Actinium-225 for Alpha-Based Radiotherapeutics in Drug Discovery

Synonyms: Actinium-225, ²²⁵Ac, alpha emitter, targeted alpha therapy (TAT), alpha radiopharmaceutical, alpha particle isotype, radiolabeled peptides, radiolabeled antibodies, Ac-225, radionuclide therapy, radioligand therapy

Actinium-225 (²²⁵Ac) is a high-energy alpha-emitting radionuclide with exceptional promise in targeted alpha therapy (TAT) for cancer treatment. Its decay chain produces multiple alpha particles, amplifying its cytotoxic effect against cancer cells while sparing healthy tissue. With a half-life conducive to systemic delivery, ²²⁵Ac has emerged as a leading isotope for both preclinical evaluation and clinical translation of radiopharmaceuticals targeting hematologic and solid malignancies.

Actinium-225 (²²⁵Ac) Details:

Radiation Type: Alpha emitter with multiple alpha decays in its chain
Half-life: ~9.9 days – ideal for systemic therapeutic delivery

Primary Applications:

• Targeted alpha therapy for hematologic and metastatic cancers
• Conjugation to antibodies, peptides, and ligands for tumor-specific delivery
• Preclinical pharmacokinetics, biodistribution, and efficacy studies

Benefits in Drug Discovery:

• Multiple alpha emissions per decay for increased therapeutic potency
• Effective for micro-metastatic and residual disease treatment
• Extended half-life supports centralized production and broad distribution
• Proven track record in advancing drug candidates to clinical evaluation
• Compatible with a variety of chelators for stable in vivo targeting
• Potential for theranostic pairing with Indium-111 and Zirconium-89 for imaging

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