Full-length Antibodies Research Articles

Pharmacokinetics and Biodistribution of 89Zr-Miltuximab and Its Antibody Fragments as Glypican-1 Targeting Immuno-PET Agents in Glioblastoma.

Glioblastoma (GBM) is the most aggressive form of primary brain cancer, accounting for about 85% of all primary central nervous system (CNS) tumors. With standard treatment strategies like surgery, radiation, and chemotherapy, the median survival time of patients with GBM is only 12-15 months from diagnosis. The poor prognosis of GBM is due to a very high tumor recurrence rate following initial treatment, indicating a dire need for improved diagnostic and therapeutic alternatives for this disease. Antibody-based immunotheranostics holds great promise in treating GBM, combining the theranostic applications of radioisotopes and target-specificity of antibodies. In this study, we developed and validated antibody-based positron emission tomography (PET) tracers targeting the heparan sulfate proteoglycan, glypican-1 (GPC-1), for noninvasive detection of disease using diagnostic molecular imaging. GPC-1 is overexpressed in multiple solid tumor types, including GBM, and is a promising biomarker for novel immunotheranostics. Here, we investigate zirconium-89 (89Zr)-conjugated Miltuximab (a clinical stage anti-GPC-1 monoclonal antibody developed by GlyTherix, Ltd.) and engineered fragments for their potential as immuno-PET tracers to detect GPC-1positive GBM tumors in preclinical models. We explore the effects of molecular size, avidity, and Fc-domain on the pharmacokinetics and biodistribution in vivo, by comparing in parallel the full-length antibody (Miltuximab), Fab'2, Fab, and single-chain variable fragment (scFv) formats. High radiolabeling efficiency (>95%) was demonstrated by all the formats and the stability post-radiolabeling was higher for larger constructs of Miltuximab and the Fab. Receptor-mediated internalization of all 89Zr-labeled formats was observed in a human GBM cell line in vitro, while full-length Miltuximab demonstrated the highest tumor retention (5.7 ± 0.94% ID/g, day-9 postinjection (p.i.)) and overall better tumor-to-background ratios than the smaller Fc-less formats. Results from in vivo PET image quantification and ex vivo scintillation counting were highly correlated. Altogether, 89Zr-DFO-Miltuximab appears to be an effective immuno-PET imaging agent for detecting GPC-1positive tumors such as GBM and the current results support utility of the Fc containing whole mAb format over smaller antibody fragments for this target.

Production of α-Synuclein Fibrillar-Specific scFv from Inclusion Bodies.

Recombinant antibody fragments such as Fab, scFvs, and diabodies against α-syn have become a viable alternative to the conventional full-length antibodies in immunotherapeutic approaches due to their benefits which include smaller size, higher stability, specificity, and affinity. However, the majority of recombinant antibody fragments typically express as inclusion bodies (IBs) in E. coli, which makes their purification incredibly difficult. Here, we describe a method involving a mild solubilizing protocol followed by slow on-column refolding to purify active single-chain variable fragment (scFv-pF) antibody that can recognize the pathogenic α-syn fibrils.

Ars2-containing bispecific, Fab- and IgG1-format BAR-bodies to target DLBCL cells.

Despite recent advances in the therapy of diffuse large B-cell lymphoma, not otherwise specified (DLBCL), around 30% of patients develop refractory disease or relapse after first-line treatment. Recently, Ars2 was reported as the auto-antigenic target of the B-cell receptor (BCR) in approximately 25% of activated B-cell DLBCL cases. Ars2 could be used to specifically target B cells expressing Ars2-reactive BCRs. However, the optimal therapeutic format to integrate Ars2 into has yet to be determined. To mimic therapeutic antibody formats, Ars2-containing bispecific and IgG1-like constructs (BCR antigens for reverse [BAR]-bodies) were developed. Two bispecific BAR-bodies connecting single-chain antibodies against CD16 or CD3 to the BCR-binding epitope of Ars2 were constructed. Both constructs showed strong binding to U2932 cells and induced effector cell-dependent and selective cytotoxicity against U2932 cells of up to 44% at concentrations of 20μg/ml. Additionally, IgG1-format Ars2 BAR-bodies were constructed by replacing the variable heavy- and light-chain regions of a full-length antibody with the Ars2 epitope. IgG1-format Ars2 BAR-bodies also bound selectively to U2932 and OCI-Ly3 cells and induced selective cytotoxicity of up to 60% at 10μg/ml. In conclusion, Ars2-containing bispecific and IgG1-format BAR-bodies both are new therapeutic formats to target DLBCL cells.

