Senolytic drug reduces intervertebral degeneration in males but not females

The senolytic PROTAC 753b, designed to eliminate senescent cells by triggering ubiquitin-mediated destruction of BCL-2/BCL-xL proteins, demonstrated strikingly different efficacy between sexes in treating intervertebral disc degeneration. In aging mice treated systemically between 16 and 22 months, males showed significant reductions in matrix metalloproteinase-mediated aggrecan breakdown, disc matrix loss, and inflammatory markers (IL-6 and TNFα), while females exhibited no therapeutic response. Although both sexes accumulated senescence markers with age—measured by p16INK4a, IL-6, IL-8, and TNFα expression in intervertebral disc tissue—the senolytic failed to reduce these signals in either group, suggesting the degenerative mechanism operates fundamentally differently by sex. The findings raise a critical question for aging-medicine development: does senescent cell burden differ qualitatively between men and women, or do females simply require alternative molecular targets? This disconnect between senescent cell clearance and clinical benefit in females signals a more complex landscape ahead for longevity therapeutics, where sex-agnostic approaches may prove insufficient for precision anti-aging interventions.