Prostate-specific Membrane Antigen Targeting Research Articles

Immunohistochemistry analysis of PSMA expression at prostatic biopsy in high-risk prostate cancer: potential implications for PSMA-PET patient selection.

Prostate-specific membrane antigen (PSMA) is a transmembrane protein expressed by normal prostatic tissue. Therefore, molecular imaging targeting PSMA (PSMA-PET) has gained particular interest and diffusion for PCa staging and restaging. Several factors may affect PSMA-PET results, and many tools have been proposed to improve patient selection. Furthermore, PSMA expression is not homogeneous among different tissues and within the prostate itself. The aims of this study were to evaluate immunohistochemistry (IHC) features of prostate biopsy samples and to assess their correlation with whole-mount specimens and PSMA-PET parameters. We included consecutive high-risk PCa patients who underwent PSMA-PET for staging proposal at our institution from January 2022 to December 2022. The PET parameters selected were SUVmax, total volume (TV), and total lesion activity (TL). Each patient underwent multiparametric MRI (mpMRI) and fusion-targeted prostate biopsy prior to surgery. IHC analyses were performed on the index lesion cores. IHC visual score (VS) (1, 2, 3) and visual pattern (VP) (membranous, cytoplasmic, and combined) and the percentage of PSMA-negative tumor areas (PSMA%neg) within biopsy cores were evaluated. Forty-three patients who underwent robotic radical prostatectomy after PSMA-PET were available for analyses. Concordance between VS and VP at biopsy and final pathology showed a Cohen's kappa coefficient of 0.39 and 0.38, respectively. Patients with PSMA%neg <20% had a higher concordance in VS and VP (Cohen's kappa 0.49 and 0.4, respectively). No difference emerged in terms of median PSMA-TV (p = 0.3) and PSMA-TL (p = 0.9) according to VS at biopsy, while median SUVmax was higher in patients with VS 3 (p = 0.04). Higher SUVmax was associated with membranous and combined VP expression (p = 0.008). No difference emerged between patients with PSMA%neg <20% or PSMA%neg >20% on biopsy cores in terms of SUVmax, PSMA-TL, and PSMA-TV (p = 0.5, p = 0.5, and p = 0.9 respectively). We found a correlation between IHC VS and VP on targeted biopsy cores and SUVmax at PSMA-PET. However, the correlation between the IHC parameters of biopsy cores and final pathology was not as high as expected. Nevertheless, the presence of PSMA%neg <20% seems to have a better concordance in terms of visual score.

Delphi consensus project on prostate-specific membrane antigen (PSMA)-targeted surgery-outcomes from an international multidisciplinary panel.

Prostate-specific membrane antigen (PSMA) is increasingly considered as a molecular target to achieve precision surgery for prostate cancer. A Delphi consensus was conducted to explore expert views in this emerging field and to identify knowledge and evidence gaps as well as unmet research needs that may help change practice and improve oncological outcomes for patients. One hundred and five statements (scored by a 9-point Likert scale) were distributed through SurveyMonkey®. Following evaluation, a consecutive second round was performed to evaluate consensus (16 statements; 89% response rate). Consensus was defined using the disagreement index, assessed by the research and development project/University of California, Los Angeles appropriateness method. Eighty-six panel participants (72.1% clinician, 8.1% industry, 15.1% scientists, and 4.7% other) participated, most with a urological background (57.0%), followed by nuclear medicine (22.1%). Consensus was obtained on the following: (1) The diagnostic PSMA-ligand PET/CT should ideally be taken < 1month before surgery, 1-3months is acceptable; (2) a 16-20-h interval between injection of the tracer and surgery seems to be preferred; (3) PSMA targeting is most valuable for identification of nodal metastases; (4) gamma, fluorescence, and hybrid imaging are the preferred guidance technologies; and (5) randomized controlled clinical trials are required to define oncological value. Regarding surgical margin assessment, the view on the value of PSMA-targeted surgery was neutral or inconclusive. A high rate of "cannot answer" responses indicates further study is necessary to address knowledge gaps (e.g., Cerenkov or beta-emissions). This Delphi consensus provides guidance for clinicians and researchers that implement or develop PSMA-targeted surgery technologies. Ultimately, however, the consensus should be backed by randomized clinical trial data before it may be implemented within the guidelines.

Long-Term Nephrotoxicity of 177Lu-PSMA Radioligand Therapy.

