PROteolysis-TArgeting Chimeras (PROTACs) and molecular glue degraders represent a transformative therapeutic modality for neurodegenerative diseases. Unlike traditional small-molecule inhibitors that block protein function, these degraders recruit the cell's own ubiquitin-proteasome system to selectively eliminate disease-causing proteins. This page provides a comprehensive analysis of this technology applied to Alzheimer's disease, Parkinson's disease, and related neurodegenerative disorders.
PROTACs are chimeric molecules consisting of three critical components:
Molecular glues are monovalent compounds that stabilize protein-protein interactions between a target protein and an E3 ligase, inducing degradation without the need for bifunctional design[1]. They offer:
The prototypical molecular glues are thalidomide analogs (lenalidomide, pomalidomide) that redirect cereblon E3 ligase activity toward neo-substrates.
Tau pathology is the strongest correlate of cognitive decline in Alzheimer's disease. PROTACs offer unique advantages over other tau-targeting approaches:
Arvinas tau PROTAC program: Preclinical studies demonstrate degradation of multiple tau species including p-tau181, p-tau217, and p-tau231, with reduced insoluble aggregated tau in mouse models[2].
Dual PROTACs: Compounds like T3 simultaneously degrade both alpha-synuclein and tau, addressing copathology common in neurodegeneration[3].
alpha-synuclein aggregation into Lewy bodies characterizes Parkinson's disease, Lewy body dementia, and multiple system atrophy.
PROTACs targeting alpha-synuclein have demonstrated:
TDP-43 proteinopathy characterizes approximately 97% of ALS and ~50% of FTD cases. PROTACs targeting mislocalized or aggregated TDP-43 are in early preclinical development.
Molecular glue approaches for TDP-43 include:
LRRK2 mutations are the most common genetic cause of familial Parkinson's disease. ARV-102 is the most clinically advanced CNS PROTAC:
PROTACs can selectively degrade mutant huntingtin while sparing wild-type protein — a key advantage over antisense oligonucleotides like tominersen that reduce both forms.
PROTACs' larger molecular weight (700-1000 Da) poses significant BBB challenges. Strategies to improve penetration include:
| Strategy | Description | Status |
|---|---|---|
| Physicochemical optimization | Lipophilicity, HBD/HBA optimization | Validated in ARV-102 |
| Prodrug approaches | Brain-targeted prodrugs | Preclinical |
| Nanoparticle delivery | Lipid nanoparticles, exosomes | Research |
| Focused ultrasound | BBB opening for enhanced delivery | Clinical trials |
| Receptor-mediated transcytosis | BBB shuttle molecules | Preclinical |
Achieving selective degradation of pathological protein species while sparing physiological forms is critical:
At high concentrations, PROTACs can saturate both target and E3 ligase separately, preventing ternary complex formation. This inverted U-shaped dose-response requires careful clinical dosing optimization.
| Compound | Target | Indication | Stage | Company |
|---|---|---|---|---|
| ARV-102 | LRRK2 | PD, PSP | Phase 1 complete | Arvinas |
| Tau PROTAC | Tau | AD, tauopathies | Preclinical | Arvinas |
| α-Syn PROTAC | α-Synuclein | PD, DLB, MSA | Preclinical | Multiple |
| mHTT PROTAC | Mutant HTT | HD | Preclinical | Academic |
| Dual PROTAC T3 | Tau + α-Syn | AD, PD | Preclinical | Academic |
LYTACs redirect extracellular and membrane proteins to lysosomes via mannose-6-phosphate receptors. Particularly useful for:
AUTACs leverage autophagy for degradation, essential for large protein aggregates that exceed proteasome capacity. Particularly relevant for:
Bispecific antibodies recruiting membrane E3 ligases (RNF43) for degradation of cell-surface and extracellular targets.
The field is rapidly evolving toward:
Klein et al. Molecular glue degraders: a new paradigm for targeted protein degradation (2024). 2024. ↩︎
Arvinas Neuroscience Pipeline — Tau, alpha-synuclein, and mHTT PROTAC Programs. ↩︎
Gao et al. Discovery of Effective Dual PROTAC Degraders for Neurodegenerative Disease-Associated Aggregates (2024). 2024. ↩︎ ↩︎
Arvinas, First-in-Human Data for ARV-102 Demonstrating Blood-Brain Barrier Penetration and LRRK2 Degradation (2025). 2025. ↩︎