Dalzanemdor

Dalzanemdor (development code SAGE-718) is a first-in-class, orally bioavailable, small-molecule positive allosteric modulator (PAM) of the N-methyl-D-aspartate receptor (NMDAR), structurally derived from the endogenous cholesterol metabolite 24(S)-hydroxycholesterol (24(S)-HC). The compound was designed by Sage Therapeutics to address cognitive impairment in neurodegenerative disorders associated with NMDAR hypofunction, including Huntington's disease, Alzheimer's disease, and Parkinson's disease. Dalzanemdor potentiates NMDAR-mediated currents at all four GluN2 subunit-containing receptor assemblies (GluN1/GluN2A through GluN1/GluN2D) with equipotency, exhibiting EC50 values in the low-nanomolar range (approximately 79 to 86 nM) and high intrinsic activity. The modulation increases NMDAR channel open probability without directly gating the receptor in the absence of endogenous glutamate, a feature that preserves physiological patterns of synaptic transmission and mitigates the excitotoxicity risk associated with direct NMDAR agonism.

The compound emerged from a research program initiated by the foundational discovery of Paul et al. (2013) demonstrating that 24(S)-HC, the major brain-specific cholesterol metabolite synthesized by CYP46A1, is a potent and selective endogenous NMDAR PAM at submicromolar concentrations. Medicinal chemistry optimization at Sage Therapeutics yielded dalzanemdor (compound 5 in the Hill et al. 2022 disclosure), a trifluoromethylated oxysterol with an optimized pharmacokinetic profile for oral dosing. In preclinical models, dalzanemdor enhanced NMDAR-mediated long-term potentiation in hippocampal slices, increased excitatory postsynaptic potential amplitude in striatal medium spiny neurons, and reversed cognitive and behavioral deficits induced by NMDAR channel blockers and cholesterol depletion, without producing epileptiform activity or neurodegeneration on chronic dosing.

Phase 1 dose-finding studies (single-ascending dose, 0.35 to 3.0 mg; multiple-ascending dose, 0.5 to 1.0 mg for 14 days) in healthy participants and Huntington's disease participants established a pharmacokinetic profile characterized by oral absorption with median Tmax of 4 to 7 hours, terminal half-life of approximately 28 to 40 hours after single doses extending to 99 to 125 hours after multiple doses, and dose-proportional exposures suitable for once-daily dosing. Exploratory cognitive assessments in Huntington's disease participants during the Phase 1 multiple-ascending dose study showed statistically significant improvement on the Two-Back Learning Task (executive function). Open-label Phase 2 studies in Parkinson's disease mild cognitive impairment (PARADIGM, n=18) and Alzheimer's disease (LUMINARY, n=26) generated signals of improvement on measures of executive function and learning. However, three subsequent randomized, double-blind, placebo-controlled Phase 2 studies (PRECEDENT in Parkinson's disease, LIGHTWAVE in Alzheimer's disease, DIMENSION in Huntington's disease) each failed to meet their primary cognitive endpoints. Sage Therapeutics discontinued all clinical development of dalzanemdor in November 2024.

This monograph documents the chemistry, structural pharmacology, oxysterol-site mechanism, human pharmacokinetics, the complete clinical trial inventory including both positive open-label signals and negative controlled results, sourcing and handling considerations for research-grade material, adverse-event profile, and a comparative assessment of five NMDAR-targeting compounds against dalzanemdor on five competency standards. The compound is not approved by any regulatory authority. Research-grade dalzanemdor is available from chemical suppliers for in vitro and in vivo investigation of NMDAR positive allosteric modulation; investigators should obtain analytical confirmation of identity and purity on every lot.