A short course of tofacitinib sustains the immunoregulatory effect of CTLA4-Ig in the presence of inflammatory cytokines and promotes long-term survival of murine cardiac allografts

Abstract

Costimulation blockade‐based regimens are a promising strategy for management of transplant recipients. However, maintenance immunosuppression via CTLA4‐Ig monotherapy is characterized by high frequency of rejection episodes. Recent evidence suggests that inflammatory cytokines contribute to alloreactive T cell activation in a CD28‐independent manner, a reasonable contributor to the limited efficacy of CTLA4‐Ig. In this study, we investigated the possible synergism of a combined short‐term inhibition of cytokine signaling and CD28 engagement on the modulation of rejection. Our results demonstrate that the JAK/STAT inhibitor tofacitinib restored the immunomodulatory effect of CTLA4‐Ig on mouse alloreactive T cells in the presence of inflammatory cytokines. Tofacitinib exposure conferred dendritic cells with a tolerogenic phenotype reducing their cytokine secretion and costimulatory molecules expression. JAK inhibition also directly affected T cell activation. In vivo, the combination of CTLA4‐Ig and tofacitinib induced long‐term survival of heart allografts and, importantly, it was equally effective when using grafts subjected to prolonged ischemia. Transplant survival correlated with a reduction in effector T cells and intragraft accumulation of regulatory T cells. Collectively, our studies demonstrate a powerful synergism between CTLA4‐Ig and tofacitinib and suggest their combined use is a promising strategy for improved management of transplanted patients.

Targeting inflammation and immune activation to improve CTLA4-Ig-based modulation of transplant rejection

“…Combination of short course of tofacitinib with CTLA4-Ig was able to extend survival of heart allografts subjected to 4h cold ischemia, settings where CTLA4-Ig monotherapy is unable to delay graft rejection. Longterm survival achieved with this combined therapy was associated to a decrease in effector T cell allo-response, and correlated with in vitro observations of a full control of T cell proliferation when T cells were stimulated in the presence of both inhibitors, even if exposed to proinflammatory conditions (29). This report highlights the versatility of combining CTLA4-Ig with JAKs-inhibition for improving immunoregulation while limiting the negative effect of inflammatory mediators and indicate the need for additional studies to prove its clinical potential for improving management of transplanted patients.…”

“…Additional analysis of data gathered from clinical trials informed that with the proper dosing and careful evaluation of the drug combination employed, the utilization of this inhibitor could provide beneficial results in the transplant field (80). In fact, as discussed in a previous section, the experimental use of a short-course tofacitinib treatment in combination with CTLA4-Ig, demonstrated a synergistic effect extending survival of heart allografts (29). In concordance with other results (142,143), exposure of DCs to tofacitinib not only reduced the upregulation of costimulatory molecules (by interfering with the JAK/STAT signaling pathway intrinsic to maturation), but it also limited the secretion of factors, like IL-1 and TNFa, that are involved in CoB-resistant transplant rejection (29).…”

“…In fact, as discussed in a previous section, the experimental use of a short-course tofacitinib treatment in combination with CTLA4-Ig, demonstrated a synergistic effect extending survival of heart allografts (29). In concordance with other results (142,143), exposure of DCs to tofacitinib not only reduced the upregulation of costimulatory molecules (by interfering with the JAK/STAT signaling pathway intrinsic to maturation), but it also limited the secretion of factors, like IL-1 and TNFa, that are involved in CoB-resistant transplant rejection (29). However, the impact of JAK-Inh on the homeostasis and function of Tregs needs to be also considered.…”

“…Long-term administration of JAK-Inh has been associated with a decrease in Treg abundance in multiple settings (144)(145)(146). However, other reports indicate that a shorter course does not have a negative impact on this population and that in all cases, the suppressive function of the remaining Treg population is unaffected by JAK-Inh (29,147,148). These results clearly suggest the need to further investigate (experimentally and clinically) the utilization of JAK-Inh for the control of multiple inflammatory responses and to support the efficacy of CoB regimens in organ transplantation.…”

“…Encouraged by the lessons learned from these reports, the use of tofacitinib as part of a very different combination strategy together with CTLA4-Ig has started to be explored. Using a mouse model of heart transplantation, the combination of CTLA4-Ig with a short period of daily tofacitinib administration revealed a profound synergistic effect that promoted long-term transplant survival (29). The protective effect of the combination of CTLA4-Ig and tofacitinib was associated with inhibition of the maturation of APCs, inhibition of the differentiation of effector T cells, and promotion of intra-graft accumulation of Tregs.…”