This study seeks to determine if administration of the drug belumosudil (KD025) will be safe and improve transplant tolerance in subjects undergoing combined Human Leukocyte Antigen (HLA) single haplotype-matched related or 0-3 antigen (at A, B, C, DR) HLA mismatched unrelated living donor kidney and hematopoietic stem cell transplantation.

The goal of achieving transplant tolerance (defined as prolonged graft survival in the absence of immunosuppression) has long been the aspiration of transplant physicians and researchers. Transplant tolerance may be achieved reliably and safely in HLA identical subjects undergoing combined living donor kidney and hematopoietic stem cell utilizing a conditioning regimen of Total Lymphoid Irradiation (TLI) and Rabbit anti-thymocyte globulin (rATG). However, the same treatment regimen has not been successful in allowing recipients of HLA single haplotype matched allografts to be completely withdrawn from immunosuppression in spite of increasing the dose of infused cluster of differentiation (CD) 34 and CD3 cells. This study seeks to determine the safety and efficacy of administering the investigational agent belumosudil to single haplotype- matched or HLA mismatched (0-3 antigen mismatch at HLA A, B, C, DR) subjects undergoing combined kidney and hematopoietic stem cell transplantation conditioned with TLI/rATG. Belumosudil has been shown to be highly active when used in the treatment of steroid refractory chronic graft vs host disease. We hypothesize that belumosudil (KD025) may increase mixed donor chimerism and lead to greater transplant tolerance due to its demonstrated ability to increase the numbers and function of regulatory T cells.

The summary of the treatment plan is as follows:

Immediately after living donor kidney transplantation, subjects will begin a conditioning regimen of rATG and TLI. An infusion of at least 8 X10^6 (target ≥ 10 X 10^6) donor CD34 cells/kg recipient weight and of at least 10 X10^6 (target 100 X10^6) donor CD3 cells/kg recipient weight will then be given. A triple immunosuppressive regimen of tacrolimus, corticosteroids, and mycophenolate will be utilized.

Corticosteroids will be given on a tapering schedule from day 0 through the first four months. Tacrolimus will be given on a tapering schedule from day 1 through month 18.

Mycophenolate will be given at a fixed dose from day 11 through month 12. Subjects will receive belumosudil 200 mg by mouth daily from day 28 following the kidney transplant through month 24. At serial time points, (1) chimerism will be measured in recipient whole blood and leukocyte subsets (2) graft function will be monitored (3) protocol biopsies of the graft will be obtained and (4) a T cell subsets from the peripheral blood including regulatory T cells will be measured.

Immunosuppression taper will be stopped and/or immunosuppression will be resumed for any of the following conditions:

(1) loss of chimerism (2) clinical or pathological evidence of acute rejection and (3) clinical or pathological evidence of graft vs host disease.

Recipient Inclusion Criteria:

1. Age 18 and older
2. Receiving an HLA single haplotype-matched related living donor or 0-3 antigen (at A, B, C, DR) HLA mismatched unrelated living donor combined kidney and hematopoietic stem cell transplant (the first six subjects will be HLA single haplotype-matched; the final two subjects may be either HLA single-haplotype-matched or 0-3 antigen (at A, B, C, DR) HLA mismatched)
3. Agreement to participate in the study and ability to give informed consent
4. Meets institutional criteria for kidney and allogeneic hematopoietic stem cell transplant
5. Resides or is willing to stay within 3 hours distance from University of California, Los Angeles Medical Center by ground transportation for the first six months post-kidney transplant
6. No known contraindication to administration of rATG or radiation
7. If a patient is a female of reproductive potential (i.e. no documented absence of ovaries or uterus, history of tubal ligation, or post-menopausal status) patient must be confirmed not pregnancy by a serum or urine pregnancy test and must agree to practice a reliable form of contraception including hormonal treatments, barrier methods or intrauterine device for duration of the study
8. Males of reproductive age must consent to use reliable and effective methods to avoid pregnancy
9. Karnofsky Performance Score (KPS) ≥ 70
10. Adequate cardiac function defined as left ventricular ejection fracture (LVEF) ≥ 40% by Multi Gated Acquisition (MUGA) scan or echocardiogram
11. Adequate pulmonary function defined as FVC and DLCO of ≥ 50% of predicted
12. Adequate liver function defined as total bilirubin ≤ 1.5 times the upper limit of normal and AST/ALT ≤ 2.0 times the upper limit of normal
13. Adequate social support based on evaluation by the UCLA renal transplant team licensed clinical social worker
14. Negative test for COVID 19 by RT -PCR and/or have received COVID 19 vaccinations. Subjects who have not received their COVID-19 vaccination may be enrolled on the trial based on clinical judgement.

Recipient Exclusion Criteria:

1. ABO incompatibility with donor

2. Previous solid organ transplant

3. Multi-organ transplantation

4. Previous treatment with rATG or a known allergy to rabbit proteins

5. Previous treatment with belumosudil (KD025)

6. History of active malignancy within the past 5 years with the exception of:

   1. Low risk cancer on active surveillance
   2. Malignancy treated with curative intent with no known active disease >2 years before the first dose of study treatment and of low potential risk of recurrence
   3. Adequately treated non-melanoma skin cancer or lentigo maligna without evidence of disease
   4. Adequately treated carcinoma in situ without evidence of disease (e.g., cervical cancer in situ, and DCIS)

7. Pregnant (confirmed by urine or serum pregnancy test) or lactating

8. Leukopenia (with a white blood cell count < 3,000/µL) or thrombocytopenia (with a platelet count < 100,000/µL)

9. INR and/or PTT ≥ 1.5X upper limits of institutional normal

10. Positive HLA DSA

11. Active bacterial, fungal, mycobacterial, or viral infection (including active hepatitis B and/or C, or West Nile Virus)

12. Seropositivity for HIV 1, HIV 2, HTLV-1 or HTLV-II

13. Renal disease with high risk of recurrence (i.e., focal segmental glomerulosclerosis)

14. Advanced hepatic fibrosis or cirrhosis

15. Congestive heart failure, symptomatic coronary artery disease, and/or uncontrolled cardiac arrhythmia

16. Active extra-renal autoimmune disease requiring immunosuppression

17. Neuropsychiatric or medical illness that precludes the ability to give informed consent and/or places the patient as high risk for non-compliance with the safety monitoring requirements of the study

18. May not have received immunosuppressive medications within one year of the study treatment. Use of corticosteroids prescribed for a time-limited indication (\