A First-in-Human Single and Multiple Ascending Dose Study of MT-251

Inclusion Criteria: 1. Male or female participants between 19 and 55 years of age (inclusive) at the time of signing informed consent. 2. Female participants must be of nonchildbearing potential, defined as postmenopausal or surgically sterile, and have official documentation, at least 6 months prior to the first dose. 3. Male subjects must use highly effective forms of contraception during sexual intercourse with female partners of childbearing potential. A non-vasectomized, male subject must agree to use a condom with a chemical barrier method. 4. Continuous non-smoker who has not used tobacco or nicotine-containing products for at least 3 months prior to the first dose of drug. 5. Good general health. 6. Able to provide written informed consent and understand and comply with the requirements of the study. Exclusion Criteria: 1. History or presence of any clinically significant organ system disease. 2. Abnormal laboratory assessments, physical exam of ECG outside the normal range that is judged by the Investigator to be clinically significant. 3. History of alcohol or drug abuse within the past 24 months. 4. Current use or history of regular tobacco or nicotine-containing products within 3 months prior to screening. 5. Administration of any prescription drug within 21 days or 5 half-lives (whichever is longer) of study drug administration; or over-the-counter drug within 7 days or 5 half-lives (whichever is longer) of study drug administration. 6. Administration or use of any investigational drug or device within 30 days preceding the first does of study drug administration. 7. Blood donation within 60 days prior to dosing or plasma donation within 14 days prior to dosing. 8. Sensitivity to any of the study drugs, or components thereof, or drug or other allergy that in the opinion of the Investigator or Sponsor Medical Monitor, contraindicates participation in the study.