IF a structured intermittent "hit-and-run" dasatinib + quercetin (D+Q) protocol — dasatinib 5 mg/kg + quercetin 50 mg/kg by oral gavage for 3 consecutive days, followed by a 28-day drug-free recovery interval, repeated for 4–6 cycles over approximately 5–6 months total — is administered to aged C57BL/6 mice (22–24 months, both sexes),

THEN cumulative senescent cell burden across peripheral tissues (skeletal muscle, liver, adipose, lung) will be reduced to an extent equivalent to or greater than low-dose continuous D+Q administration, as measured by tissue p16^INK4a and p21^CIP1 protein expression, SA-β-galactosidase staining density, circulating SASP cytokine panels (IL-6, IL-8, MCP-1), and circulating cell-free mitochondrial DNA (cf-mtDNA) as a novel longitudinal biomarker — while hematological toxicity indices (platelet count, absolute neutrophil count, lymphocyte count) will recover to baseline within the 28-day inter-cycle window, confirming the immunological safety advantage of the intermittent schedule,

BECAUSE the following mechanistic chain operates:

1. Primary senescent cell elimination: D+Q transiently disables the Bcl-2/Bcl-xL and PI3K/p21-dependent senescent cell anti-apoptotic pathways (SCAPs) within 3 days of administration, triggering apoptosis selectively in senescent cells that have upregulated these survival nodes; drug clearance within days then terminates on-target killing, leaving dividing cell populations largely unaffected. (Intermittent D+Q eliminates senescent cells, alleviates physical dysfunction, and extends lifespan in aged mice)[https://doi.org/10.1038/s41591-018-0092-9]

2. SASP-driven secondary "bystander" senescence occupies the 28-day window — the core novel mechanistic link [SPECULATIVE]: Surviving or newly differentiated cells exposed to the residual SASP microenvironment after each D+Q hit are induced into a secondary, paracrine senescent state via ROS, IL-6, and TGF-β signaling. These bystander-senescent cells require approximately 2–4 weeks to fully upregulate SCAPs to the threshold required for D+Q sensitivity. The 28-day inter-cycle interval is therefore not merely passive immune recovery time — it is the biologically necessary maturation period for bystander-induced secondary senescent cells to become newly vulnerable to the next D+Q cycle, enabling each successive cycle to target a fresh wave of cells rather than re-clearing only the slowly replenishing primary pool. (Small numbers of senescent cells induce senescence in neighboring host cells and accelerate dysfunction)[https://doi.org/10.1038/s41591-018-0092-9]

3. cf-mtDNA links SASP-mediated sterile inflammation to senescent cell burden longitudinally: Senolytic clearance of senescent cells reduces circulating cell-free mitochondrial DNA (cf-mtDNA), a damage-associated molecular pattern (DAMP) released by senescent cells that drives inflammatory T cell responses. The reduction in cf-mtDNA after each D+Q cycle provides a non-invasive, c...

SENS category: GlycoSENS

Key references: • doi.org/10.1038/s41591-018-0092-9] • doi.org/10.1038/s41467-020-18039-x] • doi.org/10.1111/acel.12931] • doi.org/10.1111/acel.13394]; • doi.org/10.1007/s11357-022-00542-2]