Obinutuzumab (glycoengineered anti-CD20) is preferred over rituximab in certain B-cell malignancies. What structural modification gives obinutuzumab enhanced antitumor activity compared to rituzumab?

• A A mutated CD20-binding Fab region with higher affinity
• B A fucose-deficient Fc region that increases Fc-gamma-RIIIa binding and ADCC ✓
• C Conjugation to a cytotoxic payload enabling direct cell killing
• D Bispecific binding to both CD20 and CD19 simultaneously

Explanation

Obinutuzumab is a glycoengineered (afucosylated) anti-CD20 antibody. Removal of fucose from the Fc region increases affinity for Fc-gamma-RIIIa on NK cells, enhancing ADCC by up to 100-fold compared to rituzumab. This is its key differentiating feature. It is not an ADC, not bispecific, and does not have higher CD20 affinity.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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