Study to Evaluate the Safety and Efficacy of the GGTA1 KO Thymokidney in Patients With ESRD (EXTEND)

EXTEND: A Prospective Study to Evaluate the Safety and Efficacy of GGTA1 KO Thymokidney XenoTransplantation in Patients With End-stage Renal Disease (ESRD)

The purpose of this study is to evaluate the safety and efficacy of the GGTA1 KO Thymokidney in patients with end-stage renal disease (ESRD) who are either not eligible for conventional allogeneic kidney transplantation (Group 1) or are on an Organ Procurement and Transplantation Network (OPTN) kidney transplant waitlist, but are more likely to die or go untransplanted within 5 years than receive a kidney transplant (Group 2).

The study consists of xenotransplantation followed by a 24-week Post-transplant Follow-up Period (Part A) to evaluate the efficacy and safety objectives followed by a Long-term Follow-up Period (Part B) to evaluate participant survival, GGTA1 KO Thymokidney survival, and screening for zoonotic infections. Part B will continue for the lifetime of the participant or for 52 weeks following nephrectomy, if required.

Study Overview

• Status: Recruiting
• Conditions: Kidney Transplantation; ESRD (End-Stage Renal Disease); Xenotransplantation
• Intervention / Treatment: Biological: GGTA1 KO Thymokidney

Detailed Description

This is a Phase 1/2/3, multicenter, open-label, safety and efficacy study of the GGTA1 KO Thymokidney in patients with ESRD. The study will be comprised of the following:

• A Screening Period up to 52 weeks.
• Part A consists of the GGTA1 KO Thymokidney transplantation followed by a 24-week Post-transplant Follow-up Period, including the evaluation of all study endpoints and safety assessments.
• Part B is a Long-term Follow-up Period that extends for the lifetime of participants who received the GGTA1 KO Thymokidney or for 52 weeks following nephrectomy, if required, including but not limited to documentation of participant survival, GGTA1 KO Thymokidney survival, and screening for zoonotic infections.

There will be 2 groups of participants enrolled in the study. Group 1 will be participants deemed ineligible for conventional allogeneic kidney transplantation due to medical reason(s). Group 2 will be participants on an OPTN kidney transplant waitlist but who are more likely to die or go untransplanted within 5 years than receive a kidney transplant.

For the purpose of the primary analysis, the end of the study is defined as the date of the final visit of the final participant in Part A of the study.

• Study Type: Interventional
• Enrollment (Estimated): 50
• Phase: Phase 2; Phase 1

Contacts and Locations

• Study Contact: Name: United Therapeutics Global Medical Information; Phone Number: 919-485-8350; Email: clinicaltrials@unither.com

Study Locations

• United States
  • New York
    • New York, New York, United States, 10016
      • Recruiting
      • New York University Langone Health
      • Contact: Karen Khalil; Phone Number: 347-514-2758; Email: karen.khalil@nyulangone.org
      • Principal Investigator: Robert A Montgomery, MD, DPhil

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria for all Participants (Groups 1 and 2):

1. Provide voluntarily informed consent to participate in the study and for lifetime follow-up.
2. Have a diagnosis of ESRD at the time of informed consent.
3. Hemodialysis dependent for a minimum of 6 months and has a functioning arterial-venous fistula/graft or permanent catheter at the time of informed consent.
4. 50 to 70 years of age at the time of informed consent, or 40 to <50 years of age with a calculated panel reactive antibody (cPRA) of ≥99.9%.
5. Evidence of thymic involution on chest computed tomography (CT) scan with a thymic region of interest score of ≤1.
6. Live within 3 hours travel time of the xenotransplant center.
7. Female participants must be postmenopausal or permanently sterilized (eg, hysterectomy, bilateral oophorectomy, or bilateral salpingectomy). Male participants must agree to the use of a highly effective method of birth control, if the possibility of conception exists.
8. Negative xeno-crossmatch at Screening and pre-transplant.
9. Estimated Post Transplant Survival Calculator score >20%.(https://optn.transplant.hrsa.gov/data/allocation-calculators/epts-calculator/).
10. Body mass index ≤35 kg/m2.
11. Have completed or have initiated and plan to complete (meningococcal A, C, W, Y and meningococcal B vaccine series only) Centers for Disease Control and Prevention-recommended courses of age- and risk-factor-appropriate vaccinations.
12. Seropositive (immunoglobulin G) for cytomegalovirus and Epstein-Barr virus.

Additional Inclusion Criteria for Group 1:

1. Ineligible for conventional allogeneic kidney transplantation due to medical reason(s) for any of the following:

1. Ineligible for a living donor transplant.
2. Ineligible for an OPTN kidney transplant waitlist (reason for ineligibility will be collected).
3. Delisted from OPTN kidney transplant waitlist (reason for delisting will be collected).

