Site-specific C-terminal dinitrophenylation to reconstitute the antibody Fc functions for nanobodies

Multivalent Rhamnose-Modified EGFR-Targeting Nanobody Gains Enhanced Innate Fc Effector Immunity and Overcomes Cetuximab Resistance via Recruitment of Endogenous Antibodies

Cetuximab resistance is a significant challenge in cancer treatment, requiring the development of novel therapeutic strategies. In this study, a series of multivalent rhamnose (Rha)-modified nanobody conjugates are synthesized and their antitumor activities and their potential to overcome cetuximab resistance are investigated. Structure-activity relationship studies reveal that the multivalent conjugate D5, bearing sixteen Rha haptens, elicits the most potent innate fragment crystallizable (Fc) effector immunity in vitro and exhibits an excellent in vivo pharmacokinetics by recruiting endogenous antibodies. Notably, it is found that the optimal conjugate D5 represents a novel entity capable of reversing cetuximab-resistance induced by serine protease (PRSS). Moreover, in a xenograft mouse model, conjugate D5 exhibits significantly improved antitumor efficacy compared to unmodified nanobodies and cetuximab. The findings suggest that Rha-Nanobody (Nb) conjugates hold promise as a novel therapeutic strategy for the treatment of cetuximab-resistant tumors by enhancing the innate Fc effector immunity and enhancing the recruitment of endogenous antibodies to promote cancer cell clearance by innate immune cells.

Reprogramming tumor-associated macrophages by a dually targeted milk exosome system as a potent monotherapy for cancer

Tumor-associated macrophages (TAMs) play a key role in inducing an immunosuppressive tumor microenvironment (TME) and cancer immune escape. We previously revealed that PDL1 (a key immune checkpoint) was upregulated in TAMs and induced M2 polarization, highlighting PDL1 in TAMs as a promising cancer therapeutic target. In this study, we developed an engineered milk exosome (mExo) system decorated with M2pep (an M2 macrophage binding peptide) and 7D12 (an anti-EGFR nanobody) (7D12-mExo-M2pep-siPDL1) to specifically deliver siPDL1 into M2 TAMs. A series of in vitro and in vivo assays showed that the dually targeted engineered mExos efficiently delivered siPDL1 into M2 TAMs and repolarized them into M1 macrophages, restoring CD8+ T cell immune activity and remodeling TME. Importantly, systemically administered 7D12-mExo-M2pep-siPDL1 showed efficient single-agent antitumor activity, resulting in nearly 90% tumor growth inhibition in a mouse model of orthotopic epidermal growth factor receptor (EGFR) cancer. Collectively, our study indicates that PDL1 is a promising target for TAM-based cancer immunotherapy, and our engineered mExo-based nanomedicine represents a novel tool for specifically targeting M2 TAMs, distinguishing this novel therapeutic method from other TAM-targeting therapies and highlighting its promising clinical potential.

Anti-CTLA-4 nanobody as a promising approach in cancer immunotherapy

Cancer is one of the most common diseases and causes of death worldwide. Since common treatment approaches do not yield acceptable results in many patients, developing innovative strategies for effective treatment is necessary. Immunotherapy is one of the promising approaches that has been highly regarded for preventing tumor recurrence and new metastases. Meanwhile, inhibiting immune checkpoints is one of the most attractive methods of cancer immunotherapy. Cytotoxic T lymphocyte-associated protein-4 (CTLA-4) is an essential immune molecule that plays a vital role in cell cycle modulation, regulation of T cell proliferation, and cytokine production. This molecule is classically expressed by stimulated T cells. Inhibition of overexpression of immune checkpoints such as CTLA-4 receptors has been confirmed as an effective strategy. In cancer immunotherapy, immune checkpoint-blocking drugs can be enhanced with nanobodies that target immune checkpoint molecules. Nanobodies are derived from the variable domain of heavy antibody chains. These small protein fragments have evolved entirely without a light chain and can be used as a powerful tool in imaging and treating diseases with their unique structure. They have a low molecular weight, which makes them smaller than conventional antibodies while still being able to bind to specific antigens. In addition to low molecular weight, specific binding to targets, resistance to temperature, pH, and enzymes, high ability to penetrate tumor tissues, and low toxicity make nanobodies an ideal approach to overcome the disadvantages of monoclonal antibody-based immunotherapy. In this article, while reviewing the cellular and molecular functions of CTLA-4, the structure and mechanisms of nanobodies' activity, and their delivery methods, we will explain the advantages and challenges of using nanobodies, emphasizing immunotherapy treatments based on anti-CTLA-4 nanobodies.

