The compound has been fully approved by the FDA for human use — meaning it passed Phase III clinical trials and was reviewed by the agency.Approval is indication-specific: an FDA-approved drug for condition X has not been evaluated by the FDA for conditions Y or Z. Prescribing an approved drug off-label is legal in the US when a physician judges it appropriate, but off-label use does not carry the same evidence weight as on-label use. Category 1 on this site means there is at least one human indication with formal regulatory approval.