TAK-653 (NBI-1065845)

TAK-653 (also designated NBI-1065845; emraclidine has the same NBI prefix, distinct compound; CAS 1626387-80-1; molecular formula C19H21F3N4O3S; molecular weight 442.46) is a small-molecule non-desensitizing positive allosteric modulator of AMPA-class glutamate receptors developed by Takeda and out-licensed to Neurocrine Biosciences for clinical development in treatment-resistant depression. The compound was selected from a structural class designed to achieve allosteric AMPA potentiation without the receptor desensitization characteristic of earlier ampakines (CX-516, CX-546), which limited potency and produced cognitive impairment at higher doses. TAK-653 binds at an allosteric site distinct from the glutamate-binding domain, slowing AMPA receptor deactivation and increasing the integrated current produced by physiological glutamate transients without persistent receptor activation in the absence of glutamate; this profile produces synaptic potentiation under physiological signaling without the off-target excitotoxicity concerns of full agonists or strongly desensitizing modulators. Phase 1 imaging studies report dose-dependent BOLD signal modulation in cortical regions consistent with AMPA potentiation. The compound was advanced through Phase 2 in treatment-resistant depression by Neurocrine; published Phase 2a results from 2023 reported numerical separation from placebo on Hamilton Depression Rating Scale change at week 4 with improvement maintained through week 8, with a favorable safety profile (no seizures, no notable sedation, no dose-limiting cognitive impairment). The compound has not yet received regulatory approval as of the most recent monograph revision. Distinguishing features versus other AMPA modulators are the absence of receptor desensitization, the minimal impairment profile at antidepressant doses, and the rapid-onset depression treatment positioning targeting the same therapeutic niche as ketamine and esketamine.