at-121 at-121 at-121 is an experimental analgesic. it was designed to be bifunctional, acting as an agonist at both the μ-opioid receptor and the nociceptin receptor. the interaction with the nociceptin receptor is expected to block the abuse and dependence-related side effects that are typical of opioids. a study in nonhuman primates found that at-121 has morphine-like analgesic effects, but suppressed the addictive effects. at-121legal statuslegal status investigational identifiers iupac name 3-oxo-1'-(4-propan-2-ylcyclohexyl)-2-spiro cas number2099681-31-7pubchem cid129188444chemical and physical dataformulac24h38n4o3smolar mass462.65 g·mol−13d model (jsmol)interactive image smiles cc(c)1cc(cc1)n1ccc2(cc1)c(=o)n(ccns(n)(=o)=o)cc1=cc=cc=c21