Shortened hinge design of Fab x sdAb-Fc bispecific antibodies enhances redirected T-Cell killing of tumor cells

T cell engager (TCE) antibodies have emerged as promising cancer therapeutics that link cytotoxic T-cells to tumor cells by simultaneously binding to CD3E on T-cells and to a tumor-associated antigen (TAA) expressed by tumor cells. We previously reported a novel bispecific format, the IgG-like Fab x sdAb-Fc (also known as half-IG_VH-h-CH2-CH3), combining a conventional antigen-binding fragment (Fab) with a single domain antibody (sdAb). Here, we evaluated this Fab x sdAb-Fc format as a T-cell redirecting bispecific antibody (TbsAbs) by targeting mEGFR on tumor cells and mCD3E on T cells. We focused our attention specifically on the hinge design of the sdAb arm of the bispecific antibody. Our data show that a TbsAb with a shorter hinge of 23 amino acids (TbsAb.short) showed a significantly better T cell redirected tumor cell elimination than the TbsAb with a longer, classical antibody hinge of 39 amino acids (TbsAb.long). Moreover, the TbsAb.short form mediated better T cell-tumor cell aggregation and increased CD69 and CD25 expression levels on T cells more than the TbsAb.long form. Taken together, our results indicate that already minor changes in the hinge design of TbsAbs can have significant impact on the anti-tumor activity of TbsAbs and may provide a new means to improve their potency

Shortened Hinge Design of Fab x sdAb-Fc Bispecific Antibodies Enhances Redirected T-Cell Killing of Tumor Cells

T cell engager (TCE) antibodies have emerged as promising cancer therapeutics that link cytotoxic T-cells to tumor cells by simultaneously binding to CD3E on T-cells and to a tumor-associated antigen (TAA) expressed by tumor cells. We previously reported a novel bispecific format, the IgG-like Fab x sdAb-Fc (also known as half-IG_VH-h-CH2-CH3), combining a conventional antigen-binding fragment (Fab) with a single domain antibody (sdAb). Here, we evaluated this Fab x sdAb-Fc format as a T-cell redirecting bispecific antibody (TbsAbs) by targeting mEGFR on tumor cells and mCD3E on T cells. We focused our attention specifically on the hinge design of the sdAb arm of the bispecific antibody. Our data show that a TbsAb with a shorter hinge of 23 amino acids (TbsAb.short) showed a significantly better T cell redirected tumor cell elimination than the TbsAb with a longer, classical antibody hinge of 39 amino acids (TbsAb.long). Moreover, the TbsAb.short form mediated better T cell-tumor cell aggregation and increased CD69 and CD25 expression levels on T cells more than the TbsAb.long form. Taken together, our results indicate that already minor changes in the hinge design of TbsAbs can have significant impact on the anti-tumor activity of TbsAbs and may provide a new means to improve their potency

Bispecific antibodies targeting dual tumor-associated antigens in cancer therapy

PURPOSE: Bispecific antibodies (BsAbs) have emerged as a leading drug class for cancer therapy and are becoming increasingly of interest for therapeutic applications. As of April 2020, over 123 BsAbs are under clinical evaluation for use in oncology (including the two marketed BsAbs Blinatumomab and Catumaxomab). The majority (82 of 123) of BsAbs under clinical evaluation can be categorized as bispecific immune cell engager whereas a second less well-discussed subclass of BsAbs targets two tumor-associated antigens (TAAs). In this review, we summarize the clinical development of dual TAAs targeting BsAbs and provide an overview of critical considerations when designing dual TAA targeting BsAbs. METHODS: Herein the relevant literature and clinical trials published in English until April 1st 2020 were searched using PubMed and ClinicalTrials.gov database. BsAbs were considered to be active in clinic if their clinical trials were not terminated, withdrawn or completed before 2018 without reporting results. Data missed by searching ClinicalTrials.gov was manually curated. RESULTS: Dual TAAs targeting BsAbs offer several advantages including increased tumor selectivity, potential to concurrently modulate two functional pathways in the tumor cell and may yield improved payload delivery. CONCLUSIONS: Dual TAAs targeting BsAbs represent a valuable class of biologics and early stage clinical studies have demonstrated promising anti-tumor efficacy in both hematologic malignancies and solid tumors

