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


OBJECTIVE
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.


METHODS
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.


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.


METHODS
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.
Behrouz
B
Alirezapour
Radiopharmacy Research Group, Radiation Application Research School, Nuclear Science and Technology Research Institute, 11365-3486, Tehran, Iran.
Amir Reza
AR
Jalilian
Saeed
S
Rajabifar
Mohammad
M
Mirzaii
Sedigheh
S
Moradkhani
Mehraban
M
Pouladi
Gholamreza
G
Aslani
D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000493:pharmacokinetics; D061067:Antibodies, Monoclonal, Humanized / Q000737:chemistry / Q000493:pharmacokinetics; D045744:Cell Line, Tumor; D002855:Chromatography, Thin Layer; D004195:Disease Models, Animal; D064593:Heterografts; D006801:Humans; D007205:Indium Radioisotopes / Q000737:chemistry / Q000493:pharmacokinetics; D007553:Isotope Labeling; D051379:Mice; D009369:Neoplasms / Q000175:diagnosis / Q000378:metabolism; D019275:Radiopharmaceuticals / Q000737:chemistry / Q000493:pharmacokinetics; D051381:Rats; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D000068878:Trastuzumab
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D007205:Indium Radioisotopes; D019275:Radiopharmaceuticals; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab