[177Lu]Lu-PSMA-617 (PluvictoTM): The First FDA-Approved Radiotherapeutical for Treatment of Prostate Cancer.

In March 2022, [177Lu]Lu-PSMA-617 (PluvictoTM) was approved by the FDA for the treatment of prostate cancer patients. Until now, the approval has been limited to patients with PSMA-positive metastatic castration-resistant prostate cancer who have previously received other therapy options (such as inhibition of the androgen receptor pathway and taxane-based chemotherapy). [177Lu]Lu-PSMA-617, which combines a PSMA-specific peptidomimetic with a therapeutical radionuclide, is used in a radioligand therapy that selectively delivers ionizing radiation to tumor cells, causing their death, while sparing the surrounding healthy tissue. In numerous clinical trials, the efficacy of [177Lu]Lu-PSMA-617 was demonstrated.

[68Ga]Ga-PSMA-11: The First FDA-Approved 68Ga-Radiopharmaceutical for PET Imaging of Prostate Cancer.

For the positron emission tomography (PET) imaging of prostate cancer, radiotracers targeting the prostate-specific membrane antigen (PSMA) are nowadays used in clinical practice. Almost 10 years after its discovery, [68Ga]Ga-PSMA-11 has been approved in the United States by the Food and Drug Administration (FDA) as the first 68Ga-radiopharmaceutical for the PET imaging of PSMA-positive prostate cancer in 2020. This radiopharmaceutical combines the peptidomimetic Glu-NH-CO-NH-Lys(Ahx)-HBED-CC with the radionuclide 68Ga, enabling specific imaging of tumor cells expressing PSMA. Such a targeting approach may also be used for therapy planning as well as potentially for the evaluation of treatment response.

Development and Validation of a GMP-Compliant High-Pressure Liquid Chromatography Method for the Determination of the Chemical and Radiochemical Purity of [18F]PSMA-1007, a PET Tracer for the Imaging of Prostate Cancer.

For the PET imaging of prostate cancer, radiotracers targeting the prostate-specific membrane antigen (PSMA) are nowadays used in clinical practice. [18F]PSMA-1007, a radiopharmaceutical labeled with fluorine-18, has excellent properties for the detection of prostate cancer. Essential for the human use of a radiotracer is its production and quality control under GMP-compliance. For this purpose, all analytical methods have to be validated. [18F]PSMA-1007 is easily radiosynthesized in a one-step procedure and isolated using solid phase extraction (SPE) cartridges followed by formulation of a buffered injection solution and for the determination of its chemical and radiochemical purity a robust, fast and reliable quality control method using radio-HPLC is necessary. After development and optimizations overcoming problems in reproducibility, the here described radio-HPLC method fulfills all acceptance criteria-for e.g., specificity, linearity, and accuracy-and is therefore well suited for the routine quality control of [18F]PSMA-1007 before release of the radiopharmaceutical. Recently a European Pharmacopeia monograph for [18F]PSMA-1007 was published suggesting a different radio-HPLC method for the determination of its chemical and radiochemical purity. Since the here described method has certain advantages, not least of all easier technical implementation, it can be an attractive alternative to the monograph method. The here described method was successfully validated on several radio-HPLC systems in our lab and used for the analysis of more than 60 batches of [18F]PSMA-1007. Using this method, the chemical and radiochemical purity of [18F]PSMA-1007 can routinely be evaluated assuring patient safety.

[68Ga]Ga-DOTA-TOC: The First FDA-Approved 68Ga-Radiopharmaceutical for PET Imaging.

In the United States, [68Ga]Ga-DOTA-TOC has been approved by the Food and Drug Administration (FDA) in 2019 as the first 68Ga-radiopharmaceutical for imaging of somatostatin receptor (SSTR) positive gastroenteropancreatic neuroendocrine tumors while employing positron emission tomography (PET). In Europe (Austria, Germany, France), [68Ga]Ga-DOTA-TOC was already approved back in 2016. This radiopharmaceutical combines the radionuclide 68Ga with the somatostatin analogue DOTA-TOC for specific imaging of tumor cells expressing SSTRs. Such a targeting approach can also be used for therapy planning in the case of both localized as well as disseminated disease and potentially for the evaluation of treatment response.

