Novel monoclonal antibodies for cancer treatment: the trifunctional antibody catumaxomab (removab)

Immunosuppressive tumor microenvironment and immunotherapy of hepatocellular carcinoma: current status and prospectives

Hepatocellular carcinoma (HCC) is a major health concern worldwide, with limited therapeutic options and poor prognosis. In recent years, immunotherapies such as immune checkpoint inhibitors (ICIs) have made great progress in the systemic treatment of HCC. The combination treatments based on ICIs have been the major trend in this area. Recently, dual immune checkpoint blockade with durvalumab plus tremelimumab has also emerged as an effective treatment for advanced HCC. However, the majority of HCC patients obtain limited benefits. Understanding the immunological rationale and exploring novel ways to improve the efficacy of immunotherapy has drawn much attention. In this review, we summarize the latest progress in this area, the ongoing clinical trials of immune-based combination therapies, as well as novel immunotherapy strategies such as chimeric antigen receptor T cells, personalized neoantigen vaccines, oncolytic viruses, and bispecific antibodies.

Unraveling the multifaceted role of EpCAM in colorectal cancer: an integrated review of its function and interplay with non-coding RNAs

The epithelial cell adhesion molecule (EpCAM) is a critical glycoprotein involved in cell cycle progression, proliferation, differentiation, migration, and immune evasion. Its role as a target for bispecific antibodies has shown promise in annihilating cancer cells. EpCAM's potential as a biomarker for tumor-initiating cells, characterized by self-renewal and tumorigenic capabilities, underscores its value in early cancer detection, immunotherapy, and targeted drug delivery. While EpCAM monotherapies have been met with limited success, bispecific antibodies targeting both EpCAM and other proteins have exhibited encouraging results in colorectal cancer (CRC) research. The integration of EpCAM-directed nanotechnology in drug delivery systems has emerged as a pivotal innovation in CRC treatment. Moreover, developing chimeric antigen receptor (CAR) T-cell and CAR natural killer (NK) cell therapies opens promising therapeutic avenues for EpCAM-positive CRC patients. Although preliminary, this review sets the stage for future advances. Additionally, this study advances our understanding of the role of non-coding RNAs in CRC, which may be pivotal in gene regulation and could provide insights into the molecular underpinning. The findings suggest that lncRNA, miRNA, and circRNA could serve as novel therapeutic targets or biomarkers, further enriching the landscape of CRC diagnostics and therapeutics.

Efficacy of Bispecific Antibody Targeting EpCAM and CD3 for Immunotherapy in Ovarian Cancer Ascites: An Experimental Study

OBJECTIVE

This study aimed to explore the value of M701, targeting epithelial cell adhesion molecule (EpCAM) and CD3, in the immunotherapy of ovarian cancer ascites by the in vitro assay.

METHODS

The expression of EpCAM in ovarian cancer tissues was analyzed by databases. The EpCAM expression and immune cell infiltration in different foci of ovarian cancer were detected by 8-channel flow cytometry. The toxic effect of M701 on OVCAR3 was tested using the in vitro cytotoxicity assay. The 3D cell culture and drug intervention experiments were performed to evaluate the therapeutic effect of M701 in ovarian cancer specimens. Flow cytometry was used to examine the effect of M701 on the binding of immune cells to tumor cells and the activation capacity of T cells.

RESULTS

The results of the bioinformatic analysis showed that the expression of EpCAM in ovarian cancer tissue was significantly higher than that in normal ovarian tissue. The 8-channel flow cytometry of clinical samples showed that the EpCAM expression and lymphocyte infiltration were significantly heterogeneous among ovarian cancer patients and lesions at different sites. The in vitro experiment results showed that M701 had a significant killing effect on OVCAR3 cells. M701 also obviously killed primary tumor cells derived from some patients with ovarian cancer ascites. M701 could mediate the binding of CD3⁺ T cells to EpCAM⁺ tumor cells and induce T cell activation in a dose-dependent manner.

CONCLUSION

M701 showed significant inhibitory activity on tumor cells derived from ovarian cancer ascites, which had a promising application in immunotherapy for patients with ovarian cancer ascites.

Immunotherapy for Peritoneal Carcinomatosis: Challenges and Prospective Outcomes

Peritoneal metastasis, also known as peritoneal carcinomatosis (PC), is a refractory cancer that is typically resistant to conventional therapies. The typical treatment for PC is a combination of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). Recently, research in this area has seen significant advances, particularly in immunotherapy as an alternative therapy for PC, which is very encouraging. Catumaxomab is a trifunctional antibody intraperitoneal (IP) immunotherapy authorized in Europe that can be used to diminish malignant ascites by targeting EpCAM. Intraperitoneal (IP) immunotherapy breaks immunological tolerance to treat peritoneal illness. Increasing T-cell responses and vaccination against tumor-associated antigens are two methods of treatment. CAR-T cells, vaccine-based therapeutics, dendritic cells (DCs) in combination with pro-inflammatory cytokines and NKs, adoptive cell transfer, and immune checkpoint inhibitors are promising treatments for PC. Carcinoembryonic antigen-expressing tumors are suppressed by IP administration of CAR-T cells. This reaction was strengthened by anti-PD-L1 or anti-Gr1. When paired with CD137 co-stimulatory signaling, CAR-T cells for folate receptor cancers made it easier for T-cell tumors to find their way to and stay alive in the body.

Development of therapeutic antibodies for the treatment of diseases

Since the first monoclonal antibody drug, muromonab-CD3, was approved for marketing in 1986, 165 antibody drugs have been approved or are under regulatory review worldwide. With the approval of new drugs for treating a wide range of diseases, including cancer and autoimmune and metabolic disorders, the therapeutic antibody drug market has experienced explosive growth. Monoclonal antibodies have been sought after by many biopharmaceutical companies and scientific research institutes due to their high specificity, strong targeting abilities, low toxicity, side effects, and high development success rate. The related industries and markets are growing rapidly, and therapeutic antibodies are one of the most important research and development areas in the field of biology and medicine. In recent years, great progress has been made in the key technologies and theoretical innovations provided by therapeutic antibodies, including antibody-drug conjugates, antibody-conjugated nuclides, bispecific antibodies, nanobodies, and other antibody analogs. Additionally, therapeutic antibodies can be combined with technologies used in other fields to create new cross-fields, such as chimeric antigen receptor T cells (CAR-T), CAR-natural killer cells (CAR-NK), and other cell therapy. This review summarizes the latest approved or in regulatory review therapeutic antibodies that have been approved or that are under regulatory review worldwide, as well as clinical research on these approaches and their development, and outlines antibody discovery strategies that have emerged during the development of therapeutic antibodies, such as hybridoma technology, phage display, preparation of fully human antibody from transgenic mice, single B-cell antibody technology, and artificial intelligence-assisted antibody discovery.

