Lowering mutant huntingtin by small molecules relieves Huntington's disease symptoms and progression

Area of Science:

• Neuroscience
• Genetics
• Pharmacology

Background:

• Huntington's disease (HD) is a fatal inherited neurodegenerative disorder.
• It results from expanded glutamine repeats in the huntingtin gene (Htt), leading to toxic mutant protein accumulation.
• Current treatments manage symptoms but do not alter disease progression.

Purpose of the Study:

• To identify small molecules that selectively downregulate mutant Htt gene expression.
• To evaluate the therapeutic potential of these inhibitors in cellular and animal models of HD.

Main Methods:

• Screening for small molecule inhibitors of Spt5-Pol II.
• Testing SPI-24 and SPI-77 in HD patient-derived cells and the BACHD mouse model.
• Assessing effects on mutant Htt levels, mitochondrial function, BDNF expression, and behavioral phenotypes.
• Conducting pharmacokinetic studies and long-term administration studies in mice.

Main Results:

• SPI-24 and SPI-77 selectively reduced mutant Htt mRNA and protein levels in HD cells.
• Direct striatal delivery in BACHD mice decreased mutant Htt, improved mitochondrial function, restored BDNF, and ameliorated motor and anxiety deficits.
• SPIs demonstrated blood-brain-barrier penetration.
• Oral or subcutaneous administration delayed disease progression in early-stage mice.
• Long-term SPI-24 treatment showed no adverse effects or global gene expression changes.

Conclusions:

• Selective downregulation of mutant Htt using small molecule inhibitors is a viable therapeutic strategy for HD.
• SPI-24 and SPI-77 represent promising drug candidates for HD treatment.
• Further development of these compounds could lead to effective therapies for Huntington's disease.