RNA activation as a precision dosing modality: MTL-CEBPA for controlled enzyme elevation in MPS I-H.

Area of Science:

• Biochemistry
• Genetics
• Molecular Biology

Background:

• Hematopoietic stem cell transplantation (HSCT) improves outcomes for severe mucopolysaccharidosis type I (MPS I-H).
• Children with MPS I-H still face progressive complications post-HSCT due to inability to safely titrate enzyme activity.
• Current gene therapies carry risks like irreversible genetic modification and re-dosing challenges.

Purpose of the Study:

• To investigate RNA activation (RNAa) as a precision dosing strategy for enhancing endogenous IDUA expression.
• To evaluate MTL-CEBPA, a small activating RNA targeting CEBPA, for its ability to upregulate IDUA without permanent genome alteration.

Main Methods:

• Characterized CEBPA-IDUA relationships in vitro, in vivo, and in human samples.
• Administered MTL-CEBPA intravenously to wild-type and humanized MPS I-H mice.
• Analyzed IDUA mRNA and plasma enzyme activity in treated subjects and correlated CEBPA and IDUA levels in cancer patient samples.

Main Results:

• MTL-CEBPA consistently increased IDUA mRNA and enzyme activity in cell lines and mouse models.
• Two doses of MTL-CEBPA in mice led to a durable, approximately 2-fold increase in IDUA activity for up to 4 weeks.
• In humanized MPS I-H mice, repeated MTL-CEBPA dosing increased circulating IDUA activity, with notable effects in the homozygous cohort.
• Increased CEBPA protein levels correlated with higher IDUA levels in cancer patient-derived monocytes.

Conclusions:

• MTL-CEBPA demonstrates controlled, reversible enhancement of IDUA activity in the context of HSCT.
• RNAa therapeutics offer a safe, titratable alternative to irreversible gene modification for MPS I-H.
• MTL-CEBPA represents a clinically relevant adjuvant strategy for HSCT-treated MPS I-H and potentially other enzyme deficiency disorders.