December 15, 2025

Spotlight on astatine-211, an alpha-emitting radionuclide with high cytotoxic potential, which represents a major step forward in nuclear medicine, within the highly promising field of targeted radiotherapy.

A collaboration between Atonco and the Institut de Cancérologie de l’Ouest

ATONCO designs and develops targeted treatments for cancers resistant to conventional approaches, notably using astatine-211.

ICO has obtained authorization for the first Phase I clinical trial, PERSEVERANCE EU, using astatine-211 in the treatment of bladder cancer.

A deep dive into cutting-edge medicine with an ultra-targeted radiotherapeutic treatment.

The PERSEVERANCE EU clinical trial evaluating the safety, tolerance, and response to ATO-101™ authorized: a first in France with astatine-211.

The Institut de Cancérologie de l’Ouest (ICO) has been authorized to launch the Phase I PERSEVERANCE EU clinical trial (NCT07260162), entitled A First In Human Phase I Trial Evaluating Safety, Tolerability and Response of [211At]At-Girentuximab (ATO-101™) in Patients With Non-Muscle-Invasive Bladder Cancer Refractory to Standard Treatment.

This trial aims to evaluate the safety, tolerability, and response to ATO-101™ treatment in patients with non-muscle-invasive bladder cancer refractory to standard treatments. The study marks an important milestone in the development of innovative therapeutic treatments based on alpha emitters.

An innovative treatment using astatine-211

ATO-101™ ([²¹¹At]At-girentuximab), supplied by Atonco, consists of an antibody directed against the CA-IX antigen (girentuximab) coupled with astatine-211, an alpha-emitting radionuclide with high cytotoxic potential. Its very short particle range should enable it to effectively target tumor cells while preserving surrounding healthy tissue.

“This trial follows on from the PERTINENCE study (NCT04897763), which validated the feasibility of imaging and the safety of administering a radiopharmaceutical (composed of the same antibody, girentuximab, but coupled with zirconium-89) via the intravesical route, both for the patient and with regard to staff radiation protection. This study notably demonstrated that the product remained exclusively in the bladder, which is precisely what is sought in this type of cancer without metastatic spread, and which suggests minimal or even non-existent whole-body toxicity in the PERSEVERANCE EU trial”, explains Dr. Caroline Rousseau, ICO Principal investigator of the PERSEVERANCE EU study.

“PERSEVERANCE EU fully illustrates Atonco’s medical ambition: to offer targeted treatments using alpha emitters for patients with limited therapeutic options. With ATO-101™, the objective is to demonstrate that astatine-211 can provide local tumor control while preserving healthy tissues as much as possible, thereby paving the way for a new generation of innovative radiotherapies in urothelial oncology”, states Dr. Jean-François Chatal, Chief Medical Officer of Atonco.

The experimental drug will be produced by GIP Arronax and Nantes University Hospital, two leading French institutions in the field of radiopharmacy and nuclear medicine research.

A first in France

This is the first clinical trial in France involving astatine-211, paving the way for a new generation of targeted radiotherapy treatments. The first patients will be enrolled at the ICO in Saint-Herblain as soon as all the prerequisites are met.

“ATONCO is taking a decisive step by entrusting the sponsorship of this pioneering study to ICO. This collaboration marks a first for the ICO Sponsorship Department! The patients enrolled will be the first to benefit from this therapeutic breakthrough, ushering in a new era of innovative care”, add Ms. Nadia Allam and Ms. Laëtitia Himpe, ICO Project Managers for this study.

“The authorization of the PERSEVERANCE EU trial confirms the potential of our targeted radiotherapy approaches and Atonco’s ability to bring its innovative radiopharmaceuticals to the clinical trial stage. We are fully committed to ensuring that developments such as ATO-101™ translate into tangible benefits for patients, with the highest standards of quality, safety and clinical evidence”, says Alexandra Paillard, Chief Operating Officer of Atonco.

ABOUT

ATONCO

Atonco is a French biotechnology company specializing in the development of innovative radiopharmaceutical therapies based on alpha emitters, particularly astatine-211.

In collaboration with research centers and hospital partners, Atonco designs and develops targeted treatments for cancers that are resistant to conventional approaches. Its mission is to offer new safe, effective, and personalized therapeutic options for cancer patients.

For more information, please visit www.atonco-pharma.com
ClinicalTrials.gov – NCT07260162

Institut de Cancérologie de l’Ouest (ICO): an expert center

ICO is a non-profit Comprehensive Cancer Center, with no extra billing, fulfilling public hospital service missions. As an expert center for care pathway coordination, it aims to make its expertise and specific skills in oncology available to patients and partners. Accredited by OECI in 2023, it received the High Quality of Care designation from HAS in January 2024. Each year, ICO’s 1,600 professionals welcome nearly 48,000 patients across its two sites in Angers and Saint-Herblain.

