RecruitingPhase 1Biological interventionPhase 1 Study on the Safety, Tolerability, and Pharmacokinetics of JST-018 in Healthy AdultsThe goal of this clinical trial is to learn if a single dose of the study drug, JST-018, is safe and tolerable when administered by injection into the arm or thigh muscle of healthy men and women aged 18 to 55. The main questions it aims to answer are: * Is a single administration of JST-018 safe? * What is the concentration of the JST-018 in the blood over time? * Do antibodies to JST-018 develop following a dose of JST-018? Researchers will compare JST-018 to Placebo to see if there are any differences in the safety and tolerability of a single dose at different dose levels. Participants will be confined to the clinic for the first 3 days. They will receive an injection on the second day, and then return for 9 more visits over the period of 1 year for: * Physical exam with vital signs * Electro-cardiogram (ECG) * Bood collection for clinical labs and research samples * Urine sample * Assessment of potential adverse effects and medications taken