The ROR1 antibody-drug conjugate huXBR1-402-G5-PNU effectively targets ROR1+ leukemia.

Antibody-drug conjugates directed against tumor-specific targets have allowed targeted delivery of highly potent chemotherapy to malignant cells while sparing normal cells. Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an oncofetal protein with limited expression on normal adult tissues and is overexpressed on the surface of malignant cells in mantle cell lymphoma, acute lymphocytic leukemia with t(1;19)(q23;p13) translocation, and chronic lymphocytic leukemia. This differential expression makes ROR1 an attractive target for antibody-drug conjugate therapy, especially in malignancies such as mantle cell lymphoma and acute lymphocytic leukemia, in which systemic chemotherapy remains the gold standard.

Partially shielded enzymes capable of processing large protein substrates.

We report the first method of enzyme protection enabling the production of partially shielded enzymes capable of processing substrates as large as proteins. We show that partially shielded sortase retains its transpeptidase activity and can perform bioconjugation reactions on antibodies. Moreover, a partially shielded trypsin is shown to outperform its soluble counterpart in terms of proteolytic kinetics.

Sortase A Enzyme-Mediated Generation of Site-Specifically Conjugated Antibody-Drug Conjugates.

Antibody-drug conjugates (ADCs) are highly potent targeted anticancer therapies. They rely on the linking of a selectively targeting antibody moiety with potent cytotoxic payloads to effect antitumoral activity. In recent years, one focus in the ADC field was to create novel methods for site-specifically conjugating payloads to antibodies.

Characterization of the housekeeping sortase from the human pathogen : first investigation of a class F sortase.

Sortase enzymes play an important role in Gram-positive bacteria. They are responsible for the covalent attachment of proteins to the surface of the bacteria and perform this task via a highly sequence-specific transpeptidation reaction. Since these immobilized proteins are often involved in pathogenicity of Gram-positive bacteria, characterization of this type of enzyme is also of medical relevance.

A novel anti-HER2 anthracycline-based antibody-drug conjugate induces adaptive anti-tumor immunity and potentiates PD-1 blockade in breast cancer.

Increasing evidence suggests that antibody-drug conjugates (ADCs) can enhance anti-tumor immunity and improve clinical outcome. Here, we elucidate the therapeutic efficacy and immune-mediated mechanisms of a novel HER2-targeting ADC bearing a potent anthracycline derivate as payload (T-PNU) in a human HER2-expressing syngeneic breast cancer model resistant to trastuzumab and ado-trastuzumab emtansine. Mechanistically, the anthracycline component of the novel ADC induced immunogenic cell death leading to exposure and secretion of danger-associated molecular signals.

Novel Antibody Drug Conjugates Targeting Tumor-Associated Receptor Tyrosine Kinase ROR2 by Functional Screening of Fully Human Antibody Libraries Using Transpo-mAb Display on Progenitor B Cells.

Receptor tyrosine kinase-like orphan receptor 2 (ROR2) has been identified as a highly relevant tumor-associated antigen in a variety of cancer indications of high unmet medical need, including renal cell carcinoma and osteosarcoma, making it an attractive target for targeted cancer therapy. Here, we describe the discovery of fully human ROR2-specific antibodies and potent antibody drug conjugates (ADCs) derived thereof by combining antibody discovery from immune libraries of human immunoglobulin transgenic animals using the Transpo-mAb mammalian cell-based IgG display platform with functional screening for internalizing antibodies using a secondary ADC assay. The discovery strategy entailed immunization of transgenic mice with the cancer antigen ROR2, harboring transgenic IgH and IgL chain gene loci with limited number of fully human V, D, and J gene segments.

Mining Naïve Rabbit Antibody Repertoires by Phage Display for Monoclonal Antibodies of Therapeutic Utility.

