Nonclinical immunogenicity risk assessment for knobs-into-holes bispecific IgG1 antibodies.

Bispecific antibodies, including bispecific IgG, are emerging as an important new class of antibody therapeutics. As a result, we, as well as others, have developed engineering strategies designed to facilitate the efficient production of bispecific IgG for clinical development. For example, we have extensively used knobs-into-holes (KIH) mutations to facilitate the heterodimerization of antibody heavy chains and more recently Fab mutations to promote cognate heavy/light chain pairing for efficient in vivo assembly of bispecific IgG in single host cells. A panel of related monospecific and bispecific IgG1 antibodies was constructed and assessed for immunogenicity risk by comparison with benchmark antibodies with known low (Avastin and Herceptin) or high (bococizumab and ATR-107) clinical incidence of anti-drug antibodies. Assay methods used include dendritic cell internalization, T cell proliferation, and T cell epitope identification by in silico prediction and MHC-associated peptide proteomics. Data from each method were considered independently and then together for an overall integrated immunogenicity risk assessment. In toto, these data suggest that the KIH mutations and in vitro assembly of half antibodies do not represent a major risk for immunogenicity of bispecific IgG1, nor do the Fab mutations used for efficient in vivo assembly of bispecifics in single host cells. Comparable or slightly higher immunogenicity risk assessment data were obtained for research-grade preparations of trastuzumab and bevacizumab versus Herceptin and Avastin, respectively. These data provide experimental support for the common practice of using research-grade preparations of IgG1 as surrogates for immunogenicity risk assessment of their corresponding pharmaceutical counterparts.

DNA Methylation-Regulated HOXC8's Role in HER2-Positive Breast Cancer Function and its Contribution to Herceptin Resistance.

BACKGROUND: The epidermal growth factor receptor 2 (HER2) is overexpressed in 30% of breast cancers, and this overexpression is strongly correlated with a poor prognosis. Herceptin is a common treatment for HER2-positive breast cancer; however, cancer cells tend to adapt gradually to the drug, rendering it ineffective. The study revealed an association between the methylation status of the Homeobox C8 (HOXC8) gene and tumor development. Therefore, it is of paramount importance to delve into the interaction between HOXC8 and HER2-positive breast cancer, along with its molecular mechanisms. This exploration holds significant implications for a deeper understanding of the pathophysiological processes underlying HER2-positive breast cancer. METHOD: Tumor tissue and pathological data from patients with HER2-positive breast cancer were systematically collected. Additionally, the human HER2-positive breast cancer cell line, SKBR3, was cultured in vitro to assess both the expression level of HOXC8 and the degree of DNA methylation. The study aimed to explore the relationship between the relative expression of HOXC8 and the clinical characteristics of breast cancer patients. The expression level of HOXC8 and the promoter methylation of HOXC8 were verified by methylation treatment of SKBR3 breast cancer cells. The regulation of HOXC8 was meticulously carried out, leading to the division of the cells into distinct groups. The study further analyzed the expression levels and biological capabilities within each group. Finally, the in vitro and in vivo sensitivity of the cells to Herceptin, a common treatment for HER2-positive breast cancer, was measured to assess the efficacy of the drug. RESULT: In HER2-positive breast cancer cases characterized by poor methylation, there was an up-regulation of HOXC8. Its expression was found to be correlated with key clinical factors such as tumor size, lymph node status, clinical tumor, node, metastasis (cTNM) staging, and Herceptin resistance (p < 0.05). Upon methylation of breast cancer cells, there was a significant decrease in HOXC8 expression (p < 0.05). The study revealed that overexpression of HOXC8 resulted in increased proliferation, cloning, and metastasis of HER2-positive breast cancer cells, along with a reduced apoptosis rate (p < 0.05). Conversely, interference with HOXC8 expression reversed this scenario (p < 0.05). A Herceptin-resistant substrain, POOL2, was established using SKBR3 cells. Animal studies demonstrated that overexpressing HOXC8 accelerated tumor development and enhanced POOL2 cells' resistance to Herceptin (p < 0.05). However, following interference with HOXC8, POOL2 cells exhibited increased responsiveness to Herceptin, leading to a gradual reduction in tumor size (p < 0.05). CONCLUSIONS: In HER2-positive breast cancer, the expression of HOXC8 is elevated in a manner dependent on DNA methylation, and this elevated expression is closely linked to the pathology of the patient. Interfering with HOXC8 expression demonstrates the potential to partially inhibit the development and spread of breast cancer, as well as to alleviate resistance to Herceptin.

