Enzymatic Inactivation of Endogenous IgG by IdeS Enhances Therapeutic Antibody Efficacy

Abstract

Endogenous plasma IgG sets an immunologic threshold that dictates the activity of tumor-directed therapeutic antibodies. Saturation of cellular antibody receptors by endogenous antibody limits antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). Here, we show how enzymatic cleavage of IgG using the bacterial enzyme IdeS can be utilized to empty both high and low affinity Fcgreceptors and clear the entire endogenous antibody pool. Using in vitro models, tumor animal models as well as ex vivo analysis of sera collected during a previous clinical trial with IdeS, we show how clearing of competing plasma antibody levels with IdeS unblocks cellular antibody receptors. We show that therapeutic antibodies against breast cancer (trastuzumab), colon cancer (cetuximab), and lymphomas (rituximab and alemtuzumab) can be potentiated when endogenous IgG is removed. Overall, IdeS is shown to be a potent tool to reboot the human antibody repertoire and to generate a window to preferentially load therapeutic antibodies onto effector cells and thereby create an armada of dedicated tumor-seeking immune cells.

Extensive substrate recognition by the streptococcal antibody-degrading enzymes IdeS and EndoS

“…The crystal structures presented here provide a structural rationale for the unique properties of these two enzymes, and can now be exploited for optimisation of their long-term clinical and biotechnological applications. Not only will they enable the design of antibodies resistant to cleavage by these enzymes, whose potency can be strengthened with removal of serum IgG (28, 29), they will also be invaluable in the synthesis of immunologically-distinct enzyme variants which retain identical activity, for their repeated therapeutic use. EndoS mutants have already been designed to expand its ability to engineer antibody glycosylation (33, 34); structural information presented here will allow this to be extended further.…”

“…The enzyme targets IgG by cleaving within the lower hinge region, yielding F(ab')2 and Fc fragments (3,6,7), an activity which has enabled its development, under the name Imlifidase, as a pre-treatment for kidney transplantation in hypersensitized patients with chronic kidney disease (8)(9)(10)(11)(12)(13)(14)(15)(16). Along with EndoS, it has further potential use in the deactivation of pathogenic antibodies in autoimmune disorders (11,(17)(18)(19)(20)(21)(22)(23)(24)(25)(26), deactivation of neutralising antibodies for in vivo gene therapy (27), and for the potentiation of therapeutic antibodies by deactivating competing serum IgG (28,29). Imlifidase has also been used in combination with EndoS for inactivation of donor-specific antibodies in murine allogeneic bone marrow transplantation (10).…”

Extensive substrate recognition by the streptococcal antibody-degrading enzymes IdeS and EndoS

“…Understanding the molecular basis of this activity is critical for expanding their clinical and biotechnological use. For example, the deactivation of serum IgG using both IdeS and EndoS can strengthen the potency of therapeutic antibodies 21,22 ; this strategy could be applied to potentiate any therapeutic antibody, in theory, if the antibody were designed to be resistant to cleavage by these enzymes, a venture which can be aided greatly with structural information. This will also be invaluable in the synthesis of immunologicallydistinct enzyme variants which retain identical activity, for their long-term therapeutic use.…”

“…The enzyme targets IgG by cleaving within the lower hinge region, yielding F(ab′) 2 and Fc fragments 3,8,9 , an activity which has enabled its development as a pre-treatment for transplantation in hypersensitized individuals with chronic kidney disease (Imli dase, brand name Ide rix®) 10− 12 . Along with EndoS, it has further potential use in the deactivation of pathogenic antibodies in autoimmune disorders 13− 19 , deactivation of neutralising antibodies for in vivo gene therapy 20 , and for the potentiation of therapeutic antibodies by deactivation of competing serum IgG 21,22 . Imli dase has also been used in combination with EndoS for inactivation of donor-speci c antibodies in murine allogeneic bone marrow transplantation 23 .…”

Rationale and clinical development of CD40 agonistic antibodies for cancer immunotherapy

“…endogenous IgG [110]. Thus, the availability of FcγR engagement will depend not only on their affinity for different Fc domains, but also the concentration of free IgG in each compartment.…”