TB4 Frag, thymosin beta-4 fragment 1–4, goralatide (INN), seraspenide, AcSDKP, N-acetyl-Ser-Asp-Lys-Pro
The four-amino-acid front tip of thymosin beta-4 (residues 1–4), which an enzyme cuts free in the body and which circulates in everyone’s blood. It holds blood-forming stem cells in a resting state, and in rats it reduced heart and kidney scarring.
None of these uses is approved. Uses tested in people come first, then claims that rest on animal studies or user reports.
Trial: tested in people, with the result. Animal: cell or animal studies only. No study: nothing published supports it.
Every compound’s uses, by body system: evidence map, and by condition: conditions A to Z.
Category 2 is FDA’s list of bulk substances that may present significant safety risks in compounding. The 503A bulks list adds substances that pharmacies may compound with. Advisory committee votes are advice; FDA makes the final decision. Sport status follows the WADA Prohibited List in force since January 1, 2026; athletes should confirm with their anti-doping organization. Checked October 5, 2026. Status outside the US checked October 7, 2026 against EMA, MHRA, Health Canada and TGA records. By country: EU, UK, Canada, Australia. Status of every compound.
Ac-SDKP is cut from the front end of thymosin beta-4 by two enzymes, ending with prolyl oligopeptidase, and circulates in everyone’s blood. It holds blood-forming stem cells in a resting state, which is why it was tested as a shield for bone marrow during chemotherapy. In rats it also reduced heart and kidney scarring and lowered two scarring signals, TGF-β and CTGF. The body clears it with ACE, the enzyme that ACE-inhibitor blood pressure drugs block, which was shown in people.
AnimalMainly from cell and animal studies; not shown in people.
No receptor has been identified, and whether swallowed capsules deliver intact peptide is untested. The two chemotherapy trials disagreed on whether it protects blood counts in people, and nothing is known about the repair uses it is sold for.
Cappelaere 1995
12.5 or 62.5 mcg per kg a day for 4 days alongside each chemotherapy cycle, in 84 adults with head, neck or esophageal cancer. Blood counts were no better than on placebo.
Ezan 1994
A single 62 mcg per kg dose (128 nmol per kg) by 12-hour IV drip, or as one injection under the skin or into muscle, in 6 healthy volunteers: a drug-level study, not a treatment.
Capsules sold as TB4 Frag hold 250 mcg and are labeled for twice-daily use. No study has tested the capsules, and injection figures quoted online have nothing behind them.
No set cycle, shown over 26 weeks
The ways TB4 fragment (Ac-SDKP) is most often run, each tagged with where it comes from.
84 adults with head, neck or esophageal cancer, randomized against placebo. No difference in blood count lows; anemia and low lymphocytes were more common on the drug.
6 healthy volunteers. Half-life about 4.5 minutes after the drip; all of a dose under the skin was absorbed, peaking at about 16 minutes.
Sold as a supplement. No study has tested whether it survives digestion or does anything when swallowed.
12.5–62.5 mcg/kg. 12.5 or 62.5 mcg per kg a day for 4 days with chemotherapy in 84 adults (Cappelaere 1995), with no benefit over placebo; a single 62 mcg per kg dose in 6 healthy volunteers (Ezan 1994).
Trials gave it by IV drip or by injection under the skin or into muscle, in hospital. Capsule products are swallowed; injecting research powder has not been studied.
No published guidance. For capsules, skip the missed dose and take the next one as usual; don’t double up.
Blood levels peak about 16 minutes after an injection under the skin, and fall by half every 4.5 minutes after an IV drip ends (Ezan 1994).
TrialIn 84 adults, blood count lows and how long they lasted matched placebo (Cappelaere 1995), although an earlier 53-patient crossover study reported protected blood cells (Carde 1992).
TrialEstablished heart scarring was reversed, along with two scarring signals, TGF-β and CTGF (Peng 2003). No human study has measured scarring.
AnimalNothing is known: no study has tested the capsules for absorption or effect.
CommunityAnemia and low lymphocytes (more frequent than on placebo in the 84-patient trial)
Seen alongside chemotherapy, so what they mean outside cancer care is unclear. A blood count would show them.
