappeared in later follow-up and was not matched by better well-being or immune measures.
Fewer COPD flare-ups
Seventy-eight people with long-standing COPD were randomised to standard care with or without intramuscular thymostimulin, 1 mg/kg daily for a week and then weekly for six months. Over a year the treated group had fewer exacerbations and admissions, though lung function and immune tests did not change.
Lymphoma: higher remission rate with chemotherapy
In 134 evaluable patients with aggressive non-Hodgkin's lymphoma, adding intramuscular thymostimulin (1 mg/kg daily for a week within each cycle) to chemotherapy raised complete remission from 42.4% to 59.1%. Four-year survival, 64.5% against 43.0%, was not significantly different, and toxicity and infections were similar.
Colorectal cancer: more tumour responses
In a multicentre trial of 211 evaluable patients with metastatic colorectal cancer on high-dose folinic acid and fluorouracil, adding thymostimulin raised objective responses from 18% to 30% and reduced mucositis and diarrhoea, without a change in blood toxicity or fever.
Small cell lung cancer chemotherapy
Twenty-six patients were randomised to chemotherapy with or without thymostimulin, 1 mg/kg intramuscularly on days 7 to 14 of each cycle. Myelosuppression, fever and infections were less severe with it, allowing higher doses at shorter intervals, and complete responses and survival were better.
Fewer infections during breast cancer chemotherapy
Fifty-one women on adjuvant CMF chemotherapy were randomised to thymostimulin or none. Infections occurred in 37% of treated women and 77% of controls, and marrow toxicity was also less common with thymostimulin.
T cells in Hodgkin's disease survivors
Nineteen people in remission from Hodgkin's disease were randomised to 50 mg intramuscularly daily or every other day for 35 days, or no treatment, then twice weekly for 22 weeks. Daily dosing raised all T-cell fractions; alternate-day dosing raised only some, and maintenance held the gains.
Hepatitis B chronic active hepatitis, two-year follow-up
In a controlled trial in HBsAg-positive chronic active hepatitis, treated patients improved more than controls in clinical, biochemical and liver biopsy measures over two years, had more viral seroconversion and spent less time in hospital. The authors noted the small numbers.
Autoimmune hepatitis: no protection from relapse
Thirty people with treated, inactive autoimmune chronic active hepatitis stopped steroids and azathioprine, half with thymostimulin at 1 mg/kg daily for seven days and then weekly. Relapse occurred in 11 of 13 treated and 15 of 17 untreated patients, and the suppressor-cell defect was the same in both.
Melanoma after surgery
Thirty-seven people with cutaneous melanoma were randomised after surgery to thymostimulin or no further treatment. More treated patients were disease-free at one year and survival was better at 15 months; no toxic or allergic effects were seen.
Infections after surgery in anergic patients
In a randomised trial in 42 surgical patients whose skin tests showed weak cellular immunity, infections after surgery fell from 28.6% without thymostimulin to 4.8% with it.
Colorectal surgery with an antibiotic
In 859 patients having colorectal surgery, adding 70 mg intramuscular thymostimulin daily for seven days, starting 48 hours before surgery, to a single dose of cefotetan reduced abdominal abscesses and surgical-site infections, and respiratory infections were more than twice as common without it.
Tetanus vaccine response in older people
Among 13 older people vaccinated against tetanus, an antigen new to them, four of six given thymostimulin and two of seven controls produced antibodies after the booster, and only treated subjects showed significant rises over baseline.
Anaphylaxis at the first injection
A patient had a severe anaphylactic reaction to a first injection of thymostimulin. Skin testing, specific IgE and histamine release confirmed allergy to it, and the patient also reacted to bovine serum albumin, fetal calf serum and cow dander; the authors warn of allergy to animal-derived products.
Kupffer cells turned against liver cancer cells
In liver cells isolated from human biopsies, thymostimulin up to 100 µg/mL was not toxic to two liver cancer lines by itself. Kupffer cells treated with it released TNF-alpha and interleukins, and their supernatant killed one of the two cancer lines.
