IF a dual-lock, galactose-capped antibody-drug conjugate (Gal-uPAR-ADC) — consisting of an anti-uPAR (anti-PLAUR) single-chain variable fragment conjugated via a lysosome-cleavable linker to a galactose-capped duocarmycin analog — is administered systemically (10–20 mg/kg, IV, weekly × 4) to naturally aged (24-month-old) male and female C57BL/6J mice,

THEN a ≥40% reduction in p16^INK4a^-positive senescent cell burden across liver, lung, and adipose tissue, a measurable decrease in circulating SASP factors (IL-6, MMP-3, GDF-15), and a statistically significant improvement in grip strength and rotarod performance relative to vehicle-treated age-matched controls will be observed within 8 weeks of treatment initiation,

BECAUSE of the following sequential mechanistic chain:

1. uPAR is broadly and specifically upregulated on the surface of senescent cells across multiple tissue types, providing a targetable extracellular handle; the anti-uPAR antibody fragment of the Gal-uPAR-ADC binds with high affinity to uPAR-expressing cells, enabling selective receptor-mediated endocytosis of the conjugate into the lysosomal compartment (uPAR broadly induced on senescent cells)[https://doi.org/10.1038/s41586-020-2403-9].

2. The lysosomal compartment of senescent cells exhibits markedly elevated senescence-associated β-galactosidase (SA-β-gal) activity relative to quiescent or proliferating cells; once the Gal-uPAR-ADC is internalized into this compartment, SA-β-gal cleaves the galactose cap on the duocarmycin payload, converting the prodrug into its cytotoxic form exclusively within senescent cell lysosomes [SPECULATIVE cross-disciplinary link from galactose-prodrug literature described in Evidence Set].

3. The released duocarmycin alkylates nuclear DNA at the minor groove, initiating apoptosis in the senescent cell, which is permissive to apoptotic signaling precisely because standard senolytics already demonstrate that bypassing the anti-apoptotic machinery of senescent cells is sufficient to kill them (targeted clearance via senescence membrane markers)[https://doi.org/10.1038/s41598-021-99852-2].

4. The dual-lock AND-gate logic — requiring BOTH surface uPAR expression AND lysosomal SA-β-gal activity — excludes healthy cells that might express uPAR in limited contexts (activated macrophages, urothelium) but lack the high-SA-β-gal phenotype, while also excluding cells with elevated SA-β-gal but no surface uPAR. This dramatically narrows off-target toxicity compared to either uPAR-targeting or galactose-prodrug strategies alone [SPECULATIVE, synthesized from two independent approaches in Evidence Set].

5. Clearance of the senescent cell burden reduces SASP paracrine signaling, decreasing local and systemic inflammatory mediators, enabling stromal and parenchymal cell populations to resume normal proliferation and differentiation, leading to measurable functional improvements in musculoskeletal performance and organ histology (senolytic ...

SENS category: GlycoSENS

Key references: • doi.org/10.1038/s41586-020-2403-9]. • doi.org/10.1038/s41598-021-99852-2]. • doi.org/10.1038/s41586-020-2403-9], • doi.org/10.1038/s41598-021-99852-2],