BBB-Penetrating Peptides for Brain Payload Transcytosis
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Solution Overview
Problem
Current methods for delivering drugs across the blood-brain barrier (BBB) and extracellular space (ECS) face challenges due to the barrier's complex molecular composition and size limitations, with existing peptides not effectively traversing these barriers to achieve therapeutic concentrations, leading to limited therapeutic efficacy and potential off-target effects.
Innovation Solution
Identification and use of peptides, such as Pep-3 and Pep-9, selected from cysteine-constrained cyclic peptide libraries through next-generation sequencing, which are capable of transcytosing across the BBB and diffusing through the extracellular matrix, linked to therapeutic or diagnostic payloads, enhancing drug delivery into the brain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional phage display panning is used to identify BBB shuttle peptides, then peptides can be identified from limited sample space, but the identified peptides may bind to BBB without effectively transcytosing and diffusing through ECS
Solution Approach 1:
The patent uses an in vitro BBB model (hCMEC/D3 cell monolayer on transwell) as an intermediary system to bridge the gap between in vitro binding assays and in vivo transcytosis. This model allows peptides to be screened for both binding capability and transcytosis efficiency in a controlled environment before in vivo validation, resolving the contradiction between identification accuracy and transcytosis reliability.
Solution Approach 2:
The patent changes the selection parameters from traditional Sanger sequencing (limited to 5-1000 clones) to next-generation sequencing (millions of clones), fundamentally expanding the sample space. This parameter change enables more comprehensive identification of peptides with both binding and transcytosis capabilities, improving both identification accuracy and transcytosis efficiency simultaneously.
2Quantity of substance
If in vivo panning is used to identify BBB penetrating peptides, then peptides can be selected from larger sequence space, but phages have short half-life in systemic circulation limiting binding and traversal time
Solution Approach 1:
The patent performs preliminary selection in an in vitro BBB model before in vivo validation. This preliminary action allows peptides to be pre-selected for both binding affinity and transcytosis capability in a controlled environment where phage circulation time is not limiting, thereby compensating for the short in vivo half-life while maintaining large sequence space coverage through NGS.
3Reliability
If peptides targeting hTfR or hLDLR are used for BBB transcytosis, then transcytosis can be achieved, but non-specific uptake in other tissues occurs leading to off-target effects
Solution Approach 1:
The patent employs peptides selected specifically against the BBB model (hCMEC/D3 cells) rather than general receptors like hTfR or hLDLR. This local quality approach ensures peptides are optimized for BBB-specific transcytosis mechanisms, achieving reliable BBB penetration while minimizing non-specific uptake in other tissues that express these ubiquitous receptors, thereby reducing off-target effects.
4Quantity of substance
If nanocarriers greater than 150 nm in diameter are used, then they can carry therapeutic payloads, but they are unable to penetrate intact BBB and diffuse through ECS
Solution Approach 1:
The patent uses BBB-penetrating peptides as intermediary shuttles that facilitate the transport of nanocarriers across the BBB. The peptides bind to the nanocarrier surface and mediate their transcytosis through the BBB via peptide-receptor interactions, enabling nanocarriers of therapeutic size (>150 nm) to penetrate the intact BBB and diffuse through the ECS without requiring size reduction that would compromise payload capacity.
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
These peptides demonstrate improved transcytosis and diffusion efficiency compared to established peptides like Angiopep-2, effectively ferrying payloads across the BBB and into the brain parenchyma, potentially improving the delivery of nanomedicines for CNS diseases.
Implementation Method 1
Peptides discovered through in vivo panning are against targets that may have different expression levels in humans. Also, in vivo panning may identify suboptimal peptides; since phages have a short half-life in systemic circulation, it is possible that candidate peptides do not have sufficient time to bind and traverse the BBB.
Implementation Method 2
The complex molecular composition and the size capacity of the BBB and the ECS limit drugs and nanoscale delivery systems that possess the desired physicochemical properties to traverse these barriers.
Data Source
AI summary
The present disclosure is directed to the identification of peptides that cross the blood brain barrier and their use to transport diagnostic and therapeutic payloads into the brain.