O2141: Intraoperative Molecular Imaging of a Mouse Model of Neuroblastoma with in-111-dinutuximab-ir800

Background: Neuroblastoma (NB) is the most common extracranial pediatric solid tumor, causing 15% of cancer-related deaths in children. While complete macroscopic resection improves outcomes, intraoperative identification of tumor margins and additional disease deposits remains challenging. Intraoperative molecular imaging (IMI) is a burgeoning field which enables targeted detection of specific epitopes on tumor tissue. Detection of targeted radioactivity (such as In-111 gamma decay) can be used to detect targeted epitopes through up to 5 cm of tissue, while near-infrared fluorescence (such as from IRDye800CW) can be used to visualize tumors and margins. GD2 is consistently and highly expressed in neuroblastoma and other cancers, with minimal expression in normal tissues and is targeted by the FDA-approved antibody, dinutuximab, for NB treatment. Here, we test the feasibility of IMI with a novel dual-labeled probe targeting GD2, In-111-dinutuximab-IR800, in an orthotopic, xenograft mouse model of neuroblastoma.

Methods: DTPA and IRDye®800CW-NHS ester were ligated to dinutuximab, purified, and radiolabeled with In-111 to generate In-111-dinutuximab-IR800. SK-N-BE(2) human neuroblastoma cells were injected into the left adrenal gland of 4-6 week old athymic nude mice. Xenograft-bearing mice were injected with probe 3-4 days prior to further experiments. Widely available handheld intraoperative detectors were then used to identify gamma decay (Neoprobe®) and near-infrared fluorescence (SPY-PHI) in the tumor-bearing mice prior to organ harvesting for gamma-count-based biodistribution measurements.

Results: Dinutuximab was successfully labeled with DTPA and IRDye®800CW-NHS, then radiolabeled with In-111 to generate In-111-dinutuximab-IR800. In-111-dinutuximab-IR800 accumulated in NB xenografts at 3 and 4 days after injection. On both days, the handheld gamma probe showed increased signal in the tumor-bearing left flank relative to other regions in vivo (p < 0.05) and greater signal in the left adrenal vs the right adrenal and kidney ex vivo (p < 0.05). Tumors were also clearly visible with sharp margins using the handheld SPY-PHI near-infrared camera (Fig. 1). Biodistribution demonstrated tumor-specific accumulation of the IMI agent, with a significant tumor to background ratio (Day 3 and 4, p< 0.05; Fig. 2). Comparing the gamma decay per gram of tissue, on days 3 and 4, the tumor-to-blood ratios were 3.21 and 3.52, respectively, while the tumor-to-muscle ratios were 22.18 and 26.99.

Conclusion: A novel dual-labeled IMI probe for radiation and fluorescence detection, In-111-dinutuximab-IR800, accumulates in GD2-positive NB tumors in a xenograft mouse model. The probe demonstrates excellent tumor-to-background ratios 3 and 4 days after injection. Furthermore, gamma decay and near-infrared fluorescence of the IMI agent in tumor tissue can be detected with widely available handheld devices.