Carbonic Anhydrase IX-Targeted α-Radionuclide Therapy with 225Ac Inhibits Tumor Growth in a Renal Cell Carcinoma Model

Robin I J Merkx; Mark Rijpkema; Gerben M Franssen; Annemarie Kip; Bart Smeets; Alfred Morgenstern; Frank Bruchertseifer; Eddie Yan; Michael P Wheatcroft; Egbert Oosterwijk; Peter F A Mulders; Sandra Heskamp

doi:10.3390/ph15050570

Carbonic Anhydrase IX-Targeted α-Radionuclide Therapy with 225Ac Inhibits Tumor Growth in a Renal Cell Carcinoma Model

Pharmaceuticals (Basel). 2022 May 2;15(5):570. doi: 10.3390/ph15050570.

Authors

Affiliations

¹ Department of Medical Imaging, Nuclear Medicine, Radboudumc, 6525 Nijmegen, The Netherlands.
² Department of Urology, Radboudumc, 6525 Nijmegen, The Netherlands.
³ Department of Pathology, Radboudumc, 6525 Nijmegen, The Netherlands.
⁴ European Commission, Joint Research Centre (JRC), 76344 Karlsruhe, Germany.
⁵ Telix Pharmaceuticals Limited, Melbourne, VIC 3051, Australia.

Abstract

In this study, we compared the tumor-targeting properties, therapeutic efficacy, and tolerability of the humanized anti-CAIX antibody (hG250) labeled with either the α-emitter actinium-225 (225Ac) or the β--emitter lutetium-177 (177Lu) in mice. BALB/c nude mice were grafted with human renal cell carcinoma SK-RC-52 cells and intravenously injected with 30 µg [225Ac] Ac-DOTA-hG250 (225Ac-hG250) or 30 µg [177Lu] Lu-DOTA-hG250 (177Lu-hG250), followed by ex vivo biodistribution studies. Therapeutic efficacy was evaluated in mice receiving 5, 15, and 25 kBq of 225Ac-hG250; 13 MBq of 177Lu-hG250; or no treatment. Tolerability was evaluated in non-tumor-bearing animals. High tumor uptake of both radioimmunoconjugates was observed and increased up to day 7 (212.8 ± 50.2 %IA/g vs. 101.0 ± 18.4 %IA/g for 225Ac-hG250 and 177Lu-hG250, respectively). Survival was significantly prolonged in mice treated with 15 kBq 225Ac-hG250, 25 kBq 225Ac-hG250, and 13 MBq 177Lu-hG250 compared to untreated control (p < 0.05). Non-tumor-bearing mice that received single-dose treatment with 15 or 25 kBq 225Ac-hG250 showed weight loss at the end of the experiment (day 126), and immunohistochemical analysis suggested radiation-induced nephrotoxicity. These results demonstrate the therapeutic potential of CAIX-targeted α-therapy in renal cell carcinoma. Future studies are required to find an optimal balance between therapeutic efficacy and toxicity.

Keywords: CAIX; G250; RCC; actinium-225; radioimmunotherapy.

Grants and funding

This study was supported financially through a clinical fellowship sponsorship agreement between the Radboudumc, Nijmegen, the Netherlands, and Telix Pharmaceuticals Ltd., Melbourne, Australia.