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Radionuclide-based Diagnosis and Therapy of Prostate Cancer
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Sven-Erik Strand, Mohamed Altai, Joanna Strand, David Ulmert
The main source of Actinium-225 is currently 229Th generators (t½=7340 y), which can be milked over a 3-wk period and allow the separation of 225Ra and 225Ac. 225Ac (t½ = 10.0 d; 5.8-MeV α-particle) decays sequentially through 6 dominant daughters to stable 209Bi. Decay of a single 225Ac atom yields 4 net α-disintegrations and 3 β-disintegrations together with the emission of 2 useful γ-emissions. The 225Ac daughter 213Bi (t½ = 45.6 min; 97.8% β, 2.2% 6-MeV α-particle) is also a widely studied radionuclide for targeted α-therapy. Dissociated free 225Ac accumulates primarily in the liver and bone. The 225Ac daughters 221Fr and 213Bi will preferentially accumulate in the kidneys. Together, this makes these organs highly prone to toxic effects caused by 225Ac-based radiopharmaceuticals. The decay scheme of 225Ac can be seen in Figure 19.9 from Schwartz and colleagues [27].
Antibody-Based Therapies
Published in David E. Thurston, Ilona Pysz, Chemistry and Pharmacology of Anticancer Drugs, 2021
Actinium Pharmaceuticals Inc is presently developing tumor-targeted antibodies conjugated to the alpha-emitting radioisotopes Actinium-225 and Bismuth-213. The company claims that the use of alpha particles (a treatment they call Alpha Particle Immunotherapy or “APIT”) has advantages over beta particles because the killing power of radioactivity is directly proportional to its energy but inversely proportional to its range. Thus, alpha particles carry the most energy (i.e., 100 times more than beta particles) but travel the shortest path. This contrasts with beta particles which are less energetic but travel further in the body causing more collateral damage to healthy tissue. Another potential advantage is that both Actinium-225 and the isotope derived from it, Bismuth-213, have relatively short half-lives (10 days and 46 minutes, respectively) and favorable pharmacokinetics. However, for logistical and cost reasons the company is focusing on antibodies conjugated to Actinium-225.
Peptide receptor radionuclide therapy in neuroendocrine neoplasms and related tumors: from fundamentals to personalization and the newer experimental approaches
Published in Expert Review of Precision Medicine and Drug Development, 2023
3. Actinium-225 (225Ac): 225Ac has grown popular in recent years because of the advantage of being an α particle emitter, which is a high linear energy transfer (LET) radiation compared to the beta-emitters and has an energy of 5.93 MeV. Its role has been emphasized in patients with advanced cases which were resistant even to 177Lu, wherein its efficacy and safety profile have been observed [17]. Interestingly, these radionuclides have lesser tissue penetration range and thereby saves surrounding non-target organs from being irradiated with unwanted irradiation. They also have a better radiation safety profile. With 10 days half-life and multiple emissions like β −, γ rays in lower abundance it is quite suitable for use in therapeutic seating. Researchers are looking forward to observing the results and whether it will improve the outcome of PRRT in metastatic/advanced NETs. Similar to 90Y, there are issues regarding production and availability 225Ac, as it is available in limited quantities by radiochemical separation from two 229Th sources, one located at Oak Ridge National Laboratory (ORNL), U.S.A, and the other at the Institute for Transuranium Elements in Karlsruhe, Germany. There have been also a few issues regarding the chemical stability of intermediate species of the decay chain of 225Ac with chelators which are under research (sumarrized in Table 2).
Lutetium-177 PSMA for the treatment of metastatic castrate resistant prostate cancer: a systematic review
Published in Expert Review of Anticancer Therapy, 2023
Kanchi Patell, Matthew Kurian, Jorge A. Garcia, Prateek Mendiratta, Pedro C. Barata, Angela Y. Jia, Daniel E. Spratt, Jason R. Brown
This review predominantly focused on 177Lu-PSMA-617 as radioligand therapy for prostate cancer; however, other radionuclides are likely to gain a foothold as viable prostate cancer treatment. In particular, the alpha-emitter actinium-225 has demonstrated efficacy when partnered with PSMA-617. Other PSMA targeted therapies have also shown promise. Bispecific T-cell engagement has been recently explored in solid tumors, and PSMA is an attractive target for prostate cancer. The United States FDA has recently cleared an investigational new drug application for JANX007, PSMA-TRACTr (Prostate-specific membrane antigen-Tumor Activated T Cell Engager) for the treatment of mCRPC [108]. Given the relatively high PSA responders and low toxicity profile of this novel therapy it can prove to play a promising role in treatment of prostate cancer.
Prostate-specific membrane antigen targeted PET/CT for recurrent prostate cancer: a clinician’s guide
Published in Expert Review of Anticancer Therapy, 2021
Sympascho Young, Wei Liu, Katherine Zukotynski, Glenn Bauman
Ongoing studies such as the Australian LuPARP (NCT03874884) and American NCT03805594 are assessing the efficacy of 177Lu labeled agents in combination with targeted therapy or immunotherapy, while trials such as TheraP (NCT03392428) are comparing its efficacy against conventional chemotherapy with promising early results [100]. Of note, recently a few studies have focused on the use of Actinium-225 labeling (225Ac). While the alpha particle emission associated with 225Ac may be preferable to the beta-particles associated with 177Lu in terms of disease therapy, toxicity including xerostomia, nephrotoxicity and hematologic toxicity is potentially higher. Also, effects associated with disintegration into daughter particles needs to be taken into account.