Management of HER2 alterations in non-small cell lung cancer - The past, present, and future.

HER2 mutations, which account for 2-4% of non-small cell lung cancer (NSCLC), are distinct molecular alterations identified via next generation sequencing (NGS). Previously, treatment outcomes in HER2-mutant metastatic NSCLC were dismal, showing limited clinical benefit with platinum-based chemotherapy with or without immunotherapy. In contrast to HER2-altered breast and gastric cancer, HER2-mutant NSCLC does not benefit from HER2 targeting agents such as trastuzumab or TDM1. HER2 mutations are also inherently different from HER2 overexpression and amplification. Currently, trastuzumab deruxtecan, a HER2 targeting antibody drug conjugate (ADC) is the first and only approved treatment option for patients with HER2-mutant metastatic NSCLC after failure with standard treatment. In this review, we summarized the biology of HER2 and detection of HER2 overexpression, amplification and mutations, as well as general landscape of landmark and ongoing clinical trials encompassing from chemotherapy to targeted agents, including tyrosine kinase inhibitors (TKIs), ADCs and investigational agents.

In Vitro and In Vivo Effects of the Combination of Polypurine Reverse Hoogsteen Hairpins against HER-2 and Trastuzumab in Breast Cancer Cells.

Therapeutic oligonucleotides are powerful tools for the inhibition of potential targets involved in cancer. We describe the effect of two Polypurine Reverse Hoogsteen (PPRH) hairpins directed against the ERBB2 gene, which is overexpressed in positive HER-2 breast tumors. The inhibition of their target was analyzed by cell viability and at the mRNA and protein levels. The combination of these specific PPRHs with trastuzumab was also explored in breast cancer cell lines, both in vitro and in vivo. PPRHs designed against two intronic sequences of the ERBB2 gene decreased the viability of SKBR-3 and MDA-MB-453 breast cancer cells. The decrease in cell viability was associated with a reduction in ERBB2 mRNA and protein levels. In combination with trastuzumab, PPRHs showed a synergic effect in vitro and reduced tumor growth in vivo. These results represent the preclinical proof of concept of PPRHs as a therapeutic tool for breast cancer.

An Fc variant with two mutations confers prolonged serum half-life and enhanced effector functions on IgG antibodies.

The pH-selective interaction between the immunoglobulin G (IgG) fragment crystallizable region (Fc region) and the neonatal Fc receptor (FcRn) is critical for prolonging the circulating half-lives of IgG molecules through intracellular trafficking and recycling. By using directed evolution, we successfully identified Fc mutations that improve the pH-dependent binding of human FcRn and prolong the serum persistence of a model IgG antibody and an Fc-fusion protein. Strikingly, trastuzumab-PFc29 and aflibercept-PFc29, a model therapeutic IgG antibody and an Fc-fusion protein, respectively, when combined with our engineered Fc (Q311R/M428L), both exhibited significantly higher serum half-lives in human FcRn transgenic mice than their counterparts with wild-type Fc. Moreover, in a cynomolgus monkey model, trastuzumab-PFc29 displayed a superior pharmacokinetic profile to that of both trastuzumab-YTE and trastuzumab-LS, which contain the well-validated serum half-life extension Fcs YTE (M252Y/S254T/T256E) and LS (M428L/N434S), respectively. Furthermore, the introduction of two identified mutations of PFc29 (Q311R/M428L) into the model antibodies enhanced both complement-dependent cytotoxicity and antibody-dependent cell-mediated cytotoxicity activity, which are triggered by the association between IgG Fc and Fc binding ligands and are critical for clearing cancer cells. In addition, the effector functions could be turned off by combining the two mutations of PFc29 with effector function-silencing mutations, but the antibodies maintained their excellent pH-dependent human FcRn binding profile. We expect our Fc variants to be an excellent tool for enhancing the pharmacokinetic profiles and potencies of various therapeutic antibodies and Fc-fusion proteins.

