Lutetium-177-PSMA-617: A Vision of the Future

Tailoring Fibroblast-Activation Protein Targeting for Theranostics: A Comparative Preclinical Evaluation of the 68Ga- and 177Lu-Labeled Monomeric and Dimeric Fibroblast-Activation Protein Inhibitors DOTA.SA.FAPi and DOTAGA.(SA.FAPi)2

BACKGROUND

FAP radiopharmaceuticals show promise for cancer diagnosis; however, their limited tumor residency hinders treatment. This study compared two FAPi derivatives, DOTA.SA.FAPi and DOTAGA.(SA.FAPi)2, labeled with gallium-68 and lutetium-177, aiming to determine an optimum combination for creating theranostic pairs.

METHODS

The radiotracers were studied for lipophilicity, binding to human serum proteins, and binding to human cancer-associated fibroblasts (CAFs) in vitro, including saturation and internalization/externalization studies. PET/SPECT/CT and biodistribution studies were conducted in PC3 and U87MG xenografts for [68Ga]Ga-DOTA.SA.FAPi and [68Ga]Ga-DOTAGA.(SA.FAPi)2. [177Lu]Lu-DOTA.SA.FAPi and [177Lu]Lu-DOTAGA.(SA.FAPi)2, were evaluated in PC3 xenografts. Biodistribution studies of [68Ga]Ga-DOTA.SA.FAPi were performed in healthy male and female mice.

RESULTS

All radiotracers exhibited strong binding to FAP. Their internalization rate was fast while only [177Lu]Lu-DOTAGA.(SA.FAPi)2 was retained longer in CAFs. [68Ga]Ga-DOTAGA.(SA.FAPi)2 and [177Lu]Lu-DOTAGA.(SA.FAPi)2 displayed elevated lipophilicity and affinity for human serum proteins compared to [68Ga]Ga-DOTA.SA.FAPi and [177Lu]Lu-DOTA.SA.FAPi. In vivo studies revealed slower washout of [68Ga]Ga-DOTAGA.(SA.FAPi)2 within 3 h compared to [68Ga]Ga-DOTA.SA.FAPi. The tumor-to-tissue ratios of [68Ga]Ga-DOTAGA.(SA.FAPi)2 versus [68Ga]Ga-DOTA.SA.FAPi did not exhibit any significant differences. [177Lu]Lu-DOTAGA.(SA.FAPi)2 maintained a significant tumor uptake even after 96 h p.i. compared to [177Lu]Lu-DOTA.SA.FAPi.

CONCLUSIONS

Dimeric compounds hold promise for therapy, while monomers are better suited for diagnostics. Finding the right combination is essential for effective disease management.

Innovative Drug Modalities for the Treatment of Advanced Prostate Cancer

Prostate cancer, a prevalent malignancy affecting the prostate gland, is a significant global health concern. Androgen-deprivation therapy (ADT) has proven effective in controlling advanced disease, with over 50% of patients surviving at the 10-year mark. However, a diverse spectrum of responses exists, and resistance to ADT may emerge over time. This underscores the need to explore innovative treatment strategies for effectively managing prostate cancer progression. Ongoing research endeavors persist in unraveling the complexity of prostate cancer and fostering the development of biologic and innovative approaches, including immunotherapies and targeted therapies. This review aims to provide a valuable synthesis of the dynamic landscape of emerging drug modalities in this context. Interestingly, the complexities posed by prostate cancer not only present a formidable challenge but also serve as a model and an opportunity for translational research and innovative therapies in the field of oncology.

Preclinical Study of Therapeutic Efficacy of a New Russian Radiopharmaceutical 177Lu-DOTA-PSMA

The therapeutic efficacy of a Russian radiopharmaceutical 177Lu-DOTA-PSMA was studied in vivo using male BALB/c nu/nu (nude) mice with prostate carcinoma 22Rv1 xenografts by tumor growth inhibition criterion. The mean tumor volumes in mice treated with 177Lu-DOTA-PSMA were significantly lower than in animals of the control group. There were no significant differences in the values of tumor growth inhibition between the groups of animals receiving 3.7 or 7.4 MBq of 177Lu-DOTA-PSMA.

Prognostic role of neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, systemic immune-inflammation index, and pan-immune-inflammation value in metastatic castration-resistant prostate cancer patients who underwent 177Lu-PSMA-617