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.

Antibody markup language (AbML) - a notation language for antibody-based drug formats and software for creating and rendering AbML (abYdraw)

As interest in antibody-based drug development continues to increase, the biopharmaceutical industry has begun to focus on complex multi-specific antibodies (MsAbs) as an up-and-coming class of biologic that differ from natural monoclonal antibodies through their ability to bind to more than one type of antigen. As techniques to generate such molecules have diversified, so have their formats and the need for standard notation. Previous efforts to develop a notation language for macromolecule drugs have been insufficient, or too complex, for MsAbs. Here, we present Antibody Markup Language (AbML), a new notation language specifically for antibody formats that overcomes the limitations of existing languages and can annotate all current antibody formats, including fusions, fragments, standard antibodies and MsAbs, as well as all currently conceivable future formats. AbML V1.1 also provides explicit support for T-cell receptor domains. To assist users of this language we have also developed a tool, abYdraw, that can draw antibody schematics from AbML strings or generate an AbML string from a drawn antibody schematic. AbML has the potential to become a standardized notation for describing new MsAb formats entering clinical trials.Abbreviations: AbML: Antibody Markup Language; ADC: Antibody-drug conjugate; CAS: Chemical Abstracts Service; CH: Constant heavy; CL: Constant light; Fv: Variable fragment; HELM: Hierarchical Editing Language for Macromolecules; HSA: Human serum albumin; INN: International Nonproprietary Names; KIH: Knobs-into-holes; mAbs: Monoclonal antibodies; MsAb: Multi-specific antibody; WHO: World Health Organization; PEG: Poly-ethylene glycol; scFv: Single-chain variable fragment; SMILES: Simplified Molecular-Input Line-Entry System; VH: Variable heavy; VHH: Single-domain (Camelid) variable heavy; VL: Variable light.

Treatment for Peritoneal Metastasis of Patients With Colorectal Cancer

From the perspective of survival outcomes, the cancer survival of colorectal cancer (CRC) in the whole stage has improved. Peritoneal metastasis (PM) is found in approximately 8% to 15% of patients with CRC, with a poorer prognosis than that associated with other sites of metastases. Randomized controlled trials and up-to-date meta-analyses provide firm evidence that cytoreductive surgery (CRS) plus hyperthermic intraperitoneal chemotherapy (HIPEC) could significantly improve overall survival compared with systemic chemotherapy alone in selected patients with CRC-PM. Practical guidelines recommend that the management of CRC-PM should be led by a multidisciplinary team carried out in experienced centers and consider CRS plus HIPEC for selected patients. In this review, we aim to provide the latest results of land mark studies and an overview of recent insights with regard to the management of CRC-PM.

Engineered Bifunctional Proteins for Targeted Cancer Therapy: Prospects and Challenges

Bifunctional proteins (BFPs) are a class of therapeutic agents produced through genetic engineering and protein engineering, and are increasingly used to treat various human diseases, including cancer. These proteins usually have two or more biological functions-specifically recognizing different molecular targets to regulate the related signaling pathways, or mediating effector molecules/cells to kill tumor cells. Unlike conventional small-molecule or single-target drugs, BFPs possess stronger biological activity but lower systemic toxicity. Hence, BFPs are considered to offer many benefits for the treatment of heterogeneous tumors. In this review, the authors briefly describe the unique structural feature of BFP molecules and innovatively divide them into bispecific antibodies, cytokine-based BFPs (immunocytokines), and protein toxin-based BFPs (immunotoxins) according to their mode of action. In addition, the latest advances in the development of BFPs are discussed and the potential limitations or problems in clinical applications are outlined. Taken together, future studies need to be centered on understanding the characteristics of BFPs for optimizing and designing more effective such drugs.

Cancer immunotherapies revisited: state of the art of conventional treatments and next-generation nanomedicines

Nowadays, the landscape of cancer treatments has broadened thanks to the clinical application of immunotherapeutics. After decades of failures, cancer immunotherapy represents an exciting alternative for those patients suffering from a wide variety of cancers, especially for those skin cancers, such as the early stages of melanoma. However, those cancers affecting internal organs still face a long way to success, because of the poor biodistribution of immunotherapies. Here, nanomedicine appears as a hopeful strategy to modulate the biodistribution aiming at target organ accumulation. In this way, efficacy will be improved, while reducing the side effects at the same time. In this review, we aim to highlight the most promising cancer immunotherapeutic strategies. From monoclonal antibodies and their traditional use as targeted therapies to their current use as immune checkpoint inhibitors; as well as adoptive cell transfer therapies; oncolytic viruses, and therapeutic cancer vaccination. Then, we aim to discuss the important role of nanomedicine to improve the performance of these immunotherapeutic tools to finally review the already marketed nanomedicine-based cancer immunotherapies.

Bispecific Antibodies: From Research to Clinical Application

Bispecific antibodies (BsAbs) are antibodies with two binding sites directed at two different antigens or two different epitopes on the same antigen. The clinical therapeutic effects of BsAbs are superior to those of monoclonal antibodies (MoAbs), with broad applications for tumor immunotherapy as well as for the treatment of other diseases. Recently, with progress in antibody or protein engineering and recombinant DNA technology, various platforms for generating different types of BsAbs based on novel strategies, for various uses, have been established. More than 30 mature commercial technology platforms have been used to create and develop BsAbs based on the heterologous recombination of heavy chains and matching of light chains. The detailed mechanisms of clinical/therapeutic action have been demonstrated with these different types of BsAbs. Three kinds of BsAbs have received market approval, and more than 110 types of BsAbs are at various stages of clinical trials. In this paper, we elaborate on the classic platforms, mechanisms, and applications of BsAbs. We hope that this review can stimulate new ideas for the development of BsAbs and improve current clinical strategies.

