Efficacy and Safety of Intranasal MSP-2017 (Etripamil) for the Conversion of PSVT to Sinus Rhythm

This is a multi-center, randomized, double-blind, placebo-controlled, dose-ranging study to
evaluate the effects of 4 different doses of MSP-2017 (Etripamil) in subjects with paroxysmal
supraventricular tachycardia. It includes an up to 21-day Screening Period, a 1-day Treatment
Visit, and either a Follow-up Visit or Early Termination Visit occurring 12 hours to 5 days
after the Treatment Visit. Subjects will be randomized to yield at least 100 evaluable
subjects distributed into 5 groups of at least 20 subjects each.

Inclusion Criteria:

- Male or female, aged 18 years and older at Screening

- Has a history of PSVT

- Is scheduled for an electrophysiology study and catheter ablation

- Has provided written informed consent

- Agrees to use a medically accepted form of contraception or abstinence to prevent
pregnancy. Males must agree to use an acceptable form of contraception or abstinence
from the time of study drug administration through the Follow-up Visit. Females must
agree to use an acceptable form of contraception or abstinence from Screening until 30
days following study drug administration. Post-menopausal female subjects must be
amenorrheic for ≥ 12 months prior to Screening or ≥ 6 weeks post-surgical bilateral
oophorectomy (with or without hysterectomy) prior to Screening, if they do not wish to
use an acceptable form of contraception or abstinence. Acceptable forms of
contraception include: A condom and an intrauterine device; A condom and hormonal
contraception; A condom and a diaphragm; Sterilization of the subject or the subject's
partner(s) (sterilization procedure must have been performed 3 or more months prior);
Hysterectomy of the subject or the subject's partner(s)

- If a female of childbearing potential: Has a negative serum pregnancy test result at
Screening (Screening must occur ≥7 days prior to randomization [ie, on or before Day
-7]) and at the Treatment Visit (pre-PSVT induction); Has had a menstrual period
within 28 days of the Treatment Visit.

Exclusion Criteria:

- Has a history of serious allergic reaction to verapamil (especially when administered
intravenously) including rash, itching or swelling (especially of the face, tongue, or
throat), severe dizziness, or trouble breathing

- Is currently participating in another drug or device study, or has received an
investigational drug or device within 30 days of Screening

- Has evidence of clinically significant cardiovascular, endocrine, gastrointestinal,
hematologic, hepatic, immunologic, neurologic, oncologic, pulmonary, psychiatric, or
renal disease or any other condition which, in the opinion of the Investigator, would
jeopardize the safety of the subject or impact the validity of study results

- Is a female who is breast feeding, pregnant, or planning to become pregnant during the
study period

- Has evidence of any clinically significant acute or chronic condition of the nasal
cavity (e.g., rhinitis or deviated septum) which could interfere with IN
administration of the study drug in either or both nasal cavities

- Has any of the following at screening or at the Treatment Visit: Systolic blood
pressure <100 mmHg, Diastolic blood pressure <50 mmHg

- Has evidence of hepatic impairment, defined as: Alanine aminotransferase or aspartate
aminotransferase levels that are greater than or equal to 3× upper limit of normal
(ULN) or Bilirubin levels that are greater than or equal to 2× ULN, unless due to
Gilbert's syndrome

- Has evidence of renal impairment, defined as an estimated glomerular filtration rate
<30 mL/min (Modification of Diet in Renal Disease method)

- Has taken digoxin, verapamil, diltiazem, or any Class I, II (e.g., beta blockers), or
III antiarrhythmic drug less than the equivalent of 5 half-lives of this drug prior to
the Treatment Visit

- Has taken amiodarone within 30 days of the Treatment Visit

- Has taken drugs of abuse which, in the opinion of the Investigator, would impact the
validity of study results

- Has had myocardial infarction, percutaneous coronary intervention, cerebrovascular
accident, transient ischemic attack, unstable angina, or acute decompensation of heart
failure within 6 months of Screening

- Has a history or evidence of second- or third-degree atrioventricular block

- Has an implanted device (e.g., pacemaker, or implantable cardioverter defibrillator)
that precludes study participation in the opinion of the Investigator and Study
Medical Monitor

- Has a history or evidence of preexcitation syndrome (e.g., Wolff-Parkinson- White
syndrome, short PR, etc.)

- Has evidence of a QT interval (Bazett's correction) (QTcB) >455 milliseconds at
Screening or at the Treatment Visit

- Has a history or evidence of familial long QT syndrome, torsades de pointes,
ventricular fibrillation, sustained ventricular tachycardia, Brugada syndrome, or
sudden cardiac death

- Has evidence of recurrent or chronic atrial tachycardia, atrial flutter, or atrial
fibrillation; that could interfere with the current investigation; or

- Has a history or evidence of congestive heart failure (except New York Heart
Association Class I) or pulmonary edema

In addition, randomized subjects who meet any of the following criteria at the Treatment
Visit (Day 1) prior to study drug administration, will be excluded from participation in
the study:

- PSVT cannot be induced or the mechanism of PSVT is neither AVRT nor A VNRT

- It is not possible to sustain an episode of PSVT for 5 minutes

- The subject requires a continuous sedative (e.g., propofol), continuous analgesic, or
inhaled anesthetic at any point until time 30. Minimally necessary dose(s) of
benzodiazepine(s) (e.g., midazolam) and/or narcotic(s) (e.g., fentanyl) (given via
single or multiple administration[s]) may be used at the Investigator's discretion.
The identity(-ies) and actual administered dose(s) of any benzodiazepine(s) and/or
narcotic(s) should be recorded in the study documentation. Local anesthetic(s) may be
used at the Investigator's discretion; any use should be recorded in the study
documentation

- The subject has undergone prior ablation, and the subject's AV node function is
abnormal in the opinion of the Investigator