This study is aimed to investigate the prognostic significance of inflammation indices, including neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), and pan-immune-inflammation value (PIV) in metastatic castration-resistant prostate cancer (mCRPC) patients who had received lutetium labeled prostate-specific membrane antigen (177Lu-PSMA-617) therapy. Sixty-one mCRPC patients who received 177Lu-PSMA-617 treatment and followed up in Kocaeli University were included. The relationship between overall survival (OS) and progression-free survival (PFS) and clinical and laboratory parameters was analyzed by multivariate analyses. The mean age was 69.8 ± 6.9 years. The mean follow-up time was 53.2 ± 24 months. The median OS was 14 (95% CI: 8.8-18.1) and the median PFS was 10.4 (95% CI: 4.7-17.2) months. NLR ≥ 2.7, PLR ≥ 134.27, SII ≥ 570.39, PIV ≥ 408.59 were considered as elevated levels. In the multivariate analysis for OS, baseline ECOG performance score (HR: 1.92, 95% CI: 1.01-3.65, P = .046), high albümin (HR: 0.36, 95% CI: 0.16-0.82, P = .015), primary resistant total prostate-specific-antigen (PSA) (HR: 4.37, 95% CI: 1.84-10.35, P = .001), high NLR (HR: 3.32, 95% CI: 1.66-6.65, P = .001), high MLR (HR: 2.53, 95% CI: 1.35-4.76, P = .004), high PLR (HR: 2.47, 95% CI: 1.23-4.96, P = .01), and high SII (HR: 2.17, 95% CI: 1.09-4.32, P = .027) were associated with shorter OS. However, PIV was not associated with survival (P = .69). No factor other than the primer-resistant PSA could be identified as having an impact on PFS (for the PSA, HR: 4.52, 95% CI: 1.89-10.76, P = .001). In this study, pretreatment NLR, MLR, PLR, and SII demonstrate as powerful independent prognostic indices predicting survival in patients with mCRPC receiving 177Lu-PSMA-617 therapy.

Multicentric 68Ga-PSMA PET radiomics for treatment response assessment of 177Lu-PSMA-617 radioligand therapy in patients with metastatic castration-resistant prostate cancer

Objective

The treatment with 177Lutetium PSMA (177Lu-PSMA) in patients with metastatic castration-resistant prostate cancer (mCRPC) has recently been approved by the FDA and EMA. Since treatment success is highly variable between patients, the prediction of treatment response and identification of short- and long-term survivors after treatment could help tailor mCRPC diagnosis and treatment accordingly. The aim of this study is to investigate the value of radiomic parameters extracted from pretreatment 68Ga-PSMA PET images for the prediction of treatment response.

Methods

A total of 45 mCRPC patients treated with 177Lu-PSMA-617 from two university hospital centers were retrospectively reviewed for this study. Radiomic features were extracted from the volumetric segmentations of metastases in the bone. A random forest model was trained and validated to predict treatment response based on age and conventionally used PET parameters, radiomic features and combinations thereof. Further, overall survival was predicted by using the identified radiomic signature and compared to a Cox regression model based on age and PET parameters.

Results

The machine learning model based on a combined radiomic signature of three features and patient age achieved an AUC of 0.82 in 5-fold cross-validation and outperformed models based on age and PET parameters or radiomic features (AUC, 0.75 and 0.76, respectively). A Cox regression model based on this radiomic signature showed the best performance to predict overall survival (C-index, 0.67).

Conclusion

Our results demonstrate that a machine learning model to predict response to 177Lu-PSMA treatment based on a combination of radiomics and patient age outperforms a model based on age and PET parameters. Moreover, the identified radiomic signature based on pretreatment 68Ga-PSMA PET images might be able to identify patients with an improved outcome and serve as a supportive tool in clinical decision making.

Synthesis and clinical application of new drugs approved by FDA in 2022

The pharmaceutical industry had a glorious year in 2022, with a total of 37 new drugs including 20 new chemical entities (NCEs) and 17 new biological entities (NBEs) approved by the Food and Drug Administration (FDA). These drugs are mainly concentrated in oncology, central nervous system, antiinfection, hematology, cardiomyopathy, dermatology, digestive system, ophthalmology, MRI enhancer and other therapeutic fields. Of the 37 drugs, 25 (68%) were approved through an expedited review pathway, and 19 (51%) were approved to treat rare diseases. These newly listed drugs have unique structures and new mechanisms of action, which can serve as lead compounds for designing new drugs with similar biological targets and enhancing therapeutic efficacy. This review aims to outline the clinical applications and synthetic methods of 19 NCEs newly approved by the FDA in 2022, but excludes contrast agent (Xenon Xe-129). We believe that an in-depth understanding of the synthetic methods of drug molecules will provide innovative and practical inspiration for the development of new, more effective, and practical synthetic techniques. According to the therapeutic areas of these 2022 FDA-approved drugs, we have classified these 19 NCEs into seven categories and will introduce them in the order of their approval for marketing.

Emerging treatment options for prostate cancer

INTRODUCTION

Prostate cancer treatment has rapidly evolved in the past few years. Androgen deprivation therapy has been the backbone of treatment for locally advanced and metastatic prostate cancer, but incremental benefits in survival have been shown by adding androgen-receptor pathway inhibitors (ARPI) across various spectrums of disease state. In addition, docetaxel chemotherapy remains the first-line chemotherapy regimen available with survival benefits shown with triplet therapy in those who are chemotherapy eligible. However, disease progression remains inevitable and novel agents such as radioligand therapy with lutetium have shown improvement in survival.

