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NCT Number: NCT07224763

Study to Evaluate the Safety and Efficacy of the GGTA1 KO Thymokidney in Patients With 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.

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Key information

Conditions

ESRD (End-Stage Renal Disease) Chronic Disease Disease Attributes Female Urogenital Diseases Female Urogenital Diseases and Pregnancy Complications Kidney Diseases Kidney Failure, Chronic Kidney Transplantation Male Urogenital Diseases Pathologic Processes Pathological Conditions, Signs and Symptoms Renal Insufficiency Renal Insufficiency, Chronic Urogenital Diseases Urologic Diseases Xenotransplantation

Age range

40 year–70 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 1 / Phase 2

Primary location

New York University Langone Health

New York, 10016, United States

Location status: Recruiting

Location contact

Karen Khalil

CONTACT

[email protected]

347-514-2758

Robert A Montgomery, MD, DPhil

PRINCIPAL_INVESTIGATOR

About this study

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.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

for all Participants (Groups 1 and 2):

  • Provide voluntarily informed consent to participate in the study and for lifetime follow-up.
  • Have a diagnosis of ESRD at the time of informed consent.
  • 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.
  • 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%.
  • Evidence of thymic involution on chest computed tomography (CT) scan with a thymic region of interest score of ≤1.
  • Live within 3 hours travel time of the xenotransplant center.
  • 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.
  • Negative xeno-crossmatch at Screening and pre-transplant.
  • Estimated Post Transplant Survival Calculator score >20%.(https://optn.transplant.hrsa.gov/data/allocation-calculators/epts-calculator/).
  • Body mass index ≤35 kg/m2.
  • 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.
  • Seropositive (immunoglobulin G) for cytomegalovirus and Epstein-Barr virus.

Additional Inclusion Criteria for Group 1:

  • Ineligible for conventional allogeneic kidney transplantation due to medical reason(s) for any of the following:
  • Ineligible for a living donor transplant.
  • Ineligible for an OPTN kidney transplant waitlist (reason for ineligibility will be collected).
  • Delisted from OPTN kidney transplant waitlist (reason for delisting will be collected).

Additional Inclusion Criteria for Group 2:

  • On an OPTN kidney transplant waitlist (active or inactive status).
  • No approved living kidney donors.
  • 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):

  • Need for multiple organ transplants.
  • Severe medical co-morbidities including, but not limited to:
  • Chronic liver disease.
  • Advanced cardiovascular disease.
  • Severe peripheral vascular disease that limits technical ability to transplant the GGTA1 KO Thymokidney.
  • Severe neurologic diseases or conditions that would preclude meaningful recovery or informed consent.
  • Oral steroid-dependent airway disorder or chronic pulmonary disease or requires chronic, intermittent, or continuous supplemental oxygen.
  • Pulmonary hypertension.
  • Uncontrolled diabetes or sequelae of diabetes mellitus including severe non-proliferative diabetic retinopathy.
  • Severe neurogenic bladder that requires intermittent catheterization.
  • ESRD due to hereditary or structural kidney disease.
  • Active or recently treated malignancy at the time of informed consent.
  • Non-renal cause of hematological disorders associated with anemia (eg, thalassemia and sickle disease).
  • Cannot discontinue chronic anticoagulation therapy (low-dose daily aspirin is permissible).
  • History of major psychiatric disorders with psychiatric hospitalization and/or suicidal ideation within 5 years of informed consent.
  • 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.
  • 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).
  • Not able to independently perform activities of daily life.
  • 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).

Treatment and study plan

GGTA1 KO Thymokidney

Biological

Porcine kidney containing an intentional genomic alteration and thymic tissue autograft for xenotransplantation

Primary outcomes

  1. Survival Rate of Patients with ESRD Receiving the GGTA1 KO Thymokidney at 24 Weeks Post Transplant

    Time frame: Day 0 (day of xenotransplantation) to 24 weeks post transplant

    Participant survival rate at 24 weeks post transplant.

  2. Survival Rate of the GGTA1 KO Thymokidney at 24 Weeks Post Transplant

    Time frame: Day 0 (day of xenotransplantation) to 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.

  3. Survival Time of Participants Receiving the GGTA1 KO Thymokidney

    Time frame: 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

    Participant survival post transplant. Participant survival is defined as time from xenotransplantation to death for any cause.

  4. Survival Time of the GGTA1 KO Thymokidney (Overall Survival)

    Time frame: 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

    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.

  5. Survival Time of the GGTA1 KO Thymokidney (Death-censored Survival)

    Time frame: 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

    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.

  6. GGTA1 KO Thymokidney Function Post Transplant (Endogenous GFR)

    Time frame: At 24 weeks post transplant

    Endogenous measured GFR (24-hour urine creatinine clearance) at 24 weeks post transplant.

  7. GGTA1 KO Thymokidney Function Post Transplant (Exogenous GFR)

    Time frame: At 24 weeks post transplant

    Exogenous measured GFR (nuclear medicine GFR) at 24 weeks post transplant.

  8. GGTA1 KO Thymokidney Function Post Transplant (Proliferative Responsiveness)

    Time frame: At 24 weeks post transplant

    Proliferative responsiveness to source GGTA1 KO Pig versus third-party pig as measured by mixed lymphocyte reaction from baseline to 24 weeks post transplant.

  9. Quality of Life in Participants Receiving the GGTA1 KO Thymokidney by EuroQol 5-Dimension 5-Level (EQ-5D-5L)

    Time frame: Baseline to 24 weeks post transplant

    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).

  10. Quality of Life in Participants Receiving the GGTA1 KO Thymokidney by Standardized Outcomes in Nephrology Life Participant (SONG-LP)

    Time frame: Baseline to 24 weeks post transplant

    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).

  11. Quality of Life in Participants Receiving the GGTA1 KO Thymokidney by Kidney Transplant Questionnaire (KTQ)

    Time frame: Baseline to 24 weeks post transplant

    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.

  12. Quality of Life in Participants Receiving the GGTA1 KO Thymokidney by Patient Global Impression of Change (PGI-C)

    Time frame: At 24 weeks post transplant

    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).

  13. Incidence of Treatment-Emergent Adverse Events (Safety of the GGTA1 KO Thymokidney)

    Time frame: 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 adverse events and serious adverse events; all-cause mortality.

  14. Incidence of Proteinuria

    Time frame: 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 proteinuria from Day 0.

  15. Incidence of Zoonotic Infection

    Time frame: 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 from Day 0.

  16. Incidence of Opportunistic Infection

    Time frame: 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 from Day 0.

Study contacts

Contact information is provided by the study sponsor or research team.

United Therapeutics Global Medical Information

CONTACT

[email protected]

919-485-8350

Sponsors and collaborators

Lead sponsor

United Therapeutics

Industry

Registry information

Official study title

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

Acronym: EXTEND

Important dates

Study start
2026
Primary completion
2029
Study completion
2076
First posted
Nov 5, 2025
Registry last updated
May 27, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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