Renibus Reports Positive Final Results from Phase 2 Study of RBT-1, a First-in-Class Preconditioning Agent for Patients Undergoing Cardiothoracic Surgery, at the American Association for Thoracic Surgery (AATS) Meeting

RBT-1 achieved the primary biomarker endpoint, as well as several key clinical outcome endpoints; positive data supports the potential for RBT-1 to improve postoperative outcomes in cardiothoracic surgery 

RBT-1 as a preconditioning agent has the potential to provide patient benefits in multiple surgical settings where organ injury during surgery increases the risk of post-operative complications-

-Planned pivotal Phase 3 study of RBT-1 to be initiated in June 2023-

Southlake, Texas, May 7, 2023 – Renibus Therapeutics® (“Renibus”), a clinical-stage biopharmaceutical company focusing on the prevention and treatment of cardio-renal diseases, today presented positive final results from a Phase 2 trial evaluating RBT-1 (stannic protoporfin/iron sucrose) in patients undergoing elective cardiac surgery during an oral presentation at the 103rd Annual American Association for Thoracic Surgery (AATS) meeting at the Los Angeles Convention Center, taking place May 6-9, 2023 in Los Angeles, CA.

“We are thrilled with the final results of RBT-1 in this Phase 2 study, demonstrating clinically meaningful reductions across key clinical endpoints that we believe will significantly improve the patient’s journey in cardiac surgery,” said Frank Stonebanks, Co-CEO of Renibus.  “These data demonstrate that RBT-1 has broad potential as a preconditioning agent across several large cardiothoracic surgery settings.  We look forward to initiating our pivotal Phase 3 study later this quarter and progressing one step closer to our goal of bringing RBT-1 to patients.”

Summary of Final Phase 2 Results:

RBT-1 was studied in a multicenter, double-blind, placebo controlled, Phase 2 clinical trial in patients undergoing coronary artery bypass graft (CABG) and/or cardiac valve surgery on cardiopulmonary bypass. The trial enrolled 152 patients from cardiac surgery centers in the US, Canada and Australia, 132 patients were evaluable for the primary endpoint (ITT population) and 121 were evaluable for clinical outcomes (mITT population), as pre-specified in the statistical analysis plan.

RBT-1 treated patients demonstrated a highly significant increase in anti-inflammatory and antioxidant biomarkers of cytoprotective preconditioning, which was the primary endpoint of the study. The biomarkers assessed were interleukin-10 (IL-10), heme oxygenase-1 (HO-1) and Ferritin. In addition, several clinically meaningful improvements were observed. These results are summarized below:

  • A statistically significant (p<0.0001) increase in biomarkers of cytoprotective preconditioning, including IL-10, HO-1, and Ferritin, which achieved the trial’s primary endpoint.
  • A statistically significant (-2.7 days, p=0.0243) reduction in days in the ICU.
  • A clinically meaningful reduction in ventilator time (1 day) and hospital length of stay (1.3 days)
  • A statistically significant reduction in 30-day cardiopulmonary readmission rates (-72%, p=0.0391) and 60- and 90-day cardiopulmonary readmission rates (-75% for both, p=0.0189)
  • A clinically meaningful reduction in atrial fibrillation (-34%), troponin I levels (-49%), and MAKE30 (-36%).
  • In a post hoc analysis of a composite endpoint of death, ICU days, 30-day cardiopulmonary readmission rates, atrial fibrillation rates, and hospital days using the win ratio method, a statistically significant benefit was observed among the treated groups (win ratio 1.63, p<0.02). (This statistical method and composite of key clinical outcomes are pre-specified as the primary endpoint in the planned Phase 3 pivotal trial expected to be initiated in June 2023.)
  • RBT-1 treatment also showed reductions vs placebo in rates of hypervolemia (-64%) and anemia (-49%) as reported by the study investigators.
  • RBT-1 demonstrated a generally well-tolerated safety profile in the Phase 2 trial.
  • Renibus is moving forward into its Phase 3 pivotal trial with the 45 mg SnPP/240 mg FeS dose of RBT-1 (administered as a single infusion); there was no statistically significant difference in efficacy between this dose and the 90 mg SnPP/240 mg FeS dose in the Phase 2 trial; however, the lower dose resulted in less photosensitivity.
  • The post hoc win ratio for the 45 mg SnPP/240 mg FeS dose was 2.02 (p=0.004).