Stoichiometry of multi-specific immune checkpoint RNA Abs for T cell activation and tumor inhibition using ultra-stable RNA nanoparticles

Immunotherapy has become a revolutionary subject in cancer therapy during the past few years. Immune checkpoint-targeting antibodies (Abs) could boost anticancer immune responses. However, certain protein-based immunotherapies revealed side effects and unfavorable biodistribution, so effective non-protein options with lower side effects are highly sought after. RNA's ability to form various three-dimensional configurations allows for the creation of a variety of ligands to bind different cell receptors. The rubber-like properties of RNA nanoparticles (NPs) allow for swift lodging to cancer vasculature with little accumulation in vital organs, resulting in a favorable pharmacokinetic/pharmacodynamic (PK/PD) profile and safe pharmacological parameters. Multi-specific drugs are expected to be the fourth wave of biopharmaceutical innovation. Herein, we report the development of multi-specific Ab-like RNA NPs carrying multiple ligands for immunotherapy. The stoichiometries and stereo conformations of the checkpoint-activating RNA NPs were optimized for T cell activation. When compared to mono- and bi-specific RNA NPs, the tri-specific Ab-like RNA NPs bound to the trimeric T cell receptor with the highest efficiency, showed the optimal T cell activation, and promoted the strongest anti-tumor function of immune cells. Animal trials demonstrated that the tri-specific RNA NPs inhibited cancer growth. This Ab-like RNA NP platform represents an alternative to protein Abs for tumor immunotherapy.

Trial Watch: Tumor-targeting monoclonal antibodies in cancer therapy

In 1997, for the first time in history, a monoclonal antibody (mAb), i.e., the chimeric anti-CD20 molecule rituximab, was approved by the US Food and Drug Administration for use in cancer patients. Since then, the panel of mAbs that are approved by international regulatory agencies for the treatment of hematopoietic and solid malignancies has not stopped to expand, nowadays encompassing a stunning amount of 15 distinct molecules. This therapeutic armamentarium includes mAbs that target tumor-associated antigens, as well as molecules that interfere with tumor-stroma interactions or exert direct immunostimulatory effects. These three classes of mAbs exert antineoplastic activity via distinct mechanisms, which may or may not involve immune effectors other than the mAbs themselves. In previous issues of OncoImmunology, we provided a brief scientific background to the use of mAbs, all types confounded, in cancer therapy, and discussed the results of recent clinical trials investigating the safety and efficacy of this approach. Here, we focus on mAbs that primarily target malignant cells or their interactions with stromal components, as opposed to mAbs that mediate antineoplastic effects by activating the immune system. In particular, we discuss relevant clinical findings that have been published during the last 13 months as well as clinical trials that have been launched in the same period to investigate the therapeutic profile of hitherto investigational tumor-targeting mAbs.

Trial Watch: Monoclonal antibodies in cancer therapy

Since the advent of hybridoma technology, dating back to 1975, monoclonal antibodies have become an irreplaceable diagnostic and therapeutic tool for a wide array of human diseases. During the last 15 years, several monoclonal antibodies (mAbs) have been approved by FDA for cancer therapy. These mAbs are designed to (1) activate the immune system against tumor cells, (2) inhibit cancer cell-intrinsic signaling pathways, (3) bring toxins in the close proximity of cancer cells, or (4) interfere with the tumor-stroma interaction. More recently, major efforts have been made for the development of immunostimulatory mAbs that either enhance cancer-directed immune responses or limit tumor- (or therapy-) driven immunosuppression. Some of these antibodies, which are thought to facilitate tumor eradication by initiating or sustaining a tumor-specific immune response, have already entered clinical trials. In this Trial Watch, we will review and discuss the clinical progress of the most important mAbs that are have entered clinical trials after January 2008.

The combination therapy with EpCAM/CD3 BsAb and MUC-1/CD3 BsAb elicited antitumor immunity by T-cell adoptive immunotherapy in lung cancer

Lung cancer remains a global challenge due to high morbidity and mortality rates and poor response to treatment, and there are still no effective strategies to solve it. The bispecific antibody (BsAb) is a novel antibody, which can target two different antigens and mediate specific killing effects by selectively redirecting effector cells to the target cells. In this study, we combined two BsAbs to achieve a dual-target therapy strategy of EpCAM⁺ and MUC-1⁺ with high affinity and specificity. The results showed that the combination of two BsAbs against EpCAM and MUC-1 could inhibit the growth of lung cancer more effectively in cell lines and primary tumors. The superior antitumor effect of two BsAbs could be attributable to enhanced CTL and increased production of type I IFNs. At the same time, the combination of EpCAM/CD3 BsAb and MUC-1/CD3 BsAb significantly regulated T population in the TDLNs. Therefore, we have found a potential immunotherapeutic strategy, which was the combination therapy with EpCAM/CD3 BsAb and MUC-1/CD3 BsAb for the treatment of non-small cell lung cancer.

Bispecific antibodies in acute lymphoblastic leukemia therapy

INTRODUCTION

Blinatumomab, first in a class of bispecific T-cell engagers, revolutionized treatment paradigm of B-cell precursor relapsed/refractory or minimal residual disease positive acute lymphoblastic leukemia (ALL) in adults and children, inducing deep remissions in a proportion of patients. However, significant numbers of patients do not respond or eventually relapse. Strategies for improvement of treatment outcomes are required.

AREAS COVERED

This review discusses the main structural and functional features of blinatumomab, and its place in the treatment of ALL. Furthermore, prospects to increase the efficacy of blinatumomab are addressed. The developments in the field of bispecific antibodies and their possible implications for treatment of ALL are reviewed.

EXPERT OPINION

Better understanding the mechanisms of response and resistance to blinatumomab might help us to identify the group of patients benefiting most from treatment and to spare potentially toxic subsequent treatment strategies. Data emerging from ongoing clinical trials might change the treatment landscape of ALL and beyond. Early use of blinatumomab in frontline protocols with more advantageous treatment sequences and in combination with other targeted therapies might reduce the failure rates. Exponentially increasing number of novel treatment options and their possible combinations might complicate treatment decision-making without data from randomized trials.