Discovery and Characterization of Intracellularly Stable hnRNPA2B1 Specific Nanobodies for Live‐Cell Imaging and Targeted Protein Degradation

AbstractBackgroundHeterogeneous nuclear ribonuclear proteins, hnRNPs, play a variety of roles in regulating transcriptional, and post‐transcriptional gene expression. A core member of the hnRNP family, hnRNPA2/B1 proteins are involved in the formation of membraneless‐organelles such as stress granules (SGs) under certain conditions. Mutations in hnRNPA2/B1 proteins are known to cause multisystem proteinopathy (MSP), a pleiotropic group of inherited disorders that cause neurodegeneration, myopathy, and bone disease. Mutations in hnRNPA2/B1 are also risk factors for the development of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Despite growing evidence implicating hnRNPA2/B1 proteins in a multitude of diseases, our ability to study them in live cells is severely limited due to the lack of intracellularly stable hnRNPA2/B1 specific antibodies. Nanobodies (sdAbs) are antibody fragments derived from heavy‐chain‐only antibodies found in camelids and sharks. Owing to their small size (∼15 kDa) and unique biochemical properties, nanobodies emerged as promising alternatives to conventional‐antibody derived protein fragments. Nanobodies have superior stability that facilitate their intracellular expression. Full length antibodies and bulkier antibody‐derived fragments, such as single chain variable fragments (scFvs), are not amenable to intracellular expression, in part due to the reducing cytoplasmic environment that prevents the formation of disulfide bonds needed for their correct folding.MethodWe have developed a high‐throughput nanobody discovery platform from synthetic yeast surface display libraries by using antigen coated magnetics beads. Furthermore, we have developed generalizable and straightforward cellular assays to characterize nanobody specificity in live cells.ResultUsing above described platforms, we have identified novel hnRNPA2/B1 specific nanobodies and characterized their intracellular stability by expressing them in HEK293 cells. In addition to using nanobodies for studying hnRNPA2/B1 biology in live cells, we have also engineered a panel of modular E3 ubiquitin ligases targeting hnRNPA2/B1 for degradation. ∼30% reduction in hnRNPA2/B1 level was observed when targeted for degradation by using hnRNPA2B1 targeting E3 ubiquitin ligase.ConclusionIn summary, we have optimized factors affecting successful high‐throughput antibody discovery using yeast‐surface display antibody libraries. We also developed generalizable methods to characterize nanobody specificity in live cells. Platforms we have developed will help build tools to study protein aggregation and protein stability in live cells.

Abstract C079: Aberrantly exposed phosphatidylserine as a drug delivery target in pancreatic cancer

Abstract Pancreatic ductal adenocarcinoma (PDA) has risen to become the 3rd leading cause of cancer related deaths in the United States with a 5-year survival rate of 11% and a median survival of just 4-6 months. PDA is notoriously chemoresistant and has shown little to no sensitivity to the current immune checkpoint blockade therapy. A novel marker for the tumor microenvironment that has emerged is phosphatidylserine, initially characterized as a selective marker of tumor vasculature. Phosphatidylserine (PS) is a phospholipid exposed on the outer leaflet of the plasma membrane of tumor associated endothelial cells, apoptotic tumor cells, and some viable tumor cells, where it functions to suppress the immune response. Exposed PS drives immunosuppression by binding to PS receptors expressed on tumor-infiltrating macrophages and dendritic cells. To this point, PS has been targeted with antibodies, such as Bavituximab, that have shown excellent specificity for tumor vasculature and an immune stimulatory environment evidence by polarization of macrophages to a pro-inflammatory M1-like phenotype, a reduction in myeloid-derived suppressor cells, enhanced maturation of dendritic cells and increased primed T cell activity. We have advanced this concept by developing the next generation of PS targeting agent, a fusion protein (betabody) that exploits the PS-binding domain of β2-glycoprotein 1 (β2GP1), an abundant serum protein that binds PS. Betabodies were constructed by fusing domain V of β2GP1 to the Fc of an IgG2a. Betabodies are smaller than full length antibodies (~85 kDa vs 150 kDa), have good affinity for PS (~1 nM) and bind directly to PS. We have demonstrated that betabodies bind specifically to externalized PS through ELISA, ICC and flow cytometry. We established that betabodies localize robustly and specifically to the tumor microenvironment through in vivo localization experiments in tumor-bearing C57Bl/6 mice. Further studies will exploit the specificity of betabodies to deliver novel microtubule-disrupting agents to exposed PS in the microenvironment of PDA. Due to the fact that betabodies are internalized inefficiently, therapeutic payloads will be linked to betabodies via enzyme cleavable linkers. This first-in-class tumor targeting therapeutic has potential to provide efficacy in therapy-resistant pancreatic tumors. Citation Format: Natalie Z. Phinney, Xianming Huang, Rolf Brekken. Aberrantly exposed phosphatidylserine as a drug delivery target in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr C079.

