Small molecule drug activity in melanoma models may be dramatically enhanced with an antibody effector

The Chemistry of Creating Chemically Programmed Antibodies (cPAbs): Site-Specific Bioconjugation of Small Molecules

Small-molecule drugs have been employed for years as therapeutics in the pharmaceutical industry. However, small-molecule drugs typically have short in vivo half-lives which is one of the largest impediments to the success of many potentially valuable pharmacologically active small molecules. The undesirable pharmacokinetics and pharmacology associated with some small molecules have led to the development of a new class of bioconjugates known as chemically programmed antibodies (cPAbs). cPAbs are bioconjugates in which antibodies are used to augment small molecules with effector functions and prolonged pharmacokinetic profiles, where the pharmacophore of the small molecule is harnessed for target binding and therefore biological targeting. Many different small molecules can be conjugated to large proteins such as full monoclonal antibodies (IgG), fragment crystallizable regions (Fc), or fragment antigen binding regions (Fab). In order to successfully and site-specifically conjugate small molecules to any class of antibodies (IgG, Fc, or Fab), the molecules must be derivatized with a functional group for ease of conjugation without altering the pharmacology of the small molecules. In this Review, we summarize the different synthetic or biological methods that have been employed to produce cPAbs. These unique chemistries have potential to be applied to other fields of antibody modification such as antibody drug conjugates, radioimmunoconjugates, and fluorophore-tagged antibodies.

Chemically Programmed Bispecific Antibodies in Diabody Format

Chemically programmed bispecific antibodies (biAbs) endow target cell-binding small molecules with the ability to recruit and activate effector cells of the immune system. Here we report a platform of chemically programmed biAbs aimed at redirecting cytotoxic T cells to eliminate cancer cells. Two different antibody technologies were merged together to make a novel chemically programmed biAb. This was achieved by combining the humanized anti-hapten monoclonal antibody (mAb) h38C2 with the humanized anti-human CD3 mAb v9 in a clinically investigated diabody format known as Dual-Affinity Re-Targeting (DART). We show that h38C2 × v9 DARTs can readily be equipped with tumor-targeting hapten-derivatized small molecules without causing a systemic response harming healthy tissues. As a proof of concept, we chemically programmed h38C2 × v9 with hapten-folate and demonstrated its selectivity and potency against folate receptor 1 (FOLR1)-expressing ovarian cancer cells in vitro and in vivo Unlike conventional biAbs, chemically programmed biAbs in DART format are highly modular with broad utility in terms of both target and effector cell engagement. Most importantly, they provide tumor-targeting compounds access to the power of cancer immunotherapy.

Fc-Small Molecule Antibody Mimetics

Antibody therapeutics are a promising drug class due to their high specificity and favorable pharmacokinetics. While there are many methods for the development of antibodies specific to disease associated antigens, selecting antibodies against functional epitopes with high specificity and affinity can be difficult for certain epitopes. We describe a generalizable method for synthesizing antibody mimetics by site specifically conjugating small molecules (with high affinity and specificity to disease associated antigens) to an Fc fragment to develop drugs with the benefits of an antibody. As a proof of concept, an E269pAcPhe Fc antibody Fc fragment was produced and subsequently site-specifically labeled with a linker-modified folic acid compound to generate an Fc-folic acid antibody-mimetic. This was chosen as the model system because the high-affinity folate receptor FR-α is highly expressed in a number of cancer types including breast and ovarian cancer. The specificity of the Fc-folic acid conjugate was assessed via flowcytometry with the folate-receptor positive breast cancer cell line MDA-MB-231 by measuring Fc-folic acid binding in both the absence and presence of an excess of folic acid. Fc-small molecule conjugates could be developed into a unique class of antibody-like therapeutics.

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.

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.

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.

