Table 1.

Strategies introduced to interfere IgE/FcεRI signaling

Strategy	Pharmaceutical agents/Abs	Description/mechanism of action	Ref
Anti-IgE monoclonal antibodies	Omalizumab	Recombinant humanized anti-IgE mAb, also known as Xolair® Approved by FDA for the treatment of mild allergic asthma Mechanism of action: binds to free IgE and decreases the availability of IgE available to interact with FcεRI Omalizumab has no interference with receptor-bound IgE	[57, 58]
	Ligelizumab (QGE031)	Humanized IgG1 mAb with ability to binding to the Cε3 domain of IgE	[59]
	Quilizumab	Structurally is a humanized, monoclonal IgG1 antibody with the ability to bind membrane-bound but not soluble IgE due to the absence of M1-prime segment in soluble IgE	[60]
Designed ankyrin repeat proteins (DARPins)	DARPin E2_79	Acts by preventing IgE-FcεRI binding and disrupting preformed IgE-FcεRI complexes in vitro	[57]
	DARPin E3_54	Inhibits IgE-FcεRI interaction	[57]
	DARPin 30/85	Bispecific molecule capable of binding to FcεRIα	[57]
Co-aggregation of FcεRI with the inhibitory FcγRIIb	GE2	GE2 structurally is comprised of the hinge-Cγ2-Cγ3 domains from IgG Fc linked to Cε2-Cε4 domains of human IgE Fc Inhibits the phosphorylation of Syk	[57]