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FDA Category 2 · restricted from compounding

This compound is on the FDA’s interim Section 503A Category 2 bulks list and cannot be legally compounded by US pharmacies. An HHS announcement in February 2026 signaled intent to restore several peptides to Category 1, but no Federal Register action has been published. Check the FDA PCAC schedule for updates.

Read the full regulatory context
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Thymosin Alpha-1

Tα1 · Zadaxin

Thymic peptide that enhances T-cell maturation and innate immune function; approved in several countries for hepatitis and as an adjuvant.

§ 01   Overview

Overview

Thymic peptide that enhances T-cell maturation and innate immune function; approved in several countries for hepatitis and as an adjuvant.

Approved in 35+ countries. Multiple Phase II/III trials for HCV and as an adjuvant.

§ 02   Mechanism

Mechanism of action

Thymosin Alpha-1 activates TLR-2 and TLR-9 on immune cells, supports dendritic cell maturation, and enhances Th1 responses. It also upregulates IL-2 receptor expression on T cells.

  • 01Immune modulation in chronic infection
  • 02Adjuvant for vaccines and oncology in some countries
  • 03Reduced severity of certain viral illnesses in trials

§ 03   Dosing

Dosing protocol

Standard Protocol

Vial
1.6 mg or 5 mg
BAC Water
2 ml BAC water
Dose Range
1.6 – 6 mg weekly (split)
Starting Dose
1.6 mg SubQ 2x/week
Route
SubQ
Timing
AM
Frequency
2x weekly
Cycle
8–12 weeks

§ 04   Evidence

Evidence & research

Clinical

Approved in 35+ countries. Multiple Phase II/III trials for HCV and as an adjuvant.

FDA Status

Not FDA-approved. Previously compounded; restricted under recent FDA guidance.

§ 06   News

In the news

7 articles from the last 12 months · updates hourly

§ 07   Sourcing

Sourcing & supply

Regulatory status

Restricted from compounding

Placed on the FDA's 503A Category 2 list and cannot be lawfully compounded in the US. No brand pharmacy alternative exists. US buyers encounter only research-use-only (RUO) channels, which the FDA's Intended Use Doctrine treats as unapproved drug sales.

Telehealth (Rx) · 1

Telehealth

Defy Medical

Rx required

Broadest peptide formulary in legitimate US telehealth. 13-year history, concierge cash-pay, no known lawsuits.

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International · 2

International

Cosmic Nootropic

The most credible Russian / Khavinson source for US buyers. Sources authentic bioregulators through 'Peptides Company' (ex-NPCRIZ).

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International

Rupharma

12+ year Russian pharmacy reseller. Reviews.io 4.84/5 (81+). Has a genuine US warehouse for common peptides.

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Research-use-only · 1

Research-use-only

Core Peptides

Broad catalog, widest payment range. Mid-credibility: Knoji 2.5/5 and one scam-impersonation report.

Third-Party Testing1 flag on record
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Listings are informational, not endorsement. Verify credentials and flags against FDA and PCAB databases before purchasing. Full directory & how to verify →

§ 09   Safety

Safety & side effects

Side effects

  • 01Injection site irritation
  • 02Mild flu-like symptoms

Contraindications

None specified.

§ 10   Questions

Thymosin Alpha-1 FAQ

What is Thymosin Alpha-1?
Thymic peptide that enhances T-cell maturation and innate immune function; approved in several countries for hepatitis and as an adjuvant. Thymosin Alpha-1 activates TLR-2 and TLR-9 on immune cells, supports dendritic cell maturation, and enhances Th1 responses. It also upregulates IL-2 receptor expression on T cells.
What is Thymosin Alpha-1 used for?
Reported uses include immune modulation in chronic infection, adjuvant for vaccines and oncology in some countries, and reduced severity of certain viral illnesses in trials. Evidence strength is rated Clinical — see the evidence section for detail.
How is Thymosin Alpha-1 dosed?
Commonly referenced dosing is 1.6 – 6 mg weekly (split), typically 2x weekly, administered SubQ. This is educational reference only; consult a licensed clinician before use.
How do you reconstitute Thymosin Alpha-1?
For Thymosin Alpha-1, vials commonly come in 1.6 mg or 5 mg and a common reconstitution is 2 ml BAC water. Use the reconstitution calculator to convert any vial size and water volume into exact insulin-syringe units.
What are the side effects of Thymosin Alpha-1?
Commonly reported side effects include injection site irritation and mild flu-like symptoms. This list is not exhaustive.
Is Thymosin Alpha-1 legal?
Placed on the FDA's 503A Category 2 list and cannot be lawfully compounded in the US. No brand pharmacy alternative exists. US buyers encounter only research-use-only (RUO) channels, which the FDA's Intended Use Doctrine treats as unapproved drug sales. FDA status: Not FDA-approved. Previously compounded; restricted under recent FDA guidance..

This site is for educational and research purposes only. It does not constitute medical advice. Always consult a qualified healthcare provider before using any peptide or supplement.