Beta-lactam-based approach for the chemical programming of aldolase antibody 38C2

Control of the antitumour activity and specificity of CAR T cells via organic adapters covalently tethering the CAR to tumour cells

On-target off-tumour toxicity limits the anticancer applicability of chimaeric antigen receptor (CAR) T cells. Here we show that the tumour-targeting specificity and activity of T cells with a CAR consisting of an antibody with a lysine residue that catalytically forms a reversible covalent bond with a 1,3-diketone hapten can be regulated by the concentration of a small-molecule adapter. This adapter selectively binds to the hapten and to a chosen tumour antigen via a small-molecule binder identified via a DNA-encoded library. The adapter therefore controls the formation of a covalent bond between the catalytic antibody and the hapten, as well as the tethering of the CAR T cells to the tumour cells, and hence the cytotoxicity and specificity of the cytotoxic T cells, as we show in vitro and in mice with prostate cancer xenografts. Such small-molecule switches of T-cell cytotoxicity and specificity via an antigen-independent 'universal' CAR may enhance the control and safety profile of CAR-based cellular immunotherapies.

The Dawn of a New Era: Targeting the "Undruggables" with Antibody-Based Therapeutics

The high selectivity and affinity of antibodies toward their antigens have made them a highly valuable tool in disease therapy, diagnosis, and basic research. A plethora of chemical and genetic approaches have been devised to make antibodies accessible to more "undruggable" targets and equipped with new functions of illustrating or regulating biological processes more precisely. In this Review, in addition to introducing how naked antibodies and various antibody conjugates (such as antibody-drug conjugates, antibody-oligonucleotide conjugates, antibody-enzyme conjugates, etc.) work in therapeutic applications, special attention has been paid to how chemistry tools have helped to optimize the therapeutic outcome (i.e., with enhanced efficacy and reduced side effects) or facilitate the multifunctionalization of antibodies, with a focus on emerging fields such as targeted protein degradation, real-time live-cell imaging, catalytic labeling or decaging with spatiotemporal control as well as the engagement of antibodies inside cells. With advances in modern chemistry and biotechnology, well-designed antibodies and their derivatives via size miniaturization or multifunctionalization together with efficient delivery systems have emerged, which have gradually improved our understanding of important biological processes and paved the way to pursue novel targets for potential treatments of various diseases.

Sculpting a Uniquely Reactive Cysteine Residue for Site-Specific Antibody Conjugation

Catalytic antibody 38C2 and its humanized version h38C2 harbor a uniquely reactive lysine at the bottom of a 11 Å deep pocket that permits site-specific conjugation of β-diketone-, β-lactam-, and heteroaryl methylsulfonyl-functionalized small and large molecules. Various dual variable domain formats pair a tumor-targeting antibody with h38C2 to enable precise, fast, and stable assembly of antibody-drug conjugates (ADCs). Here, we expand the scope of this ADC assembly strategy by mutating h38C2's reactive lysine to a cysteine. X-ray crystallography of this point mutant, h38C2_K99C, confirmed a deeply buried unpaired cysteine. Probing h38C2_K99C with maleimide, monobromomaleimide, and dibromomaleimide derivatives of a fluorophore revealed highly disparate conjugation efficiencies and stabilities. Dibromomaleimide emerged as a suitable electrophile for the precise, fast, efficient, and stable assembly of ADCs with the h38C2_K99C module. Mass spectrometry indicated the presence of a thio-monobromomaleimide linkage which was further supported by in silico docking studies. Using a dibromomaleimide derivative of the highly potent tubulin polymerization inhibitor monomethyl auristatin F, h38C2_K99C-based ADCs were found to be as potent as h38C2-based ADCs and afford a new assembly route for ADCs with single and dual payloads.

