Anti–PD-1 antibodies recognizing the membrane-proximal region are PD-1 agonists that can down-regulate inflammatory diseases

Abstract

The PD-1 receptor triggers a negative immunoregulatory mechanism that prevents overactivation of immune cells and subsequent inflammatory diseases. Because of its biological significance, PD-1 has been a drug target for modulating immune responses. Immunoenhancing anti–PD-1 blocking antibodies have become a widely used cancer treatment; however, little is known about the required characteristics for anti–PD-1 antibodies to be capable of stimulating immunosuppressive activity. Here, we show that PD-1 agonists exist in the group of anti–PD-1 antibodies recognizing the membrane-proximal extracellular region in sharp contrast to the binding of the membrane-distal region by blocking antibodies. This trend was consistent in an analysis of 81 anti-human PD-1 monoclonal antibodies. Because PD-1 agonist antibodies trigger immunosuppressive signaling by cross-linking PD-1 molecules, Fc engineering to enhance FcγRIIB binding of PD-1 agonist antibodies notably improved human T cell inhibition. A PD-1 agonist antibody suppressed inflammation in murine disease models, indicating its clinical potential for treatment of various inflammatory disorders, including autoimmune diseases.

Programmed death receptor 1 (PD‐1) ligand Fc fusion proteins reduce T‐cell proliferation in vitro independently of PD‐1

“…Consistent with our proposed mechanism, a recent study showed equal inhibition of interferon‐γ production in WT and PD‐1 −/− mouse T cells by PD‐L1.Fc when coimmobilized directly on tissue culture plates with anti‐CD3 mAb 21 . Of note, the authors also showed that the delivery of soluble PD‐L1.Fc crosslinked with anti‐Fc did not deliver a PD‐1–specific signal, 21 in line with evidence that anti‐CD3 and PD‐L1.Fc need to be coimmobilized together 9,11,16 . Only optimization of anti‐CD3 mAb and PD‐L1.Fc concentrations and the introduction of a biotin–streptavidin binding interface on the plate surface to capture both reagents were able to alleviate the nonspecific effect 21 …”

“…Of note, the authors also showed that the delivery of soluble PD‐L1.Fc crosslinked with anti‐Fc did not deliver a PD‐1–specific signal, 21 in line with evidence that anti‐CD3 and PD‐L1.Fc need to be coimmobilized together 9,11,16 . Only optimization of anti‐CD3 mAb and PD‐L1.Fc concentrations and the introduction of a biotin–streptavidin binding interface on the plate surface to capture both reagents were able to alleviate the nonspecific effect 21 …”

“…9,11,16 Only optimization of anti-CD3 mAb and PD-L1.Fc concentrations and the introduction of a biotin-streptavidin binding interface on the plate surface to capture both reagents were able to alleviate the nonspecific effect. 21 There are many different formulations of PD-L1.Fc and Ctrl.Fc available and the formulations used in different studies vary and are sometimes not specified. 9,[18][19][20]33 Although we obtained the same results when using fusion proteins from a different supplier (data not shown), it cannot be excluded that differences in the manufacturing and formulation of the fusion proteins may contribute to different outcomes, potentially because of different steric properties.…”

“…Therefore, delivery of PD‐L1.Fc in the context of the TCR signal appears critical for inducing the inhibitory mechanism of PD‐1. As such, coimmobilization of anti‐CD3 monoclonal antibody (mAb) alongside PD‐L1.Fc on polystyrene tissue culture plates is commonly used to investigate PD‐1 signaling in T cells 9,18–21 . This approach has the benefit of being easy to control, flexible in the amount of stimulus being delivered and able to be combined with other signaling inputs, apparently making it ideal for inclusion into existing quantitative in vitro T‐cell assay systems.…”

Transmembrane domain–driven PD-1 dimers mediate T cell inhibition

“…In addition, it was recently reported that a single SHP2 molecule can bridge two PD-1 cytoplasmic tails with its two SH2 domains ( 51 ), a conformation that would be facilitated by upstream, intrinsic dimerization of the receptor. Last, membrane proximal anti–PD-1 mAbs impart PD-1 agonism ( 52 ), a finding for which this work provides mechanistic support. Peresolimab, a PD-1 agonist mAb, was recently reported in a phase 2 clinical trial to be effective in treating rheumatoid arthritis ( 11 ).…”