AREAS COVERED

This review discusses the pivotal trials that led to the U.S. FDA approval of agents utilized in metastatic prostate cancer and explores the use of novel agents including prostate-specific membrane antigen-targeting agents, radioligands, cell-based therapy, chimeric antigen receptor T-cell, BiTE, and antibody drug conjugates.

EXPERT OPINION

Treatment landscape for metastatic castrate-resistant prostate cancer (mCRPC) has evolved beyond additional agents with ARPI and/or docetaxel, including other treatments with sipuleucel-T, radium, cabazitaxel, PARP inhibitors, and lutetium, which have specific indications and roles in sequencing. Novel therapies remain critically needed after progression from lutetium.

Clinical Trials of Prostate-Specific Membrane Antigen Radiopharmaceutical Therapy

Prostate-specific membrane antigen (PSMA) theranostics has been a momentous triumph for nuclear medicine. The recent approvals of PSMA-targeted imaging agents (⁶⁸Ga-PSMA-11, ¹⁸F-DCFPyL) and radiopharmaceutical therapy (¹⁷⁷Lu-PSMA-617) have paved the way for theranostics as a viable care strategy for men with metastatic castration-resistant prostate cancer. The imaging clinical trials OSPREY, CONDOR, and those conducted at the University of California (Los Angeles and San Francisco), as well as the randomized phase 3 therapy trial VISION, have been the fruitful beginnings for PSMA theranostics. There are currently several ongoing clinical trials to expand the reach of PSMA theranostics to the earlier phases of prostate cancer and to optimize its utility in combination therapeutic regimens. We provide a brief narrative review of the many PSMA-directed radiopharmaceutical therapy clinical trials with the β-emitter ¹⁷⁷Lu-PSMA-617 and the α-emitter ²²⁵Ac-PSMA-617 in prostate cancer.

Fundamentals of Rhenium-188 Radiopharmaceutical Chemistry

The β^- emitter, rhenium-188 (¹⁸⁸Re), has long been recognized as an attractive candidate for targeted cancer radionuclide therapy (TRNT). This transition metal shares chemical similarities with its congener element technetium, whose nuclear isomer technetium-99m (^99mTc) is the current workhorse of diagnostic nuclear medicine. The differences between these two elements have a significant impact on the radiolabelling methods and should always receive critical attention. This review aims to highlight what needs to be considered to design a successful radiopharmaceutical incorporating ¹¹⁸Re. Some of the most effective strategies for preparing therapeutic radiopharmaceuticals with ¹⁸⁸Re are illustrated and rationalized using the concept of the inorganic functional group (core) and a simple ligand field theoretical model combined with a qualitative definition of frontiers orbitals. Of special interest are the Re(V) oxo and Re(V) nitrido functional groups. Suitable ligands for binding to these cores are discussed, successful clinical applications are summarized, and a prediction of viable future applications is presented. Rhenium-188 decays through the emission of a high energy beta particle (2.12 MeV max energy) and a half-life of 16.9 h. An ideal biological target would therefore be a high-capacity target site (transporters, potential gradients, tumour microenvironment) with less emphasis on saturable targets such as overexpressed receptors on smaller metastases.

Exceptional Response of Rare Plasmacytoid Variant Prostate Cancer Post 177Lu-PSMA Therapy Seen on 68Ga-PSMA PET/CT

ABSTRACT

Plasmacytoid is a rare variant of acinar prostatic adenocarcinoma. The aggressive type is characterized by an aggressive clinical course, lack of responsiveness to hormonal therapies, and an overall poor prognosis. Here we present pretherapy and posttherapy 68Ga-PSMA PET/CT images showing an exceptional response to 177Lu-PSMA therapy. This case demonstrates the usefulness of both 68Ga-PSMA PET/CT in assessing the tumor PSMA avidity and the potential of 177Lu-PSMA therapy in these patients.

Potential Ophthalmological Side Effects Induced by Anti-Neoplastic Regimens for the Treatment of Genitourinary Cancers: A Review

The outcomes of patients with genitourinary (GU) cancers have been steadily improving in recent years. Novel therapies have entered our armamentarium, while several other regimens are currently being studied in clinical trials. This recent explosion of new agents has improved patient survival and the quality of life for patients, but has also significantly increased the frequency of several side effects. The current review will focus on the potential ocular adverse reactions of GU neoplastic treatments. The broad spectrum of manifestations of ocular toxicity underscores the uniqueness and complexity of the anatomic, physiologic, and metabolic features of the human eye. Most side effects are mild in severity and transient, but some can be severe, disabling, and irreversible. Clinicians should be aware of complications that might be vision threatening and impact the patient's quality of life. In this review, we focused on the ocular toxicity of the antineoplastic regimens that are currently used for the treatment of GU, including prostate cancer, bladder cancer, renal cell carcinoma, testicular cancer, pheochromocytoma, adrenocortical carcinoma, and penile cancer.