More natural killer activity in breast cancer patients' cells
Blood cells from 15 breast cancer patients and 10 controls were incubated with thymostimulin. Killing of NK-sensitive target cells rose with dose and time, significantly at 1,000 ng/mL in patients who had finished chemotherapy, and thymostimulin worked together with interleukin-2.
Toxicology in rats and monkeys
Six weeks of repeated intramuscular dosing at 10 or 100 mg/kg, and subcutaneous dosing at 1,000 mg/kg, caused no substance-related effects in monkeys. Rats given the highest subcutaneous dose had inflammation at the injection sites.
Antibodies to thymostimulin across species
Rabbit antiserum raised against thymostimulin was used to stain mammalian and human thymus and to probe species specificity, and was injected into chick embryos to study the bird thymus and bursa.
A 1994 clinical review
A Hungarian review summarises thymostimulin's reported roles in marrow failure, lymphocyte regeneration, viral infections including herpes, hepatitis and HIV, and immune deficiency in cancer.
Dosing Data
Thymostimulin is not approved in the US or the EU. These are the amounts given in published trials, as their abstracts state them; the schedules varied widely and none established a treatment dose.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or 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 Thymostimulin is sold in. A vial's own label is a seller's claim, not a source.
Mixing a vial: a worked example
An arithmetic example, not a recommendation: a 10 mg vial mixed with 3 mL of bacteriostatic water holds 3,333.3 mcg per mL, so 75 mg, the “Study: advanced liver cancer, phase III (135 patients) and phase II (44)” row would be 2250.0 units, more than a 1 mL U-100 syringe holds. Put your own vial's numbers into the reconstitution calculator.
Source: dose: Used in human trials, PMID 20735834; PMID 18366627 (Dosing Data below); vial and water: the calculator's default example, not a vial size we have a source for.
Storage before and after mixing
Unknown: no label or published stability study on file says how to store Thymostimulin, 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 Thymostimulin stays intact once mixed.
How it is taken
As it was given in human studies: Subcutaneous (Five times a week; Study: advanced liver cancer, phase III (135 patients) and phase II (44)); Intramuscular (Daily for 14 days, then twice a week; Study: chronic sinusitis with immune defects, 20 patients (crossover)).
For injection technique, sites and needle disposal, see the mixing guide.
Source: Used in human trials: the route and frequency of each row in Dosing Data below.
What to expect, and when
How long it stays in the body: not established by a measurement cited on this entry.
How long the doses were given: Study: advanced liver cancer, phase III (135 patients) and phase II (44): Until progression; median 8.2 months in phase II; Study: chronic sinusitis with immune defects, 20 patients (crossover): 8 weeks in all; Study: COPD, 78 patients: 6 months.
When effects appear: unknown; no source on this page gives a time to effect for Thymostimulin. Results reported in the studies are under Published Research.
Source: Used in human trials, the duration of each row in Dosing Data below.
Side effects, and when to stop or get help
From the Side Effects section: Severe anaphylaxis at a first injection in a person allergic to bovine proteins (PMID 2058819); No toxicity seen in a six-month HIV trial (PMID 1975746) or in a melanoma trial (PMID 6542371); Injection-site inflammation in rats at a very high subcutaneous dose (PMID 3927927); Quality of life was similar to placebo in the phase III liver cancer trial (PMID 20735834). Full list and cautions ↓
When to stop or get help: unknown; no label or trial on file sets rules for stopping Thymostimulin. Treat a severe or unexpected reaction as a reason to stop and see a doctor.
Source: the Side Effects section below (“From the trials and reports above; most reported few side effects”).
Interactions
Unknown: a PubMed search for human interaction studies of Thymostimulin (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 Thymostimulin 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. Trust & Verification explains what independent testing can and cannot show.
