Thymosin alpha-1: where it stands with the FDA, and what it costs
Approved in some other countries (as Zadaxin), not in the US.
Go to clinicLowest per monthThymosin alpha-1 injection
Biotech Lifestyle · from $199/mo
Where Thymosin alpha-1 stands today
No FDA-approved drug contains thymosin alpha-1 (thymalfasin is approved in other countries, not the US; Drugs@FDA has no entry). FDA had it in 503A Category 2 from September 2023 until September 2024 (nomination withdrawn). On December 4, 2024 the advisory committee voted 4-17 against listing either form. It is not on the 503A bulks list, is in no 503A category, and is not in HHS's October 2026 interim policy; for outsourcing facilities it is in 503B Category 3 (outside the interim policy).
For pharmacies compounding one patient's prescription (section 503A)
Not in any 503A category and not on the 503A bulks list. Removed from Category 2 in September 2024 (nomination withdrawn); the advisory committee voted 4-17 against listing it (Dec 4, 2024); no final rule. Not in HHS's Oct 2026 interim policy.
“Bulk drug substances nominated but withdrawn ... Thymosin-alpha 1 (Ta1) Compounded drugs containing thymosin-alpha-1 (Ta1) may pose significant risk for immunogenicity for certain routes of administration and may have complexities with regard to peptide-related impurities and API characterization.”
““Thymosin alpha-1 (Ta1)” has been removed from Category 2 because the nomination was withdrawn by the nominator.”
FDA interim 503A bulks policy: a substance outside Category 1 gets no interim enforcement discretion
“Drug products compounded using a bulk drug substance for which each of the above circumstances are not present are not within the scope of the policy described in this guidance.”
For outsourcing facilities (section 503B)
503B Category 3 (Bulk Drug Substances Nominated Without Adequate Support): outside FDA's 503B interim policy. Not on the 503B bulks list.
“503B Category 3: Bulk Drug Substances Nominated Without Adequate Support ... Thymosin alpha-1”
“The substances are not eligible for the policy that applies to substances in category 1.”
The FDA's compounding advisory committee
4 December 2024: Should thymosin alpha-1 (free base) be placed on the 503A bulks list? Should thymosin alpha-1 acetate?. Vote: Free base: Yes 4, No 17. Acetate: Yes 4, No 17.. Committee advised against listing; FDA has published no rule since
“VOTE: FDA is proposing that Thymosin alpha-1 (free base) NOT be included on the 503A Bulks List. Should Thymosin alpha-1 (free base) be placed on the list? Vote Result: Yes: 4 No: 17 Abstain: 0”
Our reading
There is no current route to lawful 503A or 503B compounding of thymosin alpha-1.
Every source above was checked again on 14 November 2026.
What 17 clinics charge
- Biotech LifestyleThymosin alpha-1 injectionfrom $199/mo
- Bodybuilding Health+Thymosin alpha-1 injection (5mg/ml)$220/mo
- FormBlendsThymosin alpha-1 injection (25mg)$224.10/mo
- PeRxThymosin alpha-1 injection$229for 30 days
- NuBloomThymosin alpha-1 injection$216.99for 28 days
What Thymosin alpha-1 is
- What it is
- Immune-modulating peptide
- How it works
- A 28-amino-acid peptide from the thymus that acts on immune cells.
- How it is given
- Subcutaneous injection
- Also called
- thymalfasin, Ta1, Zadaxin
About Thymosin alpha-1
Is Thymosin alpha-1 FDA-approved?
No. No FDA-approved drug contains Thymosin alpha-1. What clinics sell is compounded by a pharmacy for a prescription, and the FDA does not review compounded products before they are sold.
Is Thymosin alpha-1 legal in the US?
Whether a pharmacy may compound it for your prescription is what decides it. No FDA-approved drug contains thymosin alpha-1 (thymalfasin is approved in other countries, not the US; Drugs@FDA has no entry). FDA had it in 503A Category 2 from September 2023 until September 2024 (nomination withdrawn). On December 4, 2024 the advisory committee voted 4-17 against listing either form. It is not on the 503A bulks list, is in no 503A category, and is not in HHS's October 2026 interim policy; for outsourcing facilities it is in 503B Category 3 (outside the interim policy).
How much does Thymosin alpha-1 cost?
17 clinics publish a price. The lowest that compares per month is from $199/mo at Biotech Lifestyle, and the middle of 11 clinics' lowest monthly prices is about $239. What a month buys differs by clinic, so each price lists what it includes. every Thymosin alpha-1 price
What forms does Thymosin alpha-1 come in?
Clinics sell it as injection (17 prices), other (1 price).