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TB-500 Side Effects: Incidence Rates Across Trials

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14 linked public sourcesEditorial, sourcing, and corrections policy

HealthRX.com

No TB-500 trial reports side-effect incidence rates

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Key numbers

  • 0.1%Concentration of the full-length protein used in eye-drop trials for dry eyeSource: pubmed.ncbi.nlm.nih.gov, as cited Nov 8, 2026
  • 72 adultsAdults with moderate to severe dry eye enrolled in a full-length protein eye-drop trialSource: pubmed.ncbi.nlm.nih.gov, as cited Nov 8, 2026
  • 28 daysLength of the placebo-controlled full-length protein eye-drop trialSource: pubmed.ncbi.nlm.nih.gov, as cited Nov 8, 2026
  • 9 patientsPatients with severe dry eye in a separate drop trial of the full-length protein, not the fragmentSource: pubmed.ncbi.nlm.nih.gov, as cited Nov 8, 2026

At a glance

  • Human trials of TB-500 / None found in FDA's July 2026 review [1]
  • Incidence rates / No TB-500 trial provides the exposed people and event counts needed to calculate them [1]
  • FDA adverse-event database / No TB-500 reports through March 26, 2025, and no published case reports [1]
  • Reported harm involving a TB-500 product / One case, from a combined BPC-157 plus TB-500 vial; cause not attributable [2]
  • Blended-product complaints / Two, through FDA's food and supplement system, with no safety assessment [1]
  • Toxicity studies / No nonclinical toxicity studies of TB-500 found [1]
  • Main stated concern / Immunogenicity from injected peptide, possibly amplified by aggregation and impurities [1][3]
  • Regulatory status / Not FDA-approved; on no compounding bulks list [1][4]

Does any TB-500 trial provide an incidence rate?

No. FDA's review searched PubMed, Embase, ClinicalTrials.gov and other sources and found no article in which TB-500 was given to a human; none of the three papers the nominator cited involved TB-500 in humans [1]. FDA also said it has not identified any human exposure data on drug products containing the fragment [3].

An incidence rate needs two counts, people exposed and events observed, and neither comes from a TB-500 clinical trial. The only exposures FDA describes are a single case report and two complaints involving a blended product, covered below.

What has been reported with a TB-500 product

FDA's review of BPC-157 describes a 40-year-old woman who injected a 'research purposes only' product containing 5 mg BPC-157 and 5 mg TB-500 subcutaneously twice daily. Within a week she developed widespread skin hyperpigmentation and darkening of the gums, and the reaction returned when she retried the product two weeks later. Because the vial held two peptides, FDA said it could not tell whether either one caused the reaction [2].

FDA's food and supplement complaint system also logged two cases about a blended TB-500 and BPC-157 product between January 1, 2004 and March 10, 2025, and those did not receive a safety assessment [1].

What people on Reddit report

Personal accounts of side effects people attributed to a TB peptide, taken alone or stacked with a second peptide, with some readers doubting the cause.

Knotty_Vegetables · PeptidePathways

I'm going to assume that he's allergic to something, but who knows what and it's probably not the peptides.

Doubts the peptides were the cause and suggests an unrelated allergy, pointing out that the timeline in the original account does not add up.

Read the source discussion

Desperate_Fox_3402 · bpc_157

Felt a lot of constipation felt like my libido dropped jjst felt super sick

Describes constipation, a drop in libido and feeling very sick after starting a two-peptide combination.

Read the source discussion

External-Cable2889 · bpc_157

I spent the first day after my first dose sleepy and more relaxed than I'd been in many years. That never happened again.

Reports one day of drowsiness and relaxation after the first dose of a two-peptide combination, which did not recur.

Read the source discussion

Questions worth asking

Choose the questions you want to keep

What the full-length thymosin beta-4 trials found

TB-500 is a synthetic, N-acetylated 7-amino-acid fragment of thymosin beta-4, covering residues 17 to 23 of the 43-amino-acid protein [1]. Trials of the full-length protein test a different molecule, so their event rates do not transfer to TB-500.

In a phase 1 study, 54 healthy volunteers were assigned to single-dose groups receiving recombinant human thymosin beta-4 (NL005) or placebo at 0.05, 0.25, 0.5, 2, 5, 12.5 or 25 microgram/kg, and 30 volunteers were enrolled in a multiple-dose trial with 0.5, 2 or 5 microgram/kg given once daily for 10 days. Adverse events were mild to moderate, with no dose-limiting toxicity and no serious adverse events, and there was no obvious accumulation [5].

Eye-drop trials of 0.1% thymosin beta-4 enrolled 72 adults with moderate to severe dry eye, drops versus placebo for 28 days, with no adverse events reported [6]; a separate trial in 9 patients with severe dry eye described the drops as safe and well tolerated [7].

