Astatinated trastuzumab, a putative agent for radionuclide immunotherapy of ErbB2-expressing tumours

Abstract

Abstract. The anti-ErbB2 antibody trastuzumab is used for the treatment of patients with advanced breast cancer, resulting in a response rate of 40-60%. Coupling with a cytotoxic nuclide, e.g. ·-emitting 211 At, may further increase tumour response. The tumour-targeting properties of trastuzumab, astatinated using N-succinimidyl-para-(tri-nmethylstannyl)-benzoate, were evaluated and compared with those of radioiodinated trastuzumab in this study. We found that astatinated trastuzumab retains high specificity towards ErbB2. While the immunoreactive fraction of radioiodinated trastuzumab was higher than that of astatinated trastuzumab (76±9% versus 54±28%), both radioconjugates showed high affinity (K D 0.75±0.16 nM versus 1.8±0.3 nM). A growth inhibition study indicated a dose-dependent cell deactivation, in which approximately 74 cell-associated astatine decays per cell gave a survival fraction of 4.5±0.8x10 -4 . Results of a comparative animal study on normal mice gave no indication that astatination would have any adverse effects on the biodistribution of the antibody. In conclusion, the results of the study suggest that astatinated trastuzumab is a promising candidate for treating ErbB2-expressing tumours.

Direct Procedure for the Production of211At-Labeled Antibodies with an ε-Lysyl-3-(Trimethylstannyl)Benzamide Immunoconjugate

“…The immunoreactivity of directly labeled 211 Attrastuzumab was compared with those of 125 I-trastuzumab and 211 At-trastuzumab produced by the 2-step procedure. The affinity data were in line with those of previous studies evaluating the characteristics of trastuzumab and labeled trastuzumab (33)(34)(35). However, a decrease in the affinity of directly astatinated trastuzumab by factors of 2 and 3 relative to the affinities of conventionally astatinated trastuzumab and iodinated trastuzumab, respectively, indicated an effect of the higher ratio of m-MeATE to antibody.…”

D-amino acid peptide residualizing agents bearing N-hydroxysuccinimido- and maleimido-functional groups and their application for trastuzumab radioiodination

“…Despite the decrease in intracellular radioactivity seen at later time points, it is important to point out that the degree of intracellular retention of radioactivity observed with trastuzumab labeled with NHS-[ 131 I]IB- d -EEEG or Mal- d -GEEEK-[ 125 I]IB was considerably higher than those reported for trastuzumab radioiodinated by other methods [27-29]. For example, with trastuzumab labeled with N -succinimidyl p -[ 125 I]iodobenzoate (P[ 125 I]IB), there was about 70 % of internalized radioactivity in SKBR-3 cells at 1 h that decreased almost threefold to only 24.3% after 20 h incubation at 37°C [29].…”

“…For example, with trastuzumab labeled with N -succinimidyl p -[ 125 I]iodobenzoate (P[ 125 I]IB), there was about 70 % of internalized radioactivity in SKBR-3 cells at 1 h that decreased almost threefold to only 24.3% after 20 h incubation at 37°C [29]. Likewise, with P[ 125 I]IB-trastuzumab, less than 12 % of radioiodine activity remained internalized in NCI-N87 cells after a 24 h incubation period [28].…”

Biodistribution of 211At labeled HER-2 binding affibody molecules in mice

“…In most cases, the biodistribution of a protein radiolabeled with 125 I and 211 At are quite similar (11,15,16), but there have been previous reported exceptions (17,18), especially when smaller molecules, such as antibody fragments have been used. The results from these studies, with high uptake in stomach, lungs and spleen, indicate that free 211 At is released in vivo.…”

“…211 At was produced at Rigshospitalet, Copenhagen, Denmark, as described by Persson et al (11) and the astatine was separated from the target using dry distillation at our laboratory. The astatine was eluted in chloroform, which was evaporated under a gentle flow of argon gas.…”