CD3 x CD28 cross-interacting bispecific antibodies improve tumor cell dependent T-cell activation

Emerging Immunotherapy Approaches for Treating Prostate Cancer

Immunotherapy has emerged as an important approach for cancer treatment, but its clinical efficacy has been limited in prostate cancer compared to other malignancies. This review summarizes key immunotherapy strategies under evaluation for prostate cancer, including immune checkpoint inhibitors, bispecific T cell-engaging antibodies, chimeric antigen receptor (CAR) T cells, therapeutic vaccines, and cytokines. For each modality, the rationale stemming from preclinical studies is discussed along with outcomes from completed clinical trials and strategies to improve clinical efficacy that are being tested in ongoing clinical trials. Imperative endeavors include biomarker discovery for patient selection, deciphering resistance mechanisms, refining cellular therapies such as CAR T cells, and early-stage intervention were reviewed. These ongoing efforts instill optimism that immunotherapy may eventually deliver significant clinical benefits and expand treatment options for patients with advanced prostate cancer.

Novel Bi-Specific Immuno-Modulatory Tribodies Potentiate T Cell Activation and Increase Anti-Tumor Efficacy

Cancer immunotherapy has already shown significant improvements by combining different antibodies specific for distinct immune checkpoints, such as Ipilimumab and Nivolumab. Here, we tested combinatorial treatments of immunomodulatory antibodies, previously generated in our laboratory, for their effects on hPBMC activation, either upon stimulation with SEB or in co-cultures with tumor cells by cytokine secretion assays. We found that some of them showed additive or synergistic effects, and on the basis of these observations, we constructed, for the first time, four novel bispecific tribodies (TR), made up of a Fab derived from one anti-IC mAb and two scFvs derived from another mAb targeting a different IC. All four TRs cotargeting either programmed cell death protein 1 (PD-1) and Lymphocyte Activating 3 (LAG-3) or programmed death-ligand 1 (PD-L1) and LAG-3 retained binding affinity for their targets and the antagonistic effects of their parental mAbs, but some of them also showed an increased ability to induce lymphocyte activation and increased in vitro cytotoxicity against tumor cells compared to parental antibodies used either alone or in combinatorial treatments. Furthermore, none of the tribodies showed significant increased cytotoxicity on human cardiomyocytes. Considering that the tribody format reduces production costs (as only one construct provides the inhibitory effects of two antibodies), has an intermediate molecular size (100 kDa) which is well suited for both tumor penetration and an acceptable half-life, we think that these novel immunomodulatory TRBs have the potential to become precious tools for therapeutic applications, particularly in monotherapy-resistant cancer patients.

Enabling the next steps in cancer immunotherapy: from antibody-based bispecifics to multispecifics, with an evolving role for bioconjugation chemistry

In the past two decades, immunotherapy has established itself as one of the leading strategies for cancer treatment, as illustrated by the exponentially growing number of related clinical trials. This trend was, in part, prompted by the clinical success of both immune checkpoint modulation and immune cell engagement, to restore and/or stimulate the patient's immune system's ability to fight the disease. These strategies were sustained by progress in bispecific antibody production. However, despite the decisive progress made in the treatment of cancer, toxicity and resistance are still observed in some cases. In this review, we initially provide an overview of the monoclonal and bispecific antibodies developed with the objective of restoring immune system functions to treat cancer (cancer immunotherapy), through immune checkpoint modulation, immune cell engagement or a combination of both. Their production, design strategy and impact on the clinical trial landscape are also addressed. In the second part, the concept of multispecific antibody formats, notably MuTICEMs (Multispecific Targeted Immune Cell Engagers & Modulators), as a possible answer to current immunotherapy limitations is investigated. We believe it could be the next step to take for cancer immunotherapy research and expose why bioconjugation chemistry might play a key role in these future developments.