Regulatory status and safety information

TB-500 is not an FDA-approved drug. FDA found no USP or National Formulary monograph for it, no FDA-approved drug containing it, and no approved product in Canada, Australia, the UK, Belgium, Ireland, France, Norway, Germany, Spain or Italy, or authorized by the European Medicines Agency [1]. It appears in none of the three categories on FDA's list for state-licensed pharmacies and physicians, or on FDA's list for outsourcing facilities [4][8][9].

FDA's stated safety concern for injectable TB-500 is immunogenicity, an immune reaction to the peptide, potentially amplified by peptide aggregation and peptide-related impurities; no study of TB-500 immunogenicity or aggregation was found [1]. FDA also reported no nonclinical toxicity studies of TB-500 [1]. Compounded drugs are not FDA-approved, and FDA does not review their safety, effectiveness or quality before marketing [10].

Check what you know

Think you have it? Try 4 quick questions and see what the article says.

1. According to the article, did FDA's review find any human study in which TB-500 was given to people?

Question 1 of 4

Score: 0 right, 0 of 4 answered

Dr Quinn Stillson on why peptide tissue repair carries a cancer concern

Dr Quinn Stillson argues that the larger thymosin beta peptide is the better choice over its shorter fragment, because the fragment keeps only one of the mechanisms that make the larger peptide useful. In his view, the main real risk is that these peptides could promote cancer through increased blood vessel growth, increased cell migration, and reduced controlled cell death. He says that anyone with current or past cancer, or a strong family history of cancer, should avoid them altogether, and that others should be properly screened before any use. He notes these peptides are not FDA approved, so he does not recommend anyone use them now. He sees topical use for superficial wounds and certain eye conditions as the best supported option.

Who is speaking?

Dr Quinn Stillson. MD and strength coach, as described in the video description Background

Episode notes and full video

Frequently asked questions

Do the thymosin beta-4 trials say anything about TB-500?
They tested a different molecule. In a phase 1 study, 54 healthy volunteers were assigned to single-dose groups receiving recombinant full-length thymosin beta-4 or placebo, and 30 were enrolled in a multiple-dose trial; adverse events were mild to moderate with no serious adverse events [5]. TB-500 is a 7-amino-acid fragment of that protein [1].
What did FDA find in its adverse-event database for TB-500?
FDA searched its adverse-event database through March 26, 2025 and retrieved no TB-500 reports, and found no published case reports [1]. Two complaints about a blended TB-500 and BPC-157 product came through FDA's food and supplement system, with no safety assessment [1].
What happened to the woman who used a TB-500 product?
A 40-year-old woman injected a 'research purposes only' product holding 5 mg BPC-157 and 5 mg TB-500 twice daily and developed widespread skin hyperpigmentation and gum darkening within a week; the reaction returned when she retried the product two weeks later. Because the vial held two peptides, FDA said it could not tell whether either caused it [2].
Can TB-500 cause cancer?
FDA's review reported no nonclinical toxicity studies of TB-500 [1]. A 2003 laboratory study found that colon cancer cells engineered to overexpress full-length thymosin beta-4 grew faster and migrated more [11], but that is cell-culture work with the parent protein, not evidence about injected TB-500 in a person.
What is the main safety concern with injectable TB-500?
FDA's stated concern is immunogenicity, an immune reaction to the injected peptide, potentially amplified by aggregation and peptide-related impurities [1]. FDA's safety-risk page makes the same point about injectable peptides containing the fragment [3].

References

Show all 14 referencesHide references
  1. U.S. Food and Drug Administration.
  2. U.S. Food and Drug Administration.
  3. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks | FDA.
  4. U.S. Food and Drug Administration.
  5. Wang X, Liu L, Qi L, Lei C, Li P, Wang Y, et al. A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin β4 in healthy Chinese volunteers. J Cell Mol Med. 2021;25(17):8222-8228.
  6. Sosne G, Ousler GW. Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, Phase II clinical trial conducted using the controlled adverse environment (CAE™) model. Clin Ophthalmol. 2015;9:877-84.
  7. Sosne G, Dunn SP, Kim C. Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. Cornea. 2015;34(5):491-6.
  8. U.S. Food and Drug Administration.
  9. Bulk Drug Substances Used in Compounding of the FD&C Act | FDA.
  10. Official web page.
  11. Wang WS, Chen PM, Hsiao HL, Ju SY, Su Y. Overexpression of the thymosin beta-4 gene is associated with malignant progression of SW480 colon cancer cells. Oncogene. 2003;22(21):3297-306.
  12. Reddit participants. I was hospitalised after running TB-500 (r/PeptidePathways). Accessed 2026-11-11.
  13. Reddit participants. Side Effects - what are your experiences? (r/bpc_157). Accessed 2026-11-11.
  14. Quinn Stillson MD. TB-500 & TB-4: Everything You Need to Know - Benefits, Risks, Dosing, & vs BPC-157. Accessed 2026-11-11.
Evidence overview for TB-500 Side Effects: Incidence Rates Across Trials