Dosimetry of a Novel 111Indium-Labeled Anti-P-Cadherin Monoclonal Antibody (FF-21101) in Non-Human Primates.

P-cadherin is associated with a wide range of tumor types, making it an attractive therapeutic target. FF-21101 is a human-mouse chimeric monoclonal antibody (mAb) directed against human P-cadherin, which has been radioconjugated with indium-111 (111In) utilizing a DOTA chelator. We investigated the biodistribution of FF-21101(111In) in cynomolgus macaques and extrapolated the results to estimate internal radiation doses of 111In- and yttrium-90 (90Y)-FF-21101 for targeted radioimmunotherapy in humans. Whole-body planar and SPECT imaging were performed at 0, 2, 24, 48, 72, 96, and 120 h post-injection, using a dual-head gamma camera. Volumes of interest of identifiable source organs of radioactivity were defined on aligned reference CT and serial SPECT images. Organs with the highest estimated dose values (mSv/MBq) for FF-21101(111In) were the lungs (0.840), spleen (0.816), liver (0.751), kidneys (0.629), and heart wall (0.451); and for FF-21101(90Y) dose values were: lungs (10.49), spleen (8.21), kidneys (5.92), liver (5.46), and heart wall (2.61). FF-21101(111In) exhibits favorable biodistribution in cynomolgus macaques and estimated human dosimetric characteristics. Data obtained in this study were used to support the filing of an investigational new drug application with the FDA for a Phase I clinical trial.

Current and Future Trends in Early Detection of Pancreatic Cancer: Molecular Targets and PET Probes.

Early detection of pancreatic cancer has been a long-standing challenge in determining prognosis and management of the deadly disease. Although the incidence of pancreatic cancer is low (2% of all malignancies), it is the fourth leading cause of deaths attributable to cancer in the U.S. A major cause for the high mortality rate, which exceeds 85%, is the difficulty in diagnosing the disease early in its development. The relative lack of reliable diagnostic tools to screen patients who are asymptomatic prior to the aggressive progression of disease has been the primary contributing factor in the high mortality rate in this patient population. Indeed, 80-90% of patients with pancreatic cancer have relatively small unresectable tumors at the time of diagnosis. Therefore, there is an unmet need for a highly sensitive diagnostic imaging modality to detect early-stage pancreatic cancer, as this may save the lives of many thousands of patients. Many literature reviews have been published on various aspects of pancreatic cancer, including biology, screening, and therapy; however, limited information is available on early detection, especially the use of highly sensitive modalities such as positron emission tomography (PET). Current [(18)F]FDG/PET imaging combined with CT (PET/CT) lacks the necessary sensitivity and specificity for detection of small lesions (~2-3 mm) of pancreatic cancer that may be resectable and curable. Furthermore, accumulation of [(18)F]FDG in inflammatory tissue is a major problem; therefore, an appropriate PET tracer that is both highly sensitive and specific for carcinoma is necessary for PET imaging of early stage pancreatic cancer. This review focuses on early detection of pancreatic cancer by PET, including new targets and the development and application of new PET tracers.

Preliminary evaluation of 1'-[(18)F]fluoroethyl-ß-D-lactose ([(18)F]FEL) for detection of pancreatic cancer in nude mouse orthotopic xenografts.