Synthesis and Evaluation of a Non-Peptide Small-Molecule Drug Conjugate Targeting Integrin αVβ3

An integrin α_Vβ₃-targeting linear RGD mimetic containing a small-molecule drug conjugate (SMDC) was synthesized by combining the antimitotic agent monomethyl auristatin E (MMAE), an enzymatically cleavable Val-Ala-PABC linker with a linear conjugable RGD mimetic. The structure proposal for the conjugable RGD mimetic was suggested upon the DAD mapping analysis of a previously synthesized small-molecule RGD mimetic array based on a tyrosine scaffold. Therefore, a diversifying strategy was developed as well as a novel method for the partial hydrogenation of pyrimidines in the presence of the hydrogenolytically cleavable Cbz group. The small-molecule RGD mimetics were evaluated in an ELISA-like assay, and the structural relationships were analyzed by DAD mapping revealing activity differences induced by structural changes as visualized in dependence on special structural motifs. This provided a lead structure for generation of an SMDC containing the antimitotic drug MMAE. The resulting SMDC containing a linear RGD mimetic was tested in a cell adhesion and an in vitro cell viability assay in comparison to reference SMDCs containing cRGDfK or cRADfK as the homing device. The linear RGD SMDC and the cRGDfK SMDC inhibited adhesion of α_Vβ₃-positive WM115 cells to vitronectin with IC₅₀ values in the low µM range, while no effect was observed for the α_Vβ₃-negative M21-L cell line. The cRADfK SMDC used as a negative control was about 30-fold less active in the cell adhesion assay than the cRGDfK SMDC. Conversely, both the linear RGD SMDC and the cRGDfK SMDC are about 55-fold less cytotoxic than MMAE against the α_Vβ₃-positive WM115 cell line with IC50 values in the nM range, while the cRADfK SMDC is 150-fold less cytotoxic than MMAE. Hence, integrin binding also influences the antiproliferative activity giving a targeting index of 2.8.

Recent developments in chemical conjugation strategies targeting native amino acids in proteins and their applications in antibody-drug conjugates

Many fields in chemical biology and synthetic biology require effective bioconjugation methods to achieve their desired functions and activities. Among such biomolecule conjugates, antibody-drug conjugates (ADCs) need a linker that provides a stable linkage between cytotoxic drugs and antibodies, whilst conjugating in a biologically benign, fast and selective fashion. This review focuses on how the development of novel organic synthesis can solve the problems of traditional linker technology. The review shall introduce and analyse the current developments in the modification of native amino acids on peptides or proteins and their applicability to ADC linker. Thereafter, the review shall discuss in detail each endogenous amino acid's intrinsic reactivity and selectivity aspects, and address the research effort to construct an ADC using each conjugation method.

A new immunochemical strategy for triple-negative breast cancer therapy

Triple-negative breast cancer (TNBC) is a highly diverse group of malignant neoplasms which tend to have poor outcomes, and the development of new targets and strategies to treat these cancers is sorely needed. Antibody-drug conjugate (ADC) therapy has been shown to be a promising targeted therapy for treating many cancers, but has only rarely been tried in patients with TNBC. A major reason the efficacy of ADC therapy in the setting of TNBC has not been more fully investigated is the lack of appropriate target molecules. In this work we were able to identify an effective TNBC target for use in immunotherapy. We were guided by our previous observation that in some breast cancer patients the protein tropomyosin receptor kinase B cell surface protein (TrkB) had become immunogenic, suggesting that it was somehow sufficiently chemically different enough (presumably by mutation) to escaped immune tolerance. We postulated that this difference might well offer a means for selective targeting by antibodies. We engineered site-specific ADCs using a dual variable domain (DVD) format which combines anti-TrkB antibody with the h38C2 catalytic antibody. This format enables rapid, one-step, and homogeneous conjugation of β-lactam-derivatized drugs. Following conjugation to β-lactam-derivatized monomethyl auristatin F, the TrkB-targeting DVD-ADCs showed potency against multiple breast cancer cell lines, including TNBC cell lines. In addition, our isolation of antibody that specifically recognized the breast cancer-associated mutant form of TrkB, but not the wild type TrkB, indicates the possibility of further refining the selectivity of anti-TrkB DVD-ADCs, which should enhance their therapeutic index. These results confirmed our supposition that TrkB is a potential target for immunotherapy for TNBC, as well as for other cancers with mutated cell surface proteins.