Revolutionizing antiviral therapy with nanobodies: Generation and prospects

As the world continues to grapple with infectious diseases, scientists are constantly searching for effective ways to combat these deadly pathogens. One promising avenue of research is the use of nanobodies as neutralization agents. These small proteins, derived from camelid antibodies, have several unique advantages over traditional antibodies, including their small size. Nanobodies are much smaller than conventional antibodies, typically weighing in at around 15 kDa compared to the 150 kDa of a typical human antibody. This small size allows them to penetrate into tight spaces that larger molecules cannot reach, such as the crevices on the surface of viruses or bacteria. This makes them highly effective at neutralizing viruses by binding to and blocking their key functional sites. In this mini-review we discuss the construction approaches of nanobodies, and some methods to increase the half-life of nanobodies. Moreover, we discuss Nanobodies and their therapeutic potential for infectious agents.

Harnessing sortase A transpeptidation for advanced targeted therapeutics and vaccine engineering

The engineering of potent prophylactic and therapeutic complexes has always required careful protein modification techniques with seamless capabilities. In this light, methods that favor unobstructed multivalent targeting and correct antigen presentations remain essential and very demanding. Sortase A (SrtA) transpeptidation has exhibited these attributes in various settings over the years. However, its applications for engineering avidity-inspired therapeutics and potent vaccines have yet to be significantly noticed, especially in this era where active targeting and multivalent nanomedications are in great demand. This review briefly presents the SrtA enzyme and its associated transpeptidation activity and describes interesting sortase-mediated protein engineering and chemistry approaches for achieving multivalent therapeutic and antigenic responses. The review further highlights advanced applications in targeted delivery systems, multivalent therapeutics, adoptive cellular therapy, and vaccine engineering. These innovations show the potential of sortase-mediated techniques in facilitating the development of simple plug-and-play nanomedicine technologies against recalcitrant diseases and pandemics such as cancer and viral infections.

SnoopLigase Enables Highly Efficient Generation of C-C-Linked Bispecific Nanobodies Targeting TNF-α and IL-17A

Bispecific antibodies (bis-Nbs) have been extensively developed since the concept was devised over the decades. Taking advantage of the superior characteristics of nanobodies, bis-Nbs exhibit an emerging tendency to become the new generation of research and diagnostic tools. Traditional strategies to connect the homo- or heterogeneous monomers are commonly applied, but there are still technical issues to generate the bispecific molecules as efficiently as designed. Here, we utilize SnoopLigase to directly tether the C terminus (C-C) of the tagged nanobodies against tumor necrosis factor-α (TNF-α) and interleukin-17A (IL-17A). Under optimal conditions, the yield of C-C-linked bis-Nbs can reach as high as 70% due to the existence of SnoopLigase. The prepared bis-Nbs possessed similar or even higher affinity as the monomers and significantly inhibited the proliferation and migration of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) induced by TNF-α and IL-17A. This study provides an innovative route for using SnoopLigase to realize a highly efficient generation of C-C-linked bis-Nbs. The approach can be applied to different and multicomponent systems for their potential applications in disease diagnosis and treatment.

Repurposing the Pentameric B-subunit of Shiga Toxin for Gb3-targeted Immunotherapy of Colorectal Cancer by Rhamnose Conjugation

Globotriaosylceramide (Gb3 or CD77) is a tumor-associated carbohydrate antigen implicated in several types of cancer that serves as a potential cancer marker for developing target-specific diagnosis and therapy. However, the development of Gb3-targeted therapeutics has been challenging due to its carbohydrate nature. In the present work, taking advantage of its natural pentamer architecture and Gb3-specific targeting of shiga toxin B subunit (StxB), we constructed a pentameric antibody recruiting chimera by site-specifically conjugating StxB with the rhamnose hapten for immunotherapy of colorectal cancer. The Sortase A-catalyzed enzymatic tethering of rhamnose moieties to the C terminus of Stx1B and Stx2B had very moderate effect on their pentamer architectures and thus the resultant conjugates maintained the potent ability to bind to Gb3 antigen both immobilized on an assay plate and expressed on colorectal cancer cells. All StxB-rhamnose constructs were capable of efficiently mediating the binding of rhamnose antibodies onto HT29 colorectal cancer cells, which was further shown to be able to induce cancer cell lysis by eliciting potent antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) in vitro. Finally, the best StxB-rhamnose conjugate, i.e. 1B-3R, was confirmed to be able to inhibit the colorectal tumor growth using a HT29-derived xenograft murine model. Taken together, our data demonstrated the potential of repurposing StxB as an excellent multivalent scaffold for developing Gb3-targeted biotherapeutics and StxB-rhamnose conjugates might be promising candidates for targeted immunotherapy of Gb3-related colorectal cancer.

