Despite the wide prevalence of mood disorders globally, there is a substantial unmet need for effective, mechanistically distinct treatments. Given that approximately 30% of individuals do not display adequate response to standard antidepressant therapies, the past 15 years have seen a shift away from traditional monoaminergic approaches toward glutamatergic and other novel mechanisms. Following the US Food and Drug Administration (FDA) approval of esketamine and brexanolone in 2019, industry investment in therapeutics with novel mechanisms for mood and anxiety disorders has expanded, catalyzing a new wave of innovative interventions. This review summarizes progress for unipolar mood disorders in four categories-glutamatergic/GABA modulators, ion channel modulators, psychedelics, and other potential therapeutic mechanisms-focusing on Phase II/III industry-sponsored US clinical trials active within the past 3 years. The drug names discussed are ALTO-100, ALTO-203, ALTO-207, ALTO-300, BHV-7000, BI-1569912, BPL-003, COMP360, DT120, ELE-101, GATE-251, GH001, GM-1020, GM-2505, HLP003, MK-1942, NBI-1065845, NBI-1070770, NV-5138, PIPE-307, SEP-363856, SPT-300, VLS-01, and XEN1101. The US Clinical Trials registry (clinicaltrials.gov), MEDLINE, conference proceedings, and company communications such as press releases were consulted to obtain up-to-date trial information and reported outcomes. Overall, the therapeutic landscape shows an expanding range of clinical compounds under active development; nonetheless, persistent challenges remain, including approaches to therapeutics where functional unblinding may occur, the ways in which to consider a novel conceptualization of occupancy-driven versus event-driven pharmacology, and the role of supporting psychotherapy.
