The purpose of this study is to evaluate the effect of RBT-1 on reducing the risk of post-operative complications in subjects undergoing cardiac surgery on cardiopulmonary bypass (CPB). A sub-study will also be conducted to evaluate the pharmacokinetic (PK) profile of a single administration of RBT-1 by means of a popPK approach in subjects scheduled to undergo cardiac surgery.

Inclusion Criteria:

1. Male or female, ≥18 years of age at Screening.
2. Planned to undergo non-emergent CABG and/or cardiac valve surgery requiring CPB; non-emergent surgery must allow for study drug infusion ≥24 but ≤48 hours prior to surgery.
3. If female, subjects must use an effective method of birth control or abstain from sexual relations with a male partner (unless has undergone tubal ligation or hysterectomy or is at least 1 year postmenopausal) for the duration of their study participation.
4. If male, subjects must use an effective method of birth control or abstain from sexual relations with a female partner for the duration of their study participation, unless the subject has had a vasectomy ≥6 months prior to infusion with study drug.
5. Willingness to comply with all study-related procedures and assessments.

Exclusion Criteria:

1. Surgery planned to occur <24 hours from the start of study drug infusion.
2. Presence of acute organ dysfunction (AKI, acute decompensated heart failure, acute respiratory failure, stroke, etc) as assessed by the Investigator at the time of Screening.
3. Surgery to be performed without CPB.
4. Chronic kidney disease (CKD) requiring dialysis.
5. Hypokalemia and/or hypomagnesemia within 24 hours prior to study drug infusion; electrolytes can be replenished if low.
6. Cardiogenic shock or immediate requirement for inotropes, vasopressors, or other mechanical devices, such as intra-aortic balloon pump (IABP).
7. Known history of cancer within the past 2 years, except for carcinoma in situ of the cervix or breast, early-stage prostate cancer, or adequately treated non-melanoma cancer of the skin.
8. Known or suspected sepsis at time of Screening.
9. Asplenia (anatomic or functional).
10. History of hemochromatosis, iron overload, or porphyria.
11. Known hypersensitivity or previous anaphylaxis to SnPP or FeS.
12. Female subject who is pregnant or breastfeeding.
13. Participation in a study involving an investigational drug or device within 30 days prior to study drug infusion or throughout participation in REN-007.
14. In the opinion of the Investigator, for any reason, the subject is an unsuitable candidate to receive RBT-1.