Abstract 12079: The Sexual Dimorphism of IgG1 Anti-angiogenic Activity Depends on Y Chromosome Genes

Section: Angiogenesis, Vascular Development and Regeneration Introduction: IgG1 antibodies possess sexually dimorphic anti-angiogenic activity independent of antigen binding. Mosaic loss of Y chromosome (LOY) is associated with numerous cardiovascular-related diseases, and the male specific region of the Y chromosome (MSY) contributes to hypertension, atherosclerosis, cancer, and male infertility. The biological mechanisms underlying these associations is largely unknown and not fully understood. A better understanding of the role of protein coding genes in the Y chromosome and angiogenesis regulation may lead to a better understanding of these associations and better treatments. Hypothesis: The loss of function of genes in the MSY of males impairs the anti-angiogenic activity IgG1 antibodies. Methods: MSY transcripts were quantified in human macrophages and primary bone marrow derived macrophages (BMDMs) from C57BL/6J male mice by qPCR. MSY genes were inhibited by siRNAs targeting DDX3Y, KDM5D, and UTY, followed by treatment with a human IgG1 in a chemotaxis assay. Laser photocoagulation-induced choroidal neovascularization (CNV) was performed in male C57BL/6J followed by intravitreous injection of full-length humanized IgG1 antibody along with a cell-permeable siRNA scrambled control or siRNA targeting DDX3Y. Results: Male macrophages from human and mouse transcribe multiple Y chromosome genes. Silencing of multiple MSY-encoded genes abrogated the ability of IgG1 to suppress chemotaxis and angiogenesis, rendering male systems to respond similarly to female systems. Male macrophages from DDX3Y knockout mice were also resistant to IgG1 treatment. siRNA targeting DDX3Y suppressed inhibition in male mice. Conclusions: The antiangiogenic activity IgG1 antibodies is greatly reduced by antagonizing Y chromosome genes. These studies highlight protein coding genes of the Y chromosome as a potential angiogenesis modulating target responsible for sexually dimorphic responses.

First direct evidence for direct cell-membrane penetrations of polycationic homopoly(amino acid)s produced by bacteria

Bacteria produce polycationic homopoly(amino acid)s, which are characterized by isopeptide backbones. Although the biological significance of polycationic homopoly(amino acid)s remains unclear, increasing attention has recently been focused on their potential use to achieve cellular internalization. Here, for the first time, we provide direct evidence that two representative bacterial polycationic isopeptides, ε-poly-l-α-lysine (ε-PαL) and ε-oligo-l-β-lysine (ε-OβL), were internalized into mammalian cells by direct cell-membrane penetration and then diffused throughout the cytosol. In this study, we used clickable ε-PαL and ε-OβL derivatives carrying a C-terminal azide group, which were enzymatically produced and then conjugated with a fluorescent dye to analyze subcellular localization. Interestingly, fluorescent proteins conjugated with the clickable ε-PαL or ε-OβL were also internalized into cells and diffused throughout the cytosol. Notably, a Cre recombinase conjugate with ε-PαL entered cells and mediated the Cre/loxP recombination, and ε-PαL was found to deliver a full-length IgG antibody to the cytosol and nucleus.