β-emitting 177Lu targeting prostate-specific membrane antigen (PSMA) is an approved treatment option for metastatic castration-resistant prostate cancer. Data on its long-term nephrotoxicity are sparse. This study aimed to retrospectively evaluate post-177Lu-PSMA estimated glomerular filtration rate (eGFR) dynamics for at least 12 mo in a cohort of metastatic castration-resistant prostate cancer patients. Methods: The institutional databases of 3 German tertiary referral centers identified 106 patients who underwent at least 4 cycles of 177Lu-PSMA and had at least 12 mo of eGFR follow-up data. eGFR (by the Chronic Kidney Disease Epidemiology Collaboration formula) at 3, 6, and 12 mo after 177Lu-PSMA radioligand therapy was estimated using monoexponentially fitted curves through available eGFR data. eGFR changes were grouped (≥15%-<30%, moderate; ≥30%-<40%, severe; and ≥40%, very severe). Associations between eGFR changes (%) and nephrotoxic risk factors, prior treatment lines, and number of 177Lu-PSMA cycles were analyzed using multivariable linear regression. Results: At least moderate eGFR decreases were present in 45% (48/106) of patients; of those, nearly half (23/48) had a severe or very severe eGFR decrease. A higher number of risk factors at baseline (-4.51, P = 0.03) was associated with a greater eGFR decrease. Limitations of the study were the retrospective design, lack of a control group, and limited number of patients with a follow-up longer than 1 y. Conclusion: A considerable proportion of patients may experience moderate or severe decreases in eGFR 1 y from initiation of 177Lu-PSMA. A higher number of risk factors at baseline seems to aggravate loss of renal function. Further prospective trials are warranted to estimate the nephrotoxic potential of 177Lu-PSMA.

Imaging and therapy targeting PSMA receptors for enhanced vision and precise treatment

SummaryIn Europe, it is estimated that more than 65,000 men die each year from the consequences of advanced and metastatic prostate cancer (PCa). Currently, approximately 3.2 million European men are living with PCa. While the majority of PCa patients have favorable outcomes, the 5‑year relative survival rate for those with metastatic PCa is only 32%. Recent advances in the diagnosis of PCa have been boosted by the introduction of the prostate-specific membrane antigen (PSMA), which might identify patients with the most aggressive form of the disease. Molecular imaging with positron emission tomography (PET) targeting PSMA receptors (PSMA-PET) has utterly revolutionized the diagnosis and staging of PCa; however, its application is still under debate. On the one hand, there has been little progress in recent years in surpassing the limitations of androgen deprivation therapy (ADT), the backbone of metastatic PCa treatment. Adding additional systemic therapy became standard in the last few decades. Current ADT is only transiently effective, and patients eventually progress during ADT treatment, a condition known as castration-resistant PCa (CRPC). On the other hand, radioligand therapy (RLT) targeting these PSMA receptors, most commonly used in the studies [177Lu]lutetium-PSMA-617, has been available for this cancer stage for nearly a decade and has been recently incorporated into the European Association of Urology (EAU) guidelines as a robust treatment option for patients with metastatic CRPC.

Targeting Prostate Cancer Using Bispecific T-Cell Engagers against Prostate-Specific Membrane Antigen.

Prostate cancer (PCa) tops the list of cancer-related deaths in men worldwide. Prostate-specific membrane antigen (PSMA) is currently the most prominent PCa biomarker, as its expression levels are robustly enhanced in advanced stages of PCa. As such, PSMA targeting is highly efficient in PCa imaging as well as therapy. For the latter, PSMA-positive tumors can be targeted directly by using small molecules or macromolecules with cytotoxic payloads or indirectly by engaging the immune system of the host. Here we describe the engineering, expression, purification, and biological characterization of bispecific T-cell engagers (BiTEs) that enable targeting PSMA-positive tumor cells by host T lymphocytes. To this end, we designed the 5D3-αCD3 BiTE as a fusion of single-chain fragments of PSMA-specific 5D3 and anti-CD3 antibodies. Detailed characterization of BiTE was performed by a combination of size-exclusion chromatography, differential scanning fluorimetry, and flow cytometry. Expressed in insect cells, BiTE was purified in monodisperse form and retained thermal stability of both functional parts and nanomolar affinity to respective antigens. 5D3-αCD3's efficiency and specificity were further evaluated in vitro using PCa-derived cell lines together with peripheral blood mononuclear cells isolated from human blood. Our data revealed that T-cells engaged via 5D3-αCD3 can efficiently eliminate tumor cells already at an 8 pM BiTE concentration in a highly specific manner. Overall, the data presented here demonstrate that the 5D3-αCD3 BiTE is a candidate molecule of high potential for further development of immunotherapeutic modalities for PCa treatment.

