pH-Selective Ipilimumab Variants for Lower-Toxicity CTLA-4 Binding
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Solution Overview
Problem
Ipilimumab exhibits dose-limiting toxicity and there is a need for improved forms that exhibit enhanced anti-tumor activity with reduced side-effects.
Innovation Solution
Development of ipilimumab variants with mutations in the variable domain that enhance target binding at low/acidic pH, specifically through histidine substitutions in the heavy chain and acidic residues in the light chain, resulting in preferential binding at pH 5.8-6.8 compared to neutral pH, and potentially reduced fucosylation for enhanced ADCC activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ipilimumab is administered at higher doses to enhance anti-tumor activity, then therapeutic efficacy is improved, but dose-limiting toxicity increases
Solution Approach 1:
The patent applies local quality by engineering pH-dependent binding characteristics into the antibody. The modified ipilimumab variants bind with high affinity to CTLA-4 in the acidic tumor microenvironment (pH 5.8-6.8) but exhibit reduced binding at neutral physiological pH (7.2-7.4), thereby concentrating therapeutic activity locally at the tumor site while reducing systemic toxicity
Solution Approach 2:
The patent implements parameter changes by modifying the binding affinity characteristics of the antibody based on pH conditions. Through amino acid substitutions in the variable domain, the antibody's dissociation constant (KD) is tuned to be approximately 10-fold lower (higher affinity) at pH 6.0 compared to pH 7.4, enabling selective activation in the acidic tumor microenvironment
2Reliability
If ipilimumab binding affinity is increased to improve anti-tumor activity, then therapeutic efficacy is enhanced, but side-effects increase
Solution Approach 1:
The patent applies dynamics by creating an environmentally responsive antibody that dynamically adjusts its binding affinity based on local pH conditions. The antibody transitions between high-affinity and low-affinity states depending on whether it encounters the acidic tumor microenvironment or neutral systemic circulation, enabling context-dependent therapeutic activity
Solution Approach 2:
The modified antibody exhibits local quality through spatially differentiated binding characteristics: high binding affinity is localized to the acidic tumor microenvironment where it is needed for anti-tumor activity, while low binding affinity prevails in neutral pH systemic circulation where it would cause off-target side effects
Data Source
AI summary
The present invention provides variant forms of anti-CTLA-4 antibodies, such as ipilimumab, that preferentially bind to CTLA-4 at low pH. Such antibody variants exhibit preferential activity in the tumor microenvironment, an enhanced ratio of anti-tumor response to side-effects, and an enhanced therapeutic index.