Redirecting cytotoxic T cells with chemically programmed antibodies

T-cell engaging bispecific antibodies (T-biAbs) mediate potent and selective cytotoxicity by combining specificities for target and effector cells in one molecule. Chemically programmed T-biAbs (cp-T-biAbs) are precisely assembled compositions of (i) small molecules that govern cancer cell surface targeting with high affinity and specificity and (ii) antibodies that recruit and activate T cells and equip the small molecule with confined biodistribution and longer circulatory half-life. Conceptually similar to cp-T-biAbs, switchable chimeric antigen receptor T cells (sCAR-Ts) can also be put under the control of small molecules by using a chemically programmed antibody as a bispecific adaptor molecule. As such, cp-T-biAbs and cp-sCAR-Ts can endow small molecules with the power of cancer immunotherapy. We here review the concept of chemically programmed antibodies for recruiting and activating T cells as a promising strategy for broadening the utility of small molecules in cancer therapy.

Chemically Programmable and Switchable CAR-T Therapy

Although macromolecules on cell surfaces are predominantly targeted and drugged with antibodies, they harbor pockets that are only accessible to small molecules and constitutes a rich subset of binding sites with immense potential diagnostic and therapeutic utility. Compared to antibodies, however, small molecules are disadvantaged by a less confined biodistribution, shorter circulatory half-life, and inability to communicate with the immune system. Presented herein is a method that endows small molecules with the ability to recruit and activate chimeric antigen receptor T cells (CAR-Ts). It is based on a CAR-T platform that uses a chemically programmed antibody fragment (cp-Fab) as on/off switch. In proof-of-concept studies, this cp-Fab/CAR-T system targeting folate binding proteins on the cell surface mediated potent and specific eradication of folate-receptor-expressing cancer cells in vitro and in vivo.

Site-Specific Antibody-Drug Conjugates in Triple Variable Domain Fab Format

The interest in replacing the conventional immunoglobulin G (IgG) format of monoclonal antibodies (mAbs) and antibody–drug conjugates (ADCs) with alternative antibody and antibody-like scaffolds reflects a need to expand their therapeutic utility and potency while retaining their exquisite specificity, affinity, and low intrinsic toxicity. For example, in the therapy of solid malignancies, the limited tumor tissue penetration and distribution of ADCs in IgG format mitigates a uniform distribution of the cytotoxic payload. Here, we report triple variable domain Fab (TVD–Fab) as a new format that affords the site-specific and stable generation of monovalent ADCs without the Fc domain and a drug-to-antibody ratio (DAR) of 2. TVD–Fabs harbor three variable fragment (Fv) domains: one for tumor targeting and two for the fast, efficient, precise, and stable conjugation of two cargos via uniquely reactive lysine residues. The biochemical and in vitro cytotoxicity properties of a HER2-targeting TVD–Fab before and after conjugation to a tubulin inhibitor were validated. In vivo, the TVD–Fab antibody carrier revealed a circulatory half-life of 13.3 ± 2.5 h and deeper tumor tissue distribution compared to our previously reported dual variable domain (DVD)–IgG1 format. Taken together, the TVD–Fab format merits further investigations as an antibody carrier of site-specific ADCs targeting solid malignancies.

Conventional and Chemically Programmed Asymmetric Bispecific Antibodies Targeting Folate Receptor 1

T-cell engaging bispecific antibodies (biAbs) can mediate potent and specific tumor cell eradication in liquid cancers. Substantial effort has been invested in expanding this concept to solid cancers. To explore their utility in the treatment of ovarian cancer, we built a set of asymmetric biAbs in IgG1-like format that bind CD3 on T cells with a conventional scFv arm and folate receptor 1 (FOLR1) on ovarian cancer cells with a conventional or a chemically programmed Fab arm. For avidity engineering, we also built an asymmetric biAb format with a tandem Fab arm. We show that both conventional and chemically programmed CD3 × FOLR1 biAbs exert specific in vitro and in vivo cytotoxicity toward FOLR1-expressing ovarian cancer cells by recruiting and activating T cells. While the conventional T-cell engaging biAb was curative in an aggressive mouse model of human ovarian cancer, the potency of the chemically programmed biAb was significantly boosted by avidity engineering. Both conventional and chemically programmed CD3 × FOLR1 biAbs warrant further investigation for ovarian cancer immunotherapy.

