Background
Thymosin Alpha-1 (Tα1) is a 28-amino-acid peptide originally isolated from thymosin fraction 5 of bovine thymus. It modulates T-cell maturation, increases CD4+ helper T-cell counts, and promotes TH1 (cellular immunity) over TH2 (humoral immunity) responses.
Tα1 (Zadaxin) is FDA-approved as an orphan drug for DiGeorge syndrome (thymic aplasia) and is widely used off-label and approved in numerous other countries for viral hepatitis and immune deficiency.
Methods
Prospective cohort study (single-arm with historical controls). Immunocompromised patients with chronic HBV, HCV, or other viral-associated immunosuppression. Thymosin Alpha-1 1.6 mg SC twice weekly for 6 months.
Primary outcomes: CD4+ count, CD4:CD8 ratio, serum IL-2 (TH1 marker), IL-4 (TH2 marker).
Key Findings
| Parameter | Baseline | 6 Months | Change |
|---|---|---|---|
| CD4+ count (cells/μL) | 312 ± 84 | 498 ± 91 | +60% |
| CD4:CD8 ratio | 0.68 | 1.12 | Normalized |
| IL-2 (TH1) | Low | Significantly increased | — |
| IL-4 (TH2) | Elevated | Decreased | — |
| NK cell activity | Reduced | Restored to reference | — |
Clinical Significance
These findings support the use of Thymosin Alpha-1 as an immunomodulatory agent that can shift immune balance toward cellular immunity — the arm needed for clearance of intracellular pathogens and cancer surveillance.
Tα1 has a well-established safety record and is approved in over 37 countries. The CD4 restoration data parallels what has been observed in larger trials for hepatitis B and C, where Tα1 improves response rates to antiviral therapy.
Limitations
- No randomized control group (historical comparator)
- Heterogeneous immune deficiency causes in the cohort
- Relatively small sample for outcome conclusions
- Mechanism specificity unclear — CD4 increase may reflect non-specific immune activation