Synthesis and evaluation of the aldolase antibody-derived chemical-antibodies targeting α5β1 integrin

Integrin α5β1 is an important therapeutic target that can be inhibited using an aldolase antibody (Ab)-derived chemical-Ab (chem-Ab) for the treatment of multiple human diseases, including cancers. A fairly optimized anti-integrin α5β1 chem-Ab 38C2-4e was obtained using an in situ convergent chemical programming (CP) approach, which minimized the time and effort needed to develop a chem-Ab. Multiple Ab-programming agents (PAs) 4a-e could be prepared rapidly using the Cu-catalyzed alkyne-azide coupling (Cu-AAC) reaction of an α5β1 inhibitor 2 with multiple linkers 3a-e, either before or after conjugating the linkers into Ab 38C2 binding sites. In these two-steps processes, the products after step 1 can be used in the next step without performing an extensive purification or analysis of the Ab-PAs or Ab-linker conjugates affording chem-Abs 38C2-(4a-e). Flow cytometry assay was used to determine the binding of the chem-Abs to U87 human glioblastoma cells expressing α5β1 integrin and identify 38C2-3e as the strongest binder. Further studies revealed that 38C2-3e strongly inhibited proliferation of U87 cells and tube formation of HUVEC in the matrigel assay, as well as tumor growth and metastasis of 4T1 cells in vivo.

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.

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.

Reprogramming urokinase into an antibody-recruiting anticancer agent

Synthetic compounds for controlling or creating human immunity have the potential to revolutionize disease treatment. Motivated by challenges in this arena, we report herein a strategy to target metastatic cancer cells for immune-mediated destruction by targeting the urokinase-type plasminogen activator receptor (uPAR). Urokinase-type plasminogen activator (uPA) and uPAR are overexpressed on the surfaces of a wide range of invasive cancer cells and are believed to contribute substantially to the migratory propensities of these cells. The key component of our approach is an antibody-recruiting molecule that targets the urokinase receptor (ARM-U). This bifunctional construct is formed by selectively, covalently attaching an antibody-binding small molecule to the active site of the urokinase enzyme. We demonstrate that ARM-U is capable of directing antibodies to the surfaces of target cancer cells and mediating both antibody-dependent cellular phagocytosis (ADCP) and antibody-dependent cellular cytotoxicity (ADCC) against multiple human cancer cell lines. We believe that the reported strategy has the potential to inform novel treatment options for a variety of deadly, invasive cancers.

RAM, an RGDS analog, exerts potent anti-melanoma effects in vitro and in vivo

Peptides containing the RGD sequence are under continuous investigation given their ability to control cell adhesion and apoptosis. Since small peptides are quickly metabolized and degraded in vivo, developing analogs resistant to serum-induced degradation is a challenging task. RGD analogs developed so far are known as molecules mostly inhibiting cell adhesion; this feature may reduce cell proliferation and tumor development but may not induce regression of tumors or metastases already formed. In the current study, carried out in melanoma in vitro and in vivo models, we show that RAM, an RGD-non-peptide Analog-Molecule, strongly inhibits cells adhesion onto plastic, vitronectin, fibronectin, laminin and von Willebrand Factor while it does not inhibit cell adhesion onto collagen IV, similarly to the RGDS template peptide. It also strongly inhibits in vitro cell proliferation, migration and DNA-synthesis, increases melanoma cells apoptosis and reduces survivin expression. All such effects were observed in collagen IV seeded cells, therefore are most likely independent from the anti adhesive properties. Further, RAM is more stable than the template RGDS; in fact it maintains its anti-proliferation and anti-adhesion effects after long serum exposure while RGDS almost completely loses its effects upon serum exposure. In a mouse metastatic melanoma in vivo model, increasing doses of RAM significantly reduce up to about 80% lung metastases development, while comparable doses of RGDS are less potent. In conclusion these data show that RAM is a potent inhibitor of melanoma growth in vitro, strongly reduces melanoma metastases development in vivo and represents a novel candidate for further in vivo investigations in the cancer treatment field.