β-Galactosidase-dependent metabolic glycoengineering of tumor cells for imaging and immunotherapy

A β-Gal-dependent metabolic glycoengineering strategy was developed for tumor cell-selective surface glycan imaging with high efficacy. Combined with an antibody-recruiting strategy, targeted immunotherapy was achieved successfully based on this strategy.

Chemical Synthesis of Antibody-Hapten Conjugates Capable of Recruiting the Endogenous Antibody to Magnify the Fc Effector Immunity of Antibody for Cancer Immunotherapy

Monoclonal antibodies (mAbs) with enhanced effector functions in cancer immunotherapy, such as complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC), could improve the clinical performance. Here, we develop an mAb-hapten conjugate strategy to augment the mAb effector functions with the engagement of endogenous antibodies. An "off-the-shelf" mAb, rituximab, is site-specifically conjugated with the rhamnose (Rha) hapten to generate rituximab-Rha conjugates. The octopus-like conjugates could recruit anti-Rha antibodies onto the cancer cell surface and further form an immune complex that is able to provide multivalent Fc domains to interact with immune cells or complement protein C1q, leading to magnified ADCC and CDC simultaneously. One optimal conjugate R2 with PEG2 as a linker exhibits the most potent in vitro cancer cell killing activity and significant in vivo antitumor efficacy in a xenograft model. This is a general and cost-effective approach to generate mAb with improved effector functions that may have broad applications.

Fully synthetic Mincle-dependent self-adjuvanting cancer vaccines elicit robust humoral and T cell-dependent immune responses and protect mice from tumor development

A new strategy based on a macrophage-inducible C-type lectin (Mincle) agonist was established to construct synthetic cancer vaccines. Using sialyl-Tn (STn) as a model antigen, four conjugates with the Mincle agonist as a built-in adjuvant were designed and synthesized through a facile and efficient method. All conjugates could induce BMDMs to produce inflammatory cytokines in a Mincle-dependent manner and were found to elicit robust humoral and T cell-dependent immune responses alone in mice. The corresponding antibodies could recognize, bind and exhibit complement-dependent cytotoxicity to STn-positive cancer cells, leading to tumor cell lysis. Moreover, all conjugates could effectively inhibit tumor growth and prolong the mice survival time in vivo, with therapeutic effects better than STn-CRM197/Al. Notably, compared to conventional glycoprotein conjugate vaccines, these fully synthetic conjugate vaccines do not cause "epitope suppression." Mincle ligands thus hold great potential as a platform for the development of new vaccine carriers with self-adjuvanting properties for cancer treatment. Preliminary structure-activity relationship analysis shows that a vaccine containing one STn antigen carried by vizantin exhibits the best efficacy, providing support for further optimization and additional investigation into Mincle agonists as the carrier of self-adjuvanting cancer vaccines.

Nanobody-Engineered Natural Killer Cell Conjugates for Solid Tumor Adoptive Immunotherapy

Cancer immunotherapy based on natural killer (NK) cells is demonstrated to be a promising strategy. However, NK cells are deficient in ligands that target specific tumors, resulting in limited antitumor efficacy. Here, a glycoengineering approach to imitate the chimeric antigen receptor strategy and decorate NK cells with nanobodies to promote NK-based immunotherapy in solid tumors is proposed. Nanobody 7D12, which specifically recognizes the human epidermal growth factor receptor (EGFR) that is overexpressed on many solid tumors, is coupled to the chemically synthesized DBCO-PEG₄ -GGG-NH₂ by sortase A-mediated ligation to generate DBCO-7D12. The NK92MI cells bearing azide groups are then equipped with DBCO-7D12 via bioorthogonal click chemistry. The resultant 7D12-NK92MI cells exhibit high specificity and affinity for EGFR-overexpressing tumor cells in vitro and in vivo by the 7D12-EGFR interaction, causing increased cytokine secretion to more effectively kill EGFR-positive tumor cells, but not EGFR-negative cancer cells. Importantly, the 7D12-NK92MI cells also show a wide anticancer spectrum and extensive tumor penetration. Furthermore, mouse experiments reveal that 7D12-NK92MI treatment achieves excellent therapeutic efficacy and outstanding safety. The authors' works provide a cell modification strategy using specific protein ligands without genetic manipulation and present a potential novel method for cancer-targeted immunotherapy by NK cells.

