A Study to Evaluate the Safety, Tolerability and Pharmacokinetics of PTT-121

This is a Phase I, single-center, randomized, double-blind, placebo-controlled SAD/MAD study to evaluate safety, tolerability, and PK of Intravenously Administered PTT-121 in healthy Chinese adults.

Inclusion Criteria: * Healthy adults aged between 18 and 55 years. * BMI 18.0-26.0. * Those who are adequate to be subjects in this study upon judgment of the investigator after physical examination, clinical laboratory test, examination, etc. Exclusion Criteria: * History of any clinically significant disease or disorder of the cardiovascular, respiratory, gastrointestinal, genitourinary, hematologic/lymphatic, neurologic, reproductive, psychiatric, endocrine, immunologic, musculoskeletal, breast, ear, ocular, thyroid, neoplastic, metabolic, or dermatologic systems, as determined by the Investigator. * History of hypersensitivity to the active ingredient of the investigational product, any of its excipients, or related compounds; or a history of severe drug-induced allergic reactions, including but not limited to angioedema and bronchospasm/asthma.