Chemically programmed antibodies targeting multiple alpha(v) integrins and their effects on tumor-related functions in vitro

Integrins αvβ3 and αvβ6 are highly expressed on tumor cells and/or by the tumor vasculature of many human cancers, and represent promising targets for anticancer therapy. Novel chemically programmed antibodies (cpAbs) targeting these integrins were prepared using the catalytic aldolase Antibody (Ab) programming strategy. The effects of the cpAbs on cellular functions related to tumor progression were examined in vitro using tumor cell lines and their cognate integrin ligands, fibronectin and osteopontin. The inhibitory functions of the conjugates and their specificity were examined based on interference with cell-cell and cell-ligand interactions related to tumor progression. Cell binding analyses of the anti-integrin cpAbs revealed high affinity for tumor cells that overexpressed αvβ3 and αvβ6 integrins, and weak interactions with αvβ1 and αvβ8 integrins, in vitro. Functional analyses demonstrated that the cpAbs strongly inhibited cell-cell interactions through osteopontin binding, and they had little or no immediate effects on cell viability and proliferation. On the basis of these characteristics, the cpAbs are likely to have a broad range of activities in vivo, as they can target and antagonize one or multiple αv integrins expressed on tumors and tumor vasculatures. Presumably, these conjugates may inhibit the establishment of metastastatic tumors in distant organs through interfering with cell adhesion more effectively than antibodies or compounds targeting one integrin only. These anti-integrin cpAbs may also provide useful reagents to study combined effect of multiple αv integrins on cellular functions in vitro, on pathologies, including tumor angiogenesis, fibrosis, and epithelial cancers, in vivo.

Rapamycin inhibits lung metastasis of B16 melanoma cells through down-regulating alphav integrin expression and up-regulating apoptosis signaling

Currently available data indicate the potential application of rapamycin and its analogues in the clinic as anticancer therapeutic agents through inhibiting tumor cell growth and tumor angiogenesis. However, whether rapamycin can directly suppress tumor metastasis remains unclear. In the present study, we demonstrated that rapamycin treatment results in reduced formation of metastatic nodules in the lung by B16 cells. This is due to two mechanisms. First, the expression of alphav integrin is down-regulated by rapamycin treatment, and subsequently, the phosphorylation of focal adhesion kinase (FAK) is reduced. Second, rapamycin promotes apoptosis by up-regulating the proapoptotic molecules Bid and Bax and down-regulating Bcl-xL. Blocking the apoptosis pathway by pan-caspase inhibitor zVAD partially reversed the suppression of rapamycin in B16 metastasis. Interestingly, rapamycin up-regulates Bax and Bid in B16 cells via the S6K1 pathway and down-regulates the expression of alphav integrin via other pathway(s). In addition, our data showed that autophagy was not involved in the mechanisms of rapamycin-mediated metastasis suppression. Our findings demonstrate a potential anti-metastatic effect of rapamycin via down-regulating alphav integrin expression and up-regulating apoptosis signaling, suggesting that rapamycin might be worthy of clinical evaluation as an antimetastatic agent.

An antibody-recruiting small molecule that targets HIV gp120

HIV/AIDS is a global pandemic for which new treatment strategies are desperately needed. We have designed a novel small molecule, designated as ARM-H, that has the potential to interfere with HIV survival through two mechanisms: (1) by recruiting antibodies to gp120-expressing virus particles and infected human cells, thus enhancing their uptake and destruction by the human immune system, and (2) by binding the viral glycoprotein gp120, inhibiting its interaction with the human protein CD4 and preventing virus entry. Here we demonstrate that ARM-H is capable of simultaneously binding gp120, a component of the Env surface viral glycoprotein (found on the surface of both HIV and virus-infected cells) and anti-2,4-dinitrophenyl antibodies (already present in the human bloodstream). The ternary complex formed between the antibody, ARM-H, and gp120 is immunologically active and leads to the complement-mediated destruction of Env-expressing cells. Furthermore, ARM-H prevents virus entry into human T-cells and should therefore be capable of inhibiting virus replication through two mutually reinforcing mechanisms (inhibition of virus entry and antibody-mediated killing). These studies demonstrate the viable anti-HIV activity of antibody-recruiting small molecules and have the potential to initiate novel paradigms in HIV treatment.

