This is a first-in-human (FIH), Phase 1, single-center, randomized, double-blind, placebo-controlled, single ascending dose study to evaluate the safety, tolerability, PK and immunogenicity of AK119, a humanized monoclonal antibody targeting the CD73. The study will consist of 4 cohorts of healthy subjects. Eight subjects will be enrolled per cohort, randomized in a 3:1 ratio to receive a single dose of either the active drug AK119 (N=6) or matching placebo (N=2). Approximately 32 subjects (24 receiving active drug and 8 receiving placebo) will participate in this study.

Inclusion Criteria:

Subjects must meet ALL the following inclusion criteria (as applicable) to be eligible for participation in this study:

• Adults between 18 and 55 years of age, inclusive, at screening.
• Must have a calculated body mass index (BMI, weight [kg]/height [m2]) within 18.0 to 30.0 kg/m2 (inclusive) at screening, and a total body weight ≥50 kg for men or ≥45 kg for women at screening and Day -1 before randomization.
• Must, in the opinion of the Investigator, be in good general health based upon medical history, physical examination (including vital signs), and 12-lead ECG; and clinical laboratory tests (up to 1 repeat permitted) must fall within the clinical laboratory"s reference normal ranges.

Exclusion Criteria:

Subjects who meet ANY of the following exclusion criteria will not be enrolled in this study

• Have a history of latent or active granulomatous infection, including histoplasmosis, candidiasis, or coccidioidomycosis prior to screening, or a history of any other infectious disease within 4 weeks prior to screening that, in the opinion of the Investigator, affects the subject"s ability to participate in the study.
• Have a history of multiple drug allergies or a known allergy or hypersensitivity to any biologic therapy at screening that is important in the opinion of the Investigator.
• Have a known allergy or reaction to any component of the AK119 formulation.
• Have any known malignancy or have a history of malignancy within the previous 5 years.
• Have a 12-lead ECG demonstrating QTcF interval > 450 msec for male subjects and >470 msec for female subjects at screening and Day -1 from average of 3 ECGs obtained after 5 minutes of supine rest.
• Blood pressure (BP) >150 mmHg (systolic) or > 95 mmHg (diastolic) at screening and Day -1, following at least 5 minutes of supine rest.
• Have had a live vaccination within 12 weeks prior to the study dosing or intend to have a live vaccination during the course of the study or have participated in a vaccine clinical study within 12 weeks prior to the study dosing.