Epithelial Ovarian Cancer and the Immune System: Biology, Interactions, Challenges and Potential Advances for Immunotherapy

Recent advances in the understanding of immune function and the interactions with tumour cells have led to the development of various cancer immunotherapies and strategies for specific cancer types. However, despite some stunning successes with some malignancies such as melanomas and lung cancer, most patients receive little or no benefit from immunotherapy, which has been attributed to the tumour microenvironment and immune evasion. Although the US Food and Drug Administration have approved immunotherapies for some cancers, to date, only the anti-angiogenic antibody bevacizumab is approved for the treatment of epithelial ovarian cancer. Immunotherapeutic strategies for ovarian cancer are still under development and being tested in numerous clinical trials. A detailed understanding of the interactions between cancer and the immune system is vital for optimisation of immunotherapies either alone or when combined with chemotherapy and other therapies. This article, in two main parts, provides an overview of: (1) components of the normal immune system and current knowledge regarding tumour immunology, biology and their interactions; (2) strategies, and targets, together with challenges and potential innovative approaches for cancer immunotherapy, with attention given to epithelial ovarian cancer.

Plant-Produced Monoclonal Antibody as Immunotherapy for Cancer

Plant-based products have expanded to include cancer immunotherapy, which has made great strides over recent years. Plants are considered inexpensive and facile production platforms for recombinant monoclonal antibody (mAb) due to the latest advancements and diversification of transgenic techniques. Current human biologics, including those based on mAbs produced by fermentation technologies using primarily mammalian cell cultures, have been replaced by plant-produced mAbs, which are cost effective, more scalable, speedy, versatile, and safer. Moreover, the use of animals for antibody production is always a question of ethical unambiguity, and the suitability of animal models for predicting the immunogenicity of therapeutic mAbs in humans and transposition of the immunogenic potential of therapeutic antibodies in animals to the human situation has no scientific rationale. Quite a few plant-based mAbs are approved for the treatment of cancer, ranging from tumors to hematological malignancies. This review focuses on the cutting-edge approaches for using plant-derived mAbs to suppress or prevent cancers. It also discusses the avenues taken to prevent infection by oncogenic viruses, solid tumors, lymphomas, and other cancerous conditions using mAbs. The review emphasizes the use of a plant-derived monoclonal antibody as a premier platform to combat cancer.

Therapeutic Monoclonal Antibodies in Clinical Practice against Cancer

The importance of monoclonal antibodies in oncology has increased drastically following the discovery of Milstein and Kohler. Since the first approval of the monoclonal antibody, i.e. Rituximab in 1997 by the FDA, there was a decline in further applications but this number has significantly increased over the last three decades for various therapeutic applications due to the lesser side effects in comparison to the traditional chemotherapy methods. Presently, numerous monoclonal antibodies have been approved and many are in queue for approval as a strong therapeutic agent for treating hematologic malignancies and solid tumors. The main target checkpoints for the monoclonal antibodies against cancer cells include EGFR, VEGF, CD and tyrosine kinase which are overexpressed in malignant cells. Other immune checkpoints like CTLA-4, PD-1 and PD-1 receptors targeted by the recently developed antibodies increase the capability of the immune system in destroying the cancerous cells. Here, in this review, the mechanism of action, uses and target points of the approved mAbs against cancer have been summarized.

Cancer immunotherapy: dawn of the death of cancer?

Cancer is one of the proficient evaders of the immune system which claims millions of lives every year. Developing therapeutics against cancer is extremely challenging as cancer involves aberrations in self, most of which are not detected by the immune system. Conventional therapeutics like chemotherapy, radiotherapy are not only toxic but they significantly lower the quality of life. Immunotherapy, which gained momentum in the 20th century, is emerging as one of the alternatives to the conventional therapies and is relatively less harmful but more costly. This review explores the modern advances in an array of such therapies and try to compare them along with a limited analysis of concerns associated with them.

Development of bispecific antibodies in China: overview and prospects

A bispecific antibody (bsAb) can simultaneously bind two different epitopes or antigens, allowing for multiple mechanistic functions with synergistic effects. BsAbs have attracted significant scientific attentions and efforts towards their development as drugs for cancers. There are 21 bsAbs currently undergoing clinical trials in China. Here, we review their platform technologies, expression and production, and biological activities and bioassay of these bsAbs, and summarize their structural formats and mechanisms of actions. T-cell redirection and checkpoint inhibition are two main mechanisms of the bsAbs that we discuss in detail. Furthermore, we provide our perspective on the future of bsAb development in China, including CD3-bsAbs for solid tumors and related cytokine release syndromes, expression and chemistry, manufacturing and controls, clinical development, and immunogenicity.

A novel bispecific antibody targeting CD3 and prolactin receptor (PRLR) against PRLR-expression breast cancer

BACKGROUND

Prolactin receptor (PRLR) is highly expressed in a subset of human breast cancer and prostate cancer, which makes it a potential target for cancer treatment. In clinical trials, the blockade of PRLR was shown to be safe but with poor efficacy. It is therefore urgent to develop new therapies against PRLR target. Bispecific antibodies (BsAbs) could guide immune cells toward tumor cells, and produced remarkable effects in some cancers.

METHODS

In this study, a bispecific antibody targeting both tumor antigen PRLR and T cell surface CD3 antigen (PRLR-DbsAb) was constructed by split intein mediated protein transsplicing (BAPTS) system for the first time. Its binding activity was determined by Biacore and Flow cytometry, and target-dependent T cell mediated cytotoxicity was detected using LDH release assay. ELISA was utilized to study the secretion of cytokines by immune cells. Subcutaneous tumor mouse models were used to analyze the in vivo anti-tumor effects of PRLR-DbsAb.

RESULTS

PRLR-DbsAb in vitro could recruit and activate T cells to promote the release of Th1 cytokines IFN- γ and TNF- α, which could kill PRLR expressed breast cancer cells. In xenograft models with breast cancer cell line T47D, NOD/SCID mice intraperitoneally injected with PRLR-DbsAb exhibited significant inhibition of tumor growth and a longer survival compared to mice treated with PRLR monoclonal antibody (PRLR mAb).

