Studied in registered human trials with published pharmacokinetic data, but not approved. Dosing outside a trial protocol has no established safety margin.
Terminal elimination half-life reported as 'less than 3 hours' (exact value not stated) after a single 900 mcg/m2 SC dose in healthy volunteers; Tmax 1-2 h; Cmax 30-80 mcg/L (PubMed 10027483). The commonly quoted flat '2 hours' figure could not be tied to a primary source, the primary study gives only '<3 h'.
1.6 mg per injection was the dose used in randomized/phase III chronic hepatitis B trials (PubMed 10607256), twice weekly; the PK study used 900 mcg/m2 (body-surface-area scaled). Both are clinical-trial / non-US-label doses, not an FDA-approved dosing.
Multiple randomized controlled trials in chronic hepatitis B/C plus a dedicated human PK study; robust for the hepatitis indication, weaker for the many off-label 'wellness' uses.
No FDA boxed warning (not FDA-approved). Generally well tolerated in hepatitis trials (local injection-site reactions most common); better tolerated than interferon-alpha in head-to-head studies. Long-term safety of off-label immune 'boosting' use is not established.
- Pharmacokinetics of thymosin alpha1 after subcutaneous injection of three different formulations in healthy volunteers · pubmed
- Thymosin alpha1 treatment of chronic hepatitis B: phase III multicentre randomized double-blind placebo-controlled study · pubmed
- PubChem CID 16130571 (Thymalfasin) molecular weight · other