Islet Transplantation in Type 1 Diabetic Patients Using Calcineurin Inhibitor-Free Immunosuppressive Protocols Based on T-Cell Adhesion or Costimulation Blockade

Background. The applicability of islet transplantation as treatment for type 1 diabetes is limited by long-term graft dysfunction, immunosuppressive drug toxicity, need for multiple donors, and increased risk of allosensitization. We describe two immunosuppressive regimens based on the costimulation blocker belatacept (BELA) or the antileukocyte functional antigen-1 antibody efalizumab (EFA), which permit long-term islet allograft survival and address some of these concerns. Methods. Ten patients with type 1 diabetes with hypoglycemic unawareness received intraportal allogeneic islet transplants. Immunosuppression consisted of antithymocyte globulin induction and maintenance with sirolimus or mycophenolate and BELA (n=5) or EFA (n=5). Results. All five BELA-treated patients achieved independence after single transplants; one resumed partial insulin use 305 days after transplant but is now independent after a second transplant. All five patients treated with EFA achieved independence after one (3/5) or two (2/5) islet transplants and remained independent while on EFA (392-804 days). After EFA was discontinued because of withdrawal of the drug from the market, two patients resumed intermittent insulin use; the others remain independent. No patient in either group developed significant side effects related to the study drugs, and none have been sensitized to alloantigens. All have stable renal function. Conclusions. These two novel immunosuppressive regimens are effective, well tolerated, and the first calcineurin inhibitor/steroid-sparing islet protocols resulting in long-term insulin independence. Although EFA is no longer available for clinical use, these early results demonstrate that a regimen using BELA may be an effective alternative to improve graft function and longevity while minimizing renal and beta-cell toxicity.