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.

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

Irreversible chemical programming of monoclonal aldolase antibody (mAb) 38C2 has been accomplished with beta-lactam-equipped targeting modules. A model study was first performed with beta-lactam conjugated to biotin. This conjugate efficiently and selectively modified the catalytic site lysine (LysH93) of mAb 38C2. We then conjugated a beta-lactam to a cyclic-RGD peptide to chemically program mAb 38C2 to target integrin receptors alpha(v)beta(3) and alpha(v)beta(5). The chemically programmed antibody bound specifically to the isolated integrin receptor proteins as well as the integrins expressed on human melanoma cells. This approach provides an efficient and versatile solution to irreversible chemical programming of aldolase antibodies.

Application of a trifunctional reactive linker for the construction of antibody-drug hybrid conjugates

A flexible, trifunctional poly(ethylene glycol)-succinamide-Lysine-Lysine-maleimide (PEG-SU-Lys-Lys-mal) linker was employed to simultaneously allow biotin tagging and cell-surface targeting through an integrin alpha(4)beta(1)-binding peptidomimetic that was regiospecifically conjugated to an IgG1-derived Fc fragment with an engineered C-terminal selenocysteine residue. The resulting antibody derivative mediates Fc receptor binding by virtue of the Fc protein and selectively targets cancer cells expressing human integrin alpha(4)beta(1). The PEG-SU-Lys-Lys-mal linker may have general utility as an organic tether for the construction of antibody-drug conjugates.

Preparation of integrin alpha(v)beta3-targeting Ab 38C2 constructs

This protocol describes the preparation of Ab constructs using agents that target cells expressing integrins alpha(v)beta3 and alpha(v)beta5, and the monoclonal aldolase Ab 38C2. The targeting agents are equipped with a diketone or vinylketone linker, and selectively react through the reactive Lys residues in the Ab binding sites to form 38C2 conjugates or chemically programmed 38C2 (i.e., cp38C2). The targeting agent possessing a diketone linker reacts with the Lys residues forming an enaminone derivative. By contrast, the vinylketone linker is used as the corresponding acetone adduct (i.e., a pro-vinylketone linker), and this pro-adapter undergoes a 38C2-catalyzed retro-aldol reaction to produce the vinylketone linker, which forms a Michael-type adduct with the Lys residues. The Ab construct formation is achieved in <1 h for the diketone compounds at ambient temperature, and in 2-16 h using the pro-vinylketone linker at 37 degrees C. The 38C2 constructs are retargeted to cells over-expressing integrins, and are potential candidates for immunotherapy.

Bifunctional ligands that target cells displaying the alpha v beta3 integrin

Strategies to eliminate tumor cells have long been sought. We envisioned that a small molecule could be used to decorate the offending cells with immunogenic carbohydrates and evoke an immune response. To this end, we describe the synthesis of bifunctional ligands possessing two functional motifs: one binds a cell-surface protein and the other binds a naturally occurring human antibody. Our conjugates combine an RGD-based peptidomimetic, to target cells displaying the alpha v beta3 integrin, with the carbohydrate antigen galactosyl-alpha(1-3)galactose [Galalpha(1-3)Gal or alpha-Gal]. To generate such bifunctional ligands, we designed and synthesized RGD mimetics 1 b and 2 c, which possess a free amino group for modification. These compounds were used to generate bifunctional derivatives 1 c and 2 d, with dimethyl squarate serving as the linchpin; thus, our synthetic approach is modular. To evaluate the binding of our peptidomimetics to the target alpha v beta3-displaying cells, we implemented a cell-adhesion assay. Results from this assay indicate that the designed, small-molecule ligands inhibit alpha v beta3-dependent cell adhesion. Additionally, our most effective bifunctional ligand exhibits a high degree of selectivity (4000-fold) for alpha v beta3 over the related alpha v beta5 integrin, a result that augurs its utility in specific cell targeting. Finally, we demonstrate that the bifunctional ligands can bind to alpha v beta3-positive cells and recruit human anti-Gal antibodies. These results indicate that both the integrin-binding and the anti-Gal-binding moieties can act simultaneously. Bifunctional conjugates of this type can facilitate the development of new methods for targeting cancer cells by exploiting endogenous antibodies. We anticipate that our modifiable alpha v beta3-binding ligands will be valuable in a variety of applications, including drug delivery and tumor targeting.

