Background
Specific blockade of T cell costimulation pathway is a promising immunomodulatory approach being developed to replace our current clinical immunosuppression therapies. The goal of this study is to compare results associated with 3 monoclonal antibodies directed against the CD40/CD154 T cell costimulation pathway.
Methods
Cynomolgus monkey heterotopic cardiac allograft recipients were treated with either IDEC-131 (humanized αCD154, n=9), 5C8H1 (mouse-human chimeric αCD154, n=5), or 2C10R4 (mouse-rhesus chimericαCD40, n=6) monotherapy using a consistent, comparable dosing regimen for 3 months after transplant.
Results
Relative to the previously reported IDEC-131 treated allografts, median survival time (MST 35±31 days) was significantly prolonged in both 5C8H1 (142±26, p<0.002) and 2C10R4 (124±37, p<0.020) treated allografts. IDEC-131 treated grafts had higher CAV severity scores during treatment relative to either 5C8H1 (p=0.008) or 2C10R4 (p=0.0002). Both 5C8H1(5 of 5 animals, p=0.02) and 2C10R4 (6/6, p=0.007), but not IDEC-131 (2/9), completely attenuated IgM antidonor alloAb production during treatment;5C8H1 (5/5) more consistently attenuated IgG alloAb production compared to 2C10R4 (4/6) and IDEC-131 (0/9). All evaluable explanted grafts experienced antibody-mediated rejection. Only 2C10R4 treated animals exhibited a modest, transient drop in CD20+ lymphocytes from baseline at d14 after transplant (-457±152 cells/μL) compared to 5C8H1 treated animals (16±25, p=0.037), and the resurgent B cells were primarily of a naïve phenotype.
Conclusion
In this model, CD154/CD40 axis blockade using IDEC-131 is an inferior immunomodulatory treatment than 5C8H1 or 2C10R4, which have similar efficacy to prolong graft survival and to delay CAV development and antidonor alloAb production during treatment.