*Purpose: Most immunosuppressive regimens used in Pig-To-Primate Xenotransplantation contain anti-CD154 agents, compounds that are currently not FDA-approved. The aim of this study was to assess whether a regimen made up of clinically available immunosuppressive agents prolonged xenograft survival.

*Methods: Cynomolgus macaques received life-sustaining kidney transplants from triple-knockout pigs with 7 additional human genes (provided by eGenesis; n=6). Animals received Thymoglobulin® as induction therapy and maintenance regimen consisted of either Belatacept/Rapamycin/MMF/Steroids (n=2) or anti-human CD154 mAb (5C8H1 clone)/MMF/Steroids (n=2). Two animals were excluded from post-transplant analysis due to technical complications.

*Results: All animals tolerated xeno-kidney transplantation well with no cases of hyperacute rejection. Animals treated with Belatacept/Rapamycin showed a trend towards prolonged graft survival compared to animals treated with anti-CD154 mAb (median survival time 35d vs. 24d, Figure 1A). One animal in the Belatacept/Rapamycin group developed class II pig-donor specific antibodies, while both animals in the anti-CD154 mAb developed both class I and class II pig-donor specific antibodies (Figure 1B).

*Conclusions: A regimen consisting of Thymoglobulin® /Belatacept/Rapamycin prolonged xenograft survival while preventing class I pig-donor specific antibodies formation. Surprisingly, both animals treated with anti-CD154 mAb developed class I and II pig-donor specific antibodies. Further studies are warranted to further characterize the efficacy of this clinically available regimen in xenotransplantation.

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