Lutathera®: The First FDA- and EMA-Approved Radiopharmaceutical for Peptide Receptor Radionuclide Therapy.

As the first radiopharmaceutical for Peptide Receptor Radionuclide Therapy (PRRT), Lutathera® was approved by the EMA in 2017 and the FDA in 2018 for the treatment of somatostatin receptor (SSTR) positive gastroenteropancreatic neuroendocrine tumors. Using the concept of PRRT, Lutathera® combines the radionuclide 177Lu with the somatostatin analogue DOTA-TATE, thus delivering ionizing radiation specifically to tumor cells expressing somatostatin receptors. As a result, DNA single- and double-strand breaks are provoked, in case of double-strand breaks leading to cell death of the tumor and its SSTR-positive lesions.

[Initiation of clinical multicentre studies with local radiotracer production - Regulatory environment and radiopharmaceutical-organisational aspects]. / Initiierung klinischer Multicenter-Studien mit lokaler Radiotracer-Herstellung.

The aim of this paper is to highlight key aspects to be considered from a radiopharmaceutical point of view when performing prospective multicentre clinical trials using short-lived PSMA-PET-radiopharmaceuticals as investigational medicinal product (IMP). Early prospective multicentre clinical trials are playing an increasingly important role in nuclear medicine translational research; in order to be able to establish new PET tracers with a short physical half-life (e. g. for prostate cancer diagnostics) in the regulatory approval process, nuclear medicine centres are working together across multiple sites in order to be able to achieve the required number of patients to be included within the clinical study in a reasonable time frame. In the following, we discuss the necessary regulatory environment for the preparation of PSMA PET-radiopharmaceuticals as corresponding investigational medicinal product (IMP) using the example of the prospective multicentre clinical trial (phases-I and -II) "[68Ga]Ga-PSMA-11 in high-risk prostate cancer", and discuss regulatory and organisational issues that need to be taken into account in a decentralized PSMA-PET tracer production from the radiopharmacy perspective.

Novel Preclinical and Radiopharmaceutical Aspects of [68Ga]Ga-PSMA-HBED-CC: A New PET Tracer for Imaging of Prostate Cancer.

The detection of prostate cancer lesions by PET imaging of the prostate-specific membrane antigen (PSMA) has gained highest clinical impact during the last years. 68Ga-labelled Glu-urea-Lys(Ahx)-HBED-CC ([68Ga]Ga-PSMA-HBED-CC) represents a successful novel PSMA inhibitor radiotracer which has recently demonstrated its suitability in individual first-in-man studies. The radiometal chelator HBED-CC used in this molecule represents a rather rarely used acyclic complexing agent with chemical characteristics favourably influencing the biological functionality of the PSMA inhibitor. The simple replacement of HBED-CC by the prominent radiometal chelator DOTA was shown to dramatically reduce the in vivo imaging quality of the respective 68Ga-labelled PSMA-targeted tracer proving that HBED-CC contributes intrinsically to the PSMA binding of the Glu-urea-Lys(Ahx) pharmacophore. Owing to the obvious growing clinical impact, this work aims to reflect the properties of HBED-CC as acyclic radiometal chelator and presents novel preclinical data and relevant aspects of the radiopharmaceutical production process of [68Ga]Ga-PSMA-HBED-CC.

BioShuttle mobility in living cells studied with high-resolution FCS & CLSM methodologies.

With the increase in molecular diagnostics and patient-specific therapeutic approaches, the delivery and targeting of imaging molecules and pharmacologically active agents gain increasing importance. The ideal delivery system does not exist yet. The realization of two features is indispensable: first, a locally high concentration of target-specific diagnostic and therapeutic molecules; second, the broad development of effective and safe carrier systems. Here we characterize the transport properties of the peptide-based BioShuttle transporter using FFM and CLSM methods. The modular design of BioShuttle-based formulations results in a multi-faceted field of applications, also as a theranostic tool.

Improved synthesis strategy for peptide nucleic acids (PNA) appropriate for cell-specific fluorescence imaging.

