Simultaneous Inhibition of PD-1 and Stimulation of CD40 Signaling Pathways by Anti-PD-L1/CD40L Bispecific Fusion Protein Synergistically Activate Target and Effector Cells

Bispecific therapeutics: a state-of-the-art review on the combination of immune checkpoint ‎inhibition with costimulatory and non-checkpoint targeted therapy

INTRODUCTION

Immune checkpoint inhibitors (ICIs) have revolutionized the field of cancer immunotherapy and have enhanced the survival of patients with malignant tumors. However, the overall efficacy of ICIs remains unsatisfactory and is faced with two major concerns of resistance development and occurrence of immune-related adverse events (irAEs). Bispecific antibodies (bsAbs) have emerged as promising strategies with unique mechanisms of action to achieve a better efficacy and safety than monoclonal antibodies (mAbs) or even their combination. BsAbs along with other bispecific platforms such as bispecific fusion proteins, nanobodies, and CAR-T cells may help to avoid development of resistance and reduce irAEs caused by on-target/off-tumor binding effects of mAbs.

AREAS COVERED

A literature search was performed using PubMed for English-language articles to provide a comprehensive overview of preclinical and clinical studies on bsAbs specified for both immune checkpoints and non-checkpoint molecules as a well-enhanced class of therapeutics.

EXPERT OPINION

Identifying suitable targets and selecting effective engineering platforms enhance the potential of bsAbs to address the challenges associated with conventional therapies such as ICIs, positioning them as a promising class of therapeutics in the landscape of cancer immunotherapy.

Immune modulation via dendritic cells by the effect of Thymosin-alpha-1 on immune synapse in HCMV infection

Tα1 (Thymosin-alpha-1) is a thymus-derived hormone that has been demonstrated to be effective on diverse immune cell subsets. The objective of this study was to determine the in vitro immunomodulatory effect of Tα1 in human cytomegalovirus (HCMV) infection. Dendritic cells (DCs) were isolated from peripheral blood mononuclear cells (PBMCs) by negative selection and cultured in the presence or absence of Tα1. The immunophenotyping of DCs was characterised by multiparametric flow cytometry assessing CD40, CD80, TIM-3 and PDL-1 markers, as well as intracellular TNFα production. Then, autologous CD4+ or CD8+ T-Lymphocytes (TLs) isolated by negative selection from PBMCs were co-cultured with DCs previously treated with Tα1 in the presence or absence of HCMV. Intracellular TNFα, IFNγ, IL-2 production, CD40-L and PD-1 expression were assessed through immunophenotyping, and polyfunctionality in total TLs and memory subsets were evaluated. The results showed that Tα1 increased CD40, CD80, TIM-3 and TNFα intracellular production while decreasing PDL-1 expression, particularly on plasmacytoid dendritic cells (pDCs). Therefore, Tα1 modulated the production of TNFα, IFNγ and IL-2 in both total and memory subsets of CD4+ and CD8+ TLs by upregulating CD40/CD40-L and downregulating PDL-1/PD-1 expression. Our study concludes that Tα1 enhances antigen-presenting capacity of DCs, improves TLs responses to HCMV infection, and enhances the polyfunctionality of CD8+ TLs. Consequently, Tα1 could be an alternative adjuvant for use in therapeutic cell therapy for immunocompromised patients.

Design and selection of anti-PD-L1 single-domain antibody and tumor necrosis factor superfamily ligands for an optimal vectorization in an oncolytic virus

Arming oncolytic viruses with transgenes encoding immunomodulators improves their therapeutic efficacy by enhancing and/or sustaining the innate and adaptive anti-tumoral immune responses. We report here the isolation, selection, and vectorization of a blocking anti-human PDL1 single-domain antibody (sdAb) isolated from PDL1-immunized alpacas. Several formats of this sdAb were vectorized into the vaccinia virus (VV) and evaluated for their programmed cell death protein 1 (PD1)/PD1 ligand (PDL1) blocking activity in the culture medium of tumor cells infected in vitro. In those conditions, VV-encoded homodimeric sdAb generated superior PDL1 blocking activity compared to a benchmark virus encoding full-length avelumab. The sdAb was further used to design simple, secreted, and small tumor necrosis factor superfamily (TNFSF) fusions with the ability to engage their cognate receptors (TNFRSF) only in the presence of PDL1-positive cells. Finally, PDL1-independent alternatives of TNFRSF agonists were also constructed by fusing different variants of surfactant protein-D (SP-D) oligomerization domains with TNFSF ectodomains. An optimal SP-D-CD40L fusion with an SP-D collagen domain reduced by 80% was identified by screening with a transfection/infection method where poxvirus transfer plasmids and vaccinia virus were successively introduced into the same cell. However, once vectorized in VV, this construct had a much lower CD40 agonist activity compared to the SP-D-CD40L construct, which is completely devoid of the collagen domain that was finally selected. This latest result highlights the importance of working with recombinant viruses early in the payload selection process. Altogether, these results bring several complementary solutions to arm oncolytic vectors with powerful immunomodulators to improve their immune-based anti-tumoral activity.