Clinical and Genomic Features of HER2 Exon 20 Insertion Mutations and Characterization of HER2 Expression by Immunohistochemistry in East Asian Non-Small-Cell Lung Cancer.

PURPOSE: HER2-altered non-small-cell lung cancer (NSCLC) represents a diverse subgroup, including mutations, amplifications, and overexpression. However, HER2 exon 20 insertion mutations are emerging as a distinct molecular subtype with expanding therapeutic options. We describe the molecular epidemiology and genomic features of HER2-altered NSCLC in an Asian tertiary cancer center. METHODS: We identified patients with HER2-mutated NSCLC in our institutional database, collating clinicopathological features and treatment outcomes. The genomic landscape of human epidermal growth factor receptor 2 (HER2)-mutated NSCLC was further evaluated using whole-exome sequencing (WES) data from combined local and publicly available data sets. HER2 amplification and overexpression as selection biomarkers in NSCLC were further interrogated using HER2 immunohistochemistry and correlations with WES and RNA sequencing data. RESULTS: Among 1,252 patients with consecutive lung adenocarcinoma undergoing routine next-generation sequencing, the prevalence of HER2 mutations was 3.1%-exon 20 insertion mutations comprised 2.7%. We examined the clinicopathological features in 55 patients with HER2-mutated NSCLC comprising 40 exon 20 insertion and 15 nonexon 20 insertion mutations. The most common exon 20 insertion mutation was HER2Y772_A775dup in 30 (75%), followed by HER2G776delinsVC in five patients (13%). There were limited responses to HER2-directed therapies apart from trastuzumab-deruxtecan, and no responses were seen with immunotherapy monotherapy. Evaluating the genomics features of HER2 exon 20 insertion mutations using WES data revealed low tumor mutational burden (TMB), low incidence of cancer driver comutations, and a predominance of aging mutational signature-similar to EGFR-mutated tumors. In contrast, uncommon (or nonexon 20 insertion) HER2-mutated tumors resembled EGFR wild-type tumors with higher TMB, higher frequency of cancer driver comutations, and greater presence of smoking and APOBEC mutational signature. Finally, in evaluating HER2 immunohistochemistry in all lung adenocarcinoma, there was significant discordance comparing different scoring systems and poor correlation with HER2 RNA expression and HER2 amplification. CONCLUSION: The incidence of HER2 mutations is 3.1% in East Asian nonsquamous NSCLC. HER2 exon 20 insertion-mutated tumors appear genomically distinct from uncommon (nonexon 20 insertion) HER2 mutations, the latter demonstrating higher TMB, co-occurring drivers, and predominant nonaging mutational signature. The therapeutic implications of the genomic and clinical features of HER2-mutated NSCLC warrant further investigation.

Patritumab deruxtecan (HER3-DXd), a novel HER3 directed antibody drug conjugate, exhibits in vitro activity against breast cancer cells expressing HER3 mutations with and without HER2 overexpression.

ErbB3 (HER3), a member of the HER family, is overexpressed in various cancers and plays an important role in cell proliferation and survival. Certain HER3 mutations have also been identified as oncogenic drivers, making them potential therapeutic targets. In the current study, antitumor activity of patritumab deruxtecan (HER3-DXd), a HER3 directed antibody drug conjugate, was evaluated in tumor models with clinically reported HER3 mutations. MDA-MB-231, a HER3-negative human triple-negative breast cancer cell line, was transduced with lentiviral vectors encoding HER3 wild type (HER3WT), one of 11 HER3 mutations, or HER3 empty vector (HER3EV), in the presence/absence of HER2 overexpression. Targeted delivery of HER3-DXd was assessed using cell-surface binding, lysosomal trafficking, and cell-growth inhibition assays. HER3-DXd bound to the surface of HER3WT and mutant cells in a similar, concentration-dependent manner but not to HER3EV. HER3-DXd was translocated to the lysosome, where time- and concentration-dependent signals were observed in the HER3 mutant and HER3WT cells. HER3-DXd inhibited the growth of HER3WT and HER3 mutant cells. HER3-DXd activity was observed in the presence and absence of HER2 overexpression. These data suggest that HER3-DXd may have activity against tumors expressing wild type HER3 or clinically observed HER3 mutations, supporting further clinical evaluation.