Isolation and Production of Human Monoclonal Antibody Proteins against a Toxocara canis Excretory-Secretory Recombinant Antigen.

Toxocariasis is a widespread zoonotic parasitic disease with a significant socioeconomic impact, particularly on underprivileged communities. Limitations of existing diagnostic tools and vague presenting symptoms may lead to misdiagnosis, thus underestimating the actual global impact of the disease. The present study describes the isolation and production of novel recombinant monoclonal antibodies against Toxocara canis recombinant TES-26 antigen (rTES-26) utilizing a human helminth scFv phage display library. The isolated antibody clones were characterized based on their gene sequences and binding characteristics. Three clones representing unique gene families (clone 48: IgHV3-LV1; clone 49: IgHV3-LV3; clone 50: IgHV6-LV3) were isolated, but only clones 48 and 49 showed successful insertion of the full-length scFv antibody sequence after sub-cloning. Both clones produced antibody proteins of good solubility and satisfactory yield and purity. Binding assays via Western blot and ELISA using rTES-26 and Toxocara canis native protein showed that both monoclonal antibodies were highly specific and sensitive to the target antigen. A preliminary antigen detection ELISA showed the diagnostic potential of the monoclonal antibody proteins. The proteins can also be useful in studying host-parasite interactions and therapeutic applications.

Bioengineering and computational analysis of programmed cell death ligand-1 monoclonal antibody.

The trans-membrane proteins of the B7 family programmed cell death ligand-1 (PD-L1) and programmed death-1 (PD-1) play important roles in inhibiting immune responses and enhancing self-tolerance via T-cell modulation. Several therapeutic antibodies are used to promote T-cell proliferation by preventing interactions between PD-1/PD-L1. Recombinant technology appears to be quite useful in the production of such potent antibodies. In this study, we constructed recombinant molecules by cloning variable regions of the PD-L1 molecule into pMH3 vectors and transferring them into mammalian cell lines for expression. G418 supplementation was used to screen the recombinant clones, which were then maintained on serum-free medium. The full-length antibody was isolated and purified from the medium supernatant at a concentration of 0.5-0.8 mg/ml. Antibody binding affinity was investigated using ELISA and immunofluorescence methods. The protein-protein interactions (PPI) were determined using a docking approach. The SWISS model was utilized for homology modeling, while ZDOCK, Chimera, and PyMOL were used to validate 3D models. The Ramachandran plots were constructed using the SWISS model, which revealed that high-quality structures had a value of more than 90%. Current technologies allow for the accurate determination of antigen-antibody interactions.

Construction of an Iodine-Labeled CS1001 Antibody for Targeting PD-L1 Detection and Comparison with Low-Molecular-Peptide Micro-PET Imaging.

Programmed death-1 (PD-1) and programmed death ligand-1 (PD-L1), the research focus in immune checkpoint regulation, play an important role in tumor immunotherapy. Inhibitors of this pathway are also the focus of tumor immunotherapy research. The PD-1/PD-L1 pathway can be blocked by selective binding to PD-L1. Clinical trials have been conducted in a variety of patients with advanced solid tumors. CS1001 is a high-affinity humanized full-length anti-PD-L1 monoclonal antibody with great clinical significance. We constructed a PD-L1-targeted radioactive molecular probe, 124/125I-labeled full-length antibody CS1001, and evaluated its binding specificity and targeting ability to PD-L1 in tumor cells and tumor models. Additionally, a comparison study with 68Ga-WL12, a PD-L1 targeting peptide, was conducted. The binding potency of 125I-CS1001 to human PD-L1 was evaluated by enzyme-linked immunosorbent assay (ELISA), and the Kd value was 52.1 ± 19.3 nM. The cellular uptake of 125I-CS1001 was examined in Chinese hamster ovary cells (CHO) and CHO expressing human PD-L1 (CHO-hPD-L1). At 2 h, the uptake values of 125I-CS1001 in CHO-hPD-L1 without blocking and in the presence of 0.1 mg non-radiolabeled CS1001 were 3.60 ± 0.08 and 0.09 ± 0.005 (%AD/2 × 105 cells, p < 0.001). Micro-PET imaging was performed between 8 to 192 h after injection of 124I-CS1001 into normal KM mice and CHO-hPD-L1 and HeLa tumor models. The standard uptake value (SUV) of relevant organs in PET images was calculated by drawing regions of interest (ROI). SUVmean of CHO-hPD-L1 tumors was significantly higher than that of HeLa tumors at 48 h (1.98 ± 0.04 vs 0.73 ± 0.14, p = 0.005). The SUVmean of 124I-CS1001 in CHO-hPD-L1 tumors at 48 h was higher than that of 68Ga-WL12 in CHO-hPD-L1 tumors at 0.5 h (1.98 ± 0.04 vs 1.09 ± 0.1 SUVmean, p = 0.007). In conclusion, this work provides a new method for monitoring and evaluating the in vivo expression of PD-L1 in tumors.

