PK modulation of haptenylated peptides via non-covalent antibody complexation

Complexation of drug and hapten-conjugated aptamer with universal hapten antibody for pancreatic cancer treatment

Owing to a lack of reliable markers and therapeutic targets, pancreatic ductal adenocarcinoma (PDAC) remains the most lethal malignant tumor despite numerous therapeutic advances. In this study, we utilized cell-SELEX to isolate a DNA aptamer recognizing the natural conformation of the target on the cell surface. PAp7T8, an aptamer optimized by size and chemical modification, exhibited specific targeting to pancreatic cancer cells and orthotopic xenograft pancreatic tumors. To confer therapeutic functions to the aptamer, we adopted a drug-conjugated oligobody (DOligobody) strategy. Monomethyl auristatin E was used as a cytotoxic drug, digoxigenin acted as a hapten, and the humanized anti-digoxigenin antibody served as a universal carrier of the aptamer. The resulting PAp7T8-DOligobody showed extended in vivo half-life and markedly inhibited tumor growth in an orthotopic pancreatic cancer xenograft model without causing significant toxicity. Therefore, PAp7T8-DOligobody represents a promising novel therapeutic delivery platform for PDAC.

Synthetic chemical ligands and cognate antibodies for biorthogonal drug targeting and cell engineering

A vast range of biomedical applications relies on the specificity of interactions between an antigen and its cognate receptor or antibody. This specificity can be highest when said antigen is a non-natural (synthetic) molecule introduced into a biological setting as a bio-orthogonal ligand. This review aims to present the development of this methodology from the early discovery of haptens a century ago to the recent clinical trials. We discuss such methodologies as antibody recruitment, artificial internalizing receptors and chemically induced dimerization, present the use of chimeric receptors and/or bispecific antibodies to achieve drug targeting and transcytosis, and illustrate how these platforms most impressively found use in the engineering of therapeutic cells such as the chimeric antigen receptor cells. This review aims to be of interest to a broad scientific audience and to spur the development of synthetic artificial ligands for biomedical applications.

Transcytosis of payloads that are non-covalently complexed to bispecific antibodies across the hCMEC/D3 blood-brain barrier model

A transcellular shuttle system was generated for the delivery of non-covalently linked payloads across blood-brain barrier (BBB) endothelial cells. Transcytosis-enabling shuttles are composed of bispecific antibodies (bsAbs) that simultaneously bind transferrin receptor (TfR) and haptens such as digoxigenin or biocytinamide. Haptenylated payloads are attached to these vehicles via non-covalent hapten-antibody complexation. This enables targeting to and internalization into human BBB-derived microvascular endothelial hCMEC/D3 cells. In contrast to other shuttles, this system does not require special affinities or formats of their TfR-binding moieties for transcytosis and subsequent release. Non-covalent payload complexation to bsAb is flexible and robust, works for a multitude of payloads and enables separation of payloads from shuttles during transcytosis. Released payloads can enter the brain without connected bsAb entities, minimizing potential interference with distribution or functionality. Intracellular separation of shuttle and payload and recycling to cell surfaces may also enable recharging of the cell-bound BBB shuttle with payload for subsequent (merry-go-round) transport cycles.

Engineered hapten-binding antibody derivatives for modulation of pharmacokinetic properties of small molecules and targeted payload delivery

Hapten‐binding antibodies have for more than 50 years played a pivotal role in immunology, paving the way to antibody generation (as haptens are very important and robust immunogens), to antibody characterization (as the first structures generated more than 40 years ago were those of hapten binders), and enabled and expanded antibody engineering technologies. The latter field of engineered antibodies evolved over many years and many steps resulting in recombinant humanized or human‐derived antibody derivatives in multiple formats. Today, hapten‐binding antibodies are applied not only as reagents and tools (where they still play an important part) but evolved also to engineered targeting and pretargeting vehicles for disease diagnosis and therapy. Here we describe recent applications of hapten‐binding antibodies and of engineered mono‐ and bispecific hapten‐binding antibody derivatives. We have designed and applied these molecules for the modulation of the pharmacokinetic properties of small compounds or peptides. They are also integrated as additional binding entities into bispecific antibody formats. Here they serve as non‐covalent or covalent coupling modules to haptenylated compounds, to enable targeted payload delivery to disease tissues or cells.

Antilipidemic effects and gene expression profiling of the glycosaminoglycans from cricket in rats on a high fat diet

Glycosaminoglycan (GAG) from cricket (Gryllus bimaculatus) was studied as a potential health supplement. Antiatherosclerotic and antilipidemic effects of the GAG of G. bimaculatus (GbG, 5 or 10 mg/kg) were investigated in 15-week old Wistar rats treated with GbG for over a month. GbG produced a meaningful anti-edema effect with inhibition of C-reactive protein (CRP). Also, the weights of abdominal and epididymidal fat were also reduced in conjunction with a mild increase in body weight. Furthermore, the sero-biochemical parameters showed an antihyperlipidemic effect with decreased levels of phospholipid, AST, ALT, total cholesterol and glucose in a dose-dependent manner. In addition anticoagulant and antithrombotic effects were seen: platelet, thrombin time, prothrombin time and Factor I were increased with GbG treatment. Furthermore, the GbG treated rat group (at 10 mg/kg) compared to control, showed that 588 genes (test/control ratio >2.0) including lipocalin 2 (Lcn2) and alpha 2-macroglobulin (A2 m) were up-regulated, and 569 genes (test/control ratio >0.5) including stearoyl-coenzyme A desaturase 1 (Scd1) were down-regulated. Based on these results, GbG could potentially prevent or treat fatty liver or hyperlipidemia in rats on a high-fat diet.

