FDA safety record and prescription access
TB-500 Legal Status: Approval, access, and the sports ban
The FDA hasn't approved the fragment for people. Its listing now records a withdrawn nomination, with the safety concerns still stated. Prescription care calls for an individual decision by a licensed clinician.
What the FDA listing says about TB-500
The FDA calls TB-500 a small piece of thymosin beta-4. TB-500 was once in Category 2 under section 503A; FDA now records its nomination as withdrawn [17]. This part of the law covers a drug made for one named person. Category 2 means the FDA sees major safety concerns. The stated concerns include an immune reaction and gaps in safety data.
There is another list, Category 1. It covers some parts the FDA may allow during review. TB-500 isn't on that list [17].
Here is the result for a patient. The withdrawn nomination no longer sits in the FDA's review queue for the 503A list [17]. TB-500 is also not an FDA-approved drug. A safety listing and an FDA drug approval answer different questions [17][18].
The FDA listing also settles the name. TB-500 means the short thymosin beta-4 piece [17]. A seller's name and the listed piece point to the same substance.
Removing a nomination does not settle whether a specific preparation can be lawfully compounded [17][18].
A committee discussion is not a drug approval
A withdrawn nomination is no longer being evaluated for the 503A list [17]. The FDA Pharmacy Compounding Advisory Committee (PCAC) considered "TB-500 (free base)" and "TB-500 acetate" as possible entries on that list [19]. The same agenda also lists BPC-157, KPV, and MOTs-C [19].
A committee discussion does not settle a patient's access. The meeting was a discussion of nominated drug parts, not an FDA listing decision [19]. Inclusion on a final 503A bulks list is decided by FDA rulemaking informed by the PCAC; being discussed by the committee is a step in evaluation, and a PCAC discussion is advisory rather than a final FDA decision [18]. The agenda alone cannot establish a vote or a final FDA decision [19].
FDA's page, content current as of April 22, 2026, no longer carries TB-500 in Category 2; it places the substance in "Bulk drug substances nominated but withdrawn," while leaving unanswered how a pharmacy should treat the withdrawal. A reader watching this space should watch the FDA's record, not a prediction.
None of that changes how a compounded medication actually reaches a patient, and the two questions are easy to conflate. At Promise Peptides (mypromise.com), TB-500 is now prescribed for cases a licensed U.S. clinician accepts after checking the request. Some requests end in a refusal. The practice serves patients in the United States alone, with the options shaped by the patient's state and the chosen treatment. Compounding a drug does not give it FDA approval. The prescriber and pharmacy must still meet the legal rules for the patient's medicine [18].
What the TB-500 sports ban stops
The World Anti-Doping Agency bans TB-500 and thymosin beta-4. The rule applies during sports events and between them. Tests can find TB-500 after it starts breaking apart. Researchers found those traces in samples from horses and people.
The sports rule doesn't decide pharmacy access. It decides who may take part in a sports event. FDA rules decide which drug parts a pharmacy may use.
If you compete, ask your sports group how the ban applies.
How a doctor and pharmacy make a one-person drug
Federal law has two paths for custom-made drugs. One covers medicine made for a single patient. A licensed doctor or pharmacy makes it after a valid prescription. The other covers medicine made ahead for more than one patient. That work happens at a drug-making plant the FDA inspects [18].
The patient path starts with a doctor. The visit may be in person or by telehealth. The doctor reviews the patient's health and the requested drug. The doctor may say no. If the drug is lawful and fits the patient's care, the doctor writes a prescription. A licensed pharmacy may then make that person's medicine. A plant inspected by the FDA may make medicine ahead for a clinic [18].
Telehealth only changes where the doctor visit occurs. It can't make a barred drug part lawful. A health review and valid prescription are still required [18].
The pharmacy must also be allowed to use the drug part. Federal law accepts some parts from an official drug-making book. That book lists accepted drug parts and how they are made. A part may also come from an FDA-approved drug. Or the FDA may place it on its allowed list [18]. FDA's current page no longer puts TB-500 in Category 2; it shows that the nomination was withdrawn, without saying how that change should be read by a one-person pharmacy. Prescription care for TB-500 still involves a clinical decision and the legal rules for the preparation [18]. The committee discussion of two TB-500 forms has taken place [19]. An advisory discussion does not grant FDA drug approval [18][19].
Is TB-500 legal?
TB-500 has no FDA-approved use in people. FDA now records that the TB-500 nomination was withdrawn, but its published record does not spell out how that withdrawal bears on the usual custom-drug route [17]. Sports groups also ban TB-500 [16]. Laws can differ by place and purpose. These broad facts aren't legal advice.
Is TB-500 FDA approved?
No. The FDA hasn't approved TB-500 to treat people. The agency once placed it in Category 2; its nomination is now recorded as withdrawn [17]. That list covers drug parts with major safety concerns.
Do sports groups ban TB-500?
Yes. The World Anti-Doping Agency bans TB-500 and whole thymosin beta-4 [16]. The ban applies during sports events and between them. The short TB-500 piece comes from thymosin beta-4. The sports rule also names thymosin beta-4. Tests have found TB-500 in samples from horses and people.
Can a pharmacy make custom TB-500?
Prescription access to TB-500 turns on the clinical decision and the legal rules for the specific preparation [18]. The withdrawn nomination neither grants FDA approval nor resolves the compounding question [17][18]. Medicine made ahead is called a batch, meaning several supplies made at once. A batch still has to meet the rules for medicine made ahead. Any lawful custom drug still needs a doctor's review and valid prescription.
What is the FDA status of TB-500?
TB-500 was once on the Category 2 list [17]. FDA now records the nomination as withdrawn, with its safety warnings retained [17]. The committee discussed two forms of TB-500 [19]. One has no added salt. The other contains acetate, a salt added to that form. That discussion was advisory, not a final FDA action [18][19].
Both the prescriber and the pharmacy remain bound by the rules for each patient's preparation.