The Fab region of IgG impairs the internalization pathway of FcRn upon Fc engagement

Binding to the neonatal Fc receptor (FcRn) extends serum half-life of IgG, and antagonizing this interaction is a promising therapeutic approach in IgG-mediated autoimmune diseases. Fc-MST-HN, designed for enhanced FcRn binding capacity, has not been evaluated in the context of a full-length antibody, and the structural properties of the attached Fab regions might affect the FcRn-mediated intracellular trafficking pathway. Here we present a comprehensive comparative analysis of the IgG salvage pathway between two full-size IgG1 variants, containing wild type and MST-HN Fc fragments, and their Fc-only counterparts. We find no evidence of Fab-regions affecting FcRn binding in cell-free assays, however, cellular assays show impaired binding of full-size IgG to FcRn, which translates into improved intracellular FcRn occupancy and intracellular accumulation of Fc-MST-HN compared to full size IgG1-MST-HN. The crystal structure of Fc-MST-HN in complex with FcRn provides a plausible explanation why the Fab disrupts the interaction only in the context of membrane-associated FcRn. Importantly, we find that Fc-MST-HN outperforms full-size IgG1-MST-HN in reducing IgG levels in cynomolgus monkeys. Collectively, our findings identify the cellular membrane context as a critical factor in FcRn biology and therapeutic targeting.

Centaur antibodies: Engineered chimeric equine-human recombinant antibodies.

Hyper-immune antisera from large mammals, in particular horses, are routinely used for life-saving anti-intoxication intervention. While highly efficient, the use of these immunotherapeutics is complicated by possible recipient reactogenicity and limited availability. Accordingly, there is an urgent need for alternative improved next-generation immunotherapies to respond to this issue of high public health priority. Here, we document the development of previously unavailable tools for equine antibody engineering. A novel primer set, EquPD v2020, based on equine V-gene data, was designed for efficient and accurate amplification of rearranged horse antibody V-segments. The primer set served for generation of immune phage display libraries, representing highly diverse V-gene repertoires of horses immunized against botulinum A or B neurotoxins. Highly specific scFv clones were selected and expressed as full-length antibodies, carrying equine V-genes and human Gamma1/Lambda constant genes, to be referred as “Centaur antibodies”. Preliminary assessment in a murine model of botulism established their therapeutic potential. The experimental approach detailed in the current report, represents a valuable tool for isolation and engineering of therapeutic equine antibodies.

Biophysical differences in IgG1 Fc-based therapeutics relate to their cellular handling, interaction with FcRn and plasma half-life

Antibody-based therapeutics (ABTs) are used to treat a range of diseases. Most ABTs are either full-length IgG1 antibodies or fusions between for instance antigen (Ag)-binding receptor domains and the IgG1 Fc fragment. Interestingly, their plasma half-life varies considerably, which may relate to how they engage the neonatal Fc receptor (FcRn). As such, there is a need for an in-depth understanding of how different features of ABTs affect FcRn-binding and transport behavior. Here, we report on how FcRn-engagement of the IgG1 Fc fragment compare to clinically relevant IgGs and receptor domain Fc fusions, binding to VEGF or TNF-α. The results reveal FcRn-dependent intracellular accumulation of the Fc, which is in line with shorter plasma half-life than that of full-length IgG1 in human FcRn-expressing mice. Receptor domain fusion to the Fc increases its half-life, but not to the extent of IgG1. This is mirrored by a reduced cellular recycling capacity of the Fc-fusions. In addition, binding of cognate Ag to ABTs show that complexes of similar size undergo cellular transport at different rates, which could be explained by the biophysical properties of each ABT. Thus, the study provides knowledge that should guide tailoring of ABTs regarding optimal cellular sorting and plasma half-life.

