Omalizumab is used as add-on therapy in severe allergic asthma. Its molecular target and mechanism are best described as:

• A Neutralizing IL-13 and thereby downregulating B-cell class switching to IgE
• B Cross-linking IgE already bound to mast cells, triggering receptor desensitization
• C Binding the Fc portion of free circulating IgE, preventing its attachment to mast cell Fc-epsilon-RI ✓
• D Blocking the high-affinity IgE receptor directly on mast cells and basophils

Explanation

Omalizumab is a humanized monoclonal antibody that binds the A-epsilon-3 domain of free soluble IgE, so IgE can no longer bind Fc-epsilon-RI on mast cells and basophils. Over months this downregulates receptor expression and reduces allergen-triggered mediator release. It deliberately cannot bind IgE already attached to effector cells, because that would cross-link receptors and provoke anaphylaxis. It targets IgE itself, not IL-13 signalling or the receptor molecule.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.