Abstract
Mutant huntingtin (mHTT) aggregates represent a key pharmacodynamic biomarker of Huntington's disease (HD). The development of positron emission tomography (PET) tracers targeting mHTT addresses a critical unmet need by enabling the noninvasive quantification of pathological burden in vivo. The first-generation tracer, [(11)C]-CHDI-180R, a benzoxazole derivative, laid the foundation for this effort. Subsequent analogs such as [(11)C]-CHDI-626 and [(18)F]-CHDI-650 were developed to improve in vivo performance; however, key challenges including limited metabolic stability and suboptimal selectivity persisted. To address these limitations, a recent study introduced a new class of isoindolinone-derived candidate tracers, including [(11)C]-CHDI-009, [(18)F]-CHDI-385, and [(18)F]-CHDI-386, identified through systematic structure-activity relationship (SAR) optimization. These next-generation tracers exhibit markedly enhanced binding affinity, selectivity, and translational potential, offering valuable tools to investigate mHTT pathology and its role in HD progression.