Photoactivatable Fluorogenic Labeling via Turn-On "Click-Like" Nitroso-Diene Bioorthogonal Reaction

Fluorogenic labeling enables imaging cellular molecules of interest with minimal background. This process is accompanied with the notable increase of the quantum yield of fluorophore, thus minimizing the background signals from unactivated profluorophores. Herein, the development of a highly efficient and bioorthogonal nitroso-based Diels-Alder fluorogenic reaction is presented and its usefulness is validated as effective and controllable in fluorescent probes and live-cell labeling strategies for dynamic cellular imaging. It is demonstrated that nitroso-based cycloaddition is an efficient fluorogenic labeling tool through experiments of further UV-activatable fluorescent labeling on proteins and live cells. The ability of tuning the fluorescence of labeled proteins by UV-irradiation enables selective activation of proteins of interest in a particular cell compartment at a given time point, while leaving the remaining labeled molecules untouched.

Harnessing a catalytic lysine residue for the one-step preparation of homogeneous antibody-drug conjugates

Current strategies to produce homogeneous antibody-drug conjugates (ADCs) rely on mutations or inefficient conjugation chemistries. Here we present a strategy to produce site-specific ADCs using a highly reactive natural buried lysine embedded in a dual variable domain (DVD) format. This approach is mutation free and drug conjugation proceeds rapidly at neutral pH in a single step without removing any charges. The conjugation chemistry is highly robust, enabling the use of crude DVD for ADC preparation. In addition, this strategy affords the ability to precisely monitor the efficiency of drug conjugation with a catalytic assay. ADCs targeting HER2 were prepared and demonstrated to be highly potent and specific in vitro and in vivo. Furthermore, the modular DVD platform was used to prepare potent and specific ADCs targeting CD138 and CD79B, two clinically established targets overexpressed in multiple myeloma and non-Hodgkin lymphoma, respectively.

Current strategies for producing antibody-drug conjugates often rely on inefficient conjugation chemistry or on generating mutations in the antibody sequence. Here the authors demonstrate a mutation-free, single-step conjugation platform utilizing a buried lysine residue.

Chemically Programmed Bispecific Antibody Targeting Legumain Protease and αvβ3 Integrin Mediates Strong Antitumor Effects

A chemically programmed bispecific antibody (cp-bsAb) that targeted cysteine protease legumain and αvβ3 integrin has been prepared using the aldolase antibody chemical programming (AACP) strategy. In vitro evaluation of the anti-legumain, anti-integrin cp-bsAb and its comparison with cpAbs targeting either integrin or legumain have shown that the former possesses superior functions, including receptor binding and inhibitory effects on cell proliferation as well as capillary tube formation, among all three cpAbs. The anti-legumain, anti-integrin cp-bsAb also inhibited growth of primary tumor more effectively than either anti-legumain or anti-integrin cpAb as observed in the MDA-MB-231 human breast cancer mouse model. The AACP-based cp-bsAb, which contains a generic aldolase antibody, can also serve as a suitable platform for combination therapy, where two equally potent compounds are used to target extracellular receptors.

Developments and recent advancements in the field of endogenous amino acid selective bond forming reactions for bioconjugation

Bioconjugation methodologies have proven to play a central enabling role in the recent development of biotherapeutics and chemical biology approaches. Recent endeavours in these fields shed light on unprecedented chemical challenges to attain bioselectivity, biocompatibility, and biostability required by modern applications. In this review the current developments in various techniques of selective bond forming reactions of proteins and peptides were highlighted. The utility of each endogenous amino acid-selective conjugation methodology in the fields of biology and protein science has been surveyed with emphasis on the most relevant among reported transformations; selectivity and practical use have been discussed.

N-Sulfonyl-β-lactam hapten as an effective labeling reagent for aldolase mAb

Utilization of chemically programmed antibodies (cpAbs) is regarded to be one of the most efficient methods for the development of therapeutic systems. cpAbs can extend the half-life of programming reagents, activate immune systems via the Fc region of antibodies and achieve universal vaccination by attaching varieties of small, programmed molecules. In the current study, we aimed to develop a novel labeling reagent for the preparation of cpAbs and found that N-sulfonyl-β-lactams (NSBLs) were optimal. NSBL can be synthesized from readily available 4-(bromomethyl)benzenesulfonyl chloride via few simple manipulations and can label the aldolase monoclonal antibody (mAb) 84G3, which could not be labeled effectively by the conventional labeling reagent, N-acyl-β-lactam (NABL). We also demonstrated that the conjugate, which consists of mAb 84G3 and an NSBL bearing a biotin moiety, maintained strong binding activity to streptavidin. In addition, the stability assay of NSBL revealed that NSBLs can tolerate aqueous media without significant decomposition over 24h.