CONCLUSIONS

Both in vitro and in vivo experiments showed PRLR-DbsAb had a potential therapy of cancer treatment potential therapy for cancer. Immunotherapy may be a promising treatment against the tumor target of PRLR.

Palliation of malignant ascites

Malignant ascites (MA) carries a poor prognosis. It can have a significant impact on quality of life (QOL), with increasing abdominal distention, pain, and dyspnea. Diuretics typically do not work well for MA. Paracentesis is effective in providing temporary symptom relief but requires frequent repeat procedures. Options for durable symptom management include indwelling catheters, peritoneal ports, peritoneovenous shunts, intraperitoneal (i.p.) catumaxomab, and hyperthermic i.p. chemotherapy. These interventions do not necessarily improve overall survival but may improve QOL.

Bioanalytical challenges and unique considerations to support pharmacokinetic characterization of bispecific biotherapeutics

Compared with conventional (monospecific) therapeutics, bispecific protein therapeutics present unique challenges for pharmacokinetic (PK) characterization – namely, the characterization of multiple functional domains as well as the consideration of biotransformation or interference by the formation of antitherapeutic antibodies against each functional domain. PK characterization is essential to the success of the overall drug development plan and for molecules with multiple binding domains; multiple bioanalytical methods may be needed to answer critical questions for each phase of drug development. The number of bispecific protein therapeutics entering drug development continues to increase, and therefore, a bioanalytical strategy for the PK characterization of bispecific molecules and study of their in vivo structure–function relationship is needed. This review presents case studies and a regulatory perspective.

Bi-specific and tri-specific antibodies- the next big thing in solid tumor therapeutics

Antibody-based therapy has revitalized the world of cancer therapeutics since rituximab was first approved for the treatment of Non-Hodgkin's Lymphoma. Monoclonal antibodies against cancer antigens have been successful strategies for only a handful of cancer types due to many reasons including lack of antibody specificity and complex nature of tumor milieu which interfere with antibody efficacy. Polyspecific antibodies are promising class of anti-cancer agents which can be directed at multiple tumor antigens to eradicate tumor cells more precisely and effectively. They may overcome some of these limitations and have already changed treatment landscape for some malignancies such as B cell acute lymphoblastic leukemia. Pre-clinical studies and early phase clinical trials have demonstrated that this approach may be an effective strategy even for solid tumors. This review focuses on the development of bispecific and trispecific antibody therapy for the treatment of solid tumor malignancies and highlights the potential they hold for future therapies to come.

Molecular engineering strategies and methods for the expression and purification of IgG1-based bispecific bivalent antibodies

In recent years, bispecific antibodies (BisAbs) have emerged as novel pharmaceutical candidates owing to their ability to engage two disease mediators simultaneously, thus providing a possible alternative therapeutic approach in complex diseases such as cancer and inflammation. Here we provide an overview of the molecular design, recombinant expression in mammalian cells and purification of BisAbs based on full-length IgG-scFv formats. Practical considerations and strategies to optimize transient expression and purification are also discussed.

Early Investigations and Recent Advances in Intraperitoneal Immunotherapy for Peritoneal Metastasis

Peritoneal metastasis (PM) is an advanced stage malignancy largely refractory to modern therapy. Intraperitoneal (IP) immunotherapy offers a novel approach for the control of regional disease of the peritoneal cavity by breaking immune tolerance. These strategies include heightening T-cell response and vaccine induction of anti-cancer memory against tumor-associated antigens. Early investigations with chimeric antigen receptor T cells (CAR-T cells), vaccine-based therapies, dendritic cells (DCs) in combination with pro-inflammatory cytokines and natural killer cells (NKs), adoptive cell transfer, and immune checkpoint inhibitors represent significant advances in the treatment of PM. IP delivery of CAR-T cells has shown demonstrable suppression of tumors expressing carcinoembryonic antigen. This response was enhanced when IP injected CAR-T cells were combined with anti-PD-L1 or anti-Gr1. Similarly, CAR-T cells against folate receptor α expressing tumors improved T-cell tumor localization and survival when combined with CD137 co-stimulatory signaling. Moreover, IP immunotherapy with catumaxomab, a trifunctional antibody approved in Europe, targets epithelial cell adhesion molecule (EpCAM) and has shown considerable promise with control of malignant ascites. Herein, we discuss immunologic approaches under investigation for treatment of PM.

Bispecific antibodies in cancer immunotherapy

Following the clinical success of immune checkpoint antibodies targeting CTLA-4, PD-1 or PD-L1 in cancer treatment, bispecific antibodies are now emerging as a growing class of immunotherapies with potential to further improve clinical efficacy and safety. We describe three classes of immunotherapeutic bispecific antibodies: (a) cytotoxic effector cell redirectors; (b) tumor-targeted immunomodulators; and (c) dual immunomodulators. Cytotoxic effector cell redirectors are dominated by T-cell redirecting compounds, bispecific compounds engaging a tumor-associated antigen and the T-cell receptor/CD3 complex, thereby redirecting T-cell cytotoxicity to malignant cells. This is the most established class of bispecific immunotherapies, with two compounds having reached the market and numerous compounds in clinical development. Tumor-targeted immunomodulators are bispecific compounds binding to a tumor-associated antigen and an immunomodulating receptor, such as CD40 or 4-1BB. Such compounds are usually designed to be inactive until binding the tumor antigen, thereby localizing immune stimulation to the tumor environment, while minimizing immune activation elsewhere. This is expected to induce powerful activation of tumor-specific T cells with reduced risk of immune-related adverse events. Finally, dual immunomodulators are bispecific compounds that bind two distinct immunomodulating targets, often combining targeting of PD-1 or PD-L1 with that of LAG-3 or TIM-3. The rationale is to induce superior tumor immunity compared to monospecific antibodies to the same targets. In this review, we describe each of these classes of bispecific antibodies, and present examples of compounds in development.

