Therapeutic control of B cell activation via recruitment of Fcgamma receptor IIb (CD32B) inhibitory function with a novel bispecific antibody scaffold.
OBJECTIVE
To exploit the physiologic Fcgamma receptor IIb (CD32B) inhibitory coupling mechanism to control B cell activation by constructing a novel bispecific diabody scaffold, termed a dual-affinity retargeting (DART) molecule, for therapeutic applications.


METHODS
DART molecules were constructed by pairing an Fv region from a monoclonal antibody (mAb) directed against CD32B with an Fv region from a mAb directed against CD79B, the beta-chain of the invariant signal-transducing dimer of the B cell receptor complex. DART molecules were characterized physicochemically and for their ability to simultaneously bind the target receptors in vitro and in intact cells. The ability of the DART molecules to negatively control B cell activation was determined by calcium mobilization, by tyrosine phosphorylation of signaling molecules, and by proliferation and Ig secretion assays. A DART molecule specific for the mouse ortholog of CD32B and CD79B was also constructed and tested for its ability to inhibit B cell proliferation in vitro and to control disease severity in a collagen-induced arthritis (CIA) model.


RESULTS
DART molecules were able to specifically bind and coligate their target molecules on the surface of B cells and demonstrated a preferential simultaneous binding to both receptors on the same cell. DART molecules triggered the CD32B-mediated inhibitory signaling pathway in activated B cells, which translated into inhibition of B cell proliferation and Ig secretion. A DART molecule directed against the mouse orthologs was effective in inhibiting the development of CIA in DBA/1 mice.


CONCLUSIONS
This innovative bispecific antibody scaffold that simultaneously engages activating and inhibitory receptors enables novel therapeutic approaches for the treatment of rheumatoid arthritis and potentially other autoimmune and inflammatory diseases in humans.
Veri
Maria-Concetta
MC
MacroGenics, Inc., Rockville, Maryland 20850, USA.
Burke
Stephen
S
Huang
Ling
L
Li
Hua
H
Gorlatov
Sergey
S
Tuaillon
Nadine
N
Rainey
G Jonah
GJ
Ciccarone
Valentina
V
Zhang
Tengfei
T
Shah
Kay
K
Jin
Linda
L
Ning
Lida
L
Minor
Tamara
T
Moore
Paul A
PA
Koenig
Scott
S
Johnson
Syd
S
Bonvini
Ezio
E
D000818:Animals; D018033:Antibodies, Bispecific / Q000276:immunology / Q000493:pharmacokinetics / Q000494:pharmacology*; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000493:pharmacokinetics / Q000494:pharmacology*; D000936:Antigen-Antibody Complex / Q000276:immunology / Q000378:metabolism; D001169:Arthritis, Experimental / Q000188:drug therapy / Q000276:immunology; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000276:immunology; D051925:CD79 Antigens / Q000276:immunology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D019281:Dimerization; D005260:Female; D006801:Humans; D007136:Immunoglobulins / Q000378:metabolism; D007166:Immunosuppressive Agents / Q000276:immunology / Q000493:pharmacokinetics / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects* / Q000276:immunology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D017452:Receptors, IgG / Q000276:immunology; D015398:Signal Transduction; D013154:Spleen / Q000166:cytology; D054457:Tissue Scaffolds
D018033:Antibodies, Bispecific; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D051925:CD79 Antigens; C080571:Fc gamma receptor IIB; D007136:Immunoglobulins; D007166:Immunosuppressive Agents; D017452:Receptors, IgG