Obinutuzumab produces higher complete response rates than rituximab when combined with chlorambucil in CLL. Which property explains this advantage?

• A It is a type I anti-CD20 antibody that clusters CD20 into lipid rafts, maximizing complement activation
• B It carries an auristatin payload released inside CD20-positive cells
• C It binds CD19 instead of CD20, giving broader B cell coverage
• D It is a glycoengineered type II anti-CD20 antibody with enhanced Fc-gamma receptor IIIa binding and stronger antibody-dependent cellular cytotoxicity ✓

Explanation

Obinutuzumab is glycoengineered (afucosylated Fc region), which increases affinity for Fc-gamma RIIIa on NK cells and macrophages, greatly enhancing ADCC. As a type II anti-CD20 antibody it induces homotypic aggregation and direct cell death rather than relying mainly on complement, unlike type I antibodies such as rituximab and ofatumumab. It still targets CD20, not CD19, and carries no payload, eliminating the other options.

Reference: Katzung Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.