Targeted Fcγ Receptor (FcγR)-mediated Clearance by a Biparatopic Bispecific Antibody

Abstract

Soluble ligands have commonly been targeted by antibody therapeutics for cancers and other diseases. Although monoclonal antibodies targeting such ligands can block their interactions with their cognate receptors, they can also significantly increase the half-life of their ligands by FcRn-mediated antibody recycling, thereby evading ligand renal clearance and requiring increasingly high antibody doses to neutralize the increasing pool of target. To overcome this issue, we generated a bispecific/biparatopic antibody (BiSAb) that targets two different epitopes on IL-6 to block IL-6-mediated signaling. The BiSAb formed large immune complexes with IL-6 that can bind Fcγ receptors on phagocytic cells and are rapidly internalized. In addition, rapid clearance of the BiSAb·IL-6 complex was observed in mice while the parental antibodies prolonged the serum half-life of IL-6. Intravital imaging of the liver in mice confirmed that the rapid clearance of these large immune complexes was associated with Fcγ receptor-dependent binding to Kupffer cells in the liver. The approach described here provides a general strategy for therapeutic antibodies with the ability to not only neutralize but also actively drive clearance of their soluble antigens.

Development and activities, including immunocomplex formation, of biparatopic antibodies and alternative scaffold proteins

“…Most other BpAbs can bridge between antigen molecules to form intermolecular crosslinks (BpAb1-2 in Fig. 1), which can sometimes result in the formation of huge immunocomplexes, as has been reported for BpAbs that are more than bivalent (e.g., tetravalent) [8,9,33]. Intermolecular crosslinks can be formed with both soluble proteins and membrane proteins.…”

“…For monomeric alternative scaffold proteins and fragment antibodies, generation of biparatopic proteins is an extremely efficient way of increasing avidity. Thus, a large number of these proteins have been developed as biparatopic agents [12,[16][17][18][19][20][21][22][23][24][25][26][27][28][29], which is not as important with conventional antibodies because they are already bivalent [5,7,8,10,[30][31][32][33][34][35][36][37].…”

“…Intermolecular crosslinks can be formed with both soluble proteins and membrane proteins. For soluble secreted proteins, the formation of large BpAb immunocomplexes enables clearance of the antigen from the blood, mediated by Fcγ receptors [30,33]. For membrane proteins, immunocomplex formation can lock the proteins in an immunologically active state and enhance effector effects, such as the complement-dependent cytotoxicity of tumor-targeting antibodies [26].…”

Sensitivity of Kupffer cells and liver sinusoidal endothelial cells to ricin toxin and ricin toxin–Ab complexes

“…The liver plays an essential role in detoxification and clearance of xenobiotics from circulation . Nonparenchymal cells also function in immune surveillance and uptake of SIC . In this report, we investigated the capacity of anti‐RTA and anti‐RTB MAbs, individually and in combination, to protect primary mouse KCs and LSECs from ricin toxin‐induced death.…”

Expanding the Boundaries of Biotherapeutics with Bispecific Antibodies

“…The molecule induced FAP-binding-dependent hyperclustering and led to more potent apoptosis [ 214 ]. In the case of soluble proteins, bispecific antibodies can be used to promote the formation of higher complexes that are cleared from circulation more efficiently, as it has been shown using biparatopic antibodies against insulin-like growth factor 2 (IGF-2) [ 176 ] and interleukin 6 [ 177 ]. Although no formal comparison between formats has been published yet for this application, it is likely that formats that are multivalent for each specificity (as is the case of the two examples cited), with high flexibility in each binding domain, will bind multiple targets simultaneously and efficiently, leading to the formation of a high-order complex.…”