Phase 1 Study on the Safety, Tolerability, and Pharmacokinetics of JST-018 in Healthy Adults

Inclusion Criteria: 1. Healthy men or women 18 to 55 years of age 2. BMI between 18 and 32 kg/m2 3. Negative serum pregnancy test 4. Use of highly effective birth control method(s) for a minimum of 60 days prior to consent and is willing to continue use for at least 12 months, or abstinence 5. In good general health as determined by medical history, exams and tests Exclusion Criteria: 1. Acute illness or fever (≥100.4°F) within 7 days prior to dosing 2. Any history of receiving treatment, vaccine, or monoclonal antibodies (mAbs) against smallpox, monkeypox, or other orthopox viruses. 3. Receipt of any vaccine within 30 days prior to Screening, planned receipt of any vaccine prior to Day 1, or planned receipt of any vaccines before 45 days post-injection. 4. Any medical condition for which IM injections would be contraindicated in the opinion of the investigator (eg, bleeding disorders, anticoagulant therapy, and severe thrombocytopenia) 5. History of congenital or acquired immunodeficiency syndrome, , including positive human immunodeficiency virus (HIV-1/-2) antibody result 6. Prior solid organ or bone marrow transplant 7. Clinically significant corneal or lens abnormality as determined by history, clinical examination, or diagnostic imaging. Including, but not limited to: * Corrected vision of less (worse) than 20/40 * History of any clinically significant history of eye trauma, in the opinion of the investigator * History of cataracts or current cataracts * Lens opacity greater than NC2, C2, or P0 as determined by the Lens Opacities Classification System (LOCS) III * History of uveitis (including acute) * Use of ocular or inhaled prescription steroids within 1 year prior to Screening nasal steroids are permissible). A single short course (ie, less than 14 days) of systemic steroid therapy is allowed provided it is concluded more than 6 months prior to Screening. * History of diabetes 8. Use of immunosuppressive agents, anticoagulants, or antiarrhythmics within 1 year prior to Screening. Nasal steroid use is permissible. 9. Upper arms and thighs are with insufficient muscular tissue for IM injections or is obscured by tattoos or rash 10. Use of any medications started within 30 days prior to Day -1, including prescription medications, nutritional supplements, and over-the-counter medications * Vitamin supplements are allowed * Recommended doses of acetaminophen are allowed, except for 24 hours prior to dosing * Recommended doses of non-steroidal anti-inflammatory drugs (NSAIDs) (eg, aspirin, ibuprofen) are also allowed, except for 7 days prior to dosing 11. Positive hepatitis B surface antigen, hepatitis B core antigen, or hepatitis C antibody 12. Positive urine drug test or cotinine (indicating active current smoking) at Screening or Day -1, positive alcohol breath test at Screening or on Day -1, or suspected/known drug abuse and/or alcohol use disorder 13. Smoking or has used nicotine or nicotine-containing products (eg, snuff, nicotine patch, nicotine chewing gum, mock cigarettes, or inhalers) within 3 months before study drug dosing 14. Dosing in any clinical research study evaluating another investigational drug or therapy within 30 days or at least 5 half-lives (whichever is longer) of receiving the investigational drug prior to Screening 15. Progressive, unstable, or uncontrolled medical conditions that have required medical attention or changes to medication for medical reasons within 90 days prior to consent 16. History of allergic reactions or hypersensitivity reactions to other therapeutic antibodies or immunoglobulins 17. Receipt of any mAbs in the 12 months prior to Screening 18. High blood pressure 19. Women who are either pregnant or breast-feeding 20. Vulnerable individuals (eg, military recruits, persons in compulsory detention, those with limited legal capacity) 21. Receipt of immunoglobulins or any blood products within 90 days prior to consent or planned receipt during the study period 22. Donation or loss of \>500 mL of blood within 30 days or plasma within 7 days of Day 1; any planned donation of blood or plasma during the study period 23. History of any malignant neoplasm within the last 5 years, with the exception of adequately treated localized or in situ non-melanoma carcinoma of the skin or the cervix 24. Strenuous activity or contact sports within 48 hours before study drug dosing and through Day 8 26\. History of relevant drug and/or food allergies