Reinstating immunogenicity using bispecific anti-checkpoint/agent inhibitors

Immune checkpoint inhibitor (ICI) resistance demands for acquisition of novel strategies in order to broaden the therapeutic repertoire of advanced cancers. Bispecific antibodies can be utilized as an emerging therapeutic paradigm and a step forward in cancer immunotherapy. Synchronous inhibition of programmed death-1 (PD-1), programmed death-ligand 1 (PD-L1) or cytotoxic T lymphocyte associated antigen-4 (CTLA-4), or with other agents can expand antibody selectivity and improve therapeutic window through tightening cell-to-cell bridge (a process called immunological synapse) within tumor immune microenvironment (TIME). There is evidence of higher potency of this co-targeting approach over combined single-agent monoclonal antibodies in reinvigorating anti-tumor immune responses, retarding tumor growth, and improving patient survival. In fact, immunological synapses formed by interactions of such bispecific agents with TIME cells directly mediate cytotoxicity against tumor cells, and durable anti-tumor immune responses are predictable after application of such agents. Besides, lower adverse events are reported for bispecific antibodies compared with individual checkpoint inhibitors. These are all indicative of the importance of exploiting novel bispecific approach as a replacement for conventional combo checkpoint inhibitor therapy particularly for tumors with immunosuppressive or cold immunity. Study in this area is still continued, and in the future more will be known about the importance of this bispecific approach in cancer immunotherapy.

The interaction between the soluble programmed death ligand-1 (sPD-L1) and PD-1+ regulator B cells mediates immunosuppression in triple-negative breast cancer

Accumulating evidence suggests that regulatory B cells (Bregs) play important roles in inhibiting the immune response in tumors. Programmed death 1 (PD-1) and programmed death ligand 1 (PD-L1) are important molecules that maintain the balance of the immune response and immune tolerance. This study aims to evaluate the soluble form of PD-L1 and its function in inducing the differentiation of B lymphocytes, investigate the relationship between soluble PD-L1 (sPD-L1) and B-cell subsets, and explore the antitumor activity of T lymphocytes after PD-L1 blockade in coculture systems. In an effort to explore the role of sPD-L1 in human breast cancer etiology, we examined the levels of sPD-L1 and interleukin-10 (IL-10) in the serum of breast tumor patients and the proportions of B cells, PD-1⁺ B cells, Bregs, and PD-1⁺ Bregs in the peripheral blood of patients with breast tumors and assessed their relationship among sPD-L1, IL-10, and B-cell subsets. The levels of sPD-L1 and IL-10 in serum were found to be significantly higher in invasive breast cancer (IBCa) patients than in breast fibroadenoma (FIBma) patients. Meanwhile, the proportions and absolute numbers of Bregs and PD-1⁺ Bregs in the peripheral blood of IBCa patients were significantly higher than those of FIBma patients. Notably, they were the highest in triple-negative breast cancer (TNBC) among other subtypes of IBCa. Positive correlations of sPD-L1 and IL-10, IL-10 and PD-1⁺ Bregs, and also sPD-L1 and PD-1⁺ Bregs were observed in IBCa. We further demonstrated that sPD-L1 could induce Breg differentiation, IL-10 secretion, and IL-10 mRNA expression in a dose-dependent manner in vitro. Finally, the induction of regulatory T cells (T_regs) by Bregs was further shown to suppress the antitumor response and that PD-L1 blockade therapies could promote the apoptosis of tumor cells. Together, these results indicated that sPD-L1 could mediate the differentiation of Bregs, expand CD4⁺ T_regs and weaken the antitumor activity of CD4⁺ T cells. PD-L1/PD-1 blockade therapies might be a powerful therapeutic strategy for IBCa patients, particularly for TNBC patients with high level of PD-1⁺ Bregs.

A TP53 Related Immune Prognostic Model for the Prediction of Clinical Outcomes and Therapeutic Responses in Lung Adenocarcinoma

TP53 is the most frequently mutated gene in lung adenocarcinoma (LUAD). The tumor immune microenvironment (TIM) is considered a vital factor that influences tumor progression and survival rate. The influence of TP53 mutation on TIM in LUAD has not been fully studied. Here we systematically investigated the relationship and potential mechanisms between TP53 mutation status and immune response in LUAD. We constructed an immune prognostic model (IPM) using immune associated genes, which were expressed differentially between the TP53 mutant and wild type LUAD patients. We discovered that TP53 mutations were significantly associated with 5 immune related biological processes. Thirty-six immune genes were expressed differentially between TP53 mutant and wild type LUAD patients. An IPM was constructed using 3 immune genes to differentiate the prognostic survival in LUAD. The high-risk LUAD group displayed significantly higher proportions of dendritic cell resting, T cell CD4 memory resting and mast cell resting, and significantly low proportions of dendritic cell activated, T cell CD4 memory activated, and mast cell activated. Moreover, IPM was found to be an independent clinical feature and can be used to predict immunotherapy responses. In summary, we constructed and validated an IPM using 3 immune related genes, which provides a better understanding of the mechanism from an immunological perspectives.