INTRODUCTION: Early detection of pancreatic cancer could save many thousands of lives. Non-invasive diagnostic imaging, including PET with [(18)F]FDG, has inadequate resolution for detection of small (2-3 mm) pancreatic tumours. We demonstrated the efficacy of PET imaging with an (18)F-labelled lactose derivative, [(18)F]FEDL, that targets HIP/PAP, a biomarker that is overexpressed in the peritumoural pancreas. We developed another analogue, 1-[(18)F]fluoroethyl lactose ([(18)F]FEL), which is simpler to synthesise, for the same application. We conducted a preliminary evaluation of the new probe and its efficacy in detecting orthotopic pancreatic carcinoma xenografts in mice. METHODS: Xenografts were developed in nude mice by injecting L3.6 pl/GL(+) pancreatic carcinoma cells into the pancreas of each mouse. Tumour growth was monitored by bioluminescence imaging (BLI); accuracy of BLI tumour size estimates was verified by MRI in two representative mice. When the tumour size reached approximately 2-3mm, the animals were injected with [(18)F]FEL (3.7 MBq) and underwent static PET/CT scans. Blood samples were collected at 2, 5, 10, 20 and 60 min after [(18)F]FEL injection to track blood clearance. Following imaging, animals were sacrificed and their organs and tumours/pancreatic tissue were collected and counted on a gamma counter. Pancreas, including tumour, was frozen, sliced and used for autoradiography and immunohistochemical analysis of HIP/PAP expression. RESULTS: Tumour growth was rapid, as observed by BLI and MRI. Blood clearance of [(18)F]FEL was bi-exponential, with half-lives of approximately 3.5 min and 40 min. Mean accumulation of [(18)F]FEL in the peritumoural pancreatic tissue was 1.29±0.295 %ID/g, and that in the normal pancreas of control animals was 0.090±0.101 %ID/g. [(18)F]FEL was cleared predominantly by the kidneys. Comparative analysis of autoradiographic images and immunostaining results demonstrated a correlation between [(18)F]FEL binding and HIP/PAP expression. CONCLUSION: [(18)F]FEL may be useful for non-invasive imaging of early-stage pancreatic tumours by PET. The results warrant further studies.

Optimization of precursor synthesis, formulation and stability of 1'-[18F]fluoroethyl-ß-D-lactose ([18F]FEL) for preclinical studies in detection of pancreatic cancer.

INTRODUCTION: 1'-[(18)F]Fluoroethyl-ß-D-lactose ([(18)F]FEL) is a new PET imaging agent for early detection of pancreatic cancer and hepatocellular carcinoma. We previously reported the syntheses of [(18)F]FEL using a bromo- and a tosyl- precursor, followed by an improved method using a nosyl-precursor. However, some steps in the synthesis of the precursor appeared to be problematic producing low yields. Here, we report on an optimized method for synthesis of the precursor and production of [(18)F]FEL; we also describe [(18)F]FEL's formulation and stability. METHODS: Acetylation of D-lactose 1 was performed following a literature procedure to obtain 1',2',3',6',2,3,4,6-D-lactose octa-acetate 2a/2b. Bromination of 2a/2b was performed using HBr/acetic acid to produce 1'-bromo-2',3',6',2,3,4,6-hepta-O-acetyl-α-D-lactose 3. Coupling of 3 with ethylene glycol was performed in the presence of Ag-tosylate and an excess of ethylene glycol to produce 4a. Compound 4a was reacted with p-nitrophenylsulfonyl chloride to produce the nosyl derivative 5. Radiofluorination of 5 was performed using K[(18)F]fluoride/kryptofix to obtain 6, which was purified by HPLC and hydrolyzed with Na-methoxide to produce 7. RESULTS: Compound 2 (2a/2b) was obtained in 83% yield as a mixture of two anomeric products. Compound 3 was obtained from the 2a/2b mixture in 80% yield as one product. Coupling of 3 with ethylene glycol produced 4a in 90% yield. Compound 5 was obtained in 64% yield, and radiofluorination of 5 produced 6 in 62.5% ± 7.5% yields (n=8). Hydrolysis of 6 with Na-methoxide produced 7 in 42.0% ± 7.0% yield (n=8) from the end of bombardment. CONCLUSIONS: A simple 4-step synthesis of the precursor, compound 5, has been achieved with improved yields. A new formulation of [(18)F]FEL has been developed that allows the product to remain stable at ambient temperature for use in animal studies. This improved synthesis of the precursor and stable formulation of [(18)F]FEL should be useful for routine production of the radiotracer and its preclinical and, possibly, clinical applications.