In vitro and in vivo evaluation of anti-HER2 antibody conjugates labelled with 225Ac

Background: Overexpression of human epidermal growth factor receptor type 2 (HER2) occurs in multiple carcinomas. For example, up to 20 % of breast cancer cases are classified as HER2 positive (HER2+). For treatment of this disease immunotherapy with monoclonal antibodies such as trastuzumab of pertuzumab is usually used. However, the precise targeting of monoclonal antibodies to HER2+ tumour lesions can be used as well in radioimmunotherapy to deliver medical radionuclides precisely to the afflicted area and therefore minimize radiation exposure of healthy tissues. In this study, DOTA conjugates of monoclonal antibodies trastuzumab and pertuzumab were prepared and tested in vitro. One of them, 225Ac-DOTA-pertuzumab, also underwent ex-vivo biodistribution study with normal and HER2+ and HER2- tumour-xenografted mice. This radioconjugate has never been described before. Results: Three DOTA-conjugates of HER2 targeting monoclonal antibodies, trastuzumab and pertuzumab, were prepared and radiolabelled with 225Ac in different molar ratios which lead to optimization of preparation and radiolabelling procedure. Prepared radioconjugates showed excellent stability in vitro in both fetal bovine serum and phosphate buffered saline under room and decreased temperature for 10 days. In in vitro cell studies with HER2-overexpressing cell-line (SKOV-3) and low HER2 expressing cell line (MDA-MB-231) radioconjugates of both antibodies proved to have high binding specificity and affinity towards HER2 receptors. These findings were confirmed for a novel radioconjugate 225Ac DOTA-pertuzumab in ex vivo biodistribution study, when uptake in HER2+ tumour was 50 ± 14 % ID/g and HER2- tumour showed uptake comparable with healthy tissues (max. 5.0 ± 1.7 % ID/g). High uptake in spleen was attributed to elimination of antibody as well as use of immune deficient mouse strain (SCID). Conclusions: During this study the optimization of preparation and radiolabelling of HER2 targeting antibodies with 225Ac was achieved and the radioconjugate 225Ac DOTA pertuzumab was prepared for the first time. Radioconjugates of both tested antibodies showed excellent qualities in terms of stability and HER2 receptor affinity and especially radioconjugate 225Ac-DOTA-pertuzumab is considered promising for further in vivo studies.

FIALOVA Katerina;  ONDRAK Lukas;  VLK M.;  KOZEMPEL J.;  NOVAKOVA Katerina;  NOVY Zbynek;  HAJDUOVA Katarina;  HAJDUCH Marian;  PETRIK Milos;  PRUSZYNSKI Marek;  BRUCHERTSEIFER Frank;  MORGENSTERN Alfred; 

2025-04-09

SPRINGER

JRC141754

1619-7089 (online),   

https://ejnmmipharmchem.springeropen.com/articles/10.1186/s41181-025-00337-8,    https://publications.jrc.ec.europa.eu/repository/handle/JRC141754,   

10.1186/s41181-025-00337-8 (online),