Bifunctional PROTAC Compounds Targeting PXR
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Solution Overview
Problem
Current treatments for colorectal cancer, particularly those targeting cancer stem cells, face challenges due to resistance and recurrence, with existing PXR antagonists being non-specific or toxic, necessitating a targeted approach to inhibit the PXR nuclear receptor.
Innovation Solution
Development of bifunctional compounds that utilize the PROTAC strategy to induce targeted proteolysis of the PXR nuclear receptor through a covalent attachment of ubiquitin to the PXR protein, leveraging the ubiquitin-proteasome pathway for protein degradation, thereby sensitizing cancer stem cells to chemotherapy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PXR antagonists (L-sulforaphane, ketoconazole, SAP-70) are used to inhibit PXR, then PXR activity is reduced, but the compounds are either non-specific or toxic at the required concentrations
Solution Approach 1:
The PROTAC molecule is segmented into three functional modules: a PXR ligand binding domain, a linker, and a cereblon binding domain. This segmentation allows each module to independently perform its function - the PXR ligand binds specifically to PXR, the linker connects to the E3 ligase recruiter, and cereblon binds to the E3 ligase complex, achieving specific PXR degradation without the toxicity of conventional antagonists
Solution Approach 2:
The PROTAC acts as an intermediary molecule that bridges PXR and the cereblon-containing E3 ligase complex. Instead of directly inhibiting PXR with toxic compounds, the PROTAC recruits the cellular ubiquitin-proteasome system to degrade PXR, using the body's own degradation machinery as an intermediary to achieve specific and safe PXR downregulation
2Reliability
If high concentrations of PXR antagonists are used to achieve saturation of the target, then PXR inhibition is improved, but systemic exposure requirements increase and toxicity worsens
Solution Approach 1:
The invention changes the mechanism of action from reversible inhibition to irreversible degradation. PROTACs induce polyubiquitination of PXR, marking it for proteasomal degradation. This parameter change from transient inhibition to permanent degradation allows effective target engagement at much lower concentrations, reducing systemic exposure requirements by several orders of magnitude
3Duration of action of moving object
If conventional inhibitors are used, then PXR activity is blocked temporarily, but the protein function rapidly recovers after inhibitor dissociation
Solution Approach 1:
The PROTAC mechanism involves the discarding of the PXR protein through ubiquitin-mediated proteasomal degradation. Once PXR is degraded into small peptides and amino acids, it cannot rapidly recover its function. The cell must de novo synthesize new PXR protein to restore function, extending the duration of inhibition far beyond the half-life of the PROTAC molecule itself
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 compounds effectively degrade the PXR protein, leading to enhanced sensitivity of cancer stem cells to current treatments, delaying tumor recurrence and improving treatment outcomes by utilizing the native cellular degradation processes with prolonged action and reduced toxicity.
Implementation Method 1
The covalent attachment of ubiquitin to specific protein substrates is obtained by the action of E3-ubiquitin ligases
Implementation Method 2
This causes poly-ubiquitination of the target protein which is thus degraded into small peptides and amino acids by the proteasome complex
Implementation Method 3
which is thus degraded into small peptides and amino acids by the proteasome complex
Data Source
AI summary
The present application relates to novel bifunctional PROTAC-type compounds simultaneously binding the target protein PXR and E3-ubiquitin ligase, to a method for preparing same, and to uses thereof for treating cancers overexpressing PXR.