CAPItello-281: PTEN Cut-Off Analyses and Disease Biology

Understanding how biomarker intensity influences treatment response is central to precision oncology. Gordon A. Brown, DO, FACOS, an associate professor at Rowan University School of Osteopathic Medicine, program director of Urologic Surgery at Rowan University School of Osteopathic Medicine, and director of New Jersey Urology’s Center for Advanced Therapeutics, reviews post hoc analyses from CAPItello-281 (NCT04493853) that evaluated increasingly stringent PTEN deficiency thresholds, including ≥95%, ≥99%, and 100% loss of expression. These analyses were designed to enrich for patients most dependent on PI3K/AKT signaling and therefore most likely to benefit from AKT inhibition.

Brown explains that as PTEN deficiency increased, outcomes in the control arm worsened substantially, reflecting increasingly aggressive disease biology. In contrast, patients receiving capivasertib maintained more favorable rPFS outcomes, resulting in progressively lower hazard ratios. This divergence supports PTEN deficiency as both a prognostic marker of risk and a predictive marker of therapeutic responsiveness.

Consistent improvements across exploratory end points—including time to subsequent therapy, symptomatic skeletal events, and progression measures—further reinforce the biologic hypothesis. Brown concludes that deeper PTEN deficiency likely reflects greater pathway dependence, explaining why tumors with complete loss demonstrate enhanced sensitivity to AKT inhibition and supporting biomarker-guided treatment intensification.