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– Aiming to establish af-001 as a new therapeutic option for radioactive iodine (RAI)-naïve patients with differentiated thyroid cancer –
TOKYO, Oct. 31, 2025 /PRNewswire/ — Alpha Fusion Inc. (Headquarters: Chiyoda-ku, Tokyo; CEO: Sunao Fujioka; hereinafter “Alpha Fusion”) today announced the initiation of a company-sponsored Phase I clinical trial (jRCT2031250472) of the alpha-emitting radiopharmaceutical af-001, which contains [211At]NaAt as its active pharmaceutical ingredient, in patients with differentiated thyroid cancer (papillary and follicular carcinoma).
This clinical trial is designed based on the results of an investigator-initiated Phase I study conducted at The University of Osaka, and consists of Part Ia and Part Ib.
In Part Ia, the maximum tolerated dose (MTD) of a single intravenous administration of af-001 will be determined in patients with differentiated thyroid cancer who are refractory to or intolerant of standard therapies. Part Ib will evaluate the efficacy and safety of multiple intravenous administrations of af-001 to determine the recommended dose for Phase II trials in patients with differentiated thyroid cancer who have not received prior radioactive iodine (RAI) therapy (RAI-naïve).
Part Ia of the study will be conducted at the National Cancer Center Hospital East (Principal Investigator: Dr. Makoto Tahara, Chief, Department of Head and Neck Medical Oncology), and Part Ib will be conducted at multiple sites in Japan.
The clinical development of af-001 will proceed with the goal of obtaining regulatory approval for use in patients with RAI-naïve differentiated thyroid cancer (papillary and follicular carcinoma). If clinical efficacy and safety are indicated in this patient population, af-001 is expected to contribute as a next-generation radiopharmaceutical and as a novel therapeutic option for differentiated thyroid cancer.
af-001 is manufactured under GMP for investigational products in collaboration with the Kobe City Medical Center General Hospital (Director: Dr. Yasuki Kihara; Chuo-ku, Kobe City, Hyogo), and promptly delivered to the National Cancer Center Hospital East after production.
(Reference: Prior release announced on PR Newswire, October 8, 2025)
Regarding the initiation of this study, Sunao Fujioka, CEO of Alpha Fusion Inc., commented as follows:
“Based on the achievements of the investigator-initiated Phase I study in patients refractory or intolerant to standard therapies, we expect to maximize the potential of af-001 by confirming its safety and efficacy in RAI-naïve patients. Alpha Fusion is fully committed to advancing the clinical development of af-001, with the ultimate goal of providing outpatient alpha-emitting radiopharmaceutical therapy to more patients with thyroid cancer. In addition, we are pursuing multiple research and development pipelines utilizing At-211, aiming to create innovative radiopharmaceuticals for various types of cancer.”
Background
RAI therapy is the standard treatment for differentiated thyroid cancer. However, in cases involving multiple metastases or insufficient therapeutic response despite clear iodine uptake, repeated RAI treatments may be required.
Moreover, due to radiation protection requirements in Japan, RAI therapy must be administered in shielded rooms, leading to hospitalization that imposes psychological stress on patients and financial burdens on hospitals. A survey in Japan reported an average waiting time of approximately 3.7 months, and 23% of facilities having a wait time exceeding six months (Survey Report on the Utilization of RI Therapy Rooms for Thyroid Cancer, 2022).
Given these challenges, there is a growing demand for patient-centric radiopharmaceuticals that can achieve potent tumor-reducing effects in an outpatient setting.
About At-211 (af-001)
af-001 is a radiopharmaceutical containing astatine-211 (At-211) as its active pharmaceutical ingredient. It is selectively taken up by differentiated thyroid cancer cells through the sodium/iodide symporter (NIS) and exerts a cytotoxic effect by emitting alpha particles.
At-211 emits alpha particles with higher energy than beta particles, inducing double-strand DNA breaks in cancer cell nuclei and leading to tumor regression.
Because alpha particles have a very limited range (approximately several tens of micrometers), af-001 can deliver strong therapeutic effects while minimizing damage to surrounding normal tissues. Consequently, substituting RAI with the limited-range alpha emitter af-001 may enable outpatient-based treatment.
With these unique characteristics, af-001 is being developed as a next-generation radiopharmaceutical and a novel treatment for differentiated thyroid cancer, offering both efficacy and safety.
Results of the Investigator-Initiated Clinical Trial and Positioning of the Company-Sponsored Trial
Prior to this company-sponsored trial, an investigator-initiated Phase I clinical trial (Alpha-T1 Trial) of [211At]NaAt, identical in composition to af-001, was conducted at The University of Osaka under the supervision of Dr. Tadashi Watabe, Principal Investigator (NCT05275946).
The study indicated the safety and tolerability of [211At]NaAt in patients with differentiated thyroid cancer refractory or intolerant to standard therapies. Additionally, the study reported a ≥50% reduction in thyroglobulin concentration (a tumor marker) and cases of disappearance of 131I uptake on imaging.
The present company-sponsored trial aims to evaluate the efficacy and safety of af-001 (identical in pharmaceutical ingredient to TAH-1005, [211At]NaAt) in RAI-naïve patients, with the objective of determining the recommended dose for subsequent Phase II studies.
About Alpha Fusion Inc.
Alpha Fusion Inc. is a biopharmaceutical company dedicated to the research and development of next-generation radiopharmaceutical therapies utilizing radioactive isotopes.
Through collaborative partnerships with domestic and international medical and research institutions, Alpha Fusion aims to create new treatment options in oncology and contribute to the advancement of precision radiopharmaceutical medicine.
Official website: https://alpha-fusion.com/en/
