Small Molecule Probes for Fluorescence-guided Head and Neck Cancer Surgery

PROJECT SUMMARY Head and neck squamous cell carcinoma (HNSCC) is the sixth most prevalent cancer type, with over 650,000 cases diagnosed annually worldwide. Positive margins are reported in up to 30% of head and neck cancer sur- geries, where margin status is a major prognostic factor for overall survival. While preoperative x-ray, computed tomography (CT) and ultrasound imaging have enabled in depth evaluation, diagnosis, and surgical planning, a gap continues to exists between preoperative imaging and intraoperative reality. Accurate surgical identification of the tumor margins and small lesions remains challenging. Surprisingly, no clinically approved technology can directly enhance intraoperative guidance for tumor resection and tis-sue preservation for head and neck cancers, which are typically performed through anatomical knowledge, visual cues and palpation. Fluorescence Guided Surgery (FGS) has successfully integrated into clinical medicine with only two FDA-approved near-infrared (NIR, 650-900 nm) fluorophores. FGS systems operate almost exclusively in the NIR region, where tissue chromo- phore absorbance, autofluorescence and scatter fall to local minima, permitting high contrast and high-resolution imaging at depths up to a centimeter. Intraoperative guidance with tumor-specific FGS could significantly improve surgical outcomes for head and neck cancer patients, providing a new paradigm for surgery. An important con- sideration for wide clinical adoption is ease of implementation into the current surgical workflow. Presently, the majority of FGS contrast agents under development are classified as “always-on” probes, where continuous fluorescence emission occurs throughout imaging, regardless of the probe proximity to its binding target. Off- target accumulation of these always-on probes leads to elevated background signal, and a considerable amount of time is required for the non-specific probe accumulation to be cleared to generate adequate tumor-to-back- ground ratio (TBR) for decision-making during the surgery. Patients are required to receive contrast agent injec- tion days before surgery. For patients, this implicates additional hospital visits with extra costs and stress. This is in part due to large probe size resulting in limited extravasation, long circulation times, and impaired tumor penetration. To alleviate these challenges, smaller targeting moieties with high specificity and affinity are highly desirable to provide superior TBR shortly after systemic administration, permitting ready integration into the ex- isting surgical workflow. Herein, we propose to develop a novel tumor-targeted FGS solution to address this unmet clinical need. We will develop first-in-class NIR fluorogenic probes that target mutants of EGFR in head and neck cancer, where high TBR will be crucial for accurate tumor margin assessment, the detection of small tumor nodules, residue lesions and multi-focal disease. These novel fluorogenic probes as intraoperative aid capable of identifying and distinguishing these tumors in real time with high sensitivity and specificity could sig- nificantly reduce positive margin rates and improve surgical outcomes for head and neck cancer patients.