PE-22-28 is a peptide derived from spadin, and it works on an unusual target: it blocks a potassium channel called TREK-1 that appears to be involved in mood regulation. In animal models it produces antidepressant-like effects quickly, within days rather than the weeks conventional antidepressants require, which is why it attracts interest. That rapid-onset finding is real and it is entirely in animals. There is no completed human trial, no registered study, and no corporate development programme. Fast-acting antidepressant mechanisms are a serious area of research, but a mechanism that works in a mouse behavioural test is at the very beginning of a long road that this compound has not started walking.