25I-NBOMe

25I-NBOMe (2-(4-iodo-2,5-dimethoxyphenyl)-N-[(2-methoxyphenyl)methyl]ethanamine; IUPAC synonym 2C-I-NBOMe; development code Cimbi-5) is a synthetic substituted phenethylamine and a member of the NBOMe (N-benzylmethoxy) series of serotonergic psychedelics derived from the 2C-x family originally described by Shulgin. The compound was first synthesized by Ralf Heim at the Freie Universitat Berlin in 2003 as a pharmacological tool for the study of serotonin 5-HT2A receptor function and was subsequently characterized pharmacologically by the laboratory of David Nichols at Purdue University. The defining pharmacological feature is ultrapotent full agonism at the human serotonin 5-HT2A receptor, with reported binding affinities (Ki) ranging from 0.044 to 2.2 nM, representing approximately 14- to 16-fold greater affinity than the parent compound 2C-I and more than 1000-fold selectivity over the 5-HT1A receptor. The compound also exhibits high-affinity binding at the 5-HT2C receptor (Ki 0.43 to 7.0 nM) and moderate affinity at the 5-HT2B receptor (Ki 1.4 to 231 nM), with significant off-target binding at alpha-1 adrenergic receptors (Ki less than 300 nM) but minimal affinity for dopamine transporters, norepinephrine transporters, serotonin transporters, histamine H1, or dopamine D1 through D5 receptors.

The carbon-11 labelled isotopologue, [11C]Cimbi-5, was synthesized and validated at the Copenhagen University Hospital as the first full-agonist positron emission tomography (PET) radioligand for the serotonin 5-HT2A receptor, enabling in vivo imaging of the high-affinity, G-protein-coupled state of the receptor in porcine and primate brain. This represents the principal legitimate research application of the compound: agonist PET tracers are theoretically more sensitive than antagonist tracers to competition from endogenous serotonin, offering a functional readout of receptor availability that antagonist ligands such as [18F]altanserin and [11C]MDL 100,907 cannot provide. The radiotracer application has produced peer-reviewed imaging data in pigs, baboons, and nonhuman primates, with cortical binding distributions consistent with known 5-HT2A receptor density.

Pharmacokinetics in humans are incompletely characterized owing to the absence of controlled human administration studies. Available data from clinical intoxication cases, forensic toxicology, and in vitro hepatic microsomal preparations indicate that 25I-NBOMe undergoes extensive first-pass hepatic metabolism, predominantly via cytochrome P450 isoforms CYP3A4, CYP2D6, CYP2C19, CYP2C9, CYP2B6, and CYP1A2. The dominant phase I metabolic transformations are O-demethylation, O,O-bis-demethylation, hydroxylation, and N-dealkylation, producing at least 15 identified phase I metabolites that subsequently undergo phase II glucuronidation and sulfation. Parent compound plasma concentrations are approximately 100-fold lower than those of the most abundant metabolites, reflecting extensive first-pass extraction. The compound is not a substrate for monoamine oxidase A or B, distinguishing it metabolically from the parent 2C-I and from tryptamine-class psychedelics.

The toxicological profile of 25I-NBOMe is severe relative to classical serotonergic psychedelics. Documented adverse effects from clinical intoxication cases include tachycardia, hypertension, agitation, visual and auditory hallucinations, seizures (single-episode and status epilepticus), hyperthermia, rhabdomyolysis, metabolic acidosis, disseminated intravascular coagulation, acute kidney injury, serotonin syndrome, and multiorgan failure. At least 19 deaths in the United States alone were documented by August 2015, with additional fatalities reported in Australia, the United Kingdom, Ireland, Poland, and Brazil. Postmortem blood concentrations in fatal cases have ranged from 0.25 ng/mL to 28 micrograms per liter, reflecting both the extreme potency of the compound and the difficulty of establishing a lethal threshold. The narrow margin between psychoactive and lethal doses, the absence of a ceiling effect on sympathomimetic toxicity, and the frequency of seizures and rhabdomyolysis distinguish 25I-NBOMe from classical psychedelics such as lysergic acid diethylamide, psilocybin, and mescaline, all of which have substantially wider therapeutic indices and lower rates of life-threatening complications.

This monograph reviews the chemistry, synthesis, and structure-activity relationships of 25I-NBOMe within the NBOMe series; the molecular pharmacology at serotonin, adrenergic, and other receptor targets; the available pharmacokinetic and metabolic data; the preclinical neurotoxicology and behavioral pharmacology; the clinical toxicology evidence base from intoxication case series and forensic reports; sourcing and analytical verification considerations for research-grade material; handling and storage; interaction considerations with serotonergic, sympathomimetic, and other compound classes; the comprehensive adverse-event and safety signal; and a comparative assessment of five related psychedelic phenethylamine and tryptamine compounds against 25I-NBOMe on five standards (receptor potency, research utility, safety margin, analytical tractability, and overall validation). The compound is a Schedule I controlled substance in the United States, a Class A drug in the United Kingdom, and is controlled in essentially all jurisdictions with novel psychoactive substance legislation. All handling requires appropriate institutional authorization, licensing, and analytical infrastructure.