Humanized anti-IL-2 receptor therapy — Preliminary clinical results with a humanized antibody against the IL-2 receptor suggested which outcome regarding HAMA (human anti-mouse antibody) responses and recognition of Ig constant regions?

Introduction / Context:
Fully murine monoclonal antibodies often elicit HAMA responses, reducing efficacy and safety. Humanization reduces murine sequences in the variable regions while retaining antigen specificity, aiming to diminish immunogenicity and extend therapeutic utility (e.g., anti-IL-2R antibodies for immune modulation).

Given Data / Assumptions:

• Humanized antibodies are predominantly human in framework and constant regions.
• Reduced murine content should lower anti-mouse immune responses (HAMA).
• Clinical endpoints include safety, immunogenicity, and pharmacokinetics.

Concept / Approach:
The logical prediction—and what early trials supported—is that humanized anti-IL-2R antibodies show reduced HAMA compared with murine counterparts, improving tolerability and enabling repeated dosing without rapid clearance or hypersensitivity.

Step-by-Step Solution:

Verification / Alternative check:
Multiple humanized therapeutics (beyond anti-IL-2R) demonstrated decreased anti-drug antibody incidence compared with murine antibodies, supporting the same conclusion.

Why Other Options Are Wrong:

• b: Contradicts the purpose and findings of humanization.
• c: Patients do recognize human Ig constant regions as self; “poor recognition” is incorrect framing.
• d/e: Overbroad or false given reduced immunogenicity with humanized constructs.

Common Pitfalls:
Equating chimeric and humanized antibodies; humanized constructs generally contain less murine sequence than chimeric antibodies and thus even lower immunogenicity.

Final Answer:
Absence of a significant human immune response against murine proteins (reduced HAMA)