Safety, Pharmacokinetics, and Efficacy of AT 1501 in Patients Undergoing Kidney Transplant

Inclusion Criteria:

1. Male or female ≥ 18 years of age

2. Recipient of their first kidney transplant from a living or deceased donor

3. Agree to comply with contraception requirements during and for at least 90 daysafter the last administration of study drug

Exclusion Criteria:

1. Induction therapy, other than study assigned rATG, planned as part of initialimmunosuppressive regimen

2. Currently treated with any systemic immunosuppressive regimen, including immunologicbiologic therapies, with the exception of 5 mg prednisone or equivalent daily;

3. Previous treatment with AT 1501 or any other anti CD40LG therapy

4. The patient has previously received a bone marrow transplant or any other solidorgan transplant, including a kidney, or will be undergoing a multi organ or dualkidney transplant

5. Will receive a kidney with an anticipated cold ischemia time of > 30 hours;

6. Will receive a kidney from a donor that meets any of the following criteria:

• Donation after Cardiac Death (DCD) criteria; or

• Extended Criteria Donor (ECD) criteria, defined as:

• Is blood group (ABO) incompatible; or

• Age ≥ 60 years; or Age 50-59 years with any 2 of the following criteria:

• Death due to cerebrovascular accident

• History of hypertension

• Terminal creatinine ≥ 133 μmol/L (1.5 mg/dL)

7. Human leukocyte antigen identical (two haplotype match or zero HLA mismatch) donor

8. Medical conditions that require chronic use of systemic steroids at a dose higherthan 5 mg prednisone or equivalent per day

9. History of a TE event, known hypercoagulable state, or condition requiring long termanticoagulation:

10. Positive T- or B-cell crossmatch that is due to HLA antibodies or presence of a DSAat Screening