What the research
actually shows.

Licensed by at least one major regulator for a specific indication, on the strength of completed phase 3 trials. Approval is for that indication in that population — it is not a general endorsement of the compound.

Large randomised trials in humans are complete or under way, but the compound is not licensed. Efficacy and common adverse effects are reasonably well characterised; long-term safety may not be.

Tested in humans for efficacy at a modest scale. Enough to show a signal and characterise short-term tolerability, not enough to establish safety or durability. Most compounds that reach this stage still fail.

Studied in small numbers of humans, usually for safety and pharmacokinetics rather than whether it works. A phase 1 result says almost nothing about effectiveness.

Evidence comes from rodents or other animal models, with no published controlled human trials. Most compounds that look promising in animals do not replicate in people — the attrition rate from animal model to approved drug is well over 90%.

Evidence comes from cell culture or biochemical assays. This can establish that a compound does something to cells in a dish. It establishes nothing about what it does in a living body.

Taken into human trials and did not outperform placebo on its primary endpoint, or development was discontinued. This is stronger evidence than "untested" — it is evidence of absence, not absence of evidence.