Expressing antigen binding fragments with high titers in a targeted integration CHO host by optimizing expression vector gene copy numbers and position: A case study.

Antigen binding fragments (Fab) are a promising class of therapeutics as they maintain high potency while having significantly smaller size relative to full-length antibodies. Because Fab molecules are aglycosylated, many expression platforms, including prokaryotic, yeast, and mammalian cells, have been developed for their expression, with Escherichia coli being the most commonly used Fab expression system. In this study, we have examined production of a difficult to express Fab molecule in a targeted integration (TI) Chinese Hamster Ovary (CHO) host. Without a need for extensive host or process optimization, as is usually required for E. coli, by simply using different vector configurations, clones with very high Fab expression titers were obtained. In this case, by increasing heavy chain (HC) gene copy numbers, clones with titers of up to 7.4g/L in the standard fed-batch production culture were obtained. Our findings suggest that having a predetermined transgene integration site, as well as the option to optimize gene copy number/dosage, makes CHO TI hosts an effective system for expression of Fab molecules, allowing Fab expression using platform process and without significant process development efforts.

NanoNet: Rapid and accurate end-to-end nanobody modeling by deep learning.

Antibodies are a rapidly growing class of therapeutics. Recently, single domain camelid VHH antibodies, and their recognition nanobody domain (Nb) appeared as a cost-effective highly stable alternative to full-length antibodies. There is a growing need for high-throughput epitope mapping based on accurate structural modeling of the variable domains that share a common fold and differ in the Complementarity Determining Regions (CDRs). We develop a deep learning end-to-end model, NanoNet, that given a sequence directly produces the 3D coordinates of the backbone and Cβ atoms of the entire VH domain. For the Nb test set, NanoNet achieves 3.16Å average RMSD for the most variable CDR3 loops and 2.65Å, 1.73Å for the CDR1, CDR2 loops, respectively. The accuracy for antibody VH domains is even higher: 2.38Å RMSD for CDR3 and 0.89Å, 0.96Å for the CDR1, CDR2 loops, respectively. NanoNet run times allow generation of ∼1M nanobody structures in less than 4 hours on a standard CPU computer enabling high-throughput structure modeling. NanoNet is available at GitHub: https://github.com/dina-lab3D/NanoNet

Collagen VI antibody reduces atherosclerosis by activating monocyte/macrophage polarization in ApoE−/− mice

Atherosclerosis (AS) has been regarded as an autoimmune disease. However, studies on immunotherapy against AS are limited. We previously found that IgG in AS patients serum binding to alpha 5 and 6 chain of collagen VI (COL6A5 or COL6A6) was significantly higher than that in healthy subjects, here we tried to identify whether they are AS-protective, and tried to develop human antibodies against them. ApoE−/− mice were immunized with COL6A5 or COL6A6 and COL6A6 was found a protective antigen against atherosclerosis. A phage display human single-chain antibody (scFv) library was constructed and COL6A6-specific scFv was obtained, and cloned into a modified pcDNA3 vector to express full-length human antibodies. ApoE−/− mice were fed a high-fat diet (HFD) for 20 weeks and administered three weekly injections of CVI monoclonal antibody (mAb) or isotype control antibody, CVI mAb was found to be able to reduce plaque area by 45 % via aorta oil red O staining. Flowcytometry method predicted that CVI mAb induced monocyte/macrophage polarization from M1 to M2. Furthermore, CVI mAb induced decreases of pro-inflammatory cytokines of MCP-1and IL-1β, and increases of IL-4 and IL-10 levels in animal serum by using theLuminexassay. Overall, we found a novel atherosclero-related antigen – Collagen VI, and its protective fragment - Collagen VI alpha 6 chain (COL6A6) and proved that humanized antibody against COL6A6 therapy regresses atherosclerosis and induces monocyte/macrophage polarization from M1 to M2 in ApoE−/− mice animal model.

