Logistical, technical, and radiation safety aspects of establishing a radiopharmaceutical therapy program: A case in Lutetium-177 prostate-specific membrane antigen (PSMA) therapy.

Prostate-specific membrane antigen (PSMA) is a cell surface protein highly expressed in nearly all prostate cancers, with restricted expression in some normal tissues. The differential expression of PSMA from tumor to non-tumor tissue has resulted in the investigation of numerous targeting strategies for therapy of patients with metastatic prostate cancer. In March of 2022, the FDA granted approval for the use of lutetium-177 PSMA-617 (Lu-177-PSMA-617) for patients with PSMA-positive metastatic castration-resistant prostate cancer (mCRPC) who have been treated with androgen receptor pathway inhibition and taxane-based chemotherapy. Therefore, the use of Lu-177-PSMA-617 is expected to increase and become more widespread. Herein, we describe logistical, technical, and radiation safety considerations for implementing a radiopharmaceutical therapy program, with particular focus on the development of operating procedures for therapeutic administrations. Major steps for a center in the U.S. to implement a new radiopharmaceutical therapy (RPT) program are listed below, and then demonstrated in greater detail via examples for Lu-177-PSMA-617 therapy.

First-in-Humans Evaluation of Safety and Dosimetry of 64Cu-LLP2A for PET Imaging.

There remains an unmet need for molecularly targeted imaging agents for multiple myeloma (MM). The integrin very late antigen 4 (VLA4), is differentially expressed in malignant MM cells and in pathogenic inflammatory microenvironmental cells. [64Cu]Cu-CB-TE1A1P-LLP2A (64Cu-LLP2A) is a VLA4-targeted, high-affinity radiopharmaceutical with promising utility for managing patients diagnosed with MM. Here, we evaluated the safety and human radiation dosimetry of 64Cu-LLP2A for potential use in MM patients. Methods: A single-dose [natCu]Cu-LLP2A (Cu-LLP2A) tolerability and toxicity study was performed on CD-1 (Hsd:ICR) male and female mice. 64Cu-LLP2A was synthesized in accordance with good-manufacturing-practice-compliant procedures. Three MM patients and six healthy participants underwent 64Cu-LLP2A-PET/CT or PET/MRI at up to 3 time points to help determine tracer biodistribution, pharmacokinetics, and radiation dosimetry. Time-activity curves were plotted for each participant. Mean organ-absorbed doses and effective doses were calculated using the OLINDA software. Tracer bioactivity was evaluated via cell-binding assays, and metabolites from human blood samples were analyzed with analytic radio-high-performance liquid chromatography. When feasible, VLA4 expression was evaluated in the biopsy tissues using 14-color flow cytometry. Results: A 150-fold mass excess of the desired imaging dose was tolerated well in male and female CD-1 mice (no observed adverse effect level). Time-activity curves from human imaging data showed rapid tracer clearance from blood via the kidneys and bladder. The effective dose of 64Cu-LLP2A in humans was 0.036 ± 0.006 mSv/MBq, and the spleen had the highest organ uptake, 0.142 ± 0.034 mSv/MBq. Among all tissues, the red marrow demonstrated the highest residence time. Image quality analysis supports an early imaging time (4-5 h after injection of the radiotracer) as optimal. Cell studies showed statistically significant blocking for the tracer produced for all human studies (82.42% ± 13.47%). Blood metabolism studies confirmed a stable product peak (>90%) up to 1 h after injection of the radiopharmaceutical. No clinical or laboratory adverse events related to 64Cu-LLP2A were observed in the human participants. Conclusion: 64Cu-LLP2A exhibited a favorable dosimetry and safety profile for use in humans.

Radiopharmaceutical Quality Control Considerations for Accelerator-Produced Actinium Therapies.

Background: Alpha-particle-emitting radiotherapies are of great interest for the treatment of disseminated cancer. Actinium-225 (225Ac) produces four α-particles through its decay and is among the most attractive radionuclides for use in targeted radiotherapy applications. However, supply issues for this isotope have limited availability and increased cost for research and translation. Efforts have focused on accelerator-based methods that produce 225Ac in addition to long-lived 227Ac. Objective: The authors investigated the impact of 225Ac/227Ac material in the radiolabeling and radiopharmaceutical quality control evaluation of a DOTA chelate-conjugated peptide under good manufacturing practices. The authors use an automated module under identical conditions with either generator or accelerator-produced actinium radiolabeling. Methods: The authors have performed characterization of the radiolabeled products, including thin-layer chromatography, high-pressure liquid chromatography, gamma counting, and high-energy resolution gamma spectroscopy. Results: Peptide was radiolabeled and assessed at >95% radiochemical purity with high yields for generator produced 225Ac. The radiolabeling results produced material with subtle but detectable differences when using 225Ac/227Ac. Gamma spectroscopy was able to identify peptide initially labeled with 227Th, and at 100 d for quantification of 225Ac-bearing peptide. Conclusion: Peptides produced using 225Ac/227Ac material may be suitable for translation, but raise new issues that include processing times, logistics, and contaminant detection.

[89Zr]Trastuzumab: Evaluation of Radiation Dosimetry, Safety, and Optimal Imaging Parameters in Women with HER2-Positive Breast Cancer.

PURPOSE: The purpose of the present study is to evaluate safety, human radiation dosimetry, and optimal imaging time of [89Zr]trastuzumab in patients with HER2-positive breast cancer. PROCEDURES: Twelve women with HER2-positive breast cancer underwent [89Zr]trastuzumab positron emission tomography (PET)/X-ray computed tomography (CT) twice within 7 days post-injection. Biodistribution data from whole-torso PET/CT images and organ time-activity curves were created using data from all patients. Human dosimetry was calculated using OLINDA with the adult female model. RESULTS: High-quality images and the greatest tumor-to-nontumor contrast were achieved with images performed 5 ± 1 day post-injection. Increased [89Zr]trastuzumab uptake was seen in at least one known lesion in ten patients. The liver was the dose-limiting organ (retention of ∼12 % of the injected dose and average dose of 1.54 mSv/MBq). The effective dose was 0.47 mSv/MBq. No adverse effects of [89Zr]trastuzumab were encountered. CONCLUSION: [89Zr]trastuzumab was safe and optimally imaged at least 4 days post-injection. The liver was the dose-limiting organ.

The role of exploratory investigational new drugs for translating radiopharmaceuticals into first-in-human studies.

The Food and Drug Administration has provided a mechanism to reduce time and resources expended on new pharmaceuticals, including radiopharmaceuticals, in order to identify the most promising agents for further development. The exploratory investigational new drug guidance describes early phase 1 exploratory approaches involving microdoses of potential drug candidates that are consistent with regulatory requirements while maintaining the safety needed for human subjects, allowing sponsors to move ahead more quickly with the development of new agents.