Chimeric 2C10R4 anti-CD40 antibody therapy is critical for long-term survival of GTKO.hCD46.hTBM pig-to-primate cardiac xenograft.

Muhammad M Mohiuddin,Robert F Hoyt,Eckhard Wolf,Aaron J Belli,Carol Phelps,David Ayares,Marvin L Thomas Iii,Billeta G Lewis,Nikolai Klymiuk,Keith A Horvath,Avneesh K Singh,Philip C Corcoran,Tannia Clark,Michael Eckhaus,Richard N Pierson Iii,Keith A Reimann

doi:10.1038/ncomms11138

Abstract

Preventing xenograft rejection is one of the greatest challenges of transplantation medicine. Here, we describe a reproducible, long-term survival of cardiac xenografts from alpha 1-3 galactosyltransferase gene knockout pigs, which express human complement regulatory protein CD46 and human thrombomodulin (GTKO.hCD46.hTBM), that were transplanted into baboons. Our immunomodulatory drug regimen includes induction with anti-thymocyte globulin and αCD20 antibody, followed by maintenance with mycophenolate mofetil and an intensively dosed αCD40 (2C10R4) antibody. Median (298 days) and longest (945 days) graft survival in five consecutive recipients using this regimen is significantly prolonged over our recently established survival benchmarks (180 and 500 days, respectively). Remarkably, the reduction of αCD40 antibody dose on day 100 or after 1 year resulted in recrudescence of anti-pig antibody and graft failure. In conclusion, genetic modifications (GTKO.hCD46.hTBM) combined with the treatment regimen tested here consistently prevent humoral rejection and systemic coagulation pathway dysregulation, sustaining long-term cardiac xenograft survival beyond 900 days.

Highlights

Preventing xenograft rejection is one of the greatest challenges of transplantation medicine
Hearts from GTKO.hCD46 pigs engineered using one of two hTBM gene constructs with different promoters (ICAM in baboons #110, #210 and #910 and TBM in baboons #15009 and #510) were used (Fig. 1a; cloned from founder lines selected for high endothelial expression of hTBM)
Further improvements may be necessary for both donor genetics and recipient treatment to achieve consistent orthotopic heart xenograft performance and justify potential clinical applications, our data show that the use of GTKO.hCD46.hTBM donor pigs and an aCD40 (2C10R4) antibody-based immunomodulatory regimen is associated with significantly prolonged graft survival

Summary

Introduction

Preventing xenograft rejection is one of the greatest challenges of transplantation medicine. We describe a reproducible, long-term survival of cardiac xenografts from alpha 1-3 galactosyltransferase gene knockout pigs, which express human complement regulatory protein CD46 and human thrombomodulin (GTKO.hCD46.hTBM), that were transplanted into baboons. Genetic modifications (GTKO.hCD46.hTBM) combined with the treatment regimen tested here consistently prevent humoral rejection and systemic coagulation pathway dysregulation, sustaining long-term cardiac xenograft survival beyond 900 days. The longest survival for heterotopic cardiac xenografts using alpha 1-3 galactosyltransferase gene knockout (GTKO) or GTKO.hCD46 Tg pigs and immunosuppression (IS) that included aCD154 antibody was 179–236 days, the xenografts succumbed to the characteristic properties of delayed rejection[4,5]. We have recently reported survival beyond 1 year of GTKO.hCD46.hTBM pig heart xenografts that were heterotopically transplanted into a baboon. We report consistent prevention of xenograft rejection in association with ongoing aCD40 (2C10R4) antibody treatment resulting in graft survival beyond 2 years

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Conclusion