Synthesis of the next-generation therapeutic antibodies that combine cell targeting and antibody-catalyzed prodrug activation

An obstacle in the utilization of catalytic Abs for selective prodrug activation in cancer therapy has been systemic tumor targeting. Here we report the generation of catalytic Abs that effectively target tumor cells with undiminished prodrug activation capability. Ab conjugates were prepared by covalent conjugation of an integrin alpha(v)beta(3)-targeting antagonist to catalytic Ab 38C2 through either sulfide groups of cysteine residues generated by reduction of the disulfide bridges in the hinge region or surface lysine residues not involved in the catalytic activity. Using flow cytometry, the Ab conjugates were shown to bind efficiently to integrin alpha(v)beta(3)-expressing human breast cancer cells. The Ab conjugates also retained the retro-aldol activity of their parental catalytic Ab 38C2, as measured by methodol and doxorubicin (dox) prodrug activation. Complementing these Ab conjugates, an evolved set of dox prodrugs was designed and synthesized. Dox prodrugs that showed higher stability and lower toxicity were evaluated both in the presence and absence of the integrin alpha(v)beta(3)-targeting 38C2 conjugates for cell-killing efficacy by using human breast cancer cells. Our study reveals that cell targeting and prodrug activation capabilities can be efficiently combined for selective chemotherapy with novel dox prodrugs.

Chemically programmed antibodies: endothelin receptor targeting CovX-Bodies

Aryl sulfonamide-based endothelin antagonists were synthesized and covalently linked to the reactive lysine of the m38C2 antibody to create a series of CovX-Bodies. These chemically programmed antibodies behaved as potent endothelin receptor antagonists in vitro and had antitumor efficacy in a prostate cancer xenograft model which, on a molar basis, far exceeded the activity of the parent small molecule.

Breaking the one antibody-one target axiom

Studies at the interface of chemistry and biology have allowed us to develop an immunotherapeutic approach called chemically programmed antibodies (cpAbs), which combines the merits of traditional small-molecule drug design with immunotherapy. In this approach, a catalytic antibody catalyzes the covalent conjugation of a small molecule or peptide to the active site of the antibody, effectively recruiting the binding specificity of the conjugated molecule to the antibody. In essence, this technology provides the tools for breaking the "one antibody-one target axiom" of immunochemistry. Our studies in this area have focused on using the chemistry of the well studied aldolase catalytic antibodies of which mAb 38C2 is a member. Previously, we explored reversible assembly of cpAbs available through diketone chemistry. In this article, we explore a unique proadapter assembly strategy wherein an antibody 38C2-catalyzed transformation unveils a reactive tag that then reacts to form a stable covalent bond with the antibody. An integrin alpha(v)beta 3 antagonist was synthesized with the designed proadapter and studied using human breast cancer cell lines MDA-MB-231 and MDA-MB-435. We demonstrate that this approach allows for (i) the effective assembly of cpAbs in vitro and in vivo, (ii) selective retargeting of 38C2 to integrin alpha(v)beta 3 expressing breast cancer cell lines, (iii) intracellular delivery of cpAbs into cells, (iv) dramatically increased circulatory half-life, and (v) substantial enhancement of the therapeutic effect over the peptidomimetic itself in animal models of breast cancer metastasis. We believe that this technology possesses potential for the treatment and diagnosis of disease.