Colon carcinoma treatment using bispecific anti-GITR/CTLA-4 antibodies: a patent evaluation of WO2018091739

The Evolving Applications of Bispecific Antibodies: Reaping the Harvest of Early Sowing and Planting New Seeds

After decades of gradual progress from conceptualization to early clinical trials (1960-2000), the therapeutic potential of bispecific antibodies (bisp Abs) is now being fully realized. Insights gained from both successful and unsuccessful trials are helping to identify which mechanisms of action, antibody formats, and targets prove most effective, and which may benefit from further refinement. While T-cell engagers remain the most commonly used class of bisp Abs, current efforts aim to increase their effectiveness by co-engaging costimulatory molecules, reducing escape mechanisms, and countering immunosuppression. Strategies to minimize cytokine release syndrome (CRS) are also actively under development. In addition, novel antibody formats that are selectively activated within tumors are an exciting area of research, as is the precise targeting of specific T-cell subsets. Beyond T cells, the recruitment of macrophages and dendritic cells is attracting increasing interest, with researchers exploring various macrophage receptors to promote phagocytosis or to carry out specialized functions, such as the immunologically silent clearance of amyloid-beta plaques in the brain. While bisp Abs targeting B cells are relatively limited, they are primarily aimed at inhibiting B-cell activity in autoimmune diseases. Another evolving application involves the forced interaction between proteins. Beyond the successful development of Hemlibra for hemophilia, bispecific antibodies that mimic cytokine activity are being explored. Additionally, the recruitment of cell surface ubiquitin ligases and other enzymes represents a novel and promising therapeutic strategy. In regard to antibody formats, some applications such as the combination of T-cell engagers with costimulatory molecules are driving the development of trispecific antibodies, at least in preclinical settings. However, the increasing structural complexity of multispecific antibodies often leads to more challenging development paths, and the number of multispecific antibodies in clinical trials remains low. The clinical success of certain applications and well-established production methods position this therapeutic class to expand its benefits into other therapeutic areas.

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.

Bispecific antibodies targeting CTLA-4: game-changer troopers in cancer immunotherapy

Antibody-based cancer immunotherapy has become a powerful asset in the arsenal against malignancies. In this regard, bispecific antibodies (BsAbs) are a ground-breaking novel approach in the therapy of cancers. Recently, BsAbs have represented a significant advancement in improving clinical outcomes. BsAbs are designed to target two different antigens specifically. Over a hundred various BsAb forms currently exist, and more are constantly being manufactured. An antagonistic regulator of T cell activation is cytotoxic T lymphocyte-associated protein 4 (CTLA-4) or CD152, a second counter-receptor for the B7 family of co-stimulatory molecules was introduced in 1996 by Professor James P. Allison and colleagues. Contrary to the explosive success of dual immune checkpoint blockade for treating cancers, a major hurdle still yet persist is that immune-related adverse events (irAEs) observed by combining immune checkpoint inhibitors (ICIs) or monoclonal antibodies such as ipilimumab (anti-CTLA-4) and nivolumab (anti-PD-1). A promising strategy to overcome this hurdle is using BsAbs. This article will summarize BsAbs targeting CTLA-4, their applications in cancer immunotherapy, and relevant clinical trial advances. We will also discuss the pre-clinical rationale for using these BsAbs, and provide the current landscape of the field.

Antibody-based cancer immunotherapy by targeting regulatory T cells

Regulatory T cells (Tregs) are among the most abundant suppressive cells, which infiltrate and accumulate in the tumor microenvironment, leading to tumor escape by inducing anergy and immunosuppression. Their presence has been correlated with tumor progression, invasiveness and metastasis. Targeting tumor-associated Tregs is an effective addition to current immunotherapy approaches, but it may also trigger autoimmune diseases. The major limitation of current therapies targeting Tregs in the tumor microenvironment is the lack of selective targets. Tumor-infiltrating Tregs express high levels of cell surface molecules associated with T-cell activation, such as CTLA4, PD-1, LAG3, TIGIT, ICOS, and TNF receptor superfamily members including 4-1BB, OX40, and GITR. Targeting these molecules often attribute to concurrent depletion of antitumor effector T-cell populations. Therefore, novel approaches need to improve the specificity of targeting Tregs in the tumor microenvironment without affecting peripheral Tregs and effector T cells. In this review, we discuss the immunosuppressive mechanisms of tumor-infiltrating Tregs and the status of antibody-based immunotherapies targeting Tregs.