Legal status
US: Not FDA Approved (Not FDA- or EMA-approved: Drugs@FDA and the EMA medicines list hold no record (searched October 28, 2026)). 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
From the trials and reports above; most reported few side effects.
Contraindications & Cautions
No current product label was found. These cautions follow from the evidence.
Legal Status
Thymostimulin is not approved as a medicine in the US or the EU in the sources read.
Frequently Asked Questions
?What is thymostimulin?
A partly purified mixture of peptides extracted from calf thymus, also called TP-1. It is not a single molecule, and no one component has been identified as the active one.
?Does thymostimulin work?
The evidence is mixed. Some small trials reported fewer infections or better immune measures, others found no effect, and its largest trial, in 135 people with advanced liver cancer, found no survival benefit over placebo.
?Is it the same as thymosin alpha-1 or thymalin?
No. Thymosin alpha-1 is a single synthetic peptide, and thymalin and thymomodulin are other thymus extracts made differently. Each has its own entry.
?How was it given in trials?
By injection, usually into muscle at 1 mg per kilogram, or later as fixed doses of 50 to 75 mg. Schedules ranged from daily to twice weekly.
?Is thymostimulin safe?
Trials reported few side effects, but it is a cow protein and a severe allergic reaction at the first injection has been reported.
?Is thymostimulin approved anywhere?
Drugs@FDA and the EMA list hold no record for it. The trials used a commercial preparation in the 1980s and 1990s, but no current approval was found in the sources read.
References
- [clinical-trial] Dollinger MM, et al. "Thymostimulin versus placebo for palliative treatment of locally advanced or metastasised hepatocellular carcinoma: a phase III clinical trial." BMC Cancer, 2010;10:457. PMID: 20735834.
- [clinical-trial] Dollinger MM, et al. "Thymostimulin in advanced hepatocellular carcinoma: a phase II trial." BMC Cancer, 2008;8:72. PMID: 18366627.
- [review] Wolf E, et al. "Thymic peptides for treatment of cancer patients." Cochrane Database Syst Rev, 2011;2011(2):CD003993. PMID: 21328265.
- [clinical-trial] Tas M, et al. "Beneficial effects of the thymic hormone preparation thymostimulin in patients with defects in cell-mediated immunity and chronic purulent rhinosinusitis. A double-blind cross-over trial on improvements in monocyte polarization and clinical effects." Clin Exp Immunol, 1990;80(3):304-13. PMID: 2197046.
- [clinical-trial] Beall G, et al. "A double-blind, placebo-controlled trial of thymostimulin in symptomatic HIV-infected patients." AIDS, 1990;4(7):679-81. PMID: 1975746.
- [clinical-trial] Harper JI, et al. "A double-blind placebo-controlled study of thymostimulin (TP-1) for the treatment of atopic eczema." Br J Dermatol, 1991;125(4):368-72. PMID: 1835403.
- [clinical-trial] Banos V, et al. "Effectiveness of immunomodulating treatment (thymostimulin) in chronic obstructive pulmonary disease." Respiration, 1997;64(3):220-3. PMID: 9154674.
- [clinical-trial] Federico M, et al. "Effects of thymostimulin with combination chemotherapy in patients with aggressive non-Hodgkin's lymphoma. A report from the Italian Lymphoma Study Group (GISL)." Am J Clin Oncol, 1995;18(1):8-14. PMID: 7847265.
- [clinical-trial] Mustacchi G, et al. "High-dose folinic acid (FA) and fluorouracil (FU) plus or minus thymostimulin (TS) for treatment of metastatic colorectal cancer: results of a randomized multicenter clinical trial." Anticancer Res, 1994;14(2B):617-9. PMID: 8010718.
- [clinical-trial] Macchiarini P, et al. "Effects of thymostimulin on chemotherapy-induced toxicity and long-term survival in small cell lung cancer patients." Anticancer Res, 1989;9(1):193-6. PMID: 2539772.
