The purpose of this study is to determine whether vonsetamig will safely decrease anti-HLA antibodies to allow for kidney transplantation.

Vonsetamig is being studied for treatment of patients in need of kidney transplantation who are highly sensitized to HLA.

The study is looking at several other research questions, including:

• Side effects that may be experienced from taking vonsetamig
• How vonsetamig works in the body
• How much vonsetamig is present in the blood
• If vonsetamig works to lower levels of antibodies to HLA

Key Inclusion Criteria:

1. Has Chronic Kidney Disease (CKD) requiring hemodialysis, and awaiting kidney transplant on the United Network for Organ Sharing (UNOS), with a cPRA ≥99.9%, or those with a cPRA >98% (98.1% to 99.8%) who have spent 5 years or longer on the waitlist, as defined in the protocol
2. Adequate hematologic and adequate hepatic function as defined in the protocol
3. Willing and able to comply with clinic visits and study-related procedures

Key Exclusion Criteria:

1. Current or active malignancy not in remission for at least 1 year
2. Central nervous system (CNS) pathology or history of CNS neurodegenerative or movement disorders
3. Patients who have had their spleen removed, including patients with functional asplenia
4. Patients who have received a stem cell transplantation within 5 years
5. Use of investigational agents within 8 weeks or 5 half-lives of study drug administration (whichever is larger)
6. Total plasma IgG <300 mg/dL at screening
7. Continuous systemic corticosteroid treatment with more than 10 mg per day of prednisone (or anti-inflammatory equivalent) within 72 hours of start of study drug administration
8. Received a calcineurin inhibitor (eg, tacrolimus, cyclosporine) within 30 days of study drug administration
9. Received cyclophosphamide, rituximab, obinutuzumab, other anti-CD20 or B cell-depleting agents, or proteasome inhibitors or anti-CD38 therapies (eg, isatuximab, daratumumab) within 12 months of study drug administration
10. Prior treatment with any anti-BCMA antibody (including antibody drug conjugate or bsAb) or BCMA-directed CAR-T cell therapy, as described in the protocol
11. Has received a COVID-19 vaccination, as described in the protocol

Note: Other protocol defined inclusion / exclusion criteria apply

All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing

When Regeneron has:

• received marketing authorization from major health authorities (e.g., FDA, European Medicines Agency (EMA), Pharmaceuticals and Medical Devices Agency (PMDA), etc.) for the product and indication or has globally discontinued development of the product for all indications on or after April 2020 and has no plans for future development
• made the study results publicly available (e.g., scientific publication, scientific conference, clinical trial registry)
• the legal authority to share the data, and
• ensured the ability to protect participant privacy

Qualified researchers can submit a proposal for access to individual patient or aggregate level data from a Regeneron-sponsored clinical trial through Vivli. Regeneron's Independent Research Request Evaluation Criteria can be found at: https://www.regeneron.com/sites/default/files/Regeneron-External-Data-Sharing-Policy-and-Independent-Research-Request-Evaluation-Criteria.pdf