ADAM10 and ADAM17 cleave PD-L1 to mediate PD-(L)1 inhibitor resistance.

ADAM10 and ADAM17 expression and soluble PD-L1 (sPD-L1) predict poor prognosis in many malignancies, including in patients treated with PD-(L)1 inhibitors. The mechanism of soluble PD-L1 production and its effects are unknown. Here we uncover a novel mechanism of ADAM10- and ADAM17-mediated resistance to PD-(L)1 inhibitors. ADAM10 and ADAM17 cleave PD-L1 from the surface of malignant cells and extracellular vesicles. This cleavage produces an active sPD-L1 fragment that induces apoptosis in CD8 + T cells and compromises the killing of tumor cells by CD8 + T cells. Reduced tumor site PD-L1 protein-to-mRNA ratios predict poor outcomes and are correlated with elevated ADAM10 and ADAM17 expression in multiple cancers. These results may explain the discordance between PD-L1 immunohistochemistry and PD-(L)1 inhibitor response. Thus, including ADAM10 and ADAM17 tissue staining may improve therapy selection. Furthermore, treatment with an ADAM10/ADAM17 inhibitor may abrogate PD-(L)1 inhibitor resistance and improve clinical responses to PD-(L)1 immunotherapy.

Checkpoint Inhibition: Programmed Cell Death 1 and Programmed Cell Death 1 Ligand Inhibitors in Hodgkin Lymphoma.

Hodgkin lymphoma (HL) is a lymphoid malignancy characterized by a reactive immune infiltrate surrounding relatively few malignant cells. In this scenario, active immune evasion seems to play a central role in allowing tumor progression. Immune checkpoint inhibitor pathways are normal mechanisms of T-cell regulation that suppress immune effector function following an antigenic challenge. Hodgkin lymphoma cells are able to escape immune surveillance by co-opting these mechanisms. The programmed cell death 1 (PD-1) pathway in particular is exploited in HL as the malignant Hodgkin and Reed-Sternberg cells express on their surface cognate ligands (PD-L1/L2) for the PD-1 receptor and thereby dampen the T-cell-mediated antitumoral response. Monoclonal antibodies that interact with and disrupt the PD-1:PD-L1/L2 axis have now been developed and tested in early-phase clinical trials in patients with advanced HL with encouraging results. The remarkable clinical activity of PD-1 inhibitors in HL highlights the importance of immune checkpoint pathways as therapeutic targets in HL. In this review, we discuss the rationale for targeting PD-1 and PD-L1 in the treatment of HL. We will evaluate the published clinical data on the different agents and highlight the safety profile of this class of agents. We discuss the available evidence on the use of biomarkers as predictors of response to checkpoint blockade and summarize the areas under active investigation in the use of PD-1/PD-L1 inhibitors for the treatment of HL.

Targeting the PD-1 pathway in patients with relapsed classic Hodgkin lymphoma following allogeneic stem cell transplant is safe and effective.

Patients with classic Hodgkin lymphoma (cHL) that has relapsed after autologous or allogeneic transplant have limited treatment options and a poor prognosis. Immunotherapy with agents that target the PROGRAMMED DEATH 1 (PD-1) receptor have demonstrated clinical activity with durable responses in early-phase clinical trials in this patient population; however, patients with a history of allogeneic stem cell transplantation (SCT) were intentionally excluded from participation in those studies due to concerns for reactivation of graft-versus-host disease (GVHD). We describe the clinical course of two patients with advanced cHL and prior treatment with allogeneic stem cell transplantation (SCT) that were treated with the PD-1 inhibitor pembrolizumab. Both patients had no active graft-versus-host disease (GVHD) at the time initiation of therapy and were maintained on low-dose prednisone. Treatment with pembrolizumab was well tolerated and not associated with reactivation of GVHD. Both patients responded (1 partial, 1 complete) and remain on therapy as of November 30, 2015. This report indicates that immunotherapy targeting the PD-1 pathway can be safely administered to patients with cHL and a history of allogeneic SCT and produce tumor responses. Further studies in this patient population are needed.