Towards Photodynamic Image-Guided Surgery of Head and Neck Tumors: Photodynamic Priming Improves Delivery and Diagnostic Accuracy of Cetuximab-IRDye800CW.

Fluorescence image-guided surgery (IGS) using antibody conjugates of the fluorophore IRDye800CW have revolutionized the surgical debulking of tumors. Cetuximab, an anti-epidermal growth factor receptor (EGFR) monoclonal antibody, conjugated to IRDye800CW (Cet-IRDye800) is the first molecular targeted antibody probe to be used for IGS in head and neck cancer patients. In addition to surgical debulking, Cetuximab-targeted photodynamic therapy (photoimmunotherapy; PIT) is emerging in the clinic as a powerful modality for head and neck tumor photodestruction. A plethora of other photoactivable agents are also in clinical trials for photodynamic-based therapies of head and neck cancer. Considering the vascular and stromal modulating effects of sub-therapeutic photodynamic therapy, namely photodynamic priming (PDP), this study explores the potential synergy between PDP and IGS for a novel photodynamic image-guided surgery (P-IGS) strategy. To the best of our knowledge, this is the first demonstration that PDP of the tumor microenvironment can augment the tumor delivery of full-length antibodies, namely Cet-IRDye800. In this study, we demonstrate a proof-of-concept that PDP primes orthotopic FaDu human head and neck tumors in mice for P-IGS by increasing the delivery of Cet-IRDye800 by up to 138.6%, by expediting its interstitial accumulation by 10.5-fold, and by increasing its fractional tumor coverage by 49.5% at 1 h following Cet-IRDye800 administration. Importantly, PDP improves the diagnostic accuracy of tumor detection by up to 264.2% with respect to vicinal salivary glands at 1 h. As such, PDP provides a time-to-surgery benefit by reducing the time to plateau 10-fold from 25.7 h to 2.5 h. We therefore propose that a pre-operative PDP regimen can expedite and augment the accuracy of IGS-mediated surgical debulking of head and neck tumors and reduce the time-to-IGS. Furthermore, this P-IGS regimen, can also enable a forward-looking post-operative protocol for the photodestruction of unresectable microscopic disease in the surgical bed. Beyond this scope, the role of PDP in the homogenous delivery of diagnostic, theranostic and therapeutic antibodies in solid tumors is of considerable significance to the wider community.

The AJ072 full-length IgG antibody labels the surface and early endosomes of HEK cells by immunofluorescence

The AJ072 full-length mouse IgG antibody, against the human transferrin receptor, labels the plasma membrane and early endosomes of HEK cells by immunofluorescence.

Abstract 3567: Comprehensive preclinical studies of BT-001: An oncolytic vaccinia virus armed with Treg-depleting @CTLA4 and GM-CSF