A novel efficient bispecific antibody format, combining a conventional antigen-binding fragment with a single domain antibody, avoids potential heavy-light chain mis-pairing

Due to the technical innovations in generating bispecific antibodies (BsAbs) in recent years, BsAbs have become important reagents for diagnostic and therapeutic applications. However, the difficulty of producing a heterodimer consisting of two different arms with high yield and purity constituted a major limitation for their application in academic and clinical settings. Here, we describe a novel Fc-containing BsAb format (Fab × sdAb-Fc) composed of a conventional antigen-binding fragment (Fab), and a single domain antibody (sdAb), which avoids heavy-light chain mis-pairing during antibody assembly. In this study, the Fab x sdAb-Fc BsAbs were efficiently produced by three widely used heavy-heavy chain heterodimerization methods: Knobs-into-holes (KIH), Charge-pairs (CP) and controlled Fab-arm exchange (cFAE), respectively. The novel Fab x sdAb-Fc format provided a rapid and efficient strategy to generate BsAb with high purity and a unique possibility to further purify desired BsAbs from undesired antibodies based on molecular weight (MW). Compared to conventional BsAb formats, the advantages of Fab x sdAb-Fc format may thus provide a straightforward opportunity to apply bispecific antibody principles to research and development of novel targets and pathways in diseases such as cancer and autoimmunity

Bispecific antibodies targeting dual tumor-associated antigens in cancer therapy

PURPOSE: Bispecific antibodies (BsAbs) have emerged as a leading drug class for cancer therapy and are becoming increasingly of interest for therapeutic applications. As of April 2020, over 123 BsAbs are under clinical evaluation for use in oncology (including the two marketed BsAbs Blinatumomab and Catumaxomab). The majority (82 of 123) of BsAbs under clinical evaluation can be categorized as bispecific immune cell engager whereas a second less well-discussed subclass of BsAbs targets two tumor-associated antigens (TAAs). In this review, we summarize the clinical development of dual TAAs targeting BsAbs and provide an overview of critical considerations when designing dual TAA targeting BsAbs. METHODS: Herein the relevant literature and clinical trials published in English until April 1st 2020 were searched using PubMed and ClinicalTrials.gov database. BsAbs were considered to be active in clinic if their clinical trials were not terminated, withdrawn or completed before 2018 without reporting results. Data missed by searching ClinicalTrials.gov was manually curated. RESULTS: Dual TAAs targeting BsAbs offer several advantages including increased tumor selectivity, potential to concurrently modulate two functional pathways in the tumor cell and may yield improved payload delivery. CONCLUSIONS: Dual TAAs targeting BsAbs represent a valuable class of biologics and early stage clinical studies have demonstrated promising anti-tumor efficacy in both hematologic malignancies and solid tumors

Generation and characterization of novel co-stimulatory anti-mouse TNFR2 antibodies

Tumor necrosis factor receptor 2 (TNFR2) has gained much research interest in recent years because of its potential pivotal role in autoimmune disease and cancer. However, its function in regulating different immune cells is not well understood. There is a need for well-characterized reagents to selectively modulate TNFR2 function, thereby enabling definition of TNFR2-dependent biology in human and mouse surrogate models. Here, we describe the generation, production, purification, and characterization of a panel of novel antibodies targeting mouse TNFR2. The antibodies display functional differences in binding affinity and potency to block TNFα. Furthermore, epitope binding showed that the anti-mTNFR2 antibodies target different domains on the TNFR2 protein, associated with varying capacity to enhance CD8+ T-cell activation and costimulation. Moreover, the anti-TNFR2 antibodies demonstrate binding to isolated splenic mouse Tregs ex vivo and activated CD8+ cells, reinforcing their potential use to establish TNFR2-dependent immune modulation in translational models of autoimmunity and cancer

