The purpose of the present research study is to investigate the pharmacokinetics, as well as safety, tolerability and pharmacodynamics of different ascending dosing regimens of AP214 in patients undergoing cardiac surgery. AP214, the investigational drug, is being developed to potentially prevent post-surgical kidney injury after thoracic aortic aneurysm repair.

Inclusion Criteria:

1. Has signed the trial-specific informed consent form.
2. Patients ≥ 18 years old, male or female, not of childbearing potential (postmenopausal or permanently sterilized, e.g. tubal ligation, hysterectomy, bilateral salpingectomy), regardless of ethnicity.
3. Patients undergoing CABG, valve(s), CABG/valve(s) and/or aortic root or ascending aortic aneurysm repair surgery.
4. Cleveland Clinic Renal Score ≥ 2 (higher than average risk for AKI).
5. EF ≥ 30%, evaluated within 2 months prior to screening visit.

Exclusion Criteria:

1. Cardiac surgery to be performed "off pump" without cardiopulmonary bypass.
2. Circulatory arrest in connection with aortic root or ascending aortic aneurysm repair surgery.
3. Confirmed or suspected endocarditis.
4. Requiring a reoperation on one of the valves within 3 months following the original valve surgical procedure.
5. Receiving Aprotinin during the trial, from Screening to Day 90.
6. Having undergone cardiovascular catheterization ≤ 48 hours prior to scheduled surgery.
7. Active peptic ulcer disease and gastritis.
8. Hemoccult positive stools, hematological, bleeding, and coagulation disorders.
9. Receiving dopamine at renal doses (2-4 mcg/kg/min), from Screening to Day of surgery.
10. S-Creatinine greater than 2.1 mg/dl.
11. Known or suspected hypersensitivity to the investigational medicinal product.
12. Known or suspected hypersensitivity to Ondansetron or other selective 5-hydroxytryptamine 3 (5-HT3) receptor antagonists.
13. Current participation in any other interventional clinical trial.
14. Previously dosed with AP214.
15. Use of investigational medicinal products within the previous 6 months.
16. Body weight above 140 kg.
17. History of any organ transplant.
18. Women who are of childbearing potential, pregnant, or breast-feeding.
19. Current abuse of alcohol or substance, according to the investigator's medical judgment.
20. Has a mental incapacity or language barriers precluding adequate understanding of trial procedures.
21. Is considered by the Investigator unsuitable to participate in the trial for any other reason, for instance due to a significant serious underlying condition.