The TARGET study is an active-controlled evaluation of AXS-05 compared to bupropion in patients with treatment-resistant major depressive disorder (MDD) who are adherent to study drug. Subjects are considered to have treatment-resistant MDD if they have had a historical inadequate response to 1 or 2 prior antidepressant treatments (ADTs) and a prospective inadequate response to treatment with bupropion SR, during the current major depressive episode.

The TARGET study will first determine treatment adherence based on analysis of drug concentrations of dextromethorphan (in the AXS-05 group) and bupropion (in the bupropion group), and then evaluate the efficacy of AXS-05 in patients determined to be treatment-adherent. Efficacy data for evaluation of treatment effect will be obtained from assessments made during study AXS-05-301.

Key Inclusion Criteria:

• Provided written informed consent to participate in Study AXS-05-301
• Has treatment-resistant depression, defined as an inadequate response to 2 or 3 prior ADTs
• Body mass index (BMI) between 18 and 40 kg/m2, inclusive

Key Exclusion Criteria:

• Suicide risk
• Treatment with any investigational drug within 6 months
• History of electroconvulsive therapy (ECT), vagus nerve stimulation, transcranial magnetic stimulation, or any experimental central nervous system treatment during the current episode or in the past 6 months
• Pregnant, breastfeeding, or planning to become pregnant or breastfeed during the study