Allergan plc / Naurex, Inc.

Major Depressive Disorder (treatment-resistant)

Disease Overview

Major depressive disorder is a chronic, relapsing mood disorder marked by persistent sadness, anhedonia, and impaired functioning that affects ~21 million US adults annually. Standard SSRIs and SNRIs work slowly (weeks) and fail roughly one-third of patients, creating a large treatment-resistant depression segment that drove industry interest in rapid-acting NMDA-targeted mechanisms in the mid-2010s.

Competitive Landscape

The depression market in 2015 was dominated by genericized SSRIs/SNRIs (Lexapro, Zoloft, Effexor, Cymbalta) with limited efficacy gains for two decades. The breakthrough thesis in 2015 was rapid-acting NMDA modulation following ketamine's off-label use in TRD. Janssen's esketamine (Spravato), an NMDA receptor antagonist nasal spray, was the leading branded entrant and won FDA approval for TRD in March 2019 and MDD with suicidal ideation in 2020. Naurex's rapastinel (GLYX-13) was positioned as a differentiated allosteric NMDA modulator with a cleaner safety profile than ketamine — no dissociation, no REMS — supporting Allergan's premium $560M upfront price. The thesis collapsed when rapastinel failed three Phase 3 trials in March 2019, missing primary and key secondary endpoints versus placebo as adjunct to antidepressants. The failure left Spravato unchallenged as the sole branded NMDA-modulating MDD therapy and reinforced industry skepticism of NMDA scaffolds beyond ketamine's pharmacology.