Ascending Multiple Intravenous Doses of AON-D21 in Healthy Male Subjects.

Inclusion Criteria: * 18 to 55 years of age inclusive, at the time of signing the informed consent. * Body mass index (BMI) within the range 18 - 30 kg/m2 with a body weight between 50 kg and 120 kg. * Male subjects * Subject is healthy as determined by medical evaluation * Subject provided written informed consent * Subject is willing to comply with all requirements and restrictions according to the study protocol. Exclusion Criteria: * Any concomitant disease, condition, or treatment that could interfere with the conduct of the study. * Any acquired or congenital immune deficiency. * Acute infection (including viral infections) in the preceding 6 weeks (8 weeks for respiratory infections). * Clinically relevant abnormality following the Investigator's review of the physical examination, vital signs, ECG and clinical study protocol-defined clinical laboratory tests that, in the opinion of the Investigator, would preclude inclusion in the trial at screening and admission. * Evidence of COVID-19 signs or symptoms, exposure to infected person or confirmed COVID-19 infection within the last 2 weeks. * Use of any concomitant medication or prescribed or non-prescribed drugs within 2 weeks or 5 times the half-life, whichever is longer, prior to the first study treatment administration. * Administration of vaccine(s) within 2 weeks prior to screening or plans to receive such vaccines during the study. * Use of any investigational drug or participation in any clinical study within 30 days or 5 half-life times, whichever is longer, prior to dosing. * Positive drug or alcohol screen at screening and admission. * Any significant blood loss, donated one unit (450 mL) of blood or more, or donated plasma, or received a transfusion of any blood or blood products within 30 days prior to dosing. * Subjects who are unable to refrain from the consumption of Seville oranges, grapefruit or grapefruit juice and /or pomelos, exotic citrus fruits, grapefruit hybrids, starfruit or fruit juices from 72 hours prior to dosing on Day 1, until completion of the last PK blood sample time point. * Legal incapacity or limited legal capacity, or incarceration. * Inability to understand or communicate reliably with the Investigator.