Unknown does not mean harmless.
A clear answer can admit what is missing. Gaps in the research cannot tell you that TB-500 will be harmless.
The main gap
The effects in people are unknown.
As of September 2026, the FDA review had no human study to establish TB-500’s side effects.
The Food and Drug Administration, or FDA, also found no animal toxicity studies of TB-500.
Toxicity studies look for harm. For TB-500, the missing work includes harm from brief or long use, effects on pregnancy, damage to the instructions inside cells (genes), and cancer.
What FDA is concerned about
The body may react to the injection.
FDA’s September 2026 record warns that the body’s defence system may react to injected TB-500. Clumps or unwanted material in the mixture add to that concern.
Peptides are short chains of small building blocks. Impurities are unwanted material in the mixture.
The body’s defence system can make antibodies, substances that react to what was injected.
FDA says these reactions can range from no clear symptoms to life-threatening illness.
FDA is warning about a possible problem. The review does not tell us how often such a reaction happens with TB-500.
Purity describes how free the tested substance is from other material. A high result does not show that an injection has no germs, harmful material from bacteria (a kind of germ), or clumps.
Do not borrow a checklist from another product.
As of September 2026, no official instructions for prescribing TB-500 have been reviewed by FDA. There is no FDA-reviewed information on how it might affect other medicines taken with it, or on use during pregnancy, breastfeeding or childhood.
It also has no FDA-reviewed monitoring checklist, meaning a plan for checks before and during use.
Safety studies of full thymosin beta-4, a different substance, followed people for short periods. They do not establish TB-500’s safety.
Bring your own health history to a clinician and ask what these unknowns mean for the care discussion.
Urgent help
A severe allergic reaction needs emergency help.
The NIH health page checked in September 2026 describes anaphylaxis as a severe allergic reaction that may begin in seconds or minutes.
NIH stands for National Institutes of Health.
Severe symptoms can include swelling in the face or tongue, difficulty with breathing or swallowing, and becoming unconscious.
For severe anaphylaxis symptoms, that page says to dial 911 or your local emergency number.
This is a general emergency sign, not a list of known TB-500 side effects.
After a product problem
Reports can help, but do not prove a cause.
MedWatch is FDA’s reporting service for medical product problems, and patients can submit a report themselves.
FDA says the product is not proven to be the cause just because someone filed a report. Reports cannot tell us how often a side effect happens.