DSIP

Isolated by Swiss researchers in the 1970s from the blood of sleeping rabbits. No gene, precursor protein or receptor for it has ever been identified, and it never became a registered drug.

Unknown in humans. In rabbits, cats and rats it increased deep (delta-wave) sleep, though some labs could not reproduce this. Its sleep effect was blocked by naloxone in rats, suggesting an indirect opioid-system link, and NMDA and glucocorticoid links have been proposed.

Small IV studies in the 1980s and 1990s studied it in insomnia, narcolepsy, and opioid and alcohol withdrawal. Some uncontrolled reports described better sleep or easier withdrawal, but the better-controlled sleep studies found no difference from placebo. Rodent studies report lower body temperature, blunted stress responses and anticonvulsant effects. Only IV formulations have been studied in people, and no modern randomized trial exists.

No reliable side-effect rates exist. Reports include altered sleep 13–22 hours after administration and rebound anxiety and insomnia after withdrawal treatment. FDA flags immunogenicity risk and poorly characterized impurities, and found no safety data for routes other than IV.

Not approved anywhere. In July 2026 FDA's Pharmacy Compounding Advisory Committee voted 6–7–1 against adding it (as emideltide) to the 503A bulks list, the only one of seven peptides reviewed that week to receive an unfavorable vote; it is not compoundable. Not named by WADA but likely prohibited under S0.