Disulfide-compatible phage-assisted continuous evolution in the periplasmic space.

The directed evolution of antibodies has yielded important research tools and human therapeutics. The dependence of many antibodies on disulfide bonds for stability has limited the application of continuous evolution technologies to antibodies and other disulfide-containing proteins. Here we describe periplasmic phage-assisted continuous evolution (pPACE), a system for continuous evolution of protein-protein interactions in the disulfide-compatible environment of the E. coli periplasm. We first apply pPACE to rapidly evolve novel noncovalent and covalent interactions between subunits of homodimeric YibK protein and to correct a binding-defective mutant of the anti-GCN4 Ω-graft antibody. We develop an intein-mediated system to select for soluble periplasmic expression in pPACE, leading to an eight-fold increase in soluble expression of the Ω-graft antibody. Finally, we evolve disulfide-containing trastuzumab antibody variants with improved binding to a Her2-like peptide and improved soluble expression. Together, these results demonstrate that pPACE can rapidly optimize proteins containing disulfide bonds, broadening the applicability of continuous evolution.

Biochemistry, structure, and cellular internalization of a four nanobody-bearing Fc dimer.

VHH stands for the variable regions of heavy chain only of camelid IgGs. The VHH family forms a set of interesting proteins derived from antibodies that maintain their capacity to recognize the antigen, despite their relatively small molecular weight (in the 12,000 Da range). Continuing our exploration of the possibilities of those molecules, we chose to design alternative molecules with maintained antigen recognition, but enhanced capacity, by fusing four VHH with one Fc, the fragment crystallizable region of antibodies. In doing so, we aimed at having a molecule with superior quantitative antigen recognition (×4) while maintaining its size below the 110 kDa. In the present paper, we described the building of those molecules that we coined VHH2 -Fc-VHH2 . The structure of VHH2 -Fc-VHH2 in complex with HER2 antigen was determined using electronic microscopy and modeling. The molecule is shown to bind four HER2 proteins at the end of its flexible arms. VHH2 -Fc-VHH2 also shows an internalization capacity via HER2 receptor superior to the reference anti-HER2 monoclonal antibody, Herceptin®, and to a simple fusion of two VHH with one Fc (VHH2 -Fc). This new type of molecules, VHH2 -Fc-VHH2 , could be an interesting addition to the therapeutic arsenal with multiple applications, from diagnostic to therapy.

Integrated in Silico and Experimental Approach towards the Design of a Novel Recombinant Protein Containing an Anti-HER2 scFv.

Biological therapies, such as recombinant proteins, are nowadays amongst the most promising approaches towards precision medicine. One of the most innovative methodologies currently available aimed at improving the production yield of recombinant proteins with minimization of costs relies on the combination of in silico studies to predict and deepen the understanding of the modified proteins with an experimental approach. The work described herein aims at the design and production of a biomimetic vector containing the single-chain variable domain fragment (scFv) of an anti-HER2 antibody fragment as a targeting motif fused with HIV gp41. Molecular modeling and docking studies were performed to develop the recombinant protein sequence. Subsequently, the DNA plasmid was produced and HEK-293T cells were transfected to evaluate the designed vector. The obtained results demonstrated that the plasmid construction is robust and can be expressed in the selected cell line. The multidisciplinary integrated in silico and experimental strategy adopted for the construction of a recombinant protein which can be used in HER2+-targeted therapy paves the way towards the production of other therapeutic proteins in a more cost-effective way.

Optimization of therapeutic antibodies by predicting antigen specificity from antibody sequence via deep learning.