CUTTING-EDGE MEDICINE IN THE SERVICE OF PATIENTS

Specialized in oncology, ICO professionals support patients at every stage of their care pathway in a personalized, innovative and multidisciplinary manner. From rapid diagnosis to surgery, chemotherapy and radiotherapy, care also includes highly developed supportive care services.

INTEGRATING CARE, RESEARCH AND INNOVATION

Research activity at ICO is a full mission in its own right, ranging from fundamental research to clinical trials, including translational research. It spans all oncology disciplines: medical oncology, radiotherapy, surgery, anesthesia, nuclear medicine, medical imaging, supportive care and human sciences. Being treated at ICO means benefiting from privileged access to cutting-edge clinical trials in oncology.

Through its teaching mission and academic expertise, the institution contributes to training the next generation of oncology professionals.

With its four missions, Prevention, Care, Research and Teaching, ICO provides comprehensive, high-level expertise across the region, exclusively dedicated to oncology.

CONTACT US

Press contacts

● Sylvain FANIER – ATONCO
President
Tel.: +33 6 07 59 01 67
Email: sylvain.fanier@atonco-pharma.com

● Édith LEGRAND – Institut de Cancérologie de l’Ouest
Communication project manager
Tel: +33 2 41 35 27 26 / +33 6 74 38 26 71
Email: edith.legrand@ico.unicancer.fr

● Sophie NOBLET – Institut de Cancérologie de l’Ouest
Communication Director
Tel: +33 2 40 67 98 68 / +33 6 82 20 81 47
Email: sophie.noblet@ico.unicancer.fr

www.institut-cancerologie-ouest.com

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Atonco Report: Overview of Clinical Developments in Alpha-Emitting Radiotherapy

Atonco publishes its November 2025 report documenting the state of clinical research in alphatherapy worldwide. Compiled from the ClinicalTrials.gov database and recent scientific publications, this document maps all clinical trials conducted and underway with the three next-generation alpha-emitting radioisotopes: actinium-225, lead-212, and astatine-211. This analysis identifies major players, their strategic choices in terms of therapeutic targets and clinical indications, as well as industrial prospects for large-scale deployment of these promising technologies.

Current State of Affairs

Clinical alphatherapy is experiencing significant growth with 28 phase 1 or 1/2 studies registered in 2025, mobilizing both pharmaceutical giants (AstraZeneca, Bayer, BMS, J&J, Eli Lilly, Novartis) and numerous innovative biotechs. The three radioisotopes currently in development—actinium-225 (14 studies), lead-212 (6 studies), and astatine-211 (8 studies)—share a decisive advantage: their linear energy transfer is 100 times higher than that of lutetium-177, inducing irreparable breaks in both strands of tumor DNA. While actinium-225 dominates clinical trials thanks to its 10-day half-life enabling long-distance transport, astatine-211 stands out for its safe production in conventional cyclotrons and the absence of toxic long-lived daughter nuclides. In this context, Atonco has demonstrated the clinical feasibility of intravesical instillation of anti-CAIX labeled antibodies, confirming excellent bladder retention and superior radiocytotoxicity of astatine-211 compared to lutetium-177, paving the way for the phase 1 FIH study of ATO-101™ in refractory non-invasive bladder cancers. The future industrial availability of these radioisotopes, particularly through IBA’s developments for astatine-211, will determine their large-scale clinical deployment once their therapeutic performance is confirmed.

Keywords: Alphatherapy, Astatine-211, Actinium-225, Lead-212, Radioligand therapy, ATO-101, CAIX, Bladder cancer

Contact : www.atonco-pharma.com

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Atonco is proud to announce that the preclinical and clinical study results have been published in the Cancers (MDPI) journal, highlighting the promising potential of its radiopharmaceutical ATO-101™ ([²¹¹At]At-girentuximab) in the alpha-immunotherapy treatment using astatine-211 of non-muscle-invasive bladder cancer (NMIBC) refractory to standard therapies, including BCG.

Non-muscle-invasive bladder cancer (NMIBC) presents a significant medical challenge, with a growing need for novel therapeutic options. A promising approach in this area is radioimmunotherapy targeting the CA-IX antigen (Carbonic Anhydrase IX), particularly the use of alpha-emitting radionuclides like astatine-211. The goal of our preclinical and clinical studies was to assess the potential of ATO-101™ in treating patients who do not respond to conventional treatments.