Additional Inclusion Criteria for Group 2:

1. On an OPTN kidney transplant waitlist (active or inactive status).
2. No approved living kidney donors.
3. More likely to die or go untransplanted within 5 years than receive a kidney transplant as measured by the Kidney Transplant Decision Aid at the time of informed consent (select United States for "Choose your state" field and National average for "Choose your transplant program" field; https://www.srtr.org/tools/kidney-transplant-decision-aid/).

Exclusion Criteria (pertain to all participants in Groups 1 and 2):

1. Need for multiple organ transplants.

2. Severe medical co-morbidities including, but not limited to:

   1. Chronic liver disease.
   2. Advanced cardiovascular disease.
   3. Severe peripheral vascular disease that limits technical ability to transplant the GGTA1 KO Thymokidney.
   4. Severe neurologic diseases or conditions that would preclude meaningful recovery or informed consent.
   5. Oral steroid-dependent airway disorder or chronic pulmonary disease or requires chronic, intermittent, or continuous supplemental oxygen.
   6. Pulmonary hypertension.
   7. Uncontrolled diabetes or sequelae of diabetes mellitus including severe non-proliferative diabetic retinopathy.
   8. Severe neurogenic bladder that requires intermittent catheterization.
3. ESRD due to hereditary or structural kidney disease.
4. Active or recently treated malignancy at the time of informed consent.
5. Non-renal cause of hematological disorders associated with anemia (eg, thalassemia and sickle disease).
6. Cannot discontinue chronic anticoagulation therapy (low-dose daily aspirin is permissible).
7. History of major psychiatric disorders with psychiatric hospitalization and/or suicidal ideation within 5 years of informed consent.
8. Being treated for active tuberculosis (TB), have received prophylaxis for positive FDA-approved interferon-gamma release assay, or test positive for TB by FDA-approved interferon-gamma release assay test during Screening.
9. Nucleic acid test (NAT) positive for hepatitis B virus and/or hepatitis C virus, hepatitis B surface antibody (anti-HBs) titer <10 mIU/mL unless the participant is determined to be a nonresponder to hepatitis B vaccination (a nonresponder is defined as having an anti-HB titer <10 mIU/mL after having completed both the standard vaccine series and a fourth booster dose and/or second standard vaccine series), and/or positive for human immunodeficiency virus (HIV; HIV-1 and HIV-2 antibody and/or NAT).
10. Not able to independently perform activities of daily life.
11. Have a history of medical noncompliance that may preclude adherence to the demands and requirements of xenotransplantation (eg, history of substance use disorder [SUD] within 1 year of informed consent, lack of social support, untreated psychological conditions).

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: GGTA1 KO Thymokidney; Participants will receive GGTA1 KO Thymokidney	Biological: GGTA1 KO Thymokidney; Porcine kidney containing an intentional genomic alteration and thymic tissue autograft for xenotransplantation