Opportunities and challenges of bi-specific antibodies

The recent clinical approval of different Bi-specific antibodies (BsAbs) has revealed the great therapeutic potential of this novel class of biologicals. For example, the bispecific T-cell engager (BiTE), Blinatumomab, demonstrated the unique capacity of BsAbs to link T-cells with tumor cells, inducing targeted tumor cell removal. Additionally, Amivantamab, recognizing the EGFR and cMet in cis, revealed a substantial improvement of therapeutic efficacy by concomitantly targeting two tumor antigens. Cis-targeting BsAbs furthermore allow discerning cell populations which concurrently express two antigens, for which each antigen expression pattern in itself might not be selective. In this way, BsAbs harbor the great prospect of being more specific and showing fewer side effects than monoclonal antibodies. Nevertheless, BsAbs have also faced major obstacles, for instance, in ensuring reliable assembly and clinical-grade purification. In this review, we summarize the different available antibody platforms currently used for the generation of IgG-like and non-IgG-like BsAbs and explain which approaches have been used to assemble those BsAbs which are currently approved for clinical application. By focusing on the example of regulatory T-cells (Tregs) and the different, ongoing approaches to develop BsAbs specifically targeting Tregs within the tumor microenvironment, our review highlights the huge potential as well as the pitfalls BsAb face in order to emerge as one of the most effective therapeutic biologicals targeting desired cell populations in a highly selective way. Such BsAb may improve treatment efficacy and reduce side effects, thereby opening novel treatment opportunities for a range of different diseases, such as cancer or autoimmune diseases.

Mechanisms of regulatory T cell infiltration in tumors: implications for innovative immune precision therapies

With the broad application of cancer immunotherapies such as immune checkpoint inhibitors in multiple cancer types, the immunological landscape in the tumor microenvironment (TME) has become enormously important for determining the optimal cancer treatment. Tumors can be immunologically divided into two categories: inflamed and non-inflamed based on the extent of immune cell infiltration and their activation status. In general, immunotherapies are preferable for the inflamed tumors than for non-inflamed tumors. Regulatory T cells (Tregs), an immunosuppressive subset of CD4⁺ T cells, play an essential role in maintaining self-tolerance and immunological homeostasis. In tumor immunity, Tregs compromise immune surveillance against cancer in healthy individuals and impair the antitumor immune response in tumor-bearing hosts. Tregs, therefore, accelerate immune evasion by tumor cells, leading to tumor development and progression in various types of cancer. Therefore, Tregs are considered to be a crucial therapeutic target for cancer immunotherapy. Abundant Tregs are observed in the TME in many types of cancer, both in inflamed and non-inflamed tumors. Diverse mechanisms of Treg accumulation, activation, and survival in the TME have been uncovered for different tumor types, indicating the importance of understanding the mechanism of Treg infiltration in each patient when selecting the optimal Treg-targeted therapy. Here, we review recent advances in the understanding of mechanisms leading to Treg abundance in the TME to optimize Treg-targeted therapy. Furthermore, in addition to the conventional strategies targeting cell surface molecules predominantly expressed by Tregs, reagents targeting molecules and signaling pathways specifically employed by Tregs for infiltration, activation, and survival in each tumor type are illustrated as novel Treg-targeted therapies. The effectiveness of immune precision therapy depends on conditions in the TME of each cancer patient.

Regulatory T cell targeting in cancer: Emerging strategies in immunotherapy

The adaptive immune system is modulated by an important subset of CD4⁺ T lymphocytes called Treg cells that function in maintaining immune homeostasis by preventing excessive immune activation. Both deficiency and overactivation of Treg cell function can result in disease pathology. While loss of Treg function can lead to autoimmunity, an overabundance of Treg activity can promote tumorigenesis. Blocking and/or depleting Tregs has emerged as a viable strategy to enhance antitumor immunity. A major limitation underlying the limited efficacy observed with Treg therapies in the clinic is lack of selective targeting, often attributed to concurrent depletion of antitumor effector T-cell populations. Novel approaches to improve the specificity of Treg targeting in the context of cancer include the use of T-cell receptor mimic antibodies, bispecific antibodies, and near-infrared photoimmunotherapy. Next-generation technology platforms and transcriptomic/computational-based screening methods have been recently developed to identify preferential Treg targets. Herein, we highlight key advancements and challenges pertaining to the development of novel Treg targeting cancer therapeutics and discuss ongoing clinical trials evaluating next-generation Treg therapies for solid tumors.