Thymosin alpha-1 vs Selank
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. It is sold as a nose spray to calm anxiety and sharpen focus. The only trial, in Russia, had 62 patients and no placebo group, so it proves little.
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
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.
There is one small controlled comparison in 62 patients with generalized anxiety disorder or neurasthenia, published in Russian without a placebo arm, plus a cytokine study in a subset of patients and two animal or in vitro studies on GABA and NMDA receptor binding. One controlled human trial meets the letter of B, but it is tiny, the abstract reports neither randomization nor blinding, and it has never been replicated outside Russia.
FDA
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.
Not approved
Selank is not approved by the FDA for any use and is sold in the United States as a research chemical. It is registered as a prescription anxiolytic in Russia. It is not on the FDA's list of substances pharmacies may compound, and it was not among the peptides the FDA's compounding advisory committee reviewed in July 2026.
Sold for
Thymosin alpha-1 is sold by wellness clinics as an immune-system booster for infections, cancer support, autoimmune disease and long COVID.
Selank is sold as a nasal spray that calms anxiety without the sedation or dependence of benzodiazepines and sharpens focus at the same time.
Studies say
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.
A single 62-patient Russian trial found anxiety relief comparable to a benzodiazepine, and animal work points to GABA and NMDA receptor effects, but there is no placebo-controlled human trial, so the claims rest on thin evidence.
Class
Immunomodulatory peptide
Anxiolytic peptide (Russian)
Route
Injection
Nasal