Magic™ Anti-CD40LG monoclonal antibody, clone 3B4

Calcineurin inhibitors (CNIs) have failed to improve long-term renal allograft survival. Their association with cardiovascular morbidity in addition to their suboptimal inhibition of a chronic alloimmune response has shifted investigative efforts toward CNI-free regimens. Sotrastaurin, a small molecule targeting protein kinase C isoforms, failed to provide adequate immunosuppression, whereas the Janus kinase 3 inhibitor tofacitinib's success in the treatment of rheumatoid arthritis led to biopharma's abandonment of it as a transplant agent. Like tofacitinib, tocilizumab, a biologic targeting the IL-6 pathway, has been approved for use in rheumatoid arthritis and interest in transplantation has been confined to several investigator-initiated trials. Belatacept, a second-generation, higher avidity variant of CTLA4Ig (abatacept), was approved by the Food and Drug Administration for prophylaxis of transplant rejection in 2011. Long-term follow-up of recipients on belatacept has demonstrated superior glomerular filtration rates as compared with CNIs, albeit with an increased risk of early and histologically severe rejection. Focus on optimizing belatacept-inclusive regimens has led to studies using lymphocyte depletion as induction and maintenance therapy with target of rapamycin inhibitors. ASKP1240, the most advanced of the anti-CD40 antibodies targeting the CD40/CD154 costimulatory pathway has just completed a phase II trial with a CNI-free arm. Animal models suggest that its highest efficacy may be in combination with belatacept. Finally, nonagonistic CD28 antibodies, which would allow CTLA4 and PD-LI binding of CD80/CD86 and activation of inhibitory pathways, have re-emerged with 2 anti-CD28 candidates in preclinical development. A reliable nontoxic CNI-free regimen may ultimately require the combination of biologic agents that provide efficacy as well as safety.

The immunosuppressive microenvironment is one of the major factors promoting the growth of glioblastoma multiforme (GBM). Infiltration of CD4+ CD25+ Foxp3+ regulatory T cells (Tregs) into the tumor microenvironment plays a significant role in the suppression of the anti-tumor immunity and portends a dismal prognosis for patients. Glioma-mediated secretion of chemoattractant C-C motif ligand 2 and 22 (CCL2/22) has previously been shown by our group to promote Treg migration in vitro. In this study, we show that a local implantation of platelet-rich fibrin patch (PRF-P) into the brain of GL261 glioma-bearing mice prolonged the survival of affected animals by 42.85% (p = 0.0011). Analysis performed on brain tumor tissue harvested from PRFP- treated mice revealed a specific decrease in intra-tumoral lymphocytes with a preferential depletion of immunosuppressive Tregs. Importantly, co-culture of GL261 or chemo-attractants (CCL2/22) with PRF-P abrogated Treg migration. Pharmacological blockade of the CCL2/22 interaction with their receptors potentiated the inhibitory effect of PRF-P on Tregs recruitment in culture. Moreover, our findings revealed the soluble CD40 ligand (sCD40L) as a major Treg inhibitory player produced by activated platelets entrapped within the fibrin matrix of the PRF-P. Blockade of sCD40L restored the migratory capacity of Tregs, emphasizing the role of PRF-P in preventing the Treg migration to glioma tissue. Our findings highlight autologous PRF-P as a personalized, Treg-selective suppression platform that can potentially supplement and enhance the efficacy of glioma therapies.