TriFabs--Trivalent IgG-Shaped Bispecific Antibody Derivatives: Design, Generation, Characterization and Application for Targeted Payload Delivery

TriFabs are IgG-shaped bispecific antibodies (bsAbs) composed of two regular Fab arms fused via flexible linker peptides to one asymmetric third Fab-sized binding module. This third module replaces the IgG Fc region and is composed of the variable region of the heavy chain (VH) fused to CH3 with “knob”-mutations, and the variable region of the light chain (VL) fused to CH3 with matching “holes”. The hinge region does not contain disulfides to facilitate antigen access to the third binding site. To compensate for the loss of hinge-disulfides between heavy chains, CH3 knob-hole heterodimers are linked by S354C-Y349C disulphides, and VH and VL of the stem region may be linked via VH44C-VL100C disulphides. TriFabs which bind one antigen bivalent in the same manner as IgGs and the second antigen monovalent “in between” these Fabs can be applied to simultaneously engage two antigens, or for targeted delivery of small and large (fluorescent or cytotoxic) payloads.

A Fab-Selective Immunoglobulin-Binding Domain from Streptococcal Protein G with Improved Half-Life Extension Properties

Background

Half-life extension strategies have gained increasing interest to improve the pharmacokinetic and pharmacodynamic properties of protein therapeutics. Recently, we established an immunoglobulin-binding domain (IgBD) from streptococcal protein G (SpG_C3) as module for half-life extension. SpG_C3 is capable of binding to the Fc region as well as the CH1 domain of Fab arms under neutral and acidic conditions.

Methodology/Principal Findings

Using site-directed mutagenesis, we generated a Fab-selective mutant (SpG_C3Fab) to avoid possible interference with the FcRn-mediated recycling process and improved its affinity for mouse and human IgG by site-directed mutagenesis and phage display selections. In mice, this affinity-improved mutant (SpG_C3FabRR) conferred prolonged plasma half-lives compared with SpG_C3Fab when fused to small recombinant antibody fragments, such as single-chain Fv (scFv) and bispecific single-chain diabody (scDb). Hence, the SpG_C3FabRR domain seems to be a suitable fusion partner for the half-life extension of small recombinant therapeutics.

Conclusions/Significance

The half-life extension properties of SpG_C3 can be retained by restricting binding to the Fab fragment of serum immunoglobulins and can be improved by increasing binding activity. The modified SpG_C3 module should be suitable to extend the half-life of therapeutic proteins and, thus to improve therapeutic activity.

Hapten-directed spontaneous disulfide shuffling: a universal technology for site-directed covalent coupling of payloads to antibodies

Humanized hapten-binding IgGs were designed with an accessible cysteine close to their binding pockets, for specific covalent payload attachment. Individual analyses of known structures of digoxigenin (Dig)- and fluorescein (Fluo) binding antibodies and a new structure of a biotin (Biot)-binder, revealed a “universal” coupling position (52⁺²) in proximity to binding pockets but without contributing to hapten interactions. Payloads that carry a free thiol are positioned on the antibody and covalently linked to it via disulfides. Covalent coupling is achieved and driven toward complete (95–100%) payload occupancy by spontaneous redox shuffling between antibody and payload. Attachment at the universal position works with different haptens, antibodies, and payloads. Examples are the haptens Fluo, Dig, and Biot combined with various fluorescent or peptidic payloads. Disulfide-bonded covalent antibody-payload complexes do not dissociate in vitro and in vivo. Coupling requires the designed cysteine and matching payload thiol because payload or antibody without the Cys/thiol are not linked (<5% nonspecific coupling). Hapten-mediated positioning is necessary as hapten-thiol-payload is only coupled to antibodies that bind matching haptens. Covalent complexes are more stable in vivo than noncovalent counterparts because digoxigeninylated or biotinylated fluorescent payloads without disulfide-linkage are cleared more rapidly in mice (approximately 50% reduced 48 hour serum levels) compared with their covalently linked counterparts. The coupling technology is applicable to many haptens and hapten binding antibodies (confirmed by automated analyses of the structures of 140 additional hapten binding antibodies) and can be applied to modulate the pharmacokinetics of small compounds or peptides. It is also suitable to link payloads in a reduction-releasable manner to tumor- or tissue-targeting delivery vehicles.—Dengl, S., Hoffmann, E., Grote, M., Wagner, C., Mundigl, O., Georges, G., Thorey, I., Stubenrauch, K.-G., Bujotzek, A., Josel, H.-P., Dziadek, S., Benz, J., Brinkmann, U. Hapten-directed spontaneous disulfide shuffling: a universal technology for site-directed covalent coupling of payloads to antibodies.