Chemically programmed antibodies

Due to their unlimited chemical diversity, small molecules can rival monoclonal antibodies (mAbs) with respect to specificity and affinity for target molecules. However, key pharmacological properties of mAbs remain unmatched by small molecules. Chemical programming strategies have been developed for site-specific and covalent conjugation of small molecules to mAbs with unique reactivity centers. In addition to blending favorable features of small molecules and mAbs, chemically programmed antibodies (cpAbs) are economically attractive because they utilize the same mAb for an almost unlimited number of target molecule specificities, reducing manufacturing costs and shortening drug discovery and development time. Preclinical studies and clinical trials have begun to demonstrate the broad utility of cpAbs for the treatment and prevention of human diseases.

Preparation and activities of macromolecule conjugates of the CCR5 antagonist Maraviroc

CCR5 antagonists are among the most advanced approaches in HIV therapy and may also be relevant to treatment of graft-versus-host disease and Staphylococcus aureus infection. To expand the potential of the only approved CCR5 antagonist, Maraviroc, we studied derivatives that would enable functional linkage of Maraviroc to long-lived carriers. Through targeted synthesis, we discovered an effective linkage site on Maraviroc and demonstrate the potential of these derivatives to prepare potent chemically programmed antibodies and PEGylated derivatives. The resulting compounds effectively neutralized a variety of HIV-1 isolates. Both chemically programmed antibody and PEGylation approaches extend the neutralization activity of serum circulating Maraviroc. Derivation of a successful conjugation strategy for Maraviroc should further enable its use in chemically programmed vaccines, novel bispecific antibodies, and topical microbicides.

Chemically Programmed Antibodies AS HIV-1 Attachment Inhibitors

Herein we describe the design and application of two small-molecule anti-HIV compounds for the creation of chemically programmed antibodies. N-acyl-β-lactam derivatives of two previously described molecules BMS-378806 and BMS-488043 that inhibit the interaction between HIV-1 gp120 and T-cells were synthesized and used to program the binding activity of aldolase antibody 38C2. Discovery of a successful linkage site to BMS-488043 allowed for the synthesis of chemically programmed antibodies with affinity for HIV-1 gp120 and potent HIV-1 neutralization activity. Derivation of a successful conjugation strategy for this family of HIV-1 entry inhibitors enables its application in chemically programmed antibodies and vaccines and may facilitate the development of novel bispecific antibodies and topical microbicides.

Antibody conjugation approach enhances breadth and potency of neutralization of anti-HIV-1 antibodies and CD4-IgG

Broadly neutralizing antibodies PG9 and PG16 effectively neutralize 70 to 80% of circulating HIV-1 isolates. In this study, the neutralization abilities of PG9 and PG16 were further enhanced by bioconjugation with aplaviroc, a small-molecule inhibitor of virus entry into host cells. A novel air-stable diazonium hexafluorophosphate reagent that allows for rapid, tyrosine-selective functionalization of proteins and antibodies under mild conditions was used to prepare a series of aplaviroc-conjugated antibodies, including b12, 2G12, PG9, PG16, and CD4-IgG. The conjugated antibodies blocked HIV-1 entry through two mechanisms: by binding to the virus itself and by blocking the CCR5 receptor on host cells. Chemical modification did not significantly alter the potency of the parent antibodies against nonresistant HIV-1 strains. Conjugation did not alter the pharmacokinetics of a model IgG in blood. The PG9-aplaviroc conjugate was tested against a panel of 117 HIV-1 strains and was found to neutralize 100% of the viruses. PG9-aplaviroc conjugate IC50s were lower than those of PG9 in neutralization studies of 36 of the 117 HIV-1 strains. These results support this new approach to bispecific antibodies and offer a potential new strategy for combining HIV-1 therapies.

Protocols for lysine conjugation

Currently, the most widely used chemical methodology for the conjugation of drugs to monoclonal antibodies involves either lysine or cysteine residues. In this chapter, several methods for the preparation of antibody-drug conjugates (ADCs) through conjugation of drugs to solvent-exposed ε-amino groups of lysine residues are described. These methods apply to various cytotoxic agents, both tubulin binders and DNA-targeting agents and different types of linkers, cleavable or not, peptidic or disulfide-based, for example.