“Post-operative complications from cardiac surgery represent a major burden for patients as well as an increased strain on healthcare costs. There are currently no approved pharmacological therapies available for use to improve the post-operative course and quality metrics for these patients,” said Kevin Lobdell, MD, System Director-Sanger Heart & Vascular Institute, Advocate Health and Clinical Professor Wake Forest University School of Medicine. “RBT-1 has the potential to make a major impact on patients by reducing post cardiac surgery complications through its unique mechanism.”

Title: A Phase 2 Randomized, Double-Blind, Placebo-Controlled, Multi-Center Trial of RBT-1 Evaluating Cytoprotective Biomarkers & Post-Operative Outcomes in Patients Undergoing Elective Coronary Artery Bypass Graft and/or Valve Surgery on Cardiopulmonary Bypass

Session: CALS and Rescue
Date and Time:
May 7, 2023, 7:45 am PDT

Presenter: Dr. Andre Lamy, MD, MSc, Cardiac Surgeon, Population Health Research Institute, McMaster University, Canada

Following conclusion of ATTS, the slides related to the oral presentation will be available on the publications page of the Renibus website at

About the Completed Phase 2 Trial of RBT-1

The Phase 2 study (NCT04564833), which was completed in February 2023, was a randomized, double-blind, multi-center, placebo-controlled trial evaluating the effect of RBT-1 in patients undergoing elective coronary artery bypass graft (CABG) and/or cardiac valve surgery.  Renibus announced final results from this study in May 2023, which support the advancement of RBT-1 into a pivotal Phase 3 study.  Renibus previously announced interim results from this RBT-1 Phase 2 study in November 2022 and June 2022, and 30-day topline results in January 2023.

About Renibus

Renibus is a clinical stage biopharmaceutical company dedicated to treating, improving and extending patients’ lives by developing breakthrough products to prevent disease progression, improve outcomes and protect against organ damage associated with cardiorenal diseases and complex surgeries. The Company has developed a robust portfolio of products that activate multiple cytoprotective pathways, including organ protection via preconditioning. Renibus’ first-in-class lead program, RBT-1 (stannic protoporfin/iron sucrose), is a potent inducer of anti-inflammatory and antioxidant pathways. RBT-1 has finished its Phase 2 development in cardiac surgery and will soon enter a Phase 3 registration study for its lead indication to reduce the risk of post-operative complications following cardiothoracic surgery. RBT-2 is an antioxidant and anti-fibrotic drug that has been shown to reduce the risk of CKD progression in preclinical models and will be in IND enabling and clinical development in 2023. RBT-3, a novel, low molecular weight iron nanoparticle, is one component of RBT-1 and is targeted at reducing the risk of cisplatin-induced nephrotoxicity and will be taken into clinical development in 2023. RBT-9 (stannic protoporfin) is a potent anti-inflammatory and antioxidant drug with broad spectrum anti-viral properties. It has been investigated in a 42-patient Phase 2, randomized, placebo-controlled trial in high-risk patients with COVID-19. The data from this trial indicated the RBT-9 has the potential to significantly improve clinical outcomes in life threatening viral infections. Additional pre-clinical work is underway to help inform the clinical development strategy.

For more information, please visit the Company’s website at and engage with us on LinkedIn.

Investor and Media Contact:

Amy Conrad
Juniper Point

Business Development Contact
Frank Stonebanks
Co-CEO, Renibus