- [clinical-trial] Iaffaioli RV, et al. "Effect of thymic extract 'thymostimulin' on the incidence of infections and myelotoxicity during adjuvant chemotherapy for breast cancer." Thymus, 1988;12(2):69-75. PMID: 3150630.
- [clinical-trial] Liberati AM, et al. "A randomized trial to evaluate the immunorestorative properties of thymostimulin in patients with Hodgkin's disease in complete remission." Cancer Immunol Immunother, 1988;26(1):87-93. PMID: 3125973.
- [clinical-trial] Romeo F, et al. "Thymostimulin in the treatment of hepatitis B surface antigen-positive chronic active hepatitis. Controlled clinical trial--two years follow-up." Arzneimittelforschung, 1987;37(4):450-6. PMID: 3300664.
- [clinical-trial] Hegarty JE, et al. "Controlled trial of a thymic hormone extract (Thymostimulin) in 'autoimmune' chronic active hepatitis." Gut, 1984;25(3):279-83. PMID: 6230296.
- [clinical-trial] Azizi E, et al. "Postsurgical adjuvant treatment of malignant melanoma patients by the thymic factor thymostimulin." Arzneimittelforschung, 1984;34(9):1043-7. PMID: 6542371.
- [clinical-trial] Farina EC, et al. "Thymostimulin prophylaxis of postoperative infections in anergic patients." Can J Surg, 1986;29(6):445-6. PMID: 3536050.
- [clinical-trial] Periti P, et al. "Antimicrobial chemoimmunoprophylaxis in colorectal surgery with cefotetan and thymostimulin: prospective, controlled multicenter study. Italian Study Group on Antimicrobial Prophylaxis in Abdominal Surgery." J Chemother, 1993;5(1):37-42. PMID: 8459263.
- [clinical-trial] Pivetti-Pezzi P, et al. "Thymic factor therapy for herpetic keratitis." Ann Ophthalmol, 1985;17(6):327-31. PMID: 3893286.
- [clinical-trial] Fagiolo U, et al. "Quantitative and qualitative analysis of anti-tetanus toxoid antibody response in the elderly. Humoral immune response enhancement by thymostimulin." Vaccine, 1993;11(13):1336-40. PMID: 8296487.
- [pubmed] Hymos A, et al. "ThymicPeptides Reverse Immune Exhaustion in Patients with Reactivated Human Alphaherpesvirus1 Infections." Int J Mol Sci, 2020;21(7). PMID: 32235584.
- [pubmed] Marcos C, et al. "Severe anaphylactic reaction to thymostimulin." Allergy, 1991;46(3):235-7. PMID: 2058819.
- [pubmed] Balch G, et al. "Activation of human Kupffer cells by thymostimulin (TP-1) to produce cytotoxicity against human hepatocellular cancer." Ann Surg Oncol, 1997;4(2):149-55. PMID: 9084852.
- [pubmed] Meneses G, et al. "Thymostimulin increases natural cytotoxic activity in patients with breast cancer." Int J Immunopharmacol, 1997;19(4):187-93. PMID: 9373769.
- [pubmed] Leuschner F, et al. "[Toxicologic studies with thymostimulin]." Arzneimittelforschung, 1985;35(5):836-8. PMID: 3927927.
- [pubmed] Aita M. "Thymostimulin: an immunohistochemical and immunological evaluation." Arch Ital Anat Embriol, 1989;94(3):211-6. PMID: 2534524.
- [review] Lengyel G, et al. "[Thymostimulin in clinical practice]." Orv Hetil, 1994;135(52):2871-5. PMID: 7845658.
Sources & Citations
Every study on this page was read from its PubMed record on October 28 or 29, 2026. Regulatory status comes from Drugs@FDA and the EMA medicines list. Searches recorded on October 28, 2026: PubMed thymostimulin[tiab] 203 records; ClinicalTrials.gov, Drugs@FDA and the EMA list 0. 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.