Diagnostic accuracy of 18F Prostate Specific Membrane Antigen (PSMA) PET-CT radiotracers in staging and restaging of high-risk prostate cancer patients and patients with biochemical recurrence: protocol for an overview of reviews.

Background: Correct staging and risk stratification is essential in ensuring prostate cancer patients are offered the most appropriate treatment. Interest has been growing in the use of radiotracers targeting prostate specific membrane antigen (PSMA), including the use of 18F-PSMA PET-CT, as part of the primary staging or restaging of prostate cancer. Preliminary scoping identified a number of relevant systematic reviews and meta-analyses; however, individually, these each appear to look at only part of the picture. An overview of reviews aims to systematically identify, appraise and synthesise multiple systematic reviews, related to a relevant research question or questions. We present a protocol for an overview of reviews, which aims to collate existing evidence syntheses exploring the diagnostic accuracy of 18F-PSMA in staging and restaging of prostate cancer. It also aims to highlight evidence gaps in prostate cancer staging or restaging. Methods: This protocol is reported in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for systematic review protocols (PRISMA-P). The search strategy will be designed in consultation with a librarian. Searches will be performed in Medline (EBSCO), Embase (Ovid), Google Scholar and the Cochrane Database for Systematic Reviews, supplemented by a targeted grey literature search, forward citation searching and searching reference lists of included reviews. No language or date restrictions will be applied to the eligibility criteria or the search strategy. Title & abstract and full text screening will be performed independently by two reviewers. Data will be extracted by one reviewer and checked in full by a second reviewer. Quality appraisal will be performed using the Risk of Bias in Systematic Reviews (ROBIS) tool independently by two reviewers, and results will be narratively synthesised. Conclusions: This overview of reviews may be of interest to healthcare professionals, academics and health policy decision-makers. Registration: OSF (September 7, 2023).

Radiolabeled iron oxide nanoparticles functionalized with PSMA/BN ligands for dual-targeting of prostate cancer

IntroductionProstate cancer (PCa) is the second most frequent cancer diagnosis in men and the fifth leading cause of death worldwide. Prostate Specific Membrane Antigen (PSMA) and Gastrin Releasing Peptide (GRP) receptors are overexpressed in PCa. In this study, we have developed iron oxide nanoparticles (IONs) functionalized with the Prostate Specific Membrane Antigen (PSMA) and Gastrin Releasing Peptide (GRP) ligands for dual targeting of Prostate cancer.MethodsIONs were developed with a thin silica layer on their surface with MPTES (carrying -SH groups, IONs-SH), and they were coupled either with a pharmacophore targeting PSMA (IONs-PSMA) or with bombesin peptide (IONs-BN), targeting GRP receptors, or with both (IONs-PSMA/BN). The functionalized IONs were characterized for their size, zeta potential, and efficiency of functionalization using dynamic light scattering (DLS) and Fourier-Transform Infrared Spectroscopy (FT-IR). All the aforementioned types of IONs were radiolabeled directly with Technetium-99m (99mTc) and evaluated for their radiolabeling efficiency, stability, and binding ability on two different PCa cell lines (PC3 and LNCaP).Results and DiscussionThe MTT assay demonstrated low toxicity of the IONs against PC3 and LNCaP cells, while the performed wound-healing assay further proved that these nanostructures did not affect cellular growth mechanisms. The observed hemolysis ratio after co-incubation with red blood cells was extremely low. Furthermore, the 99mTc-radiolabeled IONs showed good stability in human serum, DTPA, and histidine, and high specific binding rates in cancer cells, supporting their future utilization as potential diagnostic tools for PCa with Single Photon Emission Computed Tomography (SPECT) imaging.

Application of targeted diagnosis of PSMA in the modality shift of prostate cancer diagnosis: a review.

Prostate cancer (PCa) is a serious threat to the health of men all over the world. The progression of PCa varies greatly among different individuals. In clinical practice, some patients often progress to advanced PCa. Therefore, accurate imaging for diagnosis and staging of PCa is particularly important for clinical management of patients. Conventional imaging examinations such as MRI and CT cannot accurately diagnose the pathological stages of advanced PCa, especially metastatic lymph node (LN) stages. As a result, developing an accurate molecular targeted diagnosis is crucial for advanced PCa. Prostate specific membrane antigen (PSMA) is of great value in the diagnosis of PCa because of its specific expression in PCa. At present, researchers have developed positron emission tomography (PET) targeting PSMA. A large number of studies have confirmed that it not only has a higher tumor detection rate, but also has a higher diagnostic efficacy in the pathological stage of advanced PCa compared with traditional imaging methods. This review summarizes recent studies on PSMA targeted PET in PCa diagnosis, analyzes its value in PCa diagnosis in detail, and provides new ideas for urological clinicians in PCa diagnosis and clinical management.

