Immune checkpoints refer to the plethora of inhibitory pathways that are crucial to maintaining self-tolerance. Tumour cells induce immune checkpoints to evade immunosurveillance. This Review discusses the progress in targeting immune checkpoints, the considerations for combinatorial therapy and the potential for additional immune-checkpoint targets.

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The blockade of immune checkpoints in cancer immunotherapy

Background Programmed death 1 (PD-1) protein, a T-cell coinhibitory receptor, and one of its ligands, PD-L1, play a pivotal role in the ability of tumor cells to evade the host's immune system. Blockade of interactions between PD-1 and PD-L1 enhances immune function in vitro and mediates antitumor activity in preclinical models. Methods In this multicenter phase 1 trial, we administered intravenous anti–PD-L1 antibody (at escalating doses ranging from 0.3 to 10 mg per kilogram of body weight) to patients with selected advanced cancers. Anti–PD-L1 antibody was administered every 14 days in 6-week cycles for up to 16 cycles or until the patient had a complete response or confirmed disease progression. Results As of February 24, 2012, a total of 207 patients — 75 with non–small-cell lung cancer, 55 with melanoma, 18 with colorectal cancer, 17 with renal-cell cancer, 17 with ovarian cancer, 14 with pancreatic cancer, 7 with gastric cancer, and 4 with breast cancer — had received anti–PD-L1 antibody. The media...

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Safety and Activity of Anti–PD-L1 Antibody in Patients with Advanced Cancer

Programmed death 1 (PD-1) and its ligands, PD-L1 and PD-L2, deliver inhibitory signals that regulate the balance between T cell activation, tolerance, and immunopathology. Immune responses to foreign and self-antigens require specific and balanced responses to clear pathogens and tumors and yet maintain tolerance. Induction and maintenance of T cell tolerance requires PD-1, and its ligand PD-L1 on nonhematopoietic cells can limit effector T cell responses and protect tissues from immune-mediated tissue damage. The PD-1:PD-L pathway also has been usurped by microorganisms and tumors to attenuate antimicrobial or tumor immunity and facilitate chronic infection and tumor survival. The identification of B7-1 as an additional binding partner for PD-L1, together with the discovery of an inhibitory bidirectional interaction between PD-L1 and B7-1, reveals new ways the B7:CD28 family regulates T cell activation and tolerance. In this review, we discuss current understanding of the immunoregulatory functions of PD-1 and its ligands and their therapeutic potential.

PD-1 and its ligands in tolerance and immunity

https://www.cell.com/cancer-cell/pdf/S1535-6108(15)00089-6.pdf

Immune checkpoint blockade: a common denominator approach to cancer therapy

▪ Abstract The discovery of new functions for the original B7 family members, together with the identification of additional B7 and CD28 family members, have revealed new ways in which the B7:CD28 family regulates T cell activation and tolerance. B7-1/B7-2:CD28 interactions not only promote initial T cell activation but also regulate self-tolerance by supporting CD4+CD25+ T regulatory cell homeostasis. CTLA-4 can exert its inhibitory effects in both B7-1/B7-2 dependent and independent fashions. B7-1 and B7-2 can signal bidirectionally by engaging CD28 and CTLA-4 on T cells and by delivering signals into B7-expressing cells. The five new B7 family members, ICOS ligand, PD-L1 (B7-H1), PD-L2 (B7-DC), B7-H3, and B7-H4 (B7x/B7-S1) are expressed on professional antigen-presenting cells as well as on cells within nonlymphoid organs, providing new means for regulating T cell activation and tolerance in peripheral tissues. The new CD28 families members, ICOS, PD-1, and BTLA, are inducibly expressed on T cells, and...

The b7 family revisited

Dendritic cells (DCs), unique antigen-presenting cells (APCs) with potent T cell stimulatory capacity, direct the activation and differentiation of T cells by providing costimulatory signals. As such, they are critical regulators of both natural and vaccine-induced immune responses. A new B7 family member, B7-DC, whose expression is highly restricted to DCs, was identified among a library of genes differentially expressed between DCs and activated macrophages. B7-DC fails to bind the B7.1/2 receptors CD28 and cytotoxic T lymphocyte–associated antigen (CTLA)-4, but does bind PD-1, a receptor for B7-H1/PD-L1. B7-DC costimulates T cell proliferation more efficiently than B7.1 and induces a distinct pattern of lymphokine secretion. In particular, B7-DC strongly costimulates interferon γ but not interleukin (IL)-4 or IL-10 production from isolated naive T cells. These properties of B7-DC may account for some of the unique activity of DCs, such as their ability to initiate potent T helper cell type 1 responses.

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B7-Dc, a New Dendritic Cell Molecule with Potent Costimulatory Properties for T Cells


 Regulatory T cells (Tregs) play an indispensable role in mediating peripheral tolerance to self-antigens. They can also promote tumor growth by suppressing the function of effector CD8+ and CD4+ T cells in the tumor microenvironment (TME). Furthermore, Tregs are identified as one of the key resistance mechanisms hampering the efficacy of immune checkpoint inhibitors (ICIs) across many tumor types. Therefore, there is a high need for safe and effective agents that would specifically deplete tumor-infiltrating Tregs while sparing both peripheral Tregs and effector T cells.
 Chemokine receptor 8 (CCR8) is predominantly expressed on activated tumor-infiltrating Tregs and marks the most suppressive and proliferative Treg population. CCR8+ Tregs are associated with high tumor grade and poor overall survival across many tumor types such as lung, breast, or head-neck cancer. Thus, unlike other approaches directed against Tregs, targeting CCR8 offers the opportunity to specifically deplete intra-tumoral Tregs without impacting peripheral Tregs or other immune cells.
 BAY 3375968 is a non-internalizing fully human glycoengineered (afucosylated) monoclonal IgG1 antibody, which in vitro selectively depleted human CCR8+ Tregs via antibody dependent cellular cytotoxicity (ADCC) and antibody dependent cellular phagocytosis (ADCP). In vivo efficacy studies using mouse surrogate antibodies showed strong monotherapeutic efficacy across a variety of murine tumor models with clear correlation of intratumoral CCR8+ Treg depletion and CD8+ T cell increase. The monotherapeutic efficacy of CCR8 depleting antibodies was further enhanced by combinations with ICIs. BAY 3375968 also showed a good safety profile in cynomolgus monkeys. In conclusion, CCR8 is a novel Treg depleting immunotherapy target, and due to its highly tumor-restricted expression profile, BAY 3375968 may provide superior clinical safety and efficacy profile comparing to other less specific Treg targeting approaches.
 Based on the promising pre-clinical data, preparations for a phase I clinical trial investigating the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary anti-tumor activity of BAY 3375968 are underway.
 Citation Format: Helge Roider, Su-Yi Tseng, Sabine Hoff, Sandra Berndt, Katharina Filarski, Uwe Gritzan, Beatrix Stelte-Ludwig, Wiebke M. Nadler, Joanna Grudzinska-Goebel, Philipp Ellinger, Mark Trautwein, Matyas Gorjanacz. BAY 3375968: An afucosylated anti-CCR8 antibody depleting activated intratumoral regulatory T cells as a cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2866.

Su Yi Tseng

Papers

B7-Dc, a New Dendritic Cell Molecule with Potent Costimulatory Properties for T Cells

Abstract 2866: BAY 3375968: An afucosylated anti-CCR8 antibody depleting activated intratumoral regulatory T cells as a cancer immunotherapy