Owing to their high affinities and specificities, rabbit monoclonal antibodies (mAbs) have demonstrated value and potential primarily as basic research and diagnostic reagents, but, in some cases, also as therapeutics. To accelerate access to rabbit mAbs bypassing immunization, we generated a large naïve rabbit antibody repertoire represented by a phage display library encompassing >10 billion independent antibodies in chimeric rabbit/human Fab format and validated it by next-generation sequencing. Panels of rabbit mAbs selected from this library against two emerging cancer targets, ROR1 and ROR2, revealed high diversity, affinity, and specificity.

Generation of an artificial human B cell line test system using Transpo-mAbTM technology to evaluate the therapeutic efficacy of novel antigen-specific fusion proteins.

The antigen-specific targeting of autoreactive B cells via their unique B cell receptors (BCRs) is a novel and promising alternative to the systemic suppression of humoral immunity. We generated and characterized cytolytic fusion proteins based on an existing immunotoxin comprising tetanus toxoid fragment C (TTC) as the targeting component and the modified Pseudomonas aeruginosa exotoxin A (ETA') as the cytotoxic component. The immunotoxin was reconfigured to replace ETA' with either the granzyme B mutant R201K or MAPTau as human effector domains.

Highly Potent, Anthracycline-based Antibody-Drug Conjugates Generated by Enzymatic, Site-specific Conjugation.

Antibody-drug conjugates (ADC) are highly potent and specific antitumor drugs, combining the specific targeting of mAbs with the potency of small-molecule toxic payloads. ADCs generated by conventional chemical conjugation yield heterogeneous mixtures with variable pharmacokinetics, stability, safety, and efficacy profiles. To address these issues, numerous site-specific conjugation technologies are currently being developed allowing the manufacturing of homogeneous ADCs with predetermined drug-to-antibody ratios.

Transpo-mAb display: Transposition-mediated B cell display and functional screening of full-length IgG antibody libraries.

In vitro antibody display and screening technologies geared toward the discovery and engineering of clinically applicable antibodies have evolved from screening artificial antibody formats, powered by microbial display technologies, to screening of natural, full-IgG molecules expressed in mammalian cells to readily yield lead antibodies with favorable properties in production and clinical applications. Here, we report the development and characterization of a novel, next-generation mammalian cell-based antibody display and screening platform called Transpo-mAb Display, offering straightforward and efficient generation of cellular libraries by using non-viral transposition technology to obtain stable antibody expression. Because Transpo-mAb Display uses DNA-transposable vectors with substantial cargo capacity, genomic antibody heavy chain expression constructs can be utilized that undergo the natural switch from membrane bound to secreted antibody expression in B cells by way of alternative splicing of Ig-heavy chain transcripts from the same genomic expression cassette.

Sortase Enzyme-Mediated Generation of Site-Specifically Conjugated Antibody Drug Conjugates with High In Vitro and In Vivo Potency.

Antibody drug conjugates (ADCs) have recently been proven to be highly potent anti-tumor drugs, typically exceeding the efficacy of conventional monoclonal antibodies (mAbs). ADCs are currently produced by chemical conjugation of a small-molecule toxin to the mAb through lysine or cysteine side chains. This leads to heterogeneous mixtures of ADCs in which variable numbers of drugs are conjugated to individual antibodies and in which the site of conjugation cannot be defined.

Retrocyte Display® technology: generation and screening of a high diversity cellular antibody library.

Over the last nearly three decades in vitro display technologies have played an important role in the discovery and optimization of antibodies and other proteins for therapeutic applications. Here we describe the use of retroviral expression technology for the display of full-length IgG on B lineage cells in vitro with a hallmark of a tight and stable genotype to phenotype coupling. We describe the creation of a high-diversity (>1.

Homeostatic and functional analysis of mature B cells in lambda5-deficient mice.

The peripheral B-cell pool is in dynamic equilibrium and is controlled by a variety of factors. The rate of generation of B cells can influence both the composition and size of the peripheral B-cell compartment. Mice deficient for lambda5 gene expression have a block in early B-cell development leading to a markedly reduced number of peripheral B cells.