Inclusion Criteria:

• Adult males and females between 18 and 60 years of age, inclusive at the time of signing the informed consent document.
• Understand and voluntarily sign an informed consent document prior to any study related assessments/procedures being conducted.
• Diagnosis of cyclic vomiting syndrome (CVS) using the Rome IV diagnostic criteria and must have:
  • Stereotypical episodes of acute onset vomiting lasting < 1 week;
  • At least 3 discrete episodes of vomiting in the prior year and 2 episodes in the past 6 months, occurring at least 1 week apart;
  • Absence of vomiting between episodes (but milder symptoms may be present);
  • Symptoms must be present for the past 3 months with onset at least 6 months prior;
  • Has a prodrome or pre-emetic symptoms for approximately half of their “typical” CVS episodes.
• If of reproductive age, female participants and female partners of male participants, willing and able to use a medically highly effective form of birth control from at least 4 weeks prior to Baseline until at least 30 days following last dose of study drug. Examples of medically highly effective forms of birth control are:
  • Surgical sterility (hysterectomy or bilateral ligation) or post‑menopausal (cessation of menses for at least 12 months prior to screening);
  • Sexual partner is sterile, or of the same sex;
  • Implants of levonorgestrel in females;
  • Oral contraceptive (combined, patch, vaginal ring, injectable, implant) in females;
  • Double-barrier method (any combination of physical and chemical methods);
  • Intrauterine device with a failure rate less than 1% per year.
• Male participants must:
  • Agree to use, with their partners, one of the highly effective contraceptive methods listed in Inclusion Criterion 5, from Baseline until at least 30 days following last dose of study drug;
  • Refrain from donating sperm during the study and for at least 30 days after the end of the study.
• Otherwise healthy, as determined by the responsible physician, based on a medical evaluation including history, physical examination, vital signs, electrocardiograms (ECGs) and laboratory tests assessed at the screening visit.
• Negative urine tests for selected drugs of abuse and alcohol breath test at Screening.
  • Note: Patients with a positive urine drug screen for benzodiazepines or opiates may be allowed in the study provided the drug was prescribed by a physician.
• Willing and able to adhere to overall study visit schedule, procedures and other protocol requirements.

Exclusion Criteria:

• Any significant medical or psychiatric condition that could, in the Investigator’s opinion, compromise the subject’s safety or interfere with the completion of this protocol.
• Any condition, including the presence of laboratory abnormalities or pulmonary condition, which according to the Investigator places the subject at unacceptable risk if he/she were to participate in the study.
• A diagnosis of any gastrointestinal disorder other than CVS that in the judgement of the Investigator could compromise the subject’s safety or interfere with the interpretation of safety or efficacy data.
• History of clinically significant neurologic (e.g., seizures), cardiac, pulmonary (e.g., asthma, COPD), metabolic, renal, or hepatic conditions.
• Use drugs known to prolong QTc. ECG findings of PR interval > 220 msec or QRS duration > 120 msec or QTcF interval > 450 msec for men and 470 msec for women obtained at screening visit or prior to the first dose of study drug.
• Aspartate transaminase (AST), alanine transaminase (ALT), gamma-glutamyl transferase (GGT), serum creatinine, or total bilirubin > 1.5 upper limit of normal (ULN) at screening or prior to the first dose of study drug. These laboratory tests may be repeated once, if they are abnormal on first screening, and if there is a medical reason to believe the results may be inaccurate. If the repeat test is within the reference range, the subject may be included only if the Investigator considers that the previous finding will not compromise the subject’s safety and will not interfere with the interpretation of safety data.
• Positive blood screen for human immunodeficiency virus (HIV antibody), hepatitis B virus surface antigen, or hepatitis C virus antibody at screening.
• History of alcohol or illicit drug abuse within 1 year before the first dose of study drug.
• Daily use of marijuana.
  • Note: Occasional use of THC/cannabinoid products is allowed in the study.
• Participation in a clinical trial and receipt of an investigational medication or a new chemical entity within 90 days, 5 half-lives, if known, or twice the duration of the biological effect of any medication (whichever is longer) prior to the first dose of current study drug.
• Donation of blood, plasma or other blood products or blood collection in excess of 470 mL within 8 weeks prior to dosing.
• Known history of sensitivity to any of the study drugs or components thereof, or to other 5-HT3 receptor antagonists, or a history of medication allergy or other allergy that, in the opinion of the Investigator, contraindicates study participation.
• Major surgery within 4 weeks of screening that could interfere with, or for which the treatment might interfere with, the conduct of the study, or that would pose an unacceptable risk to the subject in the opinion of the Investigator.
• Uncontrolled current illness (i.e., active infection).
• Has a current or a history of cancer, with the exception of basal cell carcinoma.