Advances in ovarian cancer therapy

Epithelial ovarian cancer is typically diagnosed at an advanced stage. Current state-of-the-art surgery and chemotherapy result in the high incidence of complete remissions; however, the recurrence rate is also high. For most patients, the disease eventually becomes a continuum of symptom-free periods and recurrence episodes. Different targeted treatment approaches and biological drugs, currently under development, bring the promise of turning ovarian cancer into a manageable chronic disease. In this review, we discuss the current standard in the therapy for ovarian cancer, major recent studies on the new variants of conventional therapies, and new therapeutic approaches, recently approved and/or in clinical trials. The latter include anti-angiogenic therapies, polyADP-ribose polymerase (PARP) inhibitors, inhibitors of growth factor signaling, or folate receptor inhibitors, as well as several immunotherapeutic approaches. We also discuss cost-effectiveness of some novel therapies and the issue of better selection of patients for personalized treatment.

Immunotherapy of hepatocellular carcinoma using chimeric antigen receptors and bispecific antibodies

Hepatocellular carcinoma (HCC) is one of the most lethal cancers worldwide with an overall survival rate of less than 15% in developed countries. Despite attempts at new therapeutic strategies, the majority of patients succumb to this cancer. Buttressed by the highly successful clinical impact in melanoma, immunotherapy is gaining momentum as the next treatment modality for many human cancers. Chimeric antigen receptors (CAR) contain the antigen binding moieties of a monoclonal antibody and the co-stimulatory and signaling domains associated with effector receptor signaling. Bispecific antibodies (BsAb) combine the binding specificities of two different monoclonal antibodies, one activating a receptor on a killer effector cell, while the other engaging a tumor-associated antigen to initiate tumor cytotoxicity. In this review, we survey the HCC targets for which CARs and bispecific antibodies have been generated. The pros and cons of these targets for T-cell and Natural Killer cell based immunotherapy will be discussed.

Intraperitoneal immunotherapy: historical perspectives and modern therapy

Intraperitoneal immunotherapy represents a novel strategy for the management of peritoneal metastases (PM). Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) has remained the gold standard of treatment for patients with PM, yet despite optimal treatment, recurrence rates remain high and long-term survival poor. From Coley's toxins to immune checkpoint inhibitors, the wide variety of anticancer immunotherapeutic strategies are now garnering attention for control of regional disease of the peritoneal cavity. Early studies with vaccine-based therapies, adoptive cell transfer, immune checkpoint inhibitors, and chimeric T cells with tumor-specific antigen receptors (CAR-T cells) are being performed, showing promise for control of peritoneal spread and induction of lasting anticancer immunity. In addition, catumaxomab, a trifunctional antibody, has been approved for intraperitoneal immunotherapy in Europe for the control of malignant ascites in patients with epithelial cell adhesion molecule positive cancers. We review a brief history of immunotherapy and current modalities under investigation for intraperitoneal use in the treatment of PM.

Leverage nonclinical development of bispecifics by translational science

Bispecific antibody constructs (Bispecifics, bsAbs) may have greater functionality compared to established monoclonal antibodies because they bind to 2 different targets or, potentially, to 2 epitopes on the same target (dual targeting). This may result in enhanced binding avidity with preferential binding to cells that express both targets or binding to targets on different cells. However, development of these next-generation biologics, including new formats, creates unique challenges due to their increased complexity. Here we review aspects of bsAbs preclinical development programs that may increase the success rates of bsAbs in clinical development.

Antigen Selection for Enhanced Affinity T-Cell Receptor-Based Cancer Therapies

Evidence of adaptive immune responses in the prevention of cancer has been accumulating for decades. Spontaneous T-cell responses occur in multiple indications, bringing the study of de novo expressed cancer antigens to the fore and highlighting their potential as targets for cancer immunotherapy. Circumventing the immune-suppressive mechanisms that maintain tumor tolerance and driving an antitumor cytotoxic T-cell response in cancer patients may eradicate the tumor or block disease progression. Multiple strategies are being pursued to harness the cytotoxic potential of T cells clinically. Highly promising results are now emerging. The focus of this review is the target discovery process for cancer immune therapeutics based on affinity-matured T-cell receptors (TCRs). Target cancer antigens in the context of adoptive cell transfer technologies and soluble biologic agents are discussed. To appreciate the impact of TCR-based technology and understand the TCR discovery process, it is necessary to understand key differences between TCR-based therapy and other immunotherapy approaches. The review first summarizes key advances in the cancer immunotherapy field and then discusses the opportunities that TCR technology provides. The nature and breadth of molecular targets that are tractable to this approach are discussed, together with the challenges associated with finding them.

Granzyme B-based cytolytic fusion protein targeting EpCAM specifically kills triple negative breast cancer cells in vitro and inhibits tumor growth in a subcutaneous mouse tumor model

Triple-negative breast cancer (TNBC) is associated with poor prognosis and high prevalence among young premenopausal women. Unlike in other breast cancer subtypes, no targeted therapy is currently available. Overexpression of epithelial cell adhesion molecule (EpCAM) in 60% of TNBC tumors correlates with poorer prognosis and is associated with cancer stem cell phenotype. Thus, selective elimination of EpCAM(+) TNBC tumor cells is of clinical importance. Therefore, we constructed a fully human targeted cytolytic fusion protein, designated GbR201K-αEpCAM(scFv), in which an EpCAM-selective single-chain antibody fragment (scFv) is genetically fused to a granzyme B (Gb) mutant with reduced sensitivity to its natural inhibitor serpin B9. In vitro studies confirmed its specific binding, internalization and cytotoxicity toward a panel of EpCAM-expressing TNBC cells. Biodistribution kinetics and tumor-targeting efficacy using MDA-MB-468 cells in a human TNBC xenograft model in mice revealed selective accumulation of GbR201K-αEpCAM(scFv) in the tumors after i.v. injection. Moreover, treatment of tumor-bearing mice demonstrated a prominent inhibition of tumor growth of up to 50 % in this proof-of-concept study. Taken together, our results indicate that GbR201K-αEpCAM(scFv) is a promising novel targeted therapeutic for the treatment of TNBC.