Overcoming the challenges associated with CD3+ T-cell redirection in cancer

The development of bispecific antibodies that redirect the cytotoxic activity of CD3+ T cells to tumours is a promising immunotherapeutic strategy for the treatment of haematological malignancies and solid cancers. Since the landmark FDA approval at the end of 2014 of the anti-CD3 × anti-CD19 bispecific antibody blinatumomab (Blincyto®) for the treatment of relapsed/refractory B-cell acute lymphoblastic leukaemia, ~100 clinical trials investigating the safety and efficacy of CD3+ bispecific T-cell redirectors for cancer have been initiated. However, despite early success, numerous challenges pertaining to CD3+ T-cell redirection in the context of cancer exist, including the recruitment of counterproductive CD3+ T-cell subsets, the release of systemic cytokines, the expansion of immune checkpoint molecules, the presence of an immunosuppressive tumour microenvironment, tumour antigen loss/escape, on-target off-tumour toxicity and suboptimal potency. The aim of the present review is to discuss novel approaches to overcome the key challenges associated with CD3+ bispecific T-cell redirection in order to achieve an optimal balance of anti-tumour activity and safety.

T-cell Activating Tribodies as a Novel Approach for Efficient Killing of ErbB2-positive Cancer Cells

The Tyrosine Kinase Receptor ErbB2 (HER2) when overexpressed in breast cancer (BC) is associated with poor prognosis. The monoclonal antibody Trastuzumab has become a standard treatment of ErbB2+BC. The antibody treatment has limited efficacy, often meets resistance and induces cardiotoxicity. T-cell recruiting bispecific antibody derivatives (TRBA) offer a more effective alternative to standard antibody therapy. We evaluated a panel of TRBAs targeting 3 different epitopes on the ErbB2 receptor either in a bivalent targeting tribody structure or as a monovalent scFv-fusion (BiTE format) for binding, cytotoxicity on Trastuzumab-resistant cell lines, and induction of cardiotoxicity. All three TRBAs bind with high affinity to the ErbB2 extracellular domain and a large panel of ErbB2-positive tumor cells. Tribodies had an increased in vitro cytotoxic potency as compared to BiTEs. It is interesting to note that, Tribodies targeting the epitopes on ErbB2 receptor domains I and II bind and activate lysis of mammary and gastric tumor cells more efficiently than a Tribody targeting the Trastuzumab epitope on domain IV. The first 2 are also active on Trastuzumab-resistant cancer cells lacking or masking the epitope recognized by Trastuzumab. None of the Tribodies studied showed significant toxicity on human cardiomyocytes. Altogether these results make these novel anti-ErbB2 bispecific Tribodies candidates for therapeutic development for treating ErbB2-positive Trastuzumab-resistant cancer patients.

RNA as a boiling-resistant anionic polymer material to build robust structures with defined shape and stoichiometry

RNA is a polyribonucleic acid belonging to a special class of anionic polymers, holding a unique property of self-assembly that is controllable in the construction of structures with defined size, shape, and stoichiometry. We report here the use of RNA as polymers to fabricate boiling-resistant triangular nanoscaffolds, which were used to construct hexagons and patterned hexagonal arrays. The RNA triangular scaffolds demonstrated promising potential to construct fluorogenic probes and therapeutic agents as functionalization with siRNA, ribozyme, folate, and fluorogenic RNA aptamers revealed independent functional activity of each RNA moiety. The ribozyme was able to cleave hepatitis genomic RNA fragments, the siRNA silenced the target genes, and all fluorogenic RNA aptamers retained their fluorescence emission property. The creation of boiling-temperature-resistant RNA nanoparticles opens a new dimension of RNA as a special polymer, feasible in industrial and nanotechnological applications.

[Bispecific antibodies: what future?]

Monoclonal antibodies have emerged as a very successful class of therapeutic agents. In their native format, monoclonal antibodies are monospecific in that they recognize only one epitope, but their Fc domain also binds to FcfR-expressing cells. Attempts to improve the cytotoxicity of antibodies, particularly in the cancer field, have led to the design of bispecific antibodies: this can occur through various strategies, such as quadroma, thioether-linked Fab' gamma fragments or genetic engineering. Such bispecific antibodies have been developped to enhance immunotherapy, by bridging tumor cells and T cells, or radioimmunotherapy by combining bispecific antibodies and radiolabeled bivalent haptens that bind cooperatively to target cells. Multiple further applications can be envisaged such as targeting two different antigens on the same cell, or two epitopes of the same antigen. Although progresses have been slowed by technical constraints, there is little doubt that this class of novel antibodies derivatives will experience a promising development.