A Proof of Concept Study of Intravenous Sodium Nitroprusside in Adults With Symptomatic Schizophrenia

This is a phase II proof of concept (POC), multi-center, prospective, randomized,
placebo-controlled, Sequential Parallel Comparison Design (SPCD) study, in which a total of
60 subjects with schizophrenia will be enrolled.

The study will be conducted in two stages. The study treatment will be administered in a
double-blind fashion for all subjects throughout both stages of the study. A total of 60
subjects with schizophrenia will be randomized in a 1:1:1 ratio to drug-drug sequence [n=20;
i.v. sodium nitroprusside (0.5 μg/kg/min for 4 hours) at week 0 and week 2], placebo-drug
sequence [n=20; i.v. placebo at week 0 and i.v. sodium nitroprusside (0.5 μg/kg/min for 4
hours) at week 2], and placebo-placebo sequence [n=20; i.v. placebo at week 0 and again at
week 2]. The 4-week double-blind phase of treatment will be divided into two phases: Phase 1,
from week 0 to week 2, and Phase 2 from week 2 to week 4. At the end of Phase 1 (week 2), the
randomized subjects will be assessed and categorized into responders and non-responders,
based on 20% or more reduction from baseline in their PANSS total score as per the
evaluations at Randomization Visit (week 0). The data from the patients deemed placebo
non-responders in phase 1 who go on to either stay on placebo or to receive treatment with
sodium nitroprusside will be pooled with the data from Phase 1 from all subjects, according
to SPCD.

Inclusion Criteria:

Each subject must meet all of the following criteria to be eligible for this study:

1. Males or Females aged 18-65 years inclusive.

2. Primary diagnosis of Schizophrenia established by a structured psychiatric evaluation
(SCID) based on Diagnostic and Statistical Manual of Mental Disorders Forth Edition
(DSM-IV-TR) criteria.

3. Written informed consent in compliance with 21 CFR part 50 and in accordance with the
International Conference on Harmonization (ICH) Good Clinical Practice (GCP)
Guidelines.

4. A Positive and Negative Syndrome Scale (PANSS) (Kay et al., 1994) total score ≥ 70
with a score of > 4 on two or more of the following PANSS items: delusions, conceptual
disorganization, hallucinatory behavior, suspiciousness, and unusual thought content.

5. A score of ≥4 on the Clinical Global Impression—Severity (CGI-S) (Guy, 1976).

6. Confirmation of both diagnosis and severity of psychosis symptoms by an independent
MGH SAFER interview.

7. Must have ongoing antipsychotic treatment for at least 8 weeks, with a stable dose for
at least 4 weeks. Subjects who have failed to achieve clinically-recognized symptom
reduction to at least 1 marketed antipsychotic agent, given at a Physician Desk
Reference (PDR)-defined therapeutic dose for ≥ 8 weeks during the past 12 months, as
assessed by the MGH FAST, will be eligible

8. Understands and is able, willing, and (in the opinion of the investigator) likely to
fully comply with the study procedures and restrictions.

Exclusion Criteria

Subjects who meet any of the following criteria will be excluded from the study:

1. Subjects with a history of renal insufficiency, congestive heart failure, cardiac
arrhythmias or history of myocardial infarction.

2. Subjects with a history of symptomatic orthostatic hypotension defined as sitting to
standing systolic blood pressure < 90mmHg or diastolic blood pressure < 60mm Hg with
any of the following symptoms: lightheaded or dizzy upon standing, blurry vision,
weakness, fainting (syncope), confusion, or nausea.

3. Subjects with any clinically significant abnormalities as determined by medical
history, physical exam, clinical and lab evaluation suggestive of an underlying
disease state that may, in the opinion of the investigator, confound the results of
study, increase risk to the subject, or lead to difficulty complying with the
protocol.

4. Subjects on chlorpromazine, PDE-5 inhibitors, nitrites and any medication with CNS
effects with the exception of antipsychotic drugs (other than chlorpromazine)
anticholinergics, b-adrenergic antagonists, amantadine, biperiden, diphenhydramine,
lorazepam, zolpidem, and temazepam.

5. Medications which in the opinion of the PI, and in conjunction with the medical
monitor, may be expected to significantly interfere with the metabolism or excretion
of sodium nitroprusside, and/or may be associated with a significant drug interaction
with sodium nitroprusside that may pose a significant risk to subjects' health and/or
confound the study data.

6. Pregnant or breast-feeding patients. Women of childbearing potential must have a
negative pregnancy test performed at screening visit prior to randomization and prior
to baseline at visits 3 and 6. Women enrolled in this trial must use adequate birth
control.

7. Subjects with a current (within the last 3 months) DSM-IV-TR diagnosis of alcohol or
substance use disorder or dependence (excluding nicotine) as established by the
clinical assessment (SCID) at the screening visit will be excluded.

8. Has tested positive for any of the following: cannabis, opioids, cocaine,
amphetamines, barbiturates methadone, methamphetamine and phencyclidine at the
screening or baseline visits. If positive, the urine drug toxicology screen may be
repeated once based on investigator judgment, but due to safety concerns, the result
must be negative for the subject to continue in the study.

9. Subjects at imminent risk of suicide or injury to self or others, as per the opinion
of the investigator, or history of significant suicide attempt within the last 6
months as per C-SSRS.

10. Subjects that have taken an investigational drug or taken part in a clinical trial
within 30 days prior to screening.

11. Any other reason that, in the opinion of the investigator, would compromise patient
safety or integrity of the study