LPH-5

LPH-5, the (S)-enantiomer of 3-(2,5-dimethoxy-4-(trifluoromethyl)phenyl)piperidine and a conformationally restricted analog of the phenethylamine psychedelic 2C-TFM, is a potent and selective partial agonist of the serotonin 5-hydroxytryptamine type 2A (5-HT2A) receptor under clinical development for treatment-resistant depression and potentially other neuropsychiatric indications. First disclosed in a 2021 patent assigned to Lophora ApS and characterized in the peer-reviewed literature by Marcher-Rorsted et al. (2024) in the Journal of Medicinal Chemistry, LPH-5 emerged from a systematic structure-activity relationship exploration of 2,5-dimethoxyphenylpiperidines in which cyclization of the flexible phenethylamine chain into a piperidine ring, combined with the 4-trifluoromethyl substituent, produced a compound with low-nanomolar 5-HT2A receptor binding affinity (Ki 1.3 nM against [125I]DOI), potent functional partial agonism in calcium mobilization assays (EC50 3.2 nM, Emax approximately 92 percent of the serotonin maximum at the 5-HT2A receptor), and approximately 60-fold functional selectivity for 5-HT2A over the 5-HT2B receptor, with no measurable agonist activity at the 5-HT2C receptor at concentrations up to 30 micromolar in receptor internalization assays. This selectivity profile distinguishes LPH-5 from classical serotonergic psychedelics such as psilocin, lysergic acid diethylamide, and N,N-dimethyltryptamine, all of which activate the 5-HT2B and 5-HT2C receptors at therapeutically relevant concentrations, and from the parent compound 2C-TFM, which retains substantial 5-HT2C agonist activity.

In preclinical pharmacology, LPH-5 dose-dependently induces the head-twitch response in rodents, a behavioral correlate of 5-HT2A receptor activation and a proxy for psychedelic potential, confirming central target engagement after systemic administration. The compound produces robust acute and persistent antidepressant-like effects in the rat forced swim test, with reduction in immobility observed both at 24 hours and at 7 days after a single administration, a temporal profile consistent with the sustained antidepressant responses reported in clinical trials of psilocybin. The stereochemistry is critical: the (S)-enantiomer (designated the eutomer) is consistently more potent at the 5-HT2A receptor and more selective against the 5-HT2C receptor than the corresponding (R)-distomer across the entire 2,5-dimethoxyphenylpiperidine series. Absolute configuration was confirmed by X-ray crystallography. Physicochemical properties are favorable for central nervous system drug development, with a LogP of 3.45, high membrane permeability (MDR1-MDCKII efflux ratio 0.94), and ligand efficiency metrics (LE 0.6, LLE 5) that position the compound in the optimal drug-like space.

Preclinical toxicology studies completed at Lophora reported no toxicology or histopathology findings, and all chemistry, manufacturing, and controls activities were completed by 2022. The European Medicines Agency authorized a Phase 1 first-in-human clinical trial in September 2024. The trial, a randomized placebo-controlled single- and multiple-ascending-dose study in healthy volunteers conducted at Biotrial in Rennes, France, began dosing subjects in May 2025, with topline results expected in the fourth quarter of 2025. LPH-5 is designed for use in psychedelic-assisted psychotherapy and represents a pharmacological strategy in which the therapeutic benefits of classical psychedelics are pursued through a compound with improved receptor subtype selectivity, reduced 5-HT2B-associated cardiac risk, and a defined stereochemical identity. This monograph reviews the chemistry, stereochemistry, and structure-activity relationships of LPH-5; the in vitro and in vivo pharmacology at serotonin receptor subtypes; the preclinical behavioral pharmacology; the development history and clinical trajectory; sourcing, reconstitution, and handling considerations for laboratory use; stack interactions; adverse-event expectations; and a structured comparative assessment of five alternative 5-HT2A receptor agonists (psilocybin/psilocin, 25CN-NBOH, DOI, LSD, and the non-hallucinogenic analog tabernanthalog) against LPH-5 on five competency standards.