The optimization of therapeutic antibodies is time-intensive and resource-demanding, largely because of the low-throughput screening of full-length antibodies (approximately 1 × 103 variants) expressed in mammalian cells, which typically results in few optimized leads. Here we show that optimized antibody variants can be identified by predicting antigen specificity via deep learning from a massively diverse space of antibody sequences. To produce data for training deep neural networks, we deep-sequenced libraries of the therapeutic antibody trastuzumab (about 1 × 104 variants), expressed in a mammalian cell line through site-directed mutagenesis via CRISPR-Cas9-mediated homology-directed repair, and screened the libraries for specificity to human epidermal growth factor receptor 2 (HER2). We then used the trained neural networks to screen a computational library of approximately 1 × 108 trastuzumab variants and predict the HER2-specific subset (approximately 1 × 106 variants), which can then be filtered for viscosity, clearance, solubility and immunogenicity to generate thousands of highly optimized lead candidates. Recombinant expression and experimental testing of 30 randomly selected variants from the unfiltered library showed that all 30 retained specificity for HER2. Deep learning may facilitate antibody engineering and optimization.

Construction of a full-length antibody phage display vector.

Antibody phage display technology plays an important role in the development of monoclonal antibodies, humanization, and affinity evolution of antibodies. Thus far, antibody phage display mainly focuses on the display of antibody variable region or antigen-binding fragments. In this study, we constructed a new phage display system that can display full-length IgG antibodies on M13 phage. The phage display vector contains open reading frames (ORFs) encoding full-length the heavy and light chains of the antibody. NcoI/XhoI restriction enzyme sites were used to clone the variable region of the heavy chain into the heavy chain ORF, and SalI/NotI sites were used to clone the light chain variable region. SnaBI and SbfI restriction enzyme sites were designed between the cloning sites of heavy and light chains, respectively, to increase the cloning efficiency. The full-length antibodies of nivolumab against programmed death factor 1, trastuzumab against human epidermal growth factor 2, diL2K against the cluster of differentiation 3 epsilon, and adalimumab against tumor necrosis factor- alpha were displayed on phage with the vector. Phage-displayed antibodies showed their original antigen-binding activity. An amber codon shifted the vector to express IgG in non-suppressed Escherichia coli. The heavy and light chains of the E. coli-expressed antibodies could be detected through western blotting, and the antigen-binding activity was confirmed using an enzyme-linked immunosorbent assay. Biopanning was carried out with a model phage display antibody library, and the results showed that the novel phage system could be used for antibody library construction and highly efficient antibody screening. The reported system is the first full-length antibody phage display system.

Deep learning identifies morphological features in breast cancer predictive of cancer ERBB2 status and trastuzumab treatment efficacy.

The treatment of patients with ERBB2 (HER2)-positive breast cancer with anti-ERBB2 therapy is based on the detection of ERBB2 gene amplification or protein overexpression. Machine learning (ML) algorithms can predict the amplification of ERBB2 based on tumor morphological features, but it is not known whether ML-derived features can predict survival and efficacy of anti-ERBB2 treatment. In this study, we trained a deep learning model with digital images of hematoxylin-eosin (H&E)-stained formalin-fixed primary breast tumor tissue sections, weakly supervised by ERBB2 gene amplification status. The gene amplification was determined by chromogenic in situ hybridization (CISH). The training data comprised digitized tissue microarray (TMA) samples from 1,047 patients. The correlation between the deep learning-predicted ERBB2 status, which we call H&E-ERBB2 score, and distant disease-free survival (DDFS) was investigated on a fully independent test set, which included whole-slide tumor images from 712 patients with trastuzumab treatment status available. The area under the receiver operating characteristic curve (AUC) in predicting gene amplification in the test sets was 0.70 (95% CI, 0.63-0.77) on 354 TMA samples and 0.67 (95% CI, 0.62-0.71) on 712 whole-slide images. Among patients with ERBB2-positive cancer treated with trastuzumab, those with a higher than the median morphology-based H&E-ERBB2 score derived from machine learning had more favorable DDFS than those with a lower score (hazard ratio [HR] 0.37; 95% CI, 0.15-0.93; P = 0.034). A high H&E-ERBB2 score was associated with unfavorable survival in patients with ERBB2-negative cancer as determined by CISH. ERBB2-associated morphology correlated with the efficacy of adjuvant anti-ERBB2 treatment and can contribute to treatment-predictive information in breast cancer.

