Potential of Small Molecule TAAR-1 Agonists for the Therapy of Neurodegenerative Psychosis: A Medicinal Chemistry Perspective

This comprehensive review critically evaluates the emerging therapeutic potential of small-molecule Trace Amine-Associated Receptor 1 (TAAR-1) agonists as a novel, diseasemodifying strategy for neurodegenerative psychosis. From a medicinal chemistry perspective, we assess Structure-Activity Relationship (SAR) data across a broad spectrum of chemotypes, including thyronamine analogues, pyrimidinone-benzimidazoles, guanfacine derivatives, thiophenedihydropyran (Ulotaront), piperidine-carboxamides, sulfonamides, and biguanides. Our analysis establishes a unified strutural model centered on four essential structural elements, such as (1) a protonatable primary or secondary amine crucial for forming a salt bridge with the conserved Asp103 residue, (2) an aromatic or heteroaromatic core enabling pivotal π-stacking interactions with key hydrophobic residues (Phe186, Phe195, Trp264, Phe267, Phe268), (3) compact, meta-substituted hydrophobic groups (e.g., methyl, chloro, isopropyl) that optimally occupy subpockets defined by Ile104, Ile290, or Val184, and (4) a strong preference for (S)-enantiomers to maximize binding complementarity. The compiled SAR reveals that agonist potency (EC₅₀ values in the nM to μM range) and selectivity are critically dependent on these features, with auxiliary hydrogen-bond acceptors or donors (e.g., near Ser107 or Tyr294) further stabilising the active receptor conformation. Conversely, structural deviations such as ortho-substitution, bulky N-alkylation, or R-enantiomers significantly compromise activity. Strategic bioisosteric replacements, such as methylene bridges and aminoethoxy chains, are highlighted for their role in enhancing metabolic stability. This robust pharmacophore underpins the rational design of advanced clinical candidates like Ulotaront, which demonstrate dual neuroprotective and symptomatic benefits over conventional antipsychotics, offering a clear roadmap for the development of next-generation TAAR-1-targeted therapeutics for complex neuropsychiatric disorders.