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Identification of a novel fusion Iduronidase with improved activity in the cardiovascular system
Sarah Kim1,2, Michael J Przybilla1, Chester B Whitley1,2
1Gene Therapy and Diagnostic Laboratory, Department of Pediatrics, University of Minnesota, Medical School, 516 Delaware St SE, 13th Floor, Rm 13-118 Minneapolis, MN 55455, USA.
Insights
A novel peptide enhanced enzyme activity for mucopolysaccharidosis type I (MPS I) gene therapy, improving heart and plasma levels. This peptide may offer new treatments for lysosomal diseases.
Area of Science:
- Biochemistry
- Genetics
- Pharmacology
Background:
- Lysosomal diseases are rare genetic disorders caused by enzyme deficiencies, leading to multi-system illness.
- Current therapies struggle to reach critical tissues like the central nervous system and cardiac valves.
- Mucopolysaccharidosis type I (MPS I), caused by IDUA gene mutations, exemplifies these limitations, particularly in neurodevelopment and cardiac health.
Purpose of the Study:
- To evaluate the efficacy of a novel gene therapy construct for delivering α-L-iduronidase (IDUA) enzyme to target tissues in MPS I.
- To investigate the impact of modified IDUA proteins, including those with CNS-targeting ligands, on enzyme activity in affected tissues.
Main Methods:
- Hydrodynamic injection of gene therapy vectors encoding wild-type or modified IDUA into MPS I mice.
- Utilized a liver-specific promoter (hAAT) for gene expression.
- Measured IDUA enzyme activity in plasma and various tissues using established enzyme assays.
Main Results:
- Modified IDUA variants did not significantly enhance brain enzyme activity compared to the unmodified version.
- One modified IDUA, LT-IDUA, demonstrated significantly higher activity in the heart (p=0.0211).
- LT-IDUA showed a 2-fold increase in plasma area under the curve (AUC) compared to unmodified IDUA (p=0.0034), indicating improved pharmacokinetic properties.
Conclusions:
- A six-amino acid peptide (LT) fused to IDUA improved enzyme activity in the heart and plasma.
- The LT peptide's small size makes it suitable for gene therapy fusion enzymes or enzyme replacement therapy.
- This peptide holds potential for developing advanced therapies for a range of lysosomal diseases.
Background:
Lysosomal diseases are a group of over 70 rare genetic conditions in which a protein deficiency (most often an enzyme deficiency) leads to multi-system disease. Current therapies for lysosomal diseases are limited in their ability to treat certain tissues that are major contributors to morbidity and mortality, such as the central nervous system (CNS) and cardiac valves. For this study, the lysosomal disease mucopolysaccharidosis type I (MPS I) was selected as the disease model. In MPS I, mutations in the IDUA gene cause a deficiency of the α-L-iduronidase (IDUA) enzyme activity, leading to disease pathology in tissues throughout the body, including the CNS and cardiac valves. Current therapies have been unable to prevent neurodevelopmental deficits and cardiac valvular disease in patients with MPS I. This study aimed to evaluate the delivery of IDUA enzyme, via a novel gene therapy construct, to target tissues.
Methods:
MPS I mice were hydrodynamically injected through the tail vein with plasmids containing either a codon-optimized cDNA encoding the wild-type IDUA protein or one of four modified IDUAs under the control of the liver-specific human α1-antitrypsin (hAAT) promoter. Two modified IDUAs contained a ligand for the CB1 receptor, which is a highly expressed receptor in the CNS. Iduronidase activity levels were measured in the tissues and plasma using an enzyme activity assay.
Results:
The modified IDUAs did not appear to have improved activity levels in the brain compared with the unmodified IDUA. However, one modified IDUA exhibited higher activity levels than the unmodified IDUA in the heart (p = 0.0211). This modified iduronidase (LT-IDUA) contained a sequence for a six amino acid peptide termed LT. LT-IDUA was further characterized using a noncompartmental pharmacokinetic approach that directly analyzed enzyme activity levels after gene delivery. LT-IDUA had a 2-fold higher area under the curve (AUC) than the unmodified IDUA (p = 0.0034) when AUC was estimated using enzyme activity levels in the plasma.
Conclusion:
The addition of a six amino acid peptide improved iduronidase's activity levels in the heart and plasma. The short length of this LT peptide facilitates its use as fusion enzymes encoded as gene therapy or administered as enzyme replacement therapy. More broadly, the LT peptide may aid in developing therapies for numerous lysosomal diseases.
