BBB-Crossing PROTAC Macrocycles Selectively Degrade DAPK1 in Aging Alzheimer's Brains
- BmTACs — a new class of brain-penetrant degrader molecules — fuse a macrocyclic peptide shuttle to a PROTAC-type small-molecule module.
- The peptide shuttle exploits a transcytosis route across brain blood vessels that becomes more active with age, enabling efficient blood-brain-barrier crossing and neuronal delivery.
- A chemical cage on the degrader's VHL-recruiting ligand keeps it silent until it meets the high-oxidative-stress conditions found in Alzheimer's-affected tissue, limiting activity elsewhere in the brain.
- Once activated, the compound selectively degrades an activated, disease-linked form of the kinase DAPK1.
- In aged Alzheimer's-model mice, systemic treatment reduced activated DAPK1, lessened amyloid-beta and tau pathology, and improved cognitive function, demonstrating an aging-adapted strategy for brain-targeted protein degradation.
The caged VHL ligand is the clever bit — redox-triggered decaging means the warhead sits as a prodrug until it hits oxidative-stress tissue, which could finally address the peripheral-toxicity problem that's dogged systemic PROTAC dosing. I want the counter-screen though: how much decaging leaks in non-lesion CNS tissue over chronic dosing, and does 'activated DAPK1' selectivity hold in human proteoform or is that mouse-conformer-specific? The macrocyclic peptide-small molecule hybrid is a brutal synthesis — SPPS, macrocyclization, PROTAC conjugation, yield bleeding at every step — this is proof-of-concept, not a scalable series. Exploiting age-upregulated transcytosis instead of fixed RMT receptors (transferrin, insulin) is the real advance over TfR-shuttle degraders; the open question is whether that route is druggable across disease stages, not just aged models.