Globin Expression Cassettes with Insulators for Hemoglobinopathy Therapy
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Solution Overview
Problem
Current globin vectors for treating β-thalassemia and sickle cell anemia face limitations due to non-erythroid activity risks and detrimental effects on vector production, such as insertional oncogenesis and reduced transduction efficiency, particularly related to the β-globin locus control region (LCR) components like Dnase I hypersensitive site-2 (HS2).
Innovation Solution
The development of expression cassettes with enhancer blocking insulators, such as those comprising CTCF binding sites, which are integrated with a β-globin locus control region (LCR) lacking the HS2 region, along with erythroid-specific enhancers and insulators, to ensure safe and high-level, erythroid-specific expression of the globin gene, reducing the risk of genotoxicity and maintaining vector titer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the complete β-globin locus control region (LCR) including HS2 is used to drive high-level globin expression, then therapeutic expression levels are achieved, but the risk of insertional oncogenesis increases due to non-erythroid activity of HS2
Solution Approach 1:
The LCR is segmented by removing the HS2 region while retaining HS1, HS3, and HS4 regions. This segmentation eliminates the harmful non-erythroid activity of HS2 while preserving the erythroid-specific high-level expression capability of the remaining LCR components.
Solution Approach 2:
The HS2 region is extracted and removed from the LCR construct. This extraction eliminates the source of non-erythroid activity and insertional oncogenesis risk while maintaining the functional integrity of the LCR for erythroid-specific expression.
2Reliability
If traditional LCR components are used in expression cassettes, then globin gene expression is achieved, but vector production titer is reduced due to detrimental effects on transduction efficiency
Solution Approach 1:
The LCR construct parameters are modified by deleting the HS2 region. This parameter change optimizes the balance between expression capability and vector production efficiency, resulting in improved vector titers while maintaining therapeutic globin expression levels.
3Object-affected harmful factors
If insulators are added to block enhancer elements and prevent insertional oncogenesis, then safety is improved, but vector production efficiency and titer are adversely impacted
Solution Approach 1:
The harmful HS2 region is converted into a benefit by its complete removal from the construct. This eliminates the need for additional insulator elements that would block enhancers, as the truncated LCR itself provides inherent erythroid-specificity without the genotoxic risks of HS2.
Data Source
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AI summary
The presently disclosed subject matter provides for expression cassettes that allow for expression of a globin gene or a functional portion thereof, vectors comprising thereof, and cells transduced with such expression cassettes and vectors. The presently disclosed subject matter further provides methods for treating a hemoglobinopathy in a subject comprising administering an effective amount of such transduced cells to the subject.