Multi-Center, Placebo-Controlled, Dose-Ranging Phase 2 Electrophysiological Study of Intranasal Administration of MSP-2017 for the Conversion of Induced Paroxysmal Supraventricular Tachycardia (PSVT) to Sinus Rhythm

• 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.