Essentially Leading Antibody Production: An Investigation of Amino Acids, Myeloma, and Natural V-Region Signal Peptides in Producing Pertuzumab and Trastuzumab Variants.

Boosting the production of recombinant therapeutic antibodies is crucial in both academic and industry settings. In this work, we investigated the usage of varying signal peptides by antibody V-genes and their roles in recombinant transient production, systematically comparing myeloma and the native signal peptides of both heavy and light chains in 168 antibody permutation variants. We found that amino acids count and types (essential or non-essential) were important factors in a logistic regression equation model for predicting transient co-transfection protein production rates. Deeper analysis revealed that the culture media were often incomplete and that the supplementation of essential amino acids can improve the recombinant protein yield. While these findings are derived from transient HEK293 expression, they also provide insights to the usage of the large repertoire of antibody signal peptides, where by varying the number of specific amino acids in the signal peptides attached to the variable regions, bottlenecks in amino acid availability can be mitigated.

Fully Productive Cell-Free Genetic Code Expansion by Structure-Based Engineering of Methanomethylophilus alvus Pyrrolysyl-tRNA Synthetase.

Pyrrolysyl-tRNA synthetase (PylRS)/tRNAPyl pairs from Methanosarcina mazei and Methanosarcina barkeri are widely used for site-specific incorporations of non-canonical amino acids into proteins (genetic code expansion). In this study, we achieved the full productivity of cell-free protein synthesis for difficult, bulky non-canonical amino acids, such as Nε-((((E)-cyclooct-2-en-1-yl)oxy)carbonyl)-l-lysine (TCO*Lys), by using Methanomethylophilus alvus PylRS. First, based on the crystal structure of M. alvus PylRS, the productivities for various non-canonical amino acids were greatly increased by rational engineering of the amino acid-binding pocket. The productivities were further enhanced by using a much higher concentration of PylRS over that of M. mazei PylRS, or by mutating the outer layer of the amino acid-binding pocket. Thus, we achieved full productivity even for TCO*Lys. The quantity and quality of the cell-free-produced antibody fragment containing TCO*Lys were drastically improved. These results demonstrate the importance of full productivity for the expanded genetic code.

Design Strategy to Create Antibody Mimetics Harbouring Immobilised Complementarity Determining Region Peptides for Practical Use.

Monoclonal antibodies (mAbs) are attractive therapeutics for treating a wide range of human disorders, and bind to the antigen through their complementarity-determining regions (CDRs). Small stable proteins containing structurally retained CDRs are promising alternatives to mAbs. In this report, we present a method to create such proteins, named fluctuation-regulated affinity proteins (FLAPs). Thirteen graft acceptor (GA) sites that efficiently immobilise the grafted peptide structure were initially selected from six small protein scaffolds by computational identification. Five CDR peptides extracted by binding energy calculations from mAbs against breast cancer marker human epithelial growth factor receptor type 2 (HER2) were then grafted to the selected scaffolds. The combination of five CDR peptides and 13 GA sites in six scaffolds revealed that three of the 65 combinations showed specific binding to HER2 with dissociation constants (KD) of 270-350 nM in biolayer interferometry and 24-65 nM in ELISA. The FLAPs specifically detected HER2-overexpressing cancer cells. Thus, the present strategy is a promising and practical method for developing small antibody mimetics.

Application of proteometric approach for identification of functional mutant sites to improve the binding affinity of anticancer biologic trastuzumab with its antigen human epidermal growth factor receptor 2.

