Atezolizumab (PD‑L1) in ASPS shows low late toxicity beyond 2 years of exposure

Atezolizumab is an anti–PD‑L1 checkpoint inhibitor; in the Phase 2 NCT03141684 trial in unresectable/metastatic alveolar soft part sarcoma (ASPS), this AACR 2026 update focused on late safety among patients treated >34 cycles (>2 years), including atezolizumab monotherapy and post‑progression crossover to atezolizumab + bevacizumab (VEGF inhibitor). As of 6/16/25, 54 patients were enrolled, and 17 patients (age 11–56; median 29) received prolonged therapy (12 mono only: 35–103 cycles; 5 mono→combo: 39–124 cycles); only 3/17 (18%) developed new-onset grade 2–3 TRAEs after cycle 34 (grade 3 AST; grade 2 hypertension + proteinuria; grade 2 pruritus), with no grade 4–5 events, no discontinuations for toxicity, and resolution of all TRAEs. Efficacy context (not the endpoint here): atezolizumab previously reported 37% ORR in advanced ASPS with now-maturing response duration cited here as 10–69 months—while historical systemic options (e.g., VEGF TKIs) can produce disease control/partial responses, they typically require chronic dosing and carry ongoing vascular/toxicity burdens, making “how long to treat” with ICI a particularly practical question in this AYA-skewing sarcoma population.