Protease-activatable Bispecific Proteins for Localized Tumor Activation
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Solution Overview
Problem
Current bispecific antibody formats, such as BiTE, have short half-lives and require continuous infusion, leading to potential side effects due to prolonged and poorly localized T cell activation, and there is a need for formats with reasonably long half-lives that are specifically activated in the disease microenvironment, like tumors.
Innovation Solution
Development of protease-activatable bispecific proteins (PABPs) that comprise polypeptide chains binding to target and effector cells, linked by a protease cleavage site, which are activated upon proteolytic cleavage, enhancing binding efficacy and extending half-life, specifically in disease microenvironments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If bispecific antibody formats are designed to have longer half-lives, then dosing frequency can be reduced, but prolonged and poorly localized T cell activation occurs leading to undesirable side effects
Solution Approach 1:
The bispecific antibody is designed with a protease cleavage site that enables preliminary circulation in an inactive or partially active state, allowing the drug to reach the tumor site before full activation occurs. The cleavage site is strategically positioned so that proteolytic cleavage by tumor-associated proteases activates the antibody locally at the tumor microenvironment, thereby achieving both prolonged circulation and localized activation to minimize systemic side effects
Solution Approach 2:
The invention introduces spatial heterogeneity in antibody activity by making the bispecific antibody conditionally active only in the tumor microenvironment. The protease cleavage site creates a local activation mechanism where only antibodies that reach the tumor site undergo conformational change or cleavage to become fully active, while antibodies in circulation remain less active or inactive, thus achieving localized therapeutic effect with reduced systemic toxicity
2Reliability
If BiTE format antibodies are used to achieve effective T cell engagement, then cancer cell lysis is achieved, but the short half-life requires continuous infusion
Solution Approach 1:
The invention modifies the structural parameters of the BiTE antibody by incorporating an Fc region and protease cleavage site, which fundamentally changes the pharmacokinetic properties. The Fc region enables FcRn-mediated recycling that extends half-life from hours to days, while the protease cleavage site provides conditional activation. This parameter change allows the antibody to maintain effective concentrations over extended periods without continuous infusion, thereby reducing treatment burden while maintaining anticancer efficacy
3Reliability
If protease cleavage sites are incorporated to enable localized activation, then binding efficacy is improved, but the protein structure becomes more complex
Solution Approach 1:
The bispecific antibody is segmented into distinct functional modules: two antigen-binding single-chain variable fragments (scFvs), a protease cleavage site, and an Fc region. This segmentation allows each component to perform its specific function independently - the scFvs provide target recognition, the cleavage site enables conditional activation, and the Fc region extends half-life. The modular architecture simplifies the design process and enables rational optimization of each component while maintaining overall functionality
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
PABPs demonstrate improved binding efficacy and prolonged activity in disease microenvironments, reducing side effects by localized activation and extended half-life, allowing for more effective cancer therapy with reduced dosing frequency.
Implementation Method 1
a linker comprising a protease cleavage site that links the third polypeptide of (c) to the remainder of the protein; wherein either the protein binds to a target cell more effectively or the protein binds to an effector cell more effectively when the protease cleavage site is essentially completely cleaved
Data Source
AI summary
Described herein are protease-activatable proteins (PABPs), which, when activated, can mediate cytolysis of target cells by effector cells. Also provided are nucleic acids encoding such PABPs and methods of making and using PABPs.