Novel cancer antigens for personalized immunotherapies: latest evidence and clinical potential

The clinical success of monoclonal antibody immune checkpoint modulators such as ipilimumab, which targets cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), and the recently approved agents nivolumab and pembrolizumab, which target programmed cell death receptor 1 (PD-1), has stimulated renewed enthusiasm for anticancer immunotherapy, which was heralded by Science as 'Breakthrough of the Year' in 2013. As the potential of cancer immunotherapy has been recognized since the 1890s when William Coley showed that bacterial products could be beneficial in cancer patients, leveraging the immune system in the treatment of cancer is certainly not a new concept; however, earlier attempts to develop effective therapeutic vaccines and antibodies against solid tumors, for example, melanoma, frequently met with failure due in part to self-tolerance and the development of an immunosuppressive tumor microenvironment. Increased knowledge of the mechanisms through which cancer evades the immune system and the identification of tumor-associated antigens (TAAs) and negative immune checkpoint regulators have led to the development of vaccines and monoclonal antibodies targeting specific tumor antigens and immune checkpoints such as CTLA-4 and PD-1. This review first discusses the established targets of currently approved cancer immunotherapies and then focuses on investigational cancer antigens and their clinical potential. Because of the highly heterogeneous nature of tumors, effective anticancer immunotherapy-based treatment regimens will likely require a personalized combination of therapeutic vaccines, antibodies and chemotherapy that fit the specific biology of a patient's disease.

Characterization of the first-in-class T-cell-engaging bispecific single-chain antibody for targeted immunotherapy of solid tumors expressing the oncofetal protein claudin 6

The fetal tight junction molecule claudin 6 (CLDN6) is virtually absent from any normal tissue, whereas it is aberrantly and frequently expressed in various cancers of high medical need. We engineered 6PHU3, a T-cell-engaging bispecific single chain molecule (bi-(scFv)₂) with anti-CD3/anti-CLDN6 specificities, and characterized its pharmacodynamic properties. Our data show that upon engagement by 6PHU3, T cells strongly upregulate cytotoxicity and activation markers, proliferate and acquire an effector phenotype. 6PHU3 exerts potent killing of cancer cells in vitro with EC₅₀ values in the pg/mL range. Subcutaneous xenograft tumors in NSG mice engrafted with human PBMCs are eradicated by 6PHU3 treatment and survival of mice is significantly prolonged. Tumors of 6PHU3-treated mice are strongly infiltrated with activated CD4⁺, CD8⁺ T cells and T_EM type cells but not T_regs and display a general activation of a mostly inflammatory phenotype. These effects are only observed upon bispecific but not monospecific engagement of 6PHU3. Together with the exceptionally cancer cell selective expression of the oncofetal tumor marker CLDN6, this provides a safeguard with regard to toxicity. In summary, our data shows that the concept of T-cell redirection combined with that of highly selective targeting of CLDN6-positive solid tumors is effective. Thus, exploring 6PHU3 for clinical therapy is warranted.

Outpatient Intraperitoneal Catumaxomab Therapy for Malignant Ascites Related to Advanced Gynecologic Neoplasms

BACKGROUND

Catumaxomab (CATU) is a trifunctional antibody approved for intraperitoneal (i.p.) treatment of malignant ascites (MA) related to carcinomas expressing the epithelial cell-adhesion molecule (EpCAM). CATU is mostly given to hospitalized patients, although outpatient treatment seems appropriate in selected individuals. This observational trial sought to obtain more detailed information regarding the feasibility of CATU in outpatients with MA related to various gynecologic tumors, including epithelial ovarian (EOC) and metastatic breast cancer (MBC).

MATERIALS AND METHODS

A total of 30 patients were included, 17 with EOC, 7 with MBC, and 6 with other malignancies. The patients had failed a median of 5 (range 1-12) previous systemic treatments. CATU was administered via an indwelling i.p. catheter at four increasing doses (i.e., 10, 20, 50, and 150 µg) given at 4-day intervals over 2 weeks. Toxicities were scored according to the Common Terminology Criteria for Adverse Events, version 4.03. Puncture-free survival (PuFS) was calculated from the start of CATU until the next puncture for MA, death, or loss to follow-up. Overall survival (OS) was calculated from the start of CATU to death from any reason or loss to follow-up. We also investigated various clinical parameters to predict PuFS and OS. These included age, tumor type, performance status, intensity of pretreatment, presence of extraperitoneal metastases, relative lymphocyte count at baseline, patient adherence to therapy, and the patients' ability to undergo systemic treatment after CATU.

RESULTS

CATU was exclusively given on an outpatient basis, and 19 patients (63.3%) received all four planned i.p. instillations. Toxicity was the reason for discontinuation in only 2 patients. Toxicity was generally manageable, with abdominal pain, nausea/vomiting, fatigue, and fever the predominant adverse effects. Secondary hospitalization was necessary for 7 patients (23.3%), with a general deteriorated condition in 5 and fever/infection or abdominal pain in 1 patient each. Subsequent systemic treatment was possible in 11 patients (36.7%). Only 5 patients (16.7%) required a second puncture after i.p. CATU. The median PuFS was 56 days, and the median OS was 79.5 days. Positive predictors of both PuFS and OS were performance status, absence of extraperitoneal tumor, the capability to receive all four CATU infusions, and the ability to undergo subsequent systemic treatment.

CONCLUSION

Outpatient i.p. CATU therapy for MA related to various gynecologic carcinomas is safe and effective in producing good ascites control in most individuals, allowing for subsequent systemic therapy in a substantial proportion of patients.

IMPLICATIONS FOR PRACTICE

Intraperitoneal treatment with the trifunctional antibody catumaxomab (CATU) was possible in a selected population of 30 outpatients with malignant ascites due to epithelial female genital tract or breast carcinoma. Toxicity was largely manageable. Patients in good condition at baseline, without extraperitoneal tumor and/or liver metastases, and with the ability to complete all four planned CATU instillations and the capability of undergoing subsequent systemic therapy benefited the most in terms of both puncture-free and overall survival. Outpatient i.p. CATU is safe and effective in a selected group of patients with malignant ascites due to various gynecologic malignancies and could be cost-saving compared with an inpatient approach.