Dinitrophenol-mediated modulation of an anti-PD-L1 VHH for Fc-dependent effector functions and prolonged serum half-life

Single-domain antibodies, VHHs or nanobodies, represent a promising set of alternatives to conventional therapeutic antibodies, gaining substantial attention in the field of cancer immunotherapy. However, inherent drawbacks of nanobodies such as fast clearance from blood circulation and lack of immune effector functions often led to unsatisfactory therapeutic efficacy. We previously reported that dinitrophenyl modification of an anti-EGFR VHH conferred Fc-dependent immune effector functions and elongated serum half-life on it through recruiting of hapten antibodies, resulting in improved immunotherapy efficacy in vivo. In the present work, we further tested the versatility of this approach in the case of an anti-PD-L1 blockade VHH (KN035). Site-specific dinitrophenyl conjugation did not impair the binding capacity of KN035 portion to PD-L1, but indirectly restored its immune effector functions, manifested by the observed antibody dependent cell-mediated cytotoxicity, antibody-dependent cellular phagocytosis and complement-dependent cytotoxicity against PD-L1 positive tumor cells. Significant delay of blood clearance of dinitrophenylated KN035 was evidenced by the prolonged half-life of ca. 22 h. This approach, using small hapten molecule conjugation, loaded additional antibody-mediated tumor killing mechanisms to PD-L1 blockade VHH and therefore improved efficacy is anticipated in the future in vivo therapeutic studies. Thus, our results underscore the power of this versatile approach for achieving desirable properties of VHH-based or similar therapeutics.

Dinitrophenol-Hyaluronan Conjugates as Multivalent Antibody-Recruiting Glycopolymers for Targeted Cancer Immunotherapy

Multivalent antibody-recruiting glycopolymers (MARGs) composed of hyaluronic acid (HA) grafted with multiple copies of dinitrophenol (DNP) were developed for targeted cancer immunotherapy. Structure-activity studies demonstrated that the MARGs were able to specifically recognize CD44-positive cancer cells and displayed remarkable antibody-recruiting capacities and tumor cell killing activities dependent on the introduced multivalent effect and the length of PEG linker. One of the MARGs, HA-[PEG₃ -DNP]₈ , showed the best capacity for clustering anti-DNP antibodies onto CD44-positive cancer cells and displayed potent in vitro anti-cancer activity by triggering complement dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC). Moreover, we found that HA-[PEG₃ -DNP]₈ significantly inhibited the xenograft tumor growth of Babl/c nude mice bearing triple negative breast cancer cells, while it did not cause detectable histological cytotoxicity. Given the easy access of this type of natural glycopolymer and the practical synthesis approach, these MARGs provide promising immunotherapeutics for cancer immunotherapy.

Exendin 4-Hapten Conjugate Capable of Binding with Endogenous Antibodies for Peptide Half-life Extension and Exerting Long-Acting Hypoglycemic Activity

Hapten-specific endogenous antibodies are naturally occurring antibodies present in human blood. Herein, we investigated a new strategy in which small-molecule haptens were utilized as naturally occurring antibody binders for peptide half-life extension. The glucagon-like peptide 1 receptor agonist exendin 4 was site-specifically functionalized with the dinitrophenyl (DNP) hapten at the C-terminus via sortase A-mediated ligation. The resulting Ex4-DNP conjugates retained GLP-1 receptor activation potency in vitro and had a similar in vivo acute glucose-lowering effect comparable to that of native Ex4. Pharmacokinetic studies and hypoglycemic duration tests demonstrated that the Ex4-DNP conjugates displayed significantly elongated half-lives and improved long-acting antidiabetic activity in the presence of endogenous anti-DNP antibodies. In chronic treatment studies, once-daily administration of optimal conjugate 7 demonstrated more beneficial effects without prominent toxicity compared with Ex4. This strategy provides a new approach and represents an alternative to the well-established peptide-Fc fusion strategy to improve the peptide half-life and the therapeutic efficacy.

Universal endogenous antibody recruiting nanobodies capable of triggering immune effectors for targeted cancer immunotherapy

Developing monoclonal antibodies (mAbs) for cancer immunotherapy is expensive and complicated. Nanobodies are small antibodies possessing favorable pharmacological properties compared with mAbs, but have limited anticancer efficacy due to the lack of an Fc region and poor pharmacokinetics. In this context, engineered universal endogenous antibody-recruiting nanobodies (UEAR Nbs), as a general and cost-effective approach, were developed to generate functional antibody-like nanobodies that could recapitulate the Fc biological functions for cancer immunotherapy. The UEAR Nbs, composed of the IgG binding domain and nanobody, were recombinantly expressed in E. coli and could recruit endogenous IgGs onto the cancer cell surface and trigger potent immune responses to kill cancer cells in vitro. Moreover, it was proved that UEAR Nbs displayed significantly improved half-lives in vivo. The in vivo antitumor efficacy of UEAR Nbs was demonstrated in a murine model using EGFR positive triple-negative breast cancer (TNBC).

Rhamnose modified bovine serum albumin as a carrier protein promotes the immune response against sTn antigen

Rhamnose and sTn antigen were co-conjugated to bovine serum albumin (BSA) for cancer vaccine development. The immune responses against sTn have been significantly augmented with the involvement of Rha-specific antibodies to enhance antigen uptake.