Targeted imaging agents for fluorescence-guided surgery in pediatric cancer models

Locally curative soft tissue sarcoma (STS) surgery is often challenged by infiltrative growth and microscopic residual disease, motivating the development of targeted intraoperative imaging. Soft-tissue sarcomas often arise in anatomically variable locations and in close proximity to critical neurovascular and visceral structures, making complete resection challenging and highlighting the potential value of fluorescence‑guided surgery for intraoperative tumor visualization. This study evaluated a clinical‑grade anti‑B7‑H3 antibody conjugated to IRDye800CW (MGA271‑IRDye800) as a near‑infrared probe for fluorescence‑guided surgery, with isotype IgG‑IRDye800 and free dye as controls. MGA271‑IRDye800 showed specific binding and strong fluorescence in B7‑H3–expressing sarcoma cells. In orthotopic rhabdomyosarcoma xenografts, longitudinal imaging revealed robust, sustained tumor uptake and significantly higher tumor-to-background ratios at 144 h (5.55 ± 2.21) versus IgG-IRDye800 (≈2.9 ± 1.07) and free IRDye800 (0.94 ± 0.13). Intraoperatively, MGA271‑IRDye800 clearly delineated tumor margins and distinguished tumor from adjacent muscle, supporting its promise to improve resection quality.