Cerebrolysin vs Thymosin alpha-1
It is an injection promoted for stroke recovery, memory and brain injury. Trials point both ways, and the biggest review found no fewer deaths and more serious side effects. A peptide sold by wellness clinics as an immune booster. Trials show a modest effect in hepatitis B, and a large sepsis trial found none.
Both sit at grade B: some human evidence. Neither is FDA approved.
Evidence
BSome human evidence
BSome human evidence
Human studies cited
Animal or cell studies cited
Why the grade
For the stroke-recovery use there are randomized placebo-controlled trials, but they point in different directions. A Cochrane review pooled six RCTs with 1,501 participants and found no reduction in deaths and more non-fatal serious adverse events; the CARS trial (208 patients) and the two CAPTAIN trials in brain injury (185 patients pooled) reported modest functional benefits. Several trials were manufacturer-supported and had high risk of bias, so the grade stops at B.
Thymosin alpha-1 has several randomized trials in chronic hepatitis B (98 and 316 patients) and a meta-analysis of five trials with 353 patients showing delayed viral suppression, which is the approved use abroad. The 1,106-patient TESTS phase 3 trial in sepsis found no mortality benefit. The general immune-boosting use it is sold for in the US has no controlled trials, so the compound grades B on its hepatitis B evidence and D on the wellness claims.
FDA
Not approved
Cerebrolysin is not approved by the FDA for any use. It is a licensed medicine in more than 50 other countries, mainly in Eastern Europe, Russia and Asia, for stroke, dementia and brain injury.
Not approved
Thymosin alpha-1 is not approved by the FDA for any use. It is approved as thymalfasin (Zadaxin) in more than 35 other countries for hepatitis B and C and as an immune adjuvant. In the United States it was taken off the FDA's Category 2 compounding list after its nominators withdrew it, and in December 2024 the Pharmacy Compounding Advisory Committee voted 17 to 4 against adding it to the 503A bulks list; it is sold online as a research chemical.
Sold for
Cerebrolysin is promoted in nootropic and longevity circles as a brain-repair injection that speeds stroke recovery, sharpens cognition and treats dementia.
Thymosin alpha-1 is sold by wellness clinics as an immune-system booster for infections, cancer support, autoimmune disease and long COVID.
Studies say
Randomized trials exist, which earns a B, but the largest independent synthesis found no effect on death or dependence after stroke and a rise in serious adverse events, while smaller manufacturer-backed trials found small functional gains.
Randomized trials support a modest, delayed antiviral effect in chronic hepatitis B, a large trial found no benefit in sepsis, and there are no trials of the immune-boosting uses marketed in the US, which is why it grades B.
Class
Neuropeptide preparation (porcine brain)
Immunomodulatory peptide
Route
Intravenous
Injection