Trial watch: Tumor-targeting monoclonal antibodies for oncological indications

An expanding panel of monoclonal antibodies (mAbs) that specifically target malignant cells or intercept trophic factors delivered by the tumor stroma is now available for cancer therapy. These mAbs can exert direct antiproliferative/cytotoxic effects as they inhibit pro-survival signal transduction cascades or activate lethal receptors at the plasma membrane of cancer cells, they can opsonize neoplastic cells to initiate a tumor-targeting immune response, or they can be harnessed to specifically deliver toxins or radionuclides to transformed cells. As an indication of the success of this immunotherapeutic paradigm, international regulatory agencies approve new tumor-targeting mAbs for use in cancer patients every year. Moreover, the list of indications for previously licensed molecules is frequently expanded to other neoplastic disorders as the results of large, randomized clinical trials become available. Here, we discuss recent advances in the preclinical and clinical development of tumor-targeting mAbs for oncological indications.

Monoclonal antibodies against human cancer stem cells

Cancer stem cells (CSCs) are a subpopulation of tumor cells that display self-renewal and tumor initiation capacity and the ability to give rise to the heterogenous lineages of cancer cells that comprise the tumor. CSCs exhibit intrinsic mechanisms of resistance to modern cancer therapeutics, allowing them to survive current cancer therapies and to initiate tumor recurrence and metastasis. Various cell surface and transmembrane proteins expressed by CSCs, including CD44, CD47, CD123, EpCAM (CD326), CD133, IGF receptor I, and proteins of the Notch and Wnt signaling pathways have been identified. Recently, monoclonal antibodies and antibody constructs raised against these CSC proteins have shown efficacy against CSCs in human cancer xenograft mice, and some of them have demonstrated antitumor activity in clinical studies. Since current cancer therapies fail to eliminate CSCs, leading to cancer recurrence and progression, selective targeting of CSCs with monoclonal antibodies and antibody constructs may represent a novel therapeutic strategy against cancer.

Immunotargeting of cancer stem cells

Cancer stem cells (CSCs) represent a distinctive population of tumour cells that control tumour initiation, progression, and maintenance. Their influence is great enough to risk the statement that successful therapeutic strategy must target CSCs in order to eradicate the disease. Because cancer stem cells are highly resistant to chemo- and radiotherapy, new tools to fight against cancer have to be developed. Expression of antigens such as ALDH, CD44, EpCAM, or CD133, which distinguish CSCs from normal cells, together with CSC immunogenicity and relatively low toxicity of immunotherapies, makes immune targeting of CSCs a promising approach for cancer treatment. This review will present immunotherapeutic approaches using dendritic cells, T cells, pluripotent stem cells, and monoclonal antibodies to target and eliminate CSCs.

Trial watch: Monoclonal antibodies in cancer therapy

During the past 20 years, dozens-if not hundreds-of monoclonal antibodies have been developed and characterized for their capacity to mediate antineoplastic effects, either as they activate/enhance tumor-specific immune responses, either as they interrupt cancer cell-intrinsic signal transduction cascades, either as they specifically delivery toxins to malignant cells or as they block the tumor-stroma interaction. Such an intense research effort has lead to the approval by FDA of no less than 14 distinct molecules for use in humans affected by hematological or solid malignancies. In the inaugural issue of OncoImmunology, we briefly described the scientific rationale behind the use of monoclonal antibodies in cancer therapy and discussed recent, ongoing clinical studies investigating the safety and efficacy of this approach in patients. Here, we summarize the latest developments in this exciting area of clinical research, focusing on high impact studies that have been published during the last 15 months and clinical trials launched in the same period to investigate the therapeutic profile of promising, yet hitherto investigational, monoclonal antibodies.

Monoclonal Antibodies in Cancer Therapy: Mechanisms, Successes and Limitations

Rituximab was the first chemotherapeutic monoclonal antibody (CmAb) approved for clinical use in cancer therapeutics in 1997 and has significantly improved the clinical outcomes in non-Hodgkin's lymphoma. Since then, numerous CmAbs have been developed and approved for the treatment of various haematologic and solid human cancers. In this review, the classification, efficacy and significantly reduced toxicity of CmAbs available for use in the United States of America are presented. Finally, the limitations of CmAbs and future considerations are explored.

Catumaxomab: in malignant ascites

Catumaxomab is a rat/murine hybrid, trifunctional, bispecific (anti-human epithelial cell adhesion molecule [EpCAM] × anti-CD3) monoclonal antibody. Compared with paracentesis alone, paracentesis followed by catumaxomab therapy was associated with significant prolongation of paracentesis-free survival and time to repeat paracentesis in a randomized, open-label, multicentre, pivotal phase II/III trial in patients with recurrent symptomatic malignant ascites due to EpCAM-positive tumours who were resistant to conventional chemotherapy. The benefits of catumaxomab were seen across a broad range of epithelial ovarian and nonovarian cancers, and irrespective of whether or not catumaxomab recipients developed human anti-mouse antibodies. Combining catumaxomab with paracentesis also resulted in more pronounced and prolonged reductions in ascites signs and symptoms and a delayed deterioration in health-related quality of life compared with paracentesis alone. Despite the study not being designed or powered to evaluate overall survival, significant differences favouring the addition of catumaxomab to paracentesis were seen in analyses of the safety population and the subpopulation of patients with gastric cancer. Catumaxomab was generally well tolerated in the pivotal phase II/III trial. The most frequent adverse events attributed to catumaxomab treatment included cytokine-release-related symptoms, which were mostly of mild to moderate severity and manageable with standard symptomatic treatment.

RECRUIT-TandAbs: harnessing the immune system to kill cancer cells

Tandem diabodies (TandAbs) are tetravalent bispecific molecules comprised of antibody variable domains with two binding sites for each antigen. RECRUIT-TandAbs can simultaneously engage an immune system effector cell, such as a natural killer cell or a cytotoxic T cell, and an antigen expressed specifically on a cancer cell, thus leading to killing of the cancer cell. Recruitment of immune effector cells is highly specific and mediated via binding of the TandAb to molecules expressed on the surface of these cells. Furthermore, the absence of an Fc domain allows TandAbs to avoid certain IgG-mediated side effects. With a molecular weight of approximately 110 kDa, TandAbs are far above the first-pass renal clearance limit, offering a pharmacokinetic advantage compared with smaller bispecific antibody formats. This article reviews the RECRUIT-TandAb technology and the therapeutic potential of these molecules.