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Survival Rate of Patients with ESRD Receiving the GGTA1 KO Thymokidney at 24 Weeks Post Transplant	Participant survival rate at 24 weeks post transplant.	Day 0 (day of xenotransplantation) to 24 weeks post transplant
Survival Time of Participants Receiving the GGTA1 KO Thymokidney	Participant survival post transplant. Participant survival is defined as time from xenotransplantation to death for any cause.	Day 0 (day of xenotransplantation) until death for any cause, assessed at least every 24 weeks after transplantation while the participant is alive, up to 50 years
GGTA1 KO Thymokidney Function Post Transplant (Endogenous GFR)	Endogenous measured GFR (24-hour urine creatinine clearance) at 24 weeks post transplant.	At 24 weeks post transplant
GGTA1 KO Thymokidney Function Post Transplant (Exogenous GFR)	Exogenous measured GFR (nuclear medicine GFR) at 24 weeks post transplant.	At 24 weeks post transplant
GGTA1 KO Thymokidney Function Post Transplant (Proliferative Responsiveness)	Proliferative responsiveness to source GGTA1 KO Pig versus third-party pig as measured by mixed lymphocyte reaction from baseline to 24 weeks post transplant.	At 24 weeks post transplant
Quality of Life in Participants Receiving the GGTA1 KO Thymokidney by EuroQol 5-Dimension 5-Level (EQ-5D-5L)	Change in the EQ-5D-5L from baseline to 24 weeks post transplant. The EQ-5D-5L questionnaire assesses health-related quality of life across 5 categories (Mobility, Self-Care, Usual Activities, Pain/Discomfort, and Anxiety/Depression). Each category has 5 levels, ranging from 1 (no problems) to 5 (extreme problems or inability to perform the activity). Higher scores indicate a worse health outcome (more mobility issues, greater pain, more anxiety, etc).	Baseline to 24 weeks post transplant
Quality of Life in Participants Receiving the GGTA1 KO Thymokidney by Standardized Outcomes in Nephrology Life Participant (SONG-LP)	Change in SONG-LP from baseline to 24 weeks post transplant. The SONG-LP assesses participation in different life activities over the past month. The minimum score (worst outcome) is 4 (if all responses are "1" - Never) and the maximum score (best outcome) is 20 (if all responses are "5" - Always). Higher scores indicate a better health outcome (greater ability to participate in activities).	Baseline to 24 weeks post transplant
Quality of Life in Participants Receiving the GGTA1 KO Thymokidney by Kidney Transplant Questionnaire (KTQ)	Change in KTQ from baseline to 24 weeks post transplant. Each question in the KTQ is scored on a 1 to 7 scale with: 1 = worst outcome (eg, "A very great deal of trouble or distress" / "All of the time") and 7 = best outcome (eg, "No trouble or distress" / "None of the time"). Higher scores indicate a better outcome, meaning less distress, fewer symptoms, and better well-being.	Baseline to 24 weeks post transplant
Quality of Life in Participants Receiving the GGTA1 KO Thymokidney by Patient Global Impression of Change (PGI-C)	PGI-C at 24 weeks post transplant. The PGI-C assesses a patient's perception of improvement or worsening over time. The minimum score (best outcome) is 1 ("Very Much Improved") and the maximum score (worst outcome) is 7 ("Very Much Worse"). Higher scores indicate a worse health outcome (greater worsening).	At 24 weeks post transplant
Incidence of Treatment-Emergent Adverse Events (Safety of the GGTA1 KO Thymokidney)	Incidence of adverse events and serious adverse events; all-cause mortality.	Baseline until last visit, assessed at least every 24 weeks after transplantation while the participant is alive and the thymokidney is functional, up to 50 years, or for 1 year after nephrectomy if required
Incidence of Proteinuria	Incidence of proteinuria from Day 0.	Day 0 (day of xenotransplantation) until last visit, assessed at least every 24 weeks after transplantation while the participant is alive and the thymokidney is functional, up to 50 years, or for 1 year after nephrectomy if required
Incidence of Zoonotic Infection	Incidence of zoonotic infection from Day 0.	Day 0 (day of xenotransplantation) until last visit, assessed at least every 24 weeks after transplantation while the participant is alive and the thymokidney is functional, up to 50 years, or for 1 year after nephrectomy if required
Incidence of Opportunistic Infection	Incidence of opportunistic infection from Day 0.	Day 0 (day of xenotransplantation) until last visit, assessed at least every 24 weeks after transplantation while the participant is alive and the thymokidney is functional, up to 50 years, or for 1 year after nephrectomy if required
Survival Rate of the GGTA1 KO Thymokidney at 24 Weeks Post Transplant	GGTA1 KO Thymokidney survival rate at 24 weeks post transplant. GGTA1 KO Thymokidney failure is defined as GGTA1 KO Thymokidney nephrectomy.	Day 0 (day of xenotransplantation) to 24 weeks post transplant
Survival Time of the GGTA1 KO Thymokidney (Overall Survival)	Overall survival of the GGTA1 KO Thymokidney post transplant. Overall survival time of the GGTA1 KO Thymokidney is defined as time from xenotransplantation to GGTA1 KO Thymokidney nephrectomy or death, whichever occurs first.	Day 0 (day of xenotransplantation) until start of chronic dialysis, nephrectomy, or death, whichever occurs first, assessed at least every 24 weeks after transplantation while the participant is alive and the thymokidney is functional, up to 50 years
Survival Time of the GGTA1 KO Thymokidney (Death-censored Survival)	Death-censored survival GGTA1 KO Thymokidney. Death-censored survival time of the GGTA1 KO Thymokidney is defined as time from xenotransplantation to GGTA1 KO Thymokidney nephrectomy censored for death.	Day 0 (day of xenotransplantation) until start of chronic dialysis, nephrectomy, or death, whichever occurs first, assessed at least every 24 weeks after transplantation while the participant is alive and the thymokidney is functional, up to 50 years

Collaborators and Investigators

• Sponsor: United Therapeutics

Study record dates

Study Major Dates

• Study Start (Estimated): March 1, 2026
• Primary Completion (Estimated): March 1, 2029
• Study Completion (Estimated): March 1, 2076

Study Registration Dates

• First Submitted: November 4, 2025
• First Submitted That Met QC Criteria: November 4, 2025
• First Posted (Estimated): November 5, 2025

Study Record Updates

• Last Update Posted (Actual): December 2, 2025
• Last Update Submitted That Met QC Criteria: November 24, 2025
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: ESRD; End-stage renal disease; Xenotransplantation; GGTA1 KO Thymokidney
• Additional Relevant MeSH Terms: Urogenital Diseases; Pathologic Processes; Male Urogenital Diseases; Kidney Diseases; Urologic Diseases; Female Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Chronic Disease; Disease Attributes; Renal Insufficiency; Pathological Conditions, Signs and Symptoms; Kidney Failure, Chronic; Renal Insufficiency, Chronic
• Other Study ID Numbers: GPT-KF-101

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No