Abstract
BACKGROUND: Anhedonia is a core symptom of major depressive disorder (MDD) that may result from aberrant lateral habenula hyperactivity. Targeting G-protein coupled receptor 139 (GPR139) may improve anhedonia by modulating lateral habenula activity. NBI-1065846 is an investigational GPR139 agonist that improved anhedonia, anxiety, and depression in rodent models. METHODS: TERPSIS was a phase 2, proof-of-concept clinical study. Adults with MDD experiencing a major depressive episode with anhedonia were randomized 1:1 to NBI-1065846 or placebo for 8 weeks. The primary endpoint was the change in the Dimensional Anhedonia Rating Scale (DARS) score. Secondary endpoints were change in total Montgomery Åsberg Depression Rating Scale (MADRS) score in participants with a baseline 17-item Hamilton Depression Rating Scale (HAM-D17) score of ≥19 (moderate to severe) and change in Clinical Global Impression of Severity (CGI-S) score. All changes were from baseline to Day 57. RESULTS: In total, 93 participants received study treatment (NBI-1065846, n = 46; placebo, n = 47). Both groups showed notable improvements in DARS scores from baseline to day 57 (least-squares mean change: NBI-1065846, 13.5; placebo, 17.4), with no statistically significant difference (NBI-1065846 vs. placebo, P = 0.8663). Similarly, MADRS ( P = 0.7008) and CGI-S ( P = 0.9051) scores showed no significant difference between groups. All treatment-emergent adverse events in the NBI-1065846 group were mild or moderate in severity. CONCLUSIONS: The TERPSIS study did not meet its primary or secondary endpoints. NBI-1065846 was generally well tolerated. Addressing the lack of treatment options for anhedonia remains an important unmet clinical need.