<i>Trans</i>-Cyclooctene Tag with Improved Properties for Tumor Pretargeting with the Diels–Alder Reaction

Radioimmunotherapy (RIT) of solid tumors is hampered by low tumor-to-nontumor (T/NT) ratios of the radiolabeled monoclonal antibodies resulting in low tumor doses in patients. Pretargeting technologies can improve the effectiveness of RIT in cancer therapy by increasing this ratio. We showed that a pretargeting strategy employing in vivo chemistry in combination with clearing agents, proceeds efficiently in tumor-bearing mice resulting in high T/NT ratios. A dosimetry study indicated that the chemical pretargeting technology, which centered on the bioorthogonal Diels–Alder click reaction between a radiolabeled tetrazine probe and a <i>trans</i>-cyclooctene-oxymethylbenzamide-tagged CC49 antibody (CC49–TCO­(<b>1</b>)), can match the performance of clinically validated high-affinity biological pretargeting approaches in mice (Rossin J Nucl Med. 2013, 54, 1989−1995). Nevertheless, the increased protein surface hydrophobicity of CC49–TCO­(<b>1</b>) led to a relatively rapid blood clearance and concomitant reduced tumor uptake compared to native CC49 antibody. Here, we present the in vivo evaluation of a TCO-oxymethylacetamide-tagged CC49 antibody (CC49–TCO­(<b>2</b>)), which is highly reactive toward tetrazines and less hydrophobic than CC49–TCO­(<b>1</b>). CC49–TCO­(<b>2</b>) was administered to healthy mice to determine its blood clearance and the in vivo stability of the TCO. Next, pretargeting biodistribution and SPECT studies with CC49–TCO­(<b>2</b>), tetrazine-functionalized clearing agent, and radiolabeled tetrazine were carried out in nude mice bearing colon carcinoma xenografts (LS174T). CC49–TCO­(<b>2</b>) had an increased circulation half-life, a 1.5-fold higher tumor uptake, and a 2.6-fold improved in vivo TCO stability compared to the more hydrophobic TCO-benzamide–CC49. As a consequence, and despite the 2-fold lower reactivity of CC49–TCO­(<b>2</b>) toward tetrazines compared with CC49–TCO­(<b>1</b>), administration of radiolabeled tetrazine afforded a significantly increased tumor accumulation and improved T/NT ratios in mice pretargeted with CC49–TCO­(<b>2</b>). In conclusion, the TCO-acetamide derivative represents a large improvement in in vivo Diels–Alder pretargeting, possibly enabling application in larger animals and eventually humans

Legomedicine - A Versatile Chemo-Enzymatic Approach for the Preparation of Targeted Dual-Labeled Llama Antibody-Nanoparticle Conjugates

Conjugation of llama single domain antibody fragments (Variable Heavy chain domains of Heavy chain antibodies, VHHs) to diagnostic or therapeutic nanoparticles, peptides, proteins, or drugs offers many opportunities for optimized targeted cancer treatment. Currently, mostly nonspecific conjugation strategies or genetic fusions are used that may compromise VHH functionality. In this paper we present a versatile modular approach for bioorthogonal VHH modification and conjugation. First, sortase A mediated transPEGylation is used for introduction of a chemical click moiety. The resulting clickable VHHs are then used for conjugation to other groups employing the Cu+-independent strain-promoted alkyne-azide cycloadition (SPAAC) reaction. Using this approach, tail-to-tail bispecific VHHs and VHH-targeted nanoparticles are generated without affecting VHH functionality. Furthermore, this approach allows the bioconjugation of multiple moieties to VHHs for simple and convenient production of VHH-based theranostics

