Calcineurin inhibitor-free immunosuppressive regimen in type 1 diabetes patients receiving islet transplantation

BACKGROUND: Our final objective is to develop an adoptive therapy with tolerogenic donor-specific type 1 T regulatory cells for patients with type 1 diabetes undergoing islet transplantation. The achievement of this objective depends on the availability of an immunosuppressive treatment compatible with the survival, function, and expansion of type 1 T regulatory cells.

METHODS: For this purpose, we designed a single-group, phase 1 to 2 trial with an immunosuppression protocol including: (i) rapamycin treatment before the first islet infusion (starting ≥ 30 days before transplantation); (ii) induction therapy with anti-thymocyte globulin (ATG) instead of anti-interleukin-2Ra monoclonal antibody (after the first islet infusion only); (iii) short-term treatment with steroids and interleukin-1Ra (right before and for 2 weeks after each infusion); rapamycin+mycophenolate mofetil treatment as maintenance therapy. The target enrollment was 10 patients.

RESULTS: Ten of 15 patients who started the pretransplant rapamycin treatment completed it. Nine of 10 patients did not complete the induction therapy with ATG, and three of 10 required adaptation of maintenance immunosuppression caused by side effects. Four of 10 patients acquired insulin independence which can be maintained up to year 3 after last infusion. All six other patients have lost their graft, and the early graft loss was associated with lower dose of ATG during induction.

CONCLUSION: This protocol resulted feasible, safe but less efficient in maintaining graft survival during the time than other T-cell depletion-based protocols. An adequate induction at the first infusion should be considered to improve the overall clinical outcome.