Fn3 Binding Molecules for Bispecific Targeting
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Solution Overview
Problem
Monoclonal antibodies are limited by their large and complex structure, which hinders their expression in simple prokaryotic systems, requires expensive mammalian cell production, and can trigger undesired effector cell functions due to their size, and are difficult to generate as bispecific or multispecific molecules.
Innovation Solution
Development of fibronectin type III (Fn3)-based binding molecules with modified bottom and top loops that can bind to target antigens, allowing for the creation of monospecific, bispecific, and multispecific molecules that can be expressed in various systems and conjugated with non-Fn3 moieties to enhance stability and half-life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If monoclonal antibodies are used for specific binding, then high affinity and specificity are achieved, but the large and complex structure hinders expression in prokaryotic systems and requires expensive mammalian cell production
Solution Approach 1:
The patent extracts only the essential binding function from the complex antibody structure by using small single-domain proteins (nanobodies, single-chain Fv fragments) that contain only the variable region responsible for antigen binding, eliminating the need for complex constant regions and enabling prokaryotic expression
Solution Approach 2:
The patent segments the antibody into smaller functional units such as single-domain antibodies (sdAbs) and single-chain Fv fragments, which can be independently expressed and folded, thereby simplifying the manufacturing process while maintaining binding functionality
2Reliability
If monoclonal antibodies are used for therapeutic applications, then specific binding is achieved, but the large size limits penetration into certain tissue spaces
Solution Approach 1:
The patent extracts only the minimal essential binding unit from the full antibody, using single-domain proteins of approximately 15 kDa compared to the full antibody size of 150 kDa, enabling better tissue penetration while retaining specific binding capability
3Reliability
If monoclonal antibodies are used for therapeutic applications, then binding function is achieved, but the Fc region triggers undesired effector cell function and clotting cascades
Solution Approach 1:
The patent removes the Fc region from the antibody structure, using only the variable domain (VH or VL) that contains the antigen-binding site, thereby eliminating all Fc-mediated effector functions including complement activation and antibody-dependent cellular cytotoxicity while preserving specific antigen binding
Solution Approach 2:
The patent segments the antibody into separate functional modules, isolating the binding function in the variable domain from the effector function in the constant domain, allowing selective use of only the binding module for applications where effector functions are undesired
4Adaptability or versatility
If traditional antibody methods are used to generate bispecific or multispecific antibodies, then multiple target binding is achieved, but the procedures are difficult and complex
Solution Approach 1:
The patent segments the multispecific binding function into separate single-domain units, each targeting a different antigen, which can be independently produced and then easily combined through genetic fusion or chemical conjugation, greatly simplifying the generation of bispecific and multispecific molecules
Solution Approach 2:
The patent creates a universal single-domain protein platform that can be easily engineered to bind multiple different targets by modifying the variable region, allowing the same basic scaffold to serve multiple binding functions without complex procedural steps
Data Source
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AI summary
The invention provides fibronectin type III (Fn3)-based binding molecules that bind to a specific target antigen. The invention further provides bispecific Fn3-based binding molecules that bind to two or more targets simultaneously. The Fn3-based binding molecules of the invention can also be linked together to form multispecific Fn3-based binding molecules, and/or can be conjugated to a non-Fn3 moiety, such as, Human Serum Albumin (HSA), for improved half life and stability. The invention also provides methods for generating, screening and using Fn3-based binding molecules in a variety of therapeutic and diagnostic applications.