Macrocyclization of a Ligand Targeting a Toxic RNA Dramatically Improves Potency

Area of Science:

• Medicinal Chemistry
• RNA Therapeutics
• Molecular Biology

Background:

• RNA molecules play critical roles in human diseases, necessitating methods to modulate their function.
• Targeting RNA structure with small molecules is a promising therapeutic strategy, but ligand discovery remains challenging.

Purpose of the Study:

• To investigate whether macrocyclization can improve the bioactivity of a linear dimeric ligand designed to inactivate the toxic RNA repeat expansion causing myotonic dystrophy type 1 (DM1).
• To evaluate the potency, target affinity, selectivity, and cell permeability of the macrocyclic compound compared to its linear counterpart.

Main Methods:

• Synthesis and characterization of a macrocyclic derivative of a known linear dimeric RNA-binding ligand.
• In vitro and cellular assays to assess the compound's ability to inactivate the r(CUG)^exp RNA.
• Measurement of target binding affinity and selectivity for r(CUG)^exp over other RNA structures.
• Assessment of cell permeability and efficacy in patient-derived myotubes exhibiting DM1-associated defects.

Main Results:

• The macrocyclic compound demonstrated a tenfold increase in potency compared to the linear ligand in ameliorating DM1-associated cellular defects.
• Enhanced potency was attributed to increased binding affinity and selectivity for the target r(CUG)^exp RNA.
• The macrocycle exhibited superior cell permeability, facilitating improved therapeutic effects in cellular models, including patient-derived cells.

Conclusions:

• Macrocyclization is an effective strategy for enhancing the bioactivity of modularly assembled ligands targeting RNA.
• This approach holds significant promise for developing improved therapeutics for RNA-mediated diseases such as DM1.
• The study highlights the potential of macrocyclic compounds as potent and cell-permeable modulators of RNA function.