Abstract Background Immune checkpoint blockade (ICB) is a clinically proven concept to treat cancer. Still, a majority of cancer patients including those with poorly immune infiltrated “cold” tumors are resistant to currently available ICB therapies. Oncolytic viruses are natural immunomodulators able to turn “cold” tumors “hot” and, for some of them, to deliver therapeutic payloads intratumorally. Payloads of choice are those with tolerability and/or pharmacokinetic/biodistribution issues, such as @CTLA4 antibodies and GM-CSF respectively. Here, Transgene and BioInvent present a preclinical characterization of a highly efficacious and potentially safe strategy to target CTLA-4 and GM-CSF using vectorization in an oncolytic vaccinia virus. Methods A novel human IgG1 CTLA-4 antibody (4-E03) was identified using function-first screening for mAbs and targets associated with checkpoint blocking and superior Treg depleting activity. A tumor-selective oncolytic Vaccinia vector was then engineered to encode this novel αCTLA-4 as full-length antibody (i.e. distinct transgenes for light and heavy chains) and GM-CSF (VVGM-αhCTLA4, BT-001). Viruses encoding matching mouse surrogate payloads were additionally generated, enabling proof-of-concept studies in syngeneic immune competent mouse tumor models. Results Our studies demonstrate that two chains cloning approach allowed to express @CTLA4 at a high level in numerous infected human tumor cell lines without affecting replication, oncolytic activity or genetic stability of the virus. Intratumoral (i.t.) administration of VVGM-αCTLA4 achieved tumor-restricted CTLA-4 receptor saturation at least for 10 days, Treg-depletion antigen cross-presentation, stronger systemic expansion of tumor-specific CD8+ T cells and antitumor immunity compared with systemic αCTLA-4 antibody or unarmed virus therapies. Remarkably, in a clinically relevant mouse model resistant to systemic immune checkpoint blockade, i.t. VVGM-αCTLA4 synergized with αPD-1 to reject “cold” tumors. Conclusion Our findings demonstrate in vivo proof-of-concept for tumor delivery by Vaccinia virus of GM-CSF and strongly Treg-depleting, immune checkpoint blocking, vectorized αCTLA-4. This vector-based delivery is a highly effective and safe strategy to target CTLA-4 which overcomes current limitations of approved αCTLA-4 regimens. A clinical trial evaluating i.t. VVGM-αhCTLA4 (BT-001) alone and in combination with αPD-1 in metastatic or advanced solid tumors has been initiated. Citation Format: Jean-Baptiste Marchand, Monika Semmrich, Christelle Ziller, Matilda Rehn, Laetitia Fend, Petra Holmkvist, Nathalie Silvestre, Carolin Svensson, Kleinpeter Patricia, Jules Deforges, Fred Junghus, Linda Mårtensson, Johann Foloppe, Ingrid Teige, Björn Frendéus, Eric Quéméneur. Comprehensive preclinical studies of BT-001: An oncolytic vaccinia virus armed with Treg-depleting @CTLA4 and GM-CSF [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3567.

Abstract 2913: Personalized ovarian cancer therapy using in vivo assembled bi-specific antibodies targeting Her2 and FSHR

Abstract According to The American Cancer Society, ovarian cancer will cause ~14,000 deaths in the US in 2021. Despite recent advances in therapy, clinical outcomes remain poor and there is a great unmet need for newer therapies for ovarian cancer patients. Bispecific T cell engagers (BiTEs) consist of two single chain variable fragments (scFVs) linked via a peptide linker and are being studied as a tool against many different cancers. BiTEs redirect T cell activity towards tumor cells in an MHC independent manner by bringing T cells close to a tumor associated antigen (TAA). A BiTE targeting CD19 has been approved for treating ALL, however the success of BiTEs in treating solid tumor remains limited. Two reasons that reduce the efficacy of BiTEs in solid tumors are 1) their short half-life which drastically reduces their availability 2) tumor heterogeneity preventing targeting by a single BiTE. Tumors downregulate TAA expression in response to targeted therapy allowing treatment escape. Development of novel BiTEs with longer serum half-lives and in vivo delivery strategies which allow rapid customization of BiTEs is important. Here we describe a strategy for in vivo assembly using the Knob-in-hole (KIH) approach. We designed two different DNA encoded KIH (dKIH), targeting Her2 and FSHR, and studied their ability to be assembled in vivo into functional therapeutics. The knobs encoded full length antibodies engineered to target either Her2 or FSHR. We designed a third construct as the hole to target CD3. Following in vitro characterization, we injected NSG mice with KIH pairs for Her2+CD3 or FSHR+ CD3 and studied their expression and function. Sera from mice injected with Her2 or FSHR dKIH bound tumor cells expressing Her2 or FSHR respectively. Sera from mice from both groups also bound to T cells. We observed that both dKIH resulted in mouse sera with high potency (pg level) killing of ovarian cancer cell lines expressing Her2 and FSHR in an in vitro killing assay. A single injection of either dKIH allowed for in vivo expression and tumor killing for over a month post injection which is a significant improvement over delivery of protein KIH. This study demonstrates the potential of in vivo assembly of KIH. The patients produce their own therapy, which allows to skip complex bioprocessing steps and makes KIH delivery simpler and cheaper. This study illustrates the potential to improve immunotherapy outcomes for ovarian cancer patients via in vivo assembly of multiple BiTEs. Citation Format: Pratik Sanjivkumar Bhojnagarwala, Ali Raza Ali, Drew Frase, Abhijeet Kulkarni, Devivasha Bordoloi, David B. Weiner. Personalized ovarian cancer therapy using in vivo assembled bi-specific antibodies targeting Her2 and FSHR [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2913.