Safety and Tolerability of IDO-1 Inhibition in the Prevention of EBV-related Pathology in EBV Negative Kidney Transplant Recipients Receiving an Organ From EBV Positive Donors

Inclusion Criteria: 1. Willing and able to provide informed consent 2. Male or female aged ≥18 years 3. EBV seronegative at the time of renal transplant 4. If women of child-bearing potential (WOCBP), participants must have a negative serum pregnancy test at screening and inclusion, and must be willing to use a highly effective method of birth control for the duration of the study. Acceptable methods of contraception: 1. Hormonal contraception associated with inhibition of ovulation 2. Intrauterine device (IUD) 3. Intrauterine hormone-releasing system (IUS) 4. Bilateral tubal occlusion 5. Vasectomised partner 6. Condom with spermicide 7. Sexual abstinence, in line with the preferred and usual lifestyle of the participant. Periodic abstinence (such as calendar, ovulation, symptothermal, post-ovulation methods) and withdrawal are not acceptable methods of contraception. 5. If male, participants must be prepared to use reliable barrier method contraception and a second method such as spermicide for the duration of the study unless surgically sterile. Exclusion Criteria: 1. EBV seropositivity at the time of transplant 2. Participants with any form of cancer within the last 12 months, or patients continuing to receive chemo or immunotherapy within the last 12 months. 3. Participants with a history of PTLD 4. Other active systemic infections requiring treatment prior to and at the time of baseline. Prophylactic agents are permitted. 5. CYP3A4 and CYP2C28 Inhibitors and Inducers (List may be found in Appendix 1) 6. Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) ≥3 x ULN 7. Any condition for which, in the opinion of the investigator, the treatment or participation in the study may pose a health risk to the participant 8. Planned or active participation in any other study with an investigational medicinal product (IMP). 9. Have taken an IMP within the last 3 months. 10. Unwilling or unable to provide fully informed consent. 11. Unwilling or unable to comply with study procedures.