Early diagnosis and treatment of melanoma are essential to minimizing morbidity and mortality. The presence of lymph node metastases is a vital prognostic predictor, and accurate identification by imaging has important implications for disease staging, prognosis, and clinical outcome. Sentinel lymph node (SLN) mapping procedures are limited by a lack of intraoperative visualization tools that can aid accurate determination of disease spread and delineate nodes from adjacent critical neural and vascular structures. Newer methods for circumventing these issues can exploit a variety of imaging tools, including biocompatible particle-based platforms coupled with portable device technologies for use with image-guided surgical and interventional procedures. We describe herein a clinically-translated, integrin-targeting platform for use with both PET and optical imaging that meets a number of key design criteria for improving SLN tissue localization and retention, target-to-background ratios, and clearance from the site of injection and the body. The use of such agents for selectively probing critical cancer targets may elucidate important insights into cellular and molecular processes that govern metastatic disease spread. Coupled with portable, real-time optical camera systems, we show that pre-operative PET imaging findings for mapping metastatic disease in clinically-relevant larger-animal models can be readily translated into the intraoperative setting for direct visualization of the draining tumor lymphatics and fluorescent SLN/s with histologic correlation. The specificity of this platform, relative to the standard-of-care radiotracer, 18F-FDG, for potentially discriminating metastatic disease from inflammatory processes is also discussed in the setting of surgically-based or interventionally-driven therapies.

Purpose Standard imaging for assessing osseous metastases in advanced prostate cancer remains focused on altered bone metabolism and is inadequate for diagnostic, prognostic, or predictive purposes. We performed a first-in-human phase I/II study of 89Zr-DFO-huJ591 (89Zr-J591) PET/CT immunoscintigraphy to assess performance characteristics for detecting metastases compared to conventional imaging modalities (CIMs) and pathology. Experimental Design Fifty patients with progressive metastatic castration-resistant prostate cancers were injected with 5 mCi of 89Zr-J591. Whole body PET/CT scans were obtained, and images were analyzed for tumor visualization. Comparison was made to contemporaneously obtained bone scintigraphy and cross-sectional imaging on a lesion-by-lesion basis, and with biopsies of metastatic sites. Results Median standardized uptake value for 89Zr-J591-positive bone lesions (n = 491) was 8.9; soft tissue lesions (n = 90): 4.8 (p < .00003). 89Zr-J591 detected 491 osseous sites compared to 339 by MDP, and 90 soft tissue lesions compared to 124 by CT. Compared to all CIMs combined, 89Zr-J591 detected an additional 99 osseous sites. Forty-six lesions (21 bone, 25 soft tissue) were biopsied in 34 patients; 18/19 89Zr-J591-positive osseous sites and 14/16 89Zr-J591-positive soft tissue sites were positive for prostate cancer. The overall accuracy of 89Zr-J591 was 95.2% (20/21) for osseous lesions and 60% (15/25) for soft tissue lesions. Conclusions 89Zr-J591 imaging demonstrated superior targeting of bone lesions relative to CIMs. Targeting soft tissue lesions was less optimal, although 89Zr-J591 had similar accuracy as individual CIMs. This study will provide benchmark data for comparing performance of proposed PSMA targeting agents for prostate cancer.

Purpose Given the bone tropism of prostate cancer, conventional imaging modalities poorly identify or quantify metastatic disease. 89Zr-huJ591 positron emission tomography (PET) imaging was performed in patients with metastatic prostate cancer to analyze and validate this as an imaging biomarker for metastatic disease. The purpose of this initial study was to assess safety, biodistribution, normal organ dosimetry, and optimal imaging time post-injection for lesion detection. Methods Ten patients with metastatic prostate cancer received 5 mCi of 89Zr-huJ591. Four whole-body scans with multiple whole-body count rate measurements and serum activity concentration measurements were obtained in all patients. Biodistribution, clearance, and lesion uptake by 89Zr-huJ591 immuno-PET imaging was analyzed and dosimetry was estimated using MIRD techniques. Initial assessment of lesion targeting of 89Zr-huJ591 was done. Optimal time for imaging post-injection was determined. Results The dose was well tolerated with mild chills and rigors seen in two patients. The clearance of 89Zr-huJ591 from serum was bi-exponential with biological half-lives of 7 ± 4.5 h (range 1.1–14 h) and 62 ± 13 h (range 51–89 h) for initial rapid and later slow phase. Whole-body biological clearance was 219 ± 48 h (range 153–317 h). The mean whole-body and liver residence time was 78.7 and 25.6 h, respectively. Dosimetric estimates to critical organs included liver 7.7 ± 1.5 cGy/mCi, renal cortex 3.5 ± 0.4 cGy/mCi, and bone marrow 1.2 ± 0.2 cGy/mCi. Optimal time for patient imaging after injection was 7 ± 1 days. Lesion targeting of bone or soft tissue was seen in all patients. Biopsies were performed in 8 patients for a total 12 lesions, all of which were histologically confirmed as metastatic prostate cancer. One biopsy-proven lesion was not positive on 89Zr-huJ591, while the remaining 11 lesions were 89Zr-huJ591 positive. Two biopsy-positive nodal lesions were noted only on 89Zr-huJ591 study, while the conventional imaging modality was negative. Conclusion 89Zr-huJ591 PET imaging of prostate-specific membrane antigen expression is safe and shows good localization of disease in prostate cancer patients. Liver is the critical organ for dosimetry, and 7 ± 1 days is the optimal imaging time. A larger study is underway to determine lesion detection in an expanded cohort of patients with metastatic prostate cancer.

Background: B7-H3 is an immune inhibitory ligand and an antigen on many solid tumors. Results: Antibody 8H9 was humanized and affinity-matured, and its epitope was mapped to the FG loop of B7-H3. Conclusion: hu8H9 antibodies had potent antitumor activity and may modulate immune inhibitory properties of B7-H3. Significance: Antibodies were developed to target solid tumors and affect immune checkpoint blockade.