PROTAC mHTT Degrader-1

PROTAC mHTT Degrader-1 is a brain-penetrable PROTAC degrader targeting mutant huntingtin protein (mHTT). It selectively recognizes pathogenic mHTT aggregates and recruits Cereblon (CRBN) to induce ubiquitination, leading to proteasomal degradation of mHTT. This compound alleviates mHTT-induced cytotoxicity and neuroinflammation. In the R6/2 Huntington's disease mouse model, PROTAC mHTT Degrader-1 reduces protein aggregation in the brain and improves weight, motor coordination, and survival rates in animals. It is applicable in studying PROTAC therapies for Huntington's disease and other neurodegenerative disorders.

PROTAC mHTT Degrader-1 (PROTAC 2') at 1 μM for 22 hours significantly reduces the proportion of cells with mHTT aggregates and the level of insoluble mHTT aggregates in N2a cells expressing HTT (Q) 109-eYFP, without notably affecting soluble mHTT levels. It also decreases the intracellular level of the DNA damage marker p-H2A.X (Ser139) and inhibits the activation of apoptosis pathways induced by mHTT. Additionally, PROTAC mHTT Degrader-1 reduces the proportion of intracellular mHTT oligomers, achieving simultaneous targeted degradation of both soluble oligomers and insoluble aggregates, a process significantly reversed by the proteasome inhibitor MG132, confirming its mechanism of action via the ubiquitin-proteasome system. PROTAC 2' (0.01–10 μM; 22 h) selectively and dose-dependently degrades mHTT aggregates in N2a cells expressing HTT (Q) 109-eYFP, with no significant effect on the levels of non-pathogenic HTT (Q) 25-eYFP. Moreover, at 1 μM for 48 hours, PROTAC 2' significantly enhances the viability of N2a cells expressing HTT (Q) 109-eYFP, alleviating mHTT-induced neurotoxicity effectively.

PROTAC mHTT Degrader-1 (PROTAC 2') at a dosage of 3 mg/kg, administered subcutaneously as a single injection, was observed for 6 hours post-administration in wild-type B6CBA mouse models, showing penetration of the blood-brain barrier and maintaining an average brain tissue concentration of approximately 1.96 ppb. When administered subcutaneously once a week for 5 weeks in the same mouse model at the same dosage, it showed no significant differences in body weight, cortical thickness, striatal volume, or serum liver and kidney function markers compared to controls, with no apparent liver, kidney, or brain toxicity. Continuous subcutaneous infusion of PROTAC mHTT Degrader-1 at 3 mg/kg per week for 4 weeks utilizing osmotic pumps in B6CBA-R6/2 Huntington's disease mouse models significantly decelerated weight loss, improved motor coordination, enhanced spontaneous exploratory behavior, and extended survival. It also reduced mHTT aggregate levels and neuroinflammation in the brain, mitigated cortical and striatal atrophy, and partially restored neuronal function.