An Observational Extension Study for Adult Patients Treated in Study R5459-RT-1944 Who Receive A Kidney Transplant

Study Overview
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Brief Summary
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The primary objective of the study is to assess adverse events (AEs) and serious adverse events (SAEs) in kidney transplant recipients previously treated with REGN5459 or REGN5458 in the R5459-RT-1944 study. The secondary objectives of the study are to evaluate each of the following in kidney transplant recipients previously treated with REGN5459 or REGN5458: Rates and classification of antibody-mediated and T-cell-mediated kidney allograft rejection Graft survival Allograft function Delayed allograft function Anti-human leukocyte antigen (HLA) alloantibody levels and calculated panel-reactive antibody (cPRA) Emergence of de novo donor-specific antibodies Circulating immunoglobulin (Ig) classes (isotypes) Pharmacokinetics (PK) of REGN5459 or REGN5458

Official Title
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A Noninterventional Extension Study for Patients Treated in Study R5459-RT-1944 With REGN5459 or REGN5458 (BCMA x CD3 Bispecific Antibodies) Who Receive A Kidney Transplant

Conditions
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Chronic Kidney Disease (CKD)

Intervention / Treatment
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* Other: Noninterventional


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Received at least 1 dose of treatment with REGN5459 or REGN5458 in study R5459-RT-1944 Received, or scheduled to receive after acceptable crossmatching, a kidney transplant while enrolled in study R5459-RT-1944 Willing and able to comply with clinic visits and study-related procedures Provide informed consent signed by study patient or legally acceptable representative Exclusion Criteria: There are no exclusion criteria for this study. Note: Other protocol defined Inclusion/Exclusion criteria may apply

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 70 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| REGN5459 in study R5459-RT-1944<br>Received a kidney transplant and were administered REGN5459 in study R5459-RT-1944. | Other: Noninterventional<br>* No investigational treatment will be given in this noninterventional extension study<br>|
| REGN5458 in study R5459-RT-1944<br>Received a kidney transplant and were administered REGN5458 in study R5459-RT-1944. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Incidence of Adverse Events |  | Up to 12 months post-kidney transplant | 
| Incidence of Serious Adverse Events |  | Up to 12 months post-kidney transplant | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Incidence of biopsy-proven kidney allograft rejection | Responsiveness to therapy by 12 months of each of the following types of biopsy-proven kidney allograft rejection according to Banff classification: Active antibody-mediated rejection (AMR) (Category 2) Chronic active AMR (Category 2) Acute t-cell-mediated rejection (TCMR) (Category 4) Chronic active TCMR (Category 4) | Up to 12 Months | 
| Time to diagnosis of biopsy-proven kidney allograft rejection | Responsiveness to therapy by 12 months of each of the following types of biopsy-proven kidney allograft rejection according to Banff classification: Active antibody-mediated rejection (AMR) (Category 2) Chronic active AMR (Category 2) Acute t-cell-mediated rejection (TCMR) (Category 4) Chronic active TCMR (Category 4) | Up to 12 Months | 
| Responsiveness to therapy by 12 months of biopsy-proven kidney allograft rejection | Responsiveness to therapy by 12 months of each of the following types of biopsy-proven kidney allograft rejection according to Banff classification: Active antibody-mediated rejection (AMR) (Category 2) Chronic active AMR (Category 2) Acute t-cell-mediated rejection (TCMR) (Category 4) Chronic active TCMR (Category 4) | Up to 12 Months | 
| Incidence of graft loss | Incidence of graft loss (defined as becoming dialysis-dependent) by 12 months | Up to 12 Months | 
| Time to graft loss | Time to graft loss (defined as becoming dialysis-dependent) by 12 months | Up to 12 Months | 
| Change in estimated glomerular filtration rate (eGFR) over time |  | Up to 12 Months | 
| Incidence of delayed graft function | Incidence of delayed graft function (defined as the use of dialysis within 7 days posttransplant) | Up to Day 7 | 
| Percent Change in anti-HLA alloantibodies | Percent Change in anti-HLA alloantibodies (SAB assay) compared with pretransplant levels at 2, 3, 6, and 12 months, and at the time of suspected clinical episodes of allograft rejection | Up to 12 months | 
| Mean Fluorescence Intensity Change in anti-HLA alloantibodies | Mean Fluorescence Intensity (MFI) Change in anti-HLA alloantibodies (SAB assay) compared with pretransplant levels at 2, 3, 6, and 12 months, and at the time of suspected clinical episodes of allograft rejection | Up to 12 months | 
| Change in Calculated panel-reactive antibody (cPRA) over time |  | Up to 12 Months | 
| Percent Change in donor-specific anti-HLA alloantibodies | Percent Change in donor-specific anti-HLA alloantibodies compared with recipient pre-transplant anti-HLA alloantibody levels | Up to 12 Months | 
| Mean Fluorescence Intensity Change in donor-specific anti-HLA alloantibodies | Mean Fluorescence Intensity Change in donor-specific anti-HLA alloantibodies compared with recipient pre-transplant anti-HLA alloantibody levels | Up to 12 Months | 
| Incidence of de novo anti-HLA alloantibody development | Cumulative incidence of de novo anti-HLA alloantibody development by SAB assay by 12 months | Up to 12 Months | 
| Serum Concentrations of Ig classes (IgG, IgA, and IgM) over time |  | Up to 12 Months | 
| Percent change from baseline of circulating serum concentrations of Ig classes | Percent change from baseline of circulating serum concentrations of Ig classes (IgG, IgA, and IgM) | Up to 12 Months | 
| Serum Concentration of R5458 |  | Up to 12 Months | 
| Serum Concentration of R5459 |  | Up to 12 Months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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kidney transplant