Targeting TIGIT for cancer immunotherapy: recent advances and future directions

As a newly identified checkpoint, T cell immunoreceptor with immunoglobulin and tyrosine-based inhibitory motif (ITIM) domain (TIGIT) is highly expressed on CD4+ T cells, CD8+ T cells, natural killer (NK) cells, regulatory T cells (Tregs), and tumor-infiltrating lymphocytes (TILs). TIGIT has been associated with NK cell exhaustion in vivo and in individuals with various cancers. It not only modulates NK cell survival but also mediates T cell exhaustion. As the primary ligand of TIGIT in humans, CD155 may be the main target for immunotherapy due to its interaction with TIGIT. It has been found that the anti-programmed cell death protein 1 (PD-1) treatment response in cancer immunotherapy is correlated with CD155 but not TIGIT. Anti-TIGIT alone and in combination with anti-PD-1 agents have been tested for cancer immunotherapy. Although two clinical studies on advanced lung cancer had positive results, the TIGIT-targeted antibody, tiragolumab, recently failed in two new trials. In this review, we highlight the current developments on TIGIT for cancer immunotherapy and discuss the characteristics and functions of TIGIT.

TIGIT in Lung Cancer: Potential Theranostic Implications

TIGIT (T cell immunoreceptor with Ig and ITIM domains) is a co-inhibitory receptor expressed on various immune cells, including T cells, NK cells, and dendritic cells. TIGIT interacts with different ligands, such as CD155 and CD112, which are highly expressed on cancer cells, leading to the suppression of immune responses. Recent studies have highlighted the importance of TIGIT in regulating immune cell function in the tumor microenvironment and its role as a potential therapeutic target, especially in the field of lung cancer. However, the role of TIGIT in cancer development and progression remains controversial, particularly regarding the relevance of its expression both in the tumor microenvironment and on tumor cells, with prognostic and predictive implications that remain to date essentially undisclosed. Here, we provide a review of the recent advances in TIGIT-blockade in lung cancer, and also insights on TIGIT relevance as an immunohistochemical biomarker and its possible theranostic implications.

Emerging immune checkpoint inhibitors for the treatment of non-small cell lung cancer

INTRODUCTION

Over the last decade, immune checkpoint inhibitors (ICIs) have impacted on the standard therapy for patients with non-small cell lung cancer (NSCLC). ICIs first showed efficacy in patients with advanced disease who had progressed after chemotherapy, later reaching the first-line therapy context alone, in combination with chemotherapy, and/or with dual-immunotherapy regimens.

AREAS COVERED

Most of their benefit is, however, restricted to just 20% of patients due to primary or emergence of acquired resistance. In this review, we will describe the role of new emerging ICIs in the current panorama of NSCLC therapeutic approaches, not only in metastatic disease but also in locally advanced stage disease, with specific focus on those drugs under investigation in Phase 2/3 clinical trials.

EXPERT OPINION

Several new ICIs are now under investigation to optimize NSCLC patient management; these are usually used in combination with other well-known agents, such as 'traditional' ICIs and chemotherapy, or with other newly developed drugs. Identification of better biomarkers will provide personalized treatment approaches to overcome patient-specific immune resistance.

Clinical Development of Anti-TIGIT Antibodies for Immunotherapy of Cancer

PURPOSE OF REVIEW

T-cell immunoglobulin and ITIM domain (TIGIT) is a next-generation inhibitory receptor with multiple antibodies under exploration in cancer therapy. Here, we review the available data from the early trials and overview upcoming clinical trials on anti-TIGIT antibodies.

RECENT FINDINGS

There is a promising activity of anti-TIGIT, particularly in combination with anti-PD-1/PD-L1 in non-small cell lung cancer (NSCLC) with already phase 3 trials currently ongoing to confirm these early findings. Numerous anti-TIGIT antibodies are in clinical trials currently, and others are in preclinical development. Therefore, more data are expected in the next few years regarding the efficacy of this new checkpoint inhibitor in multiple solid and hematologic malignancies. However, preliminary data are promising, and anti-TIGIT treatment seems to confer more favorable responses when combined with anti-PD-1/anti-PD-L1 compared to either agent alone.

Tislelizumab: A Modified Anti-tumor Programmed Death Receptor 1 Antibody

Tislelizumab is an anti-programmed death receptor 1 (PD-1) monoclonal immunoglobulin G 4 antibody developed by BeiGene. The structure of tislelizumab has been modified to maximally inhibit the binding of PD-1 to programmed death ligand 1 (PD-L1) and minimize the binding of tislelizumab to Fcγ receptors. In clinical studies, tislelizumab has shown preliminary anti-tumor effects in various solid tumors, such as Hodgkin's lymphoma, urothelial carcinoma, lung cancer, gastric and esophageal cancer, liver cancer, nasopharyngeal carcinoma, colorectal cancer, and microsatellite instability-high/mismatch repair-deficient tumors. In addition, it also showed new promise in solid tumor treatment in combination with ociperlimab. Due to its satisfactory anti-tumor effects, tislelizumab has received approvals in China for the treatment of classical Hodgkin's lymphoma, urothelial carcinoma, squamous non-small cell lung cancer, non-squamous non-small cell lung cancer, and hepatocellular carcinoma, and it is now under investigation for a new indication in microsatellite instability-high/mismatch repair-deficient tumors. Moreover, it has been granted orphan designations in hepatocellular carcinoma, esophageal cancer, and gastric cancer, including cancer of the gastroesophageal junction, by the US Food and Drug Administration. Tislelizumab has an acceptable safety profile; the most common adverse effects include fatigue, anemia, and decreased neutrophil count, while the most fatal events have been related to respiratory infection or failure, and hepatic injury. Tislelizumab has an economic advantage compared with other well-studied PD-1/PD-L1 inhibitors; thus, the introduction of it could provide clinical oncologists with an effective weapon against tumors and may alleviate the burden of cancer patients.

Current Landscape of Non-Small Cell Lung Cancer: Epidemiology, Histological Classification, Targeted Therapies, and Immunotherapy

Non-small cell lung cancer (NSCLC) is a subtype of the most frequently diagnosed cancer in the world. Its epidemiology depends not only on tobacco exposition but also air quality. While the global trends in NSCLC incidence have started to decline, we can observe region-dependent differences related to the education and the economic level of the patients. Due to an increasing understanding of NSCLC biology, new diagnostic and therapeutic strategies have been developed, such as the reorganization of histopathological classification or tumor genotyping. Precision medicine is focused on the recognition of a genetic mutation in lung cancer cells called "driver mutation" to provide a variety of specific inhibitors of improperly functioning proteins. A rapidly growing group of approved drugs for targeted therapy in NSCLC currently allows the following mutated proteins to be treated: EGFR family (ERBB-1, ERBB-2), ALK, ROS1, MET, RET, NTRK, and RAF. Nevertheless, one of the most frequent NSCLC molecular sub-types remains without successful treatment: the K-Ras protein. In this review, we discuss the current NSCLC landscape treatment focusing on targeted therapy and immunotherapy, including first- and second-line monotherapies, immune checkpoint inhibitors with chemotherapy treatment, and approved predictive biomarkers.