SPECT imaging of fibrin using fibrin-binding peptides

Noninvasive detection of fibrin in vivo using diagnostic imaging modalities may improve clinical decision-making on possible therapeutic options in atherosclerosis, cancer and thrombus-related pathologies such as pulmonary embolism and deep venous thrombosis. The aim of this study was to assess the potential of a novel (111)In-labeled fibrin-binding peptide (FibPep) to visualize thrombi in mice noninvasively using single-photon emission computed tomography (SPECT). FibPep and a negative control peptide (NCFibPep) were synthesized and their fibrin-binding properties were assessed in vitro. FibPep showed enhanced binding compared with NCFibPep to both fibrin and blood clots. FibPep bound to fibrin with a dissociation constant (K(d)) of 0.8 μ m, whereas NCFibPep displayed at least a 100-fold lower affinity towards fibrin. A FeCl3 -injury carotid artery thrombosis mouse model was used to evaluate the peptides in vivo. FibPep and NCFibPep displayed rapid blood clearance and were eliminated via the renal pathway. In vivo SPECT imaging using FibPep allowed clear visualization of thrombi. Ex vivo biodistribution showed significantly increased uptake of FibPep in the thrombus-containing carotid in comparison to the noninjured carotid (5.7 ± 0.7 and 0.6 ± 0.4% injected dose per gram (%ID g(-1)), respectively; p < 0.01; n = 4), whereas nonspecific NCFibPep did not (0.4 ± 0.2 and 0.3 ± 0.0%ID g(-1), respectively; n = 4). In conclusion, FibPep displayed high affinity towards fibrin in vitro and rapid blood clearance in vivo, and allowed sensitive detection of thrombi using SPECT imaging. Therefore, this particular imaging approach may provide a new tool to diagnose and monitor diseases such as atherosclerosis and cance

Evaluation of 111In-labeled EPep and FibPep as tracers for fibrin SPECT imaging

Fibrin targeting is an attractive strategy for nuclear imaging of thrombosis, atherosclerosis and cancer. Recently, FibPep, an (111)In-labeled fibrin-binding peptide, was established as a tracer for fibrin SPECT imaging and was reported to allow sensitive detection of minute thrombi in mice using SPECT. In this study, we developed EPep, a novel (111)In-labeled fibrin-binding peptide containing the fibrin-binding domain of the clinically verified EP-2104R peptide, and sought to compare the potential of EPep and FibPep as tracers for fibrin SPECT imaging. In vitro, both EPep and FibPep showed high stability in serum, but were less stable in liver and kidney homogenate assays. Both peptide probes displayed comparable affinities toward human and mouse derived fibrin (Kd ≈ 1 μM), and similarly to FibPep, EPep showed fast blood clearance, low nontarget uptake and high thrombus uptake (6.8 ± 1.2% ID g(-1)) in a mouse carotid artery thrombosis model. Furthermore, EPep showed a similar affinity toward rat derived fibrin (Kd ≈ 1 μM), displayed high thrombus uptake in a rat carotid artery thrombosis model (0.74 ± 0.39% ID g(-1)), and allowed sensitive detection of thrombosis in rats using SPECT. In contrast, FibPep displayed a significantly lower affinity toward rat derived fibrin (Kd ≈ 14 μM) and low uptake in rat thrombi (0.06 ± 0.02% ID g(-1)) and did not allow clear visualization of carotid artery thrombosis in rats using SPECT. These results were confirmed ex vivo by autoradiography, which showed a 7-fold higher ratio of activity in the thrombus over the contralateral carotid artery for EPep in comparison to FibPep. These findings suggest that the FibPep binding fibrin epitope is not fully homologous between humans and rats, and that preclinical rat models of disease should not be employed to gauge the clinical potential of FibPep. In conclusion, both peptides showed approximately similar metabolic stability and affinity toward human and mouse derived fibrin, and displayed high thrombus uptake in a mouse carotid artery thrombosis model. Therefore, both EPep and FibPep are promising fibrin targeted tracers for translation into clinical settings to serve as novel tools for molecular imaging of fibri