About Actinium-225



Why theranostics ?

Radiotheranostics is an innovative field in medicine that combines diagnostic imaging and therapeutic treatment into a single system, designed to improve personalized patient care. By using radioactive isotopes, radiotheranostics allows for precise imaging of disease at a cellular level, as well as the targeted treatment of diseases, particularly cancer. This enables healthcare providers to personalize treatments, track the effectiveness of therapy, and adjust plans as necessary in real-time, significantly improving the potential for successful patient outcomes.

Radioactive isotopes, or radioisotopes, are elements that have an unstable nucleus, and as a result, emit radiation. This process is known as the decay of the radioisotope. In the medical field, this decay has significant uses in both diagnosis and treatment.


Radioisotopes are used in the creation of images that can help diagnose diseases. One of the most common techniques is Positron Emission Tomography (PET). Here, the patient is administered a radioisotope (commonly fluorine-18) attached to a glucose analog. As cancer cells consume more glucose than normal cells, they accumulate more of these radioisotopes. The gamma radiation emitted by the radioisotope is detected by the PET scanner to generate images, helping to locate and understand the extent of the disease.


In therapeutic applications, radioisotopes are used to destroy diseased cells. An example is the use of iodine-131 for the treatment of thyroid cancer. The thyroid cells take up iodine, so when a patient is given radioactive iodine, it accumulates in the thyroid cells. The emitted radiation can destroy the cancerous cells with minimal impact on the rest of the body.

Further Information

Radioligand therapy

Visit the website

What are radiotheranostics for cancer care?

Watch the video

Why Ac-225

Ac-225 emits a type of radiation known as alpha particles. These particles are highly energetic, yet their path is short within the body, typically traveling only a few cells deep. This characteristic makes Ac-225 incredibly potent but very localized in its effect. When it is delivered to cancerous cells, it can cause serious damage, leading to the death of those cells. Thanks to its short path, the impact on nearby healthy cells is minimized. This reduces potential side effects and leads to more effective, targeted treatments.

Ac-225 has a half-life of 10 days, an appropriate timescale for therapeutic use. It decays through a series of daughter isotopes, each emitting an alpha particle with high linear energy transfer (LET), resulting in the release of 4 alpha particles per decay of Ac-225.

Alpha particles are densely ionizing, meaning they can cause severe damage to the DNA within cells. This is particularly effective in killing cancer cells, which have a reduced capacity to repair such damage compared to healthy cells. The short range of these alpha particles in tissue (typically less than 0.1 mm, or a few cell diameters) allows for highly localized treatment. When Ac-225 is delivered directly to cancer cells, the high-energy alpha particles can destroy the targeted cells while sparing most of the surrounding healthy tissue, leading to fewer side effects compared to other types of radiation therapy.

To deliver Ac-225 to cancer cells, it can be bound to a targeting molecule, typically an antibody, creating what's known as a radioimmunoconjugate. These molecules are designed to specifically bind to a protein that is overexpressed on the surface of cancer cells. When the radioimmunoconjugate locates and binds to a cancer cell, Ac-225 releases its alpha particles, leading to the targeted cell's death.

Overall, the combination of Ac-225's high-LET, localized cell killing power, its half-life that is compatible with the pharmacokinetics of antibodies, and the ability to target specific cells, make it an extremely promising candidate for the treatment of certain types of cancers, including those resistant to conventional therapy.

Further Information

Clinical trials on Ac-225

Visit the website

The Rarest Drug on Earth

Watch the video


There are multiple production routes available to produce Actinium-225, each with its unique advantages and drawbacks. However, in the view of PanTera, four of these routes stand out due to their substantial impact on the supply landscape of this promising isotope. The Table below summarizes the characteristics of those four production routes.


Mainstream Ac-225 Production methods

229Th      225Ac

Limited to Th retrieved
Already available (low quality)
Good reliability for limited quantities

232Th (p,x)      225Ac

Ac-227 contaminated
Upscaling program
Already available
Long downtime for maintenance
Lots of waste coproduced

226Ra (p,2n)    .   225Ac

Decay required to reach expected quality
Cyclotron "farms" (costly)
Could supply clinical amounts
Large infrastructure required

226Ra (y,n) 225Ra      225Ac

As of 2025 for commercial use