A chemically programmed antibody is a long-lasting and potent inhibitor of influenza neuraminidase

Programming an anti-flu strategy: A new and potent neuraminidase inhibitor that maintains long-term systemic exposure of an antibody and the therapeutic activity of the neuraminadase inhibitor zanamivir has been created. This strategy could provide a promising new class of influenza A drugs for therapy and prophylaxis, and validates enzyme inhibitors as programming agents in synthetic immunology.

Regio- and diastereoselective synthesis of β-lactam-triazole hybrids via Passerini/CuAAC sequence

Passerini (P-3CR) and Passerini-Smiles reactions were investigated in azetidine-2,3-diones, affording the corresponding 3,3-disubstituted-β-lactams with complete diastereoselectivity in high yields. The study has been carried out using different isocyanides, carboxylic acids, and phenols showing the scope of both reactions. In addition, the regioselective synthesis of highly functionalized β-lactam-triazole hybrids has been developed via a Passerini/CuAAC sequence. Interestingly, the use of dialkynes/diazides or trialkynes/triazides as linkers in the CuAAC step has allowed the synthesis of C(2) and C(3) symmetric β-lactam-triazole hybrids, respectively.

Antibody-recruiting molecules: an emerging paradigm for engaging immune function in treating human disease

Synthetic immunology, the development of synthetic systems capable of modulating and/or manipulating immunological functions, represents an emerging field of research with manifold possibilities. One focus of this area has been to create low molecular weight synthetic species, called antibody-recruiting molecules (ARMs), which are capable of enhancing antibody binding to disease-relevant cells or viruses, thus leading to their immune-mediated clearance. This article provides a thorough discussion of contributions in this area, beginning with the history of small-molecule-based technologies for modulating antibody recognition, followed by a systematic review of the various applications of ARM-based strategies. Thus, we describe ARMs capable of targeting cancer, bacteria, and viral pathogens, along with some of the scientific discoveries that have resulted from their development. Research in this area underscores the many exciting possibilities at the interface of organic chemistry and immunobiology and is positioned to advance both basic and clinical science in the years to come.

Chemoenzymatic methods for site-specific protein modification

In the past decade, numerous chemical technologies have been developed to allow the site-specific post-translational modification of proteins. Traditionally covalent chemical protein modification has been accomplished by the attachment of synthetic groups to nucleophilic amino acids on protein surfaces. These chemistries, however, are rarely sufficiently selective to distinguish one residue within a literal sea of chemical functionality. One solution to this problem is to introduce a unique chemical handle into the target protein that is orthogonal to the remainder of the proteome. In practice, this handle can be a novel peptide sequence, which forms a 'tag' that is selectively and irreversibly modified by enzymes. Furthermore, if the enzymes can tolerate substrate analogs, it becomes possible to engineer chemically modified proteins in a site-specific fashion. This review details the significant progress in creating techniques for the chemoenzymatic generation of protein-small molecule constructs and provides examples of novel applications of these methodologies.

Chemically modified antibodies as diagnostic imaging agents

Notable new applications of antibodies for imaging involve genetically extracting the essential molecular recognition properties of an antibody, and in some cases enhancing them by mutation, before protein expression. The classic paradigm of intravenous administration of a labeled antibody to image not only its target but also its metabolism can be improved on. Protocols involving molecular targeting with an engineered unlabeled protein derived from an antibody, followed by capture of a small probe molecule that provides a signal, are being developed to a high level of utility. This is accompanied by new strategies for probe capture such as irreversible binding, incorporation of engineered enzyme active sites, and antibody-ligand systems that generate a signal only upon binding or uptake.

