Preclinical evaluation of [¹¹¹ In]-DOTA-trastuzumab for clinical trials.

CONTEXT: Herceptin and its fragments have been radiolabeled and used in the imaging of human epidermal growth factor receptor 2 (HER2)/neu-positive tumors and development of diagnostic kits is of great importance in radiopharmacy. AIMS: In this study, ¹¹¹ In-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-trastuzumab (¹¹¹ In-DOTA-trastuzumab) was successively prepared and evaluated for ultimate use in the HER2 antigen imaging in oncology. SETTINGS AND DESIGN: The conjugate was prepared, labeled and evaluated using in vitro (radioimmunoassay [RIA], enzyme-linked immunosorbent assay (ELISA), stability, binding, internalization)/in vivo (bio-distribution, single-photon emission computed tomography [SPECT]) experiments. MATERIALS AND METHODS: ¹¹¹ In-DOTA-trastuzumab was prepared followed by determination of radiochemical purity (RCP), integrity of protein, immunoreactivity of radiolabeled antibody with HER2/neu antigen (by SkBr3 cell line binding and RIA methods) were determined followed by stability tests, internalization studies and the tissue bio-distribution determination in wild-type rats as well as SPECT imaging in SkBr3-bearing mice. STATISTICAL ANALYSIS USED: All values were expressed as mean ± standard deviation (mean ± SD) and the data were compared using Student's t-test. Statistical significance was defined as P < 0.05. RESULTS: ¹¹¹ In-DOTA-trastuzumab was prepared (RCP >95 ± 0.5%, S.A. 5.3 µCi/µg) with the average number of chelators per antibody of 6:1 showing significant immune-reactivity retention using ELISA. In vitro stability was >90% in phosphate buffered saline and 80 ± 0.5% in serum over 48 h. Cell binding was significant (>0.79). In vitro internalization reached up to %12-13 in 10 h. Significant tumor uptake was observed. CONCLUSIONS: In vitro and in vivo/SPECT imaging in SkBr3-bearing mice demonstrated that ¹¹¹ In-DOTA-trastuzumab is a potential compound for molecular imaging of SPECT for diagnosis and follow-up of HER2 expression in oncology.

Synthesis and Evaluation of [(67)Ga]-AMD3100: A Novel Imaging Agent for Targeting the Chemokine Receptor CXCR4.

In order to develop a possible C-X-C chemokine receptor type 4 (CXCR4) imaging agent for oncological scintigraphy, [(67)Ga]-labeled 1,1'-[1,4-Phenylene-bis(methylene)]bis(1,4,8,11-tetraazacyclotetradecane) ([(67)Ga]-AMD3100) was prepared by using [(67)Ga]GaCl3 and AMD-3100 for 2 h at 50 °C (radiochemical purity: >95% ITLC, >99% HPLC, specific activity: 1800-2000 TBq/mmol) in acetate buffer. The stability of the complex was checked in the presence of human serum (37 °C) and in the final formulation for four days. The biodistribution of the labeled compound in the vital organs of wild type Sprague-Dawley rats was determined and compared with that of the free Ga(3+) cation up to 48 h. Considering the spleen as the target organ, the best target:non target ratios were obtained 48 h post-injection (spleen:blood ratio; 14.5 and spleen:muscle ratio; 88.4). Initial SPECT images and biodistribution results in the wild type rats matched each other and demonstrated rapid washout of the tracer from the urinary tract. SPECT images in human breast carcinoma-bearing mice demonstrated a detectable tumor uptake in 48 h post-injection.

Development of ga-67 maltolate complex as an imaging agent.

Due to the antitumor activity of Gallium MAL complex, as well as recent findings on new targeted biomolecules in malignant cells through this complex, the development of radiolabeled gallium complex for future imaging studies was targeted. Ga-67 labeled 3-hydroxy-2-methyl-4H-pyran-4-onate (Ga-67 MAL) was prepared using freshly prepared Ga-67 chloride and 3-hydroxy-2-methyl-4H-pyran-4-onate in a sodium salt form in 25 min at 40° C. The stability of the complex was checked in final formulation and human serum for 24 h followed by the administration in Swiss mice for biodistribution studies. The complex was prepared in high radiochemical purity (> 97% ITLC, > 98% HPLC) and specific activity of 13-14 GBq/mmol and was stable in the presence of serum for 48 h. The partition coefficient was calculated for the compound (log p = 0.40). A detailed comparative pharmacokinetic study was performed for Ga-67 cation and Ga-67-MAL. The complex is more rapidly washed out from the circulation through kidneys and liver compared to Ga-67 cation and can be an interesting tumor imaging agent due to the fact that the cold compound is undergoing clinical trials as a safe and potential therapeutic agent for cancer.