In vivo T cell costimulation blockade with abatacept for acute graft-versus-host disease prevention: a first-in-disease trial.

We performed a first-in-disease trial of in vivo CD28:CD80/86 costimulation blockade with abatacept for acute graft-versus-host disease (aGVHD) prevention during unrelated-donor hematopoietic cell transplantation (HCT). All patients received cyclosporine/methotrexate plus 4 doses of abatacept (10 mg/kg/dose) on days -1, +5, +14, +28 post-HCT. The feasibility of adding abatacept, its pharmacokinetics, pharmacodynamics, and its impact on aGVHD, infection, relapse, and transplantation-related mortality (TRM) were assessed. All patients received the planned abatacept doses, and no infusion reactions were noted. Compared with a cohort of patients not receiving abatacept (the StdRx cohort), patients enrolled in the study (the ABA cohort) demonstrated significant inhibition of early CD4(+) T cell proliferation and activation, affecting predominantly the effector memory (Tem) subpopulation, with 7- and 10-fold fewer proliferating and activated CD4(+) Tem cells, respectively, at day+28 in the ABA cohort compared with the StdRx cohort (P < .01). The ABA patients demonstrated a low rate of aGVHD, despite robust immune reconstitution, with 2 of 10 patients diagnosed with grade II-IV aGVHD before day +100, no deaths from infection, no day +100 TRM, and with 7 of 10 evaluable patients surviving (median follow-up, 16 months). These results suggest that costimulation blockade with abatacept can significantly affect CD4(+) T cell proliferation and activation post-transplantation, and may be an important adjunct to standard immunoprophylaxis for aGVHD in patients undergoing unrelated-donor HCT.

LFA-1-specific therapy prolongs allograft survival in rhesus macaques.

Outcomes in transplantation have been limited by suboptimal long-term graft survival and toxicities associated with current immunosuppressive approaches. T cell costimulation blockade has shown promise as an alternative strategy to avoid the side effects of conventional immunosuppressive therapies, but targeting CD28-mediated costimulation alone has proven insufficient to prevent graft rejection in primates. Donor-specific memory T (TM) cells have been implicated in costimulation blockade-resistant transplant rejection, due to their enhanced effector function and decreased reliance on costimulatory signaling. Thus, we have tested a potential strategy to overcome TM cell-driven rejection by targeting molecules preferentially expressed on these cells, such as the adhesion molecule lymphocyte function-associated antigen 1 (LFA-1). Here, we show that short-term treatment (i.e., induction therapy) with the LFA-1-specific antibody TS-1/22 in combination with either basiliximab (an IL-2Rα-specific mAb) and sirolimus (a mammalian target of rapamycin inhibitor) or belatacept (a high-affinity variant of the CD28 costimulation-blocker CTLA4Ig) prolonged islet allograft survival in nonhuman primates relative to control treatments. Moreover, TS-1/22 masked LFA-1 on TM cells in vivo and inhibited the generation of alloproliferative and cytokine-producing effector T cells that expressed high levels of LFA-1 in vitro. These results support the use of LFA-1-specific induction therapy to neutralize costimulation blockade-resistant populations of T cells and further evaluation of LFA-1-specific therapeutics for use in transplantation.