Molecularly defined antibody conjugation through a selenocysteine interface

Antibody conjugates have broad utility in basic, preclinical, and clinical applications. Conventional antibody conjugation through the amine group of lysine or the thiol group of cysteine residues yields heterogeneous products of undefined stoichiometry and considerable batch-to-batch variability. To preserve the two hallmarks of the antibody molecule, precision and predictability, methods that enable site-specific antibody conjugation are in high demand. On the basis of a mammalian cell expression system, we describe the utilization of the 21st natural amino acid selenocysteine for the generation of IgG and Fab molecules with unique nucleophilic reactivity that affords site-specific conjugation to electrophilic derivatives of biotin, fluorescein, and poly(ethylene glycol). The resulting antibody conjugates were found to fully retain their antigen binding capability and, in the case of IgG, the ability to mediate effector functions. Gain of function was demonstrated in vitro and in vivo. While these antibody conjugates are relevant for a variety of proteomic, diagnostic, and therapeutic applications, they also constitute a proof of principle for the generation of molecularly defined antibody-drug conjugates and radioimmunoconjugates. Compared to other site-specific antibody conjugation methods, selenocysteine interface technology (i) only involves a minor modification at the C-terminus that does not interfere with disulfide bridges, (ii) does not require activation, and (iii) generates unique 1:1 stoichiometries of biological and chemical components. Collectively, our method affords the generation of highly defined antibody conjugates with broad utility from proteomic applications to therapeutic intervention.

Multiple catalytic aldolase antibodies suitable for chemical programming

Chemical programming of nine murine antibodies with catalytic aldolase activity was examined using compounds, equipped with diketone or pro-vinyl ketone linkers that inhibit integrin adhesion receptor functions. The results showed that most Abs were programmed using the diketone compounds in a manner similar to previously reported catalytic antibody 38C2. On the other hand, only those antibodies, which catalyzed the retro aldol reaction of the pro-vinyl ketone linkers efficiently, were programmed. Conjugated to integrin targeting compounds, at least three new antibodies, including 84G3, 85H6, and 90G8, exhibited high specific binding to human tumor cells expressing integrin alpha(v)beta(3.).

An efficient chemical approach to bispecific antibodies and antibodies of high valency

Irreversible chemical programming of monoclonal aldolase antibody (mAb) 38C2 has been accomplished with beta-lactam equipped mono- and bifunctional targeting modules, including a cyclic-RGD peptide linked to either the peptide (D-Lys(6))-LHRH or another cyclic RGD unit and a small-molecule integrin inhibitor SCS-873 conjugated to (D-Lys(6))LHRH. We also prepared monofunctional targeting modules containing either cyclic RGD or (D-Lys(6))-LHRH peptides. Binding of the chemically programmed antibodies to integrin receptors alpha(v)beta(3) and alpha(v)beta(5) and to the luteinizing hormone releasing hormone receptor were evaluated. The bifunctional and bivalent c-RGD/LHRH and SCS-783/LHRH, the monofunctional and tetravalent c-RGD/c-RGD, and the monofunctional bivalent c-RGD chemically programmed antibodies bound specifically to the isolated integrin receptor proteins as well as to integrins expressed on human melanoma M-21 cells. c-RGD/LHRH, SCS-783/LHRH, and LHRH chemically programmed antibodies bound specifically to the LHRH receptors expressed on human ovarian cancer cells. This approach provides an efficient, versatile, and economically viable route to high-valency therapeutic antibodies that target defined combinations of specific receptors. Additionally, this approach should be applicable to chemically programmed vaccines.

Instant immunity through chemically programmable vaccination and covalent self-assembly

The ability to instantly create a state of immunity as achieved in the passive transfer of hyperimmune globulin has had a tremendous impact on public health. Unlike passive immunization, active immunization, which is the foundation of vaccinology, is an anticipatory strategy with inherent limitations. Here we show that elements of active and passive immunization can be combined to create an effective chemistry-driven approach to vaccinology. Reactive immunization was used to create a reservoir of covalent polyclonal antibodies in 3 mouse strains that were subsequently engrafted with syngeneic CT26 colon or B16F10 melanoma tumors. Upon administration of designed integrin alpha(v)beta(3) and alpha(v)beta(5) adapter ligands, the induced covalent polyclonal antibodies self-assembled with the adapter ligands and the animals mounted an instant, chemically programmed, polyclonal response against the implanted tumors. Significant therapeutic responses were observed without recourse to adjuvant therapy. The chemically programmed immune responses were driven by antibody-dependent cellular cytotoxicity and complement-directed cytotoxicity. We suggest that this type of chemistry-driven approach to vaccinology is underexplored and may provide routes to vaccines to protect against diseases that have proven intractable to biology-driven vaccine approaches.