Progress in genomics and proteomics attended to the door for better understanding the recent rapid expanding complex research field of metabolomics. This trend in biomedical research increasingly focuses to the development of patient-specific therapeutic approaches with higher efficiency and sustainability. Simultaneously undesired adverse reactions are avoided. In parallel, the development of molecules for molecular imaging is required not only for the imaging of morphological structures but also for the imaging of metabolic processes like the aberrant expression of the cysteine protease cathepsin B (CtsB) gene and the activity of the resulting product associated with metastasis and invasiveness of malign tumors. Finally the objective is to merge imaging and therapy at the same level. The design of molecules which fulfil these responsibilities is pivotal and requires proper chemical methodologies. In this context our modified solid phase peptide chemistry using temperature shifts during synthesis is considered as an appropriate technology. We generated highly variable conjugates which consist of molecules useful as diagnostically and therapeutically active molecules. As an example the modular PNA products with the complementary sequence to the CtsB mRNA and additionally with a cathepsin B cleavage site had been prepared as functional modules for distinction of cell lines with different CtsB gene expression. After ligation to the modular peptide-based BioShuttle carrier, which was utilized to facilitate the delivery of the functional modules into the cells' cytoplasm, the modules were scrutinized.

Synthesis and in vitro evaluation of 68Ga-DOTA-4-FBn-TN14003, a novel tracer for the imaging of CXCR4 expression.

The expression of the chemokine receptor CXCR4 in tumors is associated with tumor aggressiveness and poor prognosis for the patient and contributes to metastatic seeding. Therefore it is of high interest to find a specific PET tracer for the imaging of CXCR4 expression in tumors. The aim of this study was the synthesis, (68)Ga labeling and first evaluation of DOTA-4-FBn-TN14003 as a potential PET tracer for this purpose. DOTA-4-FBn-TN14003 was synthesized using solid phase peptide synthesis and radiolabeling of this versatile precursor was performed with (68)Ga, which was obtained from a (68)Ge/(68)Ga generator. (68)Ga-DOTA-4-FBn-TN14003 was reproducibly obtained in isolated radiochemical yields of 72.5±4.9% with an excellent radiochemical purity of >99.5%. Specific activities of up to 29.8±3.1 GBq/µmol were achieved. In competition binding assays with SDF-1α, human T cell lymphoma Jurkat cells expressed high levels of CXCR4 whereas human breast cancer MDA-MB-231 cells expressed significantly lower levels of this chemokine receptor. The inhibition constants (IC(50)) of Ga-DOTA-4-FBn-TN14003 and 4-FBn-TN14003 to CXCR4 were determined in a competition assay against (125)I-SDF-1α using Jurkat as well as MDA-MB-231 cells. The IC(50) values of Ga-DOTA-4-FBn-TN14003 (1.99±0.31 nM) and 4-FBn-TN14003 (4.07±1.00 nM) proved to be comparable, indicating negligible influence of the metal complex. These results suggest (68)Ga-DOTA-4-FBn-TN14003 as a promising agent for the imaging of CXCR4 expression in tumors and metastases.

Theranostic cRGD-BioShuttle Constructs Containing Temozolomide- and Cy7 For NIR-Imaging and Therapy.

Innovative and personalized therapeutic approaches result from the identification and control of individual aberrantly expressed genes at the transcriptional and post-transcriptional level. Therefore, it is of high interest to establish diagnostic, therapeutic and theranostic strategies at these levels. In the present study, we used the Diels-Alder Reaction with inverse electron demand (DAR(inv)) click chemistry to prepare a series of cyclic RGD-BioShuttle constructs. These constructs carry the near-infrared (NIR) imaging agent Cy7 and the chemotherapeutic agent temozolomide (TMZ). We evaluated their uptake by and their efficacy against integrin α(v)ß(3)-expressing MCF7 human breast carcinoma cells. In addition, using a mouse phantom, we analyzed the suitability of this targeted theranostic agent for NIR optical imaging. We observed that the cyclic RGD-based carriers containing TMZ and/or Cy7 were effectively taken up by α(v)ß(3)-expressing cells, that they were more effective than free TMZ in inducing cell death, and that they could be quantitatively visualized using NIR fluorescence imaging. Therefore, these targeted theranostic agents are considered to be highly suitable systems for improving disease diagnosis and therapy.