Almost everywhere in the world, thymosin alpha-1 is a normal prescription drug you pick up at a pharmacy. In the one country buying most of it grey-market, it is sold as an "immune booster" research chemical, for things it has never been tested to treat.
The peptide itself is a 28-letter snippet of a protein your own thymus makes. It is a genuine, approved-abroad drug, which is rare for anything sold this way. It is cleared in more than 35 countries, has run through multiple randomized human trials and meta-analyses, and carries a clean safety record going back decades. [proven in humans] [regulatory fact]
Bthe grade is BIt earns B because the human evidence here is broad, drug-like, and unusually deep for anything near this tier. What keeps it off A is two-fold. First, where it was tested rigorously and at scale, the big modern trials of its broader claims came back null: the definitive sepsis trial, three failed hepatitis C Phase 3 trials, a melanoma trial that missed survival, mixed acute-COVID data. Second, the grey market buys it for long COVID, ME-CFS, and "general immune support," indications with essentially zero human treatment evidence. [proven in humans]