IF an anti-DPP4/CD26 antibody-drug conjugate (ADC) — constructed using a high-affinity, internalizing anti-human DPP4 monoclonal antibody conjugated via a protease-cleavable valine-alanine (Val-Ala) dipeptide linker to a pyrrolobenzodiazepine (PBD) dimer payload (analogous to SG3249/tesirine, drug-to-antibody ratio [DAR] 2) — is administered systemically (intravenous, 1–3 mg/kg, q2w × 3 cycles) or via local intra-adipose injection to aged (20–24 month) male and female C57BL/6J mice bearing high visceral fat burden (or, in Phase 1, to primary human adipose-derived stromal cells [hASCs] driven to senescence in vitro),

THEN a ≥50% selective depletion of DPP4-high senescent cells in visceral and subcutaneous white adipose tissue (WAT) — quantified by flow cytometry for DPP4⁺/p16^INK4a⁺/SA-β-gal⁺ co-positivity, and by single-cell RNA sequencing — will be observed at 4–8 weeks post-treatment compared to isotype-ADC-treated age-matched controls, accompanied by ≥30% reduction in adipose tissue SASP cytokines (IL-6, IL-8, MMP-3 by ELISA/Luminex), improved systemic insulin sensitivity (glucose tolerance test), and preserved non-senescent adipose progenitor cell viability (DPP4-low/negative fraction ≥85% survival),

BECAUSE the following mechanistic chain is operative:

1. DPP4/CD26 is transcriptionally induced and selectively enriched on the plasma membrane of senescent human cells — identified and validated by mass spectrometry of the senescent membrane proteome — making it a bona fide, accessible extracellular target that distinguishes senescent from non-senescent cells in human adipose tissue. (DPP4 identified as senescent cell surface targetable protein)[ https://doi.org/10.1101/gad.302570.117]
2. Anti-DPP4 antibody binding to surface DPP4/CD26 triggers receptor-mediated endocytosis via clathrin-coated vesicles; DPP4 undergoes internalization kinetics sufficient for ADC cargo delivery, as supported by precedent from DPP4-targeting immunotoxin and peptide-conjugate studies described in the Evidence Set literature review (Evidence Set: DPP4/CD26 Biology section), with recycling half-times that allow net intracellular payload accumulation. [SPECULATIVE: the precise internalization rate constant in primary senescent human ASCs has not been formally quantified and must be confirmed in Phase 1.]
3. Upon internalization, the ADC is trafficked to the lysosomal compartment, where cathepsin B cleaves the Val-Ala dipeptide linker, releasing the free PBD dimer payload intracellularly. PBD dimers form sequence-selective, covalent interstrand DNA crosslinks in the minor groove of genomic DNA (Evidence Set: ADC Designs and Payloads section), a mechanism that is entirely cell-cycle-independent — unlike tubulin-targeting payloads (MMAE, DM1) which depend on active mitosis for cytotoxicity. Because senescent cells are permanently cell-cycle arrested (G1 or G2/M), PBD-based DNA crosslinking provides a critical mechanistic advantage: apoptosis is induced via ATM/ATR-p53 r...

SENS category: GlycoSENS

Key references: • doi.org/10.1101/gad.302570.117] • doi.org/10.1101/gad.302570.117]. • doi.org/10.1101/gad.302570.117