AXS-05 Phase II Trial on Smoking Behavior

This study aims to investigate the potential efficacy of a combination of two FDA-approved
agents, sustained release (SR) Bupropion (BUP) and immediate release (IR) Dextromethorphan
(DXM), for the purpose of smoking cessation treatment. DXM, a widely used over-the-counter
cough suppressant, is a nicotine receptor antagonist. In fact, studies by Duke's Center for
Smoking Cessation (CSC) have shown that administration of DXM leads to a decrease in
self-administration of nicotine in nicotine-dependent rats. DXM, however, has not been
studied in humans. DXM, when taken alone, is not expected to be useful for treating nicotine
dependence in humans given DXM rapidly metabolizes in humans via CYP2D6. As a result,
therapeutic concentrations needed to bind to nicotine receptors are not obtained. Therapeutic
concentrations of DXM are required, therefore, to allow DXM to bind to nicotine receptors and
act as a nicotine antagonist. In order to attain therapeutic concentrations of DXM a
metabolism inhibitor must be introduced. BUP is a well-known FDA approved smoking cessation
medication that has been shown to inhibit the metabolism of DXM. When BUP is co-administered
with DXM to healthy volunteers, a significant increase in DXM plasma levels is observed.

Currently, Axsome Therapeutics Inc. (Axsome) is developing and testing an oral fixed-dose
combination of IR DXM with SR BUP to achieve therapeutic concentrations of DXM. This
investigational drug has been named AXS-05. Axsome has found AXS-05 to be generally safe and
well-tolerated in three Phase 1 studies. The adverse event profile of AXS-05 was similar to
that of BUP alone.

Given the distinct mechanisms by which BUP and DXM interact, it is hoped that combining DXM
and BUP will prove more efficacious than either drug administered alone for the purpose of
tobacco use treatment in humans.

Key Inclusion Criteria:

1. Age 18 years or above

2. Daily smoker using 10 or more cigarettes per day

3. Willing to be smoke-free for 7 days

4. Is able to provide written informed consent (in English) to participate in the study
and able to understand the procedures and study requirements.

5. Is willing to voluntarily sign and date an informed consent form that is approved by
an institutional review board before the conduct of any study procedure.

Key Exclusion Criteria:

1. Current use of a smoking cessation medication (e.g. nicotine replacement, Varenicline,
bupropion)

2. Current use of tobacco product other than cigarettes (e.g. e-cigarettes, smokeless
tobacco)

3. Not pregnant or breastfeeding

4. Contraindication to the use of bupropion.

5. Additional criteria may apply.