Ruxolitinib, a clinically approved JAK1/2 inhibitor, administered early and intermittently during radiotherapy suppressed the pro-inflammatory senescence-associated secretory phenotype (SASP) and prevented chronic bone damage across three preclinical radiation regimens in male mice — 30Gy (5×6Gy), 60Gy (5×12Gy), and a single 24Gy dose. Critically, clinical data from prostate cancer patients receiving spinal metastasis radiotherapy showed parallel acute elevation of circulating SASP proteins, lending direct translational relevance to the mouse findings. JAKi treatment reduced telomere dysfunction, lowered senescence marker expression, and markedly decreased bone-marrow adiposity compared to irradiated controls, performing comparably to the senolytic combination dasatinib plus quercetin.
This finding matters because radiation-induced bone loss represents a poorly managed late toxicity affecting hundreds of thousands of cancer survivors annually, with fracture risk persisting years post-treatment. While senolytics eliminate senescent cells outright, senomorphics like ruxolitinib suppress their harmful secretome without cell clearance — a potentially safer strategy when residual senescent cells may serve repair functions. Ruxolitinib is already FDA-approved for myelofibrosis and graft-versus-host disease, dramatically lowering the translational barrier. However, this remains predominantly a preclinical study in male mice only; sex-specific effects on bone metabolism are well-documented, and female cohort data are absent. The clinical SASP data are correlative, not interventional. Still, the mechanistic coherence across species and the use of an approved drug positions this as a genuinely actionable finding — incremental in concept but potentially paradigm-shifting for radioprotection protocols.