The purpose of this clinical trial is to evaluate whether a temporary reprogramming of the immune system can help highly sensitized (hyperimmunized) patients with end-stage kidney disease safely receive a compatible kidney transplant.

Patients who are highly sensitized have developed an extremely high level of antibodies against human leukocyte antigens (HLA), often due to previous transplants, pregnancies, or blood transfusions. This condition makes it nearly impossible for them to find a compatible organ donor, leaving them stuck on dialysis indefinitely.

This study tests an innovative strategy using Autologous Hematopoietic Stem Cell Transplantation (AHSCT). The procedure involves an intensive conditioning regimen using a combination of medications (cyclophosphamide, thymoglobulin, and rituximab) to deeply clear out the patient's existing mature immune cells. This is followed by the reinfusion of the patient's own previously collected and purified blood stem cells (CD34+ cells) to rebuild the immune system from scratch.

The investigators hypothesize that this procedure will eliminate the "immunological memory" cells responsible for producing the problematic anti-HLA antibodies, resetting the immune system to a "naive" or inactive state. This immune reset is expected to eliminate or significantly lower circulating HLA antibodies, creating a critical window of opportunity for these patients to successfully receive a compatible kidney transplant from the deceased-donor waiting list.

This single-center, open-label, non-randomized phase Ib/II pilot study will evaluate the safety, feasibility, and immunological effects of autologous hematopoietic stem cell transplantation (AHSCT) in highly sensitized patients awaiting kidney transplantation.

A total of 10 hyperimmunized patients on the kidney transplant waiting list will be enrolled in two sequential phases. In Phase 1, four participants will undergo AHSCT with close safety monitoring during a 12-month follow-up period. In the absence of severe adverse events, participants will be reactivated on the deceased-donor kidney transplant waiting list at 6 months post-AHSCT. Following safety evaluation of the initial cohort, an additional six participants will be enrolled in Phase 2 to further assess the efficacy and safety of the strategy.

The intervention includes a non-myeloablative lymphodepletion and stem cell mobilization regimen followed by collection, CD34+ selection, and reinfusion of autologous hematopoietic progenitor cells. After AHSCT, eligible participants may undergo deceased-donor kidney transplantation following confirmation of HLA compatibility by standard crossmatch techniques.

Kidney transplant recipients will receive standard-of-care induction and maintenance immunosuppressive therapy according to institutional clinical practice.

The study also includes longitudinal immunological monitoring to characterize adaptive immune reconstitution and anti-HLA responses after AHSCT and kidney transplantation. Peripheral blood and bone marrow samples will be collected at predefined time points to evaluate T- and B-cell memory compartments, donor-specific antibodies, and pathogen-specific immune responses.

Primary objectives include assessment of safety and feasibility, as well as evaluation of changes in sensitization status and access to HLA-compatible kidney transplantation following AHSCT.

Inclusion Criteria:

• Patients aged between 18 and 60 years.
• Diagnosis of end-stage kidney disease (ESRD) currently maintained on chronic dialysis.
• Highly sensitized/hyperimmunized status, defined by a high calculated Panel Reactive Antibody (cPRA) level (e.g., >= 95%).
• Active status on the deceased-donor kidney transplant waiting list.
• Adequate bone marrow, hepatic, cardiac, and pulmonary function to safely undergo the conditioning regimen and AHSCT.
• Capable of understanding the study requirements and providing written informed consent.

Exclusion Criteria:

• Contraindications to the conditioning regimen medications (rituximab, cyclophosphamide, or rATG).
• Active, uncontrolled systemic infection, or chronic active infection (including HIV, active Hepatitis B or C, or active tuberculosis).
• Significant cardiac dysfunction (e.g., Left Ventricular Ejection Fraction < 50%) or severe underlying pulmonary disease.
• History of malignant neoplasm within the past 5 years, excluding successfully treated non-melanoma skin cancer or carcinoma in situ.
• Previous autologous or allogeneic hematopoietic stem cell transplantation.
• Pregnancy or breastfeeding.
• Any psychiatric, medical, or geographical condition that, in the investigator's opinion, prevents compliance with the protocol and long-term follow-up.

Individual participant data will not be shared to protect patient privacy and maintain confidentiality, in accordance with institutional data protection policies and the small sample size of this pilot study.