Otherwise well tolerated in the 1990s trials
Both trials described tolerability as excellent or without toxicity, over a few days at a time.
Much higher levels with ACE inhibitors and kidney failure
Natural levels run 4–5 times higher on an ACE inhibitor and about 22 times higher with kidney failure plus one. Adding more has never been studied.
Unknown with capsules or longer use
No study has tested the capsules, or any use beyond a few days per chemotherapy cycle.
Hives, face or throat swelling or trouble breathing: emergency care. Unusual tiredness, breathlessness or repeated infections are reasons for a blood count.
The side effects people ask about most, answered one by one. Each answer says where it comes from.
Trial: reported in human studies. Precaution: a concern that follows from how it works or from a related drug, not measured. Not reported: studied in people and not reported. No data: no human safety data. A side effect that hasn’t been reported can still happen, especially with long or high-dose use. Any of these across every compound: the side-effect finder.
No product label covers TB4 fragment (Ac-SDKP), so these come from human studies and from precautions based on how it works. Most important first.
Only interactions stated on a product label or measured in a human study are listed.
Trial: seen in human studies, or a group those studies left out. Precaution: follows from how it works or from a related drug, and hasn’t been tested. This isn’t a complete list: a pharmacist or doctor can check a specific medicine or condition. Every documented interaction, by medicine: drug interactions.
What’s known about pregnancy, breastfeeding, kidney and liver problems, age and surgery. Where nothing has been studied, the row says so.
Trial: from human studies. Precaution: not studied, so the caution follows from how it works or from a related drug. Ages are given as approved or studied; this site never gives doses for children. Across every compound: pregnancy, breastfeeding, kidney disease, liver disease, older adults and surgery.
A different piece of the same protein (residues 17–23), with a different proposed action. Sometimes confused with this one; never tested together.
The whole protein begins with this sequence, and the body releases this piece from it. Never tested together.
3 key published human studies, with how many people took part. Animal studies aren’t listed here.
No significant difference in blood count lows (white cells, granulocytes, platelets, hemoglobin) or in how long they lasted; anemia and low lymphocytes were more frequent on goralatide, and tolerability was described as excellent.
Cappelaere et al., Bull Cancer 1995, PMID 8535033
The authors reported significant protection of circulating blood cells and no toxicity; the paper is in French and its abstract gives no figures.
Carde et al., C R Acad Sci III 1992, PMID 1300237
Half-life about 4.5 minutes after IV; absorption 100% under the skin and 81% into muscle; exposure rose in step with dose, and clearance in patients was about half that in volunteers.
Ezan et al., Drug Metab Dispos 1994, PMID 7895600
No ongoing trial of TB4 fragment (Ac-SDKP) is registered, and none has finished recently without publishing its results. Checked on ClinicalTrials.gov, October 7, 2026. Every compound: trials under way.
About 150 people received it in the 1990s, nearly all with cancer and for a few days per chemotherapy cycle; the two efficacy trials disagreed, and the larger, placebo-controlled one was negative. The anti-scarring and anti-inflammation evidence is rodent work. Capsules, the main form sold under the TB4 Frag name, and injected research powder have never been tested.
The name misleads. Products called TB4 Frag hold this four-amino-acid piece (residues 1–4); TB-500, as usually sold, is a seven-amino-acid piece from further along the chain (residues 17–23); and thymosin beta-4 is the whole 43-amino-acid protein. Powder vials of this piece are sold for injection, but no study has tested that use. The sequence on the label, not the name, says which one is in the package.
Every compound side by side: the half-life chart and the storage chart.
Every compound’s numbers: the identifiers table.
Capsules sold as TB4 Frag hold 250 mcg, and one product describes a modified, amidated variant rather than natural Ac-SDKP (487.5 g/mol, free acid). Not to be confused with TB-500 (seven amino acids) or whole thymosin beta-4.
The four-amino-acid front tip of thymosin beta-4 (residues 1–4), which an enzyme cuts free in the body and which circulates in everyone’s blood. It holds blood-forming stem cells in a resting state, and in rats it reduced heart and kidney scarring.