The aim of the present study was to develop a linear regression model aiding to a quick scan of the most important sites for mutation of an anticancer biologic trastuzumab. The important sites identified on trastuzumab can be used to carry out site-directed mutagenesis to improve the binding affinity of the drug towards its antigen, human epidermal growth factor receptor 2 (HER2). This will lead to low dosage requirement of the drug for treating cancer patients, which in turn help to cut the cost and combat development of resistance. A quantitative structure-activity relationship (QSAR) model was built by multiple linear regressions using genetic algorithm-based feature selection (GA-MLR) method using 48 dependent variables (dissociation constant Kd ) and 226 independent variables (theoretical descriptors generated using a proteometrics approach). The final QSAR model selected in the study was more on the basis of ability to predict accurately independent test data and generalization ability of the model rather than mere statistical significance of the model. With combined analysis of descriptors presented in final QSAR model and most frequent descriptors pooled from all solution models, it was demonstrated that the modeling procedure was able to bring on the factors important for antigen-antibody interactions with an example of HER2-trastuzumab interaction reported in previous experimental studies. This paper will allow the prediction of the most preferable site to mutate for improving the binding affinity of trastuzumab with HER2 and also will be helpful in selecting most preferable amino acids to substitute in the selected site for mutations. This is the novel report on proteometrics approach with autocorrelation formalism for antibody engineering, which can be extended to other antibody-antigen pairs.

Bridging the Clinical Gap for DNA-Based Antibody Therapy Through Translational Studies in Sheep.

Clinical translation of DNA-based administration of monoclonal antibodies (mAbs) is uncertain due to lack of large animal data. To bridge the clinical gap, we evaluated a panel of novel plasmid DNA (pDNA)-encoded mAbs in 40-70 kg sheep with a clinical intramuscular electroporation protocol. Injection of 4.8 mg of pDNA, encoding ovine anti-human CEA mAb (OVAC), led to peak plasma mAb titers of 300 ng/mL. OVAC remained detectable for 3 months and was boosted by a second pOVAC administration. Hyaluronidase muscle pretreatment increased OVAC concentrations up to 10-fold. These higher plasma titers, however, led to anti-drug antibodies (ADAs) toward the OVAC variable regions, resulting in loss of mAb detection and of adequate redosing. Transient immune suppression avoided ADA formation, with OVAC peaking at 3.5 µg/mL and remaining detectable for 11 months after pOVAC injection. DNA-based delivery of ovine anti-human EGFR mAb (OVAE), identical to OVAC except for the variable regions, preceded by hyaluronidase, allowed for at least three consecutive administrations in an immune-competent sheep, without ADA response. When tripling the pOVAE dose to 15 mg, transient ADAs of limited impact were observed; plasma OVAE peaked at 2.6 µg/mL and was detected up to 7 months. DNA-based anti-HER2 trastuzumab in sheep gave no detectable mAb concentrations despite previous validation in mice, highlighting the limitations of relying on small-rodent data only. In conclusion, our results highlight the potential and caveats of clinical DNA-based antibody therapy, can expedite preclinical and clinical development, and benefit the field of gene transfer as a whole.

Site-Specific Conjugation of Thiol-Reactive Cytotoxic Agents to Nonnative Cysteines of Engineered Monoclonal Antibodies.

Antibody-drug conjugates (ADCs) have been proven to be a successful therapeutic concept, allowing targeted delivery of highly potent active pharmaceutical ingredients (HPAPIs) selectively to tumor tissue. So far, HPAPIs have been mainly attached to the antibody via a chemical reaction of the payload with lysine or cysteine side chains of the antibody backbone. However, these conventional conjugation technologies result in formation of rather heterogeneous products with undesired properties. To overcome the limitations of heterogeneous ADC mixtures, several site-specific conjugation technologies have been developed over the last years. Originally pioneered by scientist from Genentech with their work on THIOMABs, several engineered cysteine mAb ADCs (ECM-ADCs) are now investigated in clinical trials. Here, we describe in detail how to engineer additional cysteines into antibodies and efficiently use them as highly site-specific conjugation sites for HPAPIs.

Engineering Dual Variable Domains for the Generation of Site-Specific Antibody-Drug Conjugates.

Site-specific antibody-drug conjugate (ADC) technologies are highly desirable for the production of therapeutics with well-defined biochemical and pharmacological characteristics. We have developed a strategy to produce site-specific ADCs using a highly reactive lysine residue embedded in a dual-variable-domain (DVD) format. Here we provide protocols for the engineering, expression, and purification of the DVDs used for this strategy. We also provide a protocol for DVD-drug conjugation and describe methods for their biochemical characterization, including a catalytic assay to monitor conjugation efficiency.