Preclinical studies demonstrated that ATO-101™ binds highly effectively to the CA-IX antigen, with a high binding affinity, and induces significant targeted cytotoxicity compared to other treatments such as [¹⁷⁷Lu]Lu-girentuximab. Additionally, biodistribution studies in healthy mice revealed minimal systemic diffusion of radioactivity, indicating the treatment’s safety. After intravesical instillation of ATO-101™, no histological abnormalities were observed in the bladder wall, further reinforcing the safety of the approach.

In the PERTINENCE study (NCT04897763) sponsored by the Institut de Cancérologie de l’Ouest (ICO) in Nantes, PET/CT imaging using [⁸⁹Zr]Zr-girentuximab (supplied by Telix Pharmaceuticals) performed on 6 patients with NMIBC demonstrated no extravesical leakage, suggesting that the approach is localized and targeted effectively. Hot spots in the bladder wall were associated with areas of recurrence or inflammatory reaction, indicating that this treatment could effectively target residual tumor cells.

Furthermore, a dosimetric study suggested that intravesical alpha-immunotherapy using astatine-211 with ATO-101™ could offer enhanced efficacy and safety for NMIBC treatment. The clinical and preclinical data confirm the therapeutic potential of this approach and underscore its promising role in NMIBC management.

With this targeted therapy, we are paving the way for a more selective, less toxic, and more effective treatment for patients suffering from non-muscle-invasive bladder cancer, particularly those whose tumors are refractory to traditional treatments, including BCG.

🔗 Learn more about this study: https://www.mdpi.com/2072-6694/17/7/1190

About ATONCO

ATONCO is a privately held French company developing molecularly targeted radiopharmaceuticals for oncology applications. Originating from the world-class nuclear medicine cluster in Nantes, France, ATONCO and its partners are committed to the clinical use of alpha-emitting radionuclides, in particular astatine-211 (²¹¹At).

For more information, visit www.atonco-pharma.com

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Atonco and GIP ARRONAX (Saint Herblain, France) have joined forces to take the next step in the implementation of alpha-immunotherapy for cancer. Their partnership aims to develop and validate the radiopharmaceutical production process under GMP (Good Manufacturing Practice) conditions for Atonco’s ATO-101 (Girentuximab radiolabeled with astatine-211), with a view to clinical intravesical instillation for the treatment of non-musculo-invasive bladder cancer. Through this collaboration, two players in Nantes’ radiopharmaceutical industry are combining their expertise: the development of innovative radiopharmaceuticals using astatine-211 (Atonco) and the production of radionuclides and radiopharmaceuticals for nuclear medicine research (GIP ARRONAX).

This collaboration represents a key step in the transfer to the clinic of astatine-211, an alpha particle emitting radionuclide enabling the selective destruction of targeted tumor cells. It builds on the astatine-211 production expertise developed within GIP ARRONAX, and follows on from the radiochemistry research work carried out in Nantes by CRCI²NA team 2, which led to the development of radiolabeling and control methods for astatine-211-labeled Girentuximab. As part of this partnership with Atonco, GIP ARRONAX plays a key role in the pharmaceutical development and validation of manufacturing processes and control methods under GMP conditions, in preparation for the production of validation batches with a view to the first human clinical trials.

Laurette Fisson, Atonco’s CMC and Product Development Director: “This collaboration reinforces Atonco’s position as a leader in the development of innovative astatine-211-based radiopharmaceuticals, contributing to the advancement of targeted therapeutic options for patients with cancers resistant to standard therapies. We are delighted to collaborate with GIP ARRONAX, a long-standing partner with recognized expertise in radiopharmaceutical research and development.”

Férid Haddad, Director of GIP ARRONAX: “This collaboration with Atonco is the culmination of nearly 15 years’ work by GIP ARRONAX on astatine-211, a promising alpha emitter. We are proud to contribute to the progress of nuclear medicine, and particularly to the development of alpha radiotherapy, a therapeutic solution with a future.”

About Atonco:

Atonco is a private company developing targeted radiopharmaceuticals for oncology applications. Atonco and its partners, who have emerged from the nuclear medicine cluster in Nantes, are committed to the clinical use of alpha-emitting radionuclides, in particular astatine-211.

For more information, visit www.atonco-pharma.com

About GIP ARRONAX :

ARRONAX is a grouping of several public and private-sector members carrying out public-interest missions in the fields of research, economic development and training. It has a high-energy, high-intensity multi-particle cyclotron for the production of non-conventional radionuclides, including astatine-211, of which it is one of two European producers. GIP ARRONAX manufactures radiopharmaceuticals to GMP/GMP standards to support early-stage clinical research.

For more information, visit https://www.arronax-nantes.fr/gip-arronax/

Contacts :

• Tony Prézeau, Director Technology Transfer and Partnerships, GIP ARRONAX
  prezeau@arronax-nantes.fr
• Sylvain Fanier, President, Atonco
  fanier@atonco-pharma.com

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