Ac-SDKP is cut from the front end of thymosin beta-4 by two enzymes, ending with prolyl oligopeptidase, and circulates in everyone’s blood. It holds blood-forming stem cells in a resting state, which is why it was tested as a shield for bone marrow during chemotherapy. In rats it also reduced heart and kidney scarring and lowered two scarring signals, TGF-β and CTGF. The body clears it with ACE, the enzyme that ACE-inhibitor blood pressure drugs block, which was shown in people. No receptor has been identified, and whether swallowed capsules deliver intact peptide is untested. The two chemotherapy trials disagreed on whether it protects blood counts in people, and nothing is known about the repair uses it is sold for.
Not approved as a drug in the US, the EU or anywhere else. As goralatide (seraspenide) it was tested in small European cancer trials in the early 1990s and then dropped. Capsules sold under the TB4 Frag name are marketed as supplements. Never nominated for pharmacy compounding, so it appears on none of FDA’s 503A or 503B bulk substance category lists (503A list updated May 14, 2026). The nomination and July 2026 committee vote concerned TB-500, the 17–23 piece.
From human studies (Cappelaere 1995): 12.5 or 62.5 mcg per kg a day for 4 days alongside each chemotherapy cycle, in 84 adults with head, neck or esophageal cancer. Blood counts were no better than on placebo. Ezan 1994: A single 62 mcg per kg dose (128 nmol per kg) by 12-hour IV drip, or as one injection under the skin or into muscle, in 6 healthy volunteers: a drug-level study, not a treatment. These are the amounts sources reference, not recommendations.
By mouth: capsules sold as supplements under the TB4 Frag name, usually 250 mcg; powder vials for injection are also sold. There’s nothing to mix or measure with a syringe.
No product label covers TB4 fragment (Ac-SDKP), so these come from human studies and from precautions based on how it works. Anyone taking an ACE inhibitor: ACE breaks it down: on these blood pressure drugs its blood levels run 4 to 5 times higher, and about 22 times higher with kidney failure. Adding more has never been studied. People with kidney failure: Levels are higher in kidney failure, much more so with an ACE inhibitor, and clearance in patients was about half that in healthy volunteers. Anyone with anemia or low lymphocytes: Anemia and low lymphocyte counts were more frequent on goralatide than on placebo in the 84-patient chemotherapy trial. The “Who should avoid it” section lists 2 more groups and one interaction.
About 4.5 minutes, measured in human studies. Mean elimination half-life after a 12-hour IV infusion in 6 healthy volunteers. After an injection under the skin, levels peaked at about 16 minutes and the whole dose was absorbed; clearance in cancer patients was about half that in volunteers.
Capsules: as labeled. Powder: freezer (about −20 °C), kept dry. Mixed powder: fridge (2–8 °C), used soon. This is common practice; no product label covers it.
Probably. Not named in the 2026 List, and never approved, so S0 non-approved substances covers it at all times. It may also fall under S2.3, which names “thymosin-β4 and its derivatives e.g. TB-500”. WADA’s 2027 List (in force January 1, 2027) adds “peptides” to S0’s examples.
Yes. The human studies section lists 3 published studies. The largest, from 1995, included 84 people. No significant difference in blood count lows (white cells, granulocytes, platelets, hemoglobin) or in how long they lasted; anemia and low lymphocytes were more frequent on goralatide, and tolerability was described as excellent.
Trial A few days at a time: 4 days per chemotherapy cycle over several cycles, in 84 adults (1995).
Trial Trials gave it by IV drip and by injection under the skin or into muscle; all of a dose under the skin was absorbed. Capsules, the main form sold, have never been tested.
No study No data. No study has looked at Ac-SDKP and alcohol together.
No study No study has combined them. No interaction is known, but none has been looked for.
Trial No label and no overdose data. The highest published dose was about 250 mcg per kg over 48 hours by drip, in patients. Call Poison Help (1-800-222-1222), or emergency services for severe symptoms.
For the protocol details
For how it works, who should avoid it and the limits of the evidence
For uses, the side-effect questions, special situations, trials, identifiers and status outside the US
Doses tagged Community come from public dosing guides and user reports, checked against at least two of them. Those sites aren’t named here because many of them sell peptides or earn commissions on them.