La tomographie par émission de positons aux ligands de l’antigène membranaire spécifique de la prostate (TEP-PSMA) dans le cancer de la prostate en France en 2023 : actualités et perspectives

Prostate-specific membrane antigen targeting positron emission tomography (PSMA-PET) has become since recent years increasingly important in the management of patients with prostate cancer. Initially limited to the use in patients with prostate cancer biochemical recurrence in France, PSMA-PET is now routinely use in various setting in prostate cancer patients, on the one hand for initial staging in patients with high-risk prostate cancer, and in the other hands to assess the eligibility for radioligand therapy using PSMA ligands. Other studies are currently assessing PSMA-PET in other settings such as the characterization of prostate disease, the guidance of biopsies or even as a tool for therapeutic assessment in patients with metastatic cancer. The objective of this review is to describe the current use of PSMA-PET in France in 2023, and the perspective of PSMA-PET imaging in the management of patients with prostate cancer in the future.

Tomographie par émission de positons aux ligands de l’antigène membranaire spécifique de la prostate (TEP-PSMA) dans le cancer de la prostate : classification PSMA-RADS et critères PROMISE

Prostate-specific membrane antigen targeting positron emission tomography (PSMA-PET) is nowadays widely used for the management of patients with prostate cancer during natural history of the disease. PSMA is not specific to prostate tissue, many benign and malignant diseases unrelated to prostate cancer are frequently found on PSMA-PET examinations, leading to false positives results and potentially to inadequate patient management. Various interpretation criteria have been proposed within classifications in order to standardize and homogenize PSMA-PET interpretation. This article describes, on the one hand the PSMA-RADS classification, and on the other hand the PROMISE criteria.

Recommandations pour la réalisation d’un examen de tomographie par émission de positons aux ligands de l’antigène membranaire spécifique de la prostate

Prostate-specific membrane antigen targeting positron emission tomography (PSMA-PET) is nowadays widely used for the management of patients with prostate cancer during natural history of the disease. Several radiopharmaceuticals labeled with Gallium-68 and Fluor-18 are now available in France, some of which have obtained marketing authorization in various indications. Patient preparation and image acquisition protocols differ from one radiopharmaceutical to another. The objective of this article is to provide practical guidelines regarding PET-PSMA protocols, for radiopharmaceuticals labeled with Gallium-68 or Fluor-18, to facilitate implementation in clinical routine in nuclear medicine departments in France.

PSMA Targeted Molecular Imaging and Radioligand Therapy for Prostate Cancer: Optimal Patient and Treatment Issues.

Theranostics (therapy + diagnosis) targeting prostate-specific membrane antigen (PSMA) is an emerging therapeutic modality that could alter treatment strategies for prostate cancer. Although PSMA-targeted radioligand therapy (PSMA-RLT) has a highly therapeutic effect on PSMA-positive tumor tissue, the efficacy of PSMA-RLT depends on PSMA expression. Moreover, predictors of treatment response other than PSMA expression are under investigation. Therefore, the optimal patient population for PSMA-RLT remains unclear. This review provides an overview of the current status of theranostics for prostate cancer, focusing on PSMA ligands. In addition, we summarize various findings regarding the efficacy and problems of PSMA-RLT and discuss the optimal patient for PSMA-RLT.

A Modular Antibody‐Oligomer T Cell Engager for Applications in Local Therapies

AbstractImmunotherapeutics, such as bispecific T cell engagers (BiTEs), have shown promise in cancer therapies, however their efficacy against solid tumors is hindered by transport barriers. Local therapies are being investigated to improve solid tumor immunotherapies and minimize systemic toxicity. Because local therapies bypass the circulatory system, drug properties can be optimized to further enhance local efficacy. Herein, the use of a larger BiTE‐like antibody‐oligomer conjugate is investigated, modular T cell engagers (MoTEs), to extend the duration of activity within local tissue mimics. Specifically, an anti‐CD3 antibody is modified with heterobifunctional ethylene oxide ((EO)4‐12) linkers, which are subsequently modified with cancer targeting ligands (CTLs). The (EO)x molecular weight and CTL grafting densities are optimized to achieve targeted cytotoxicity within in vitro co‐cultures against prostate‐specific membrane antigen (PSMA) positive and human epidermal growth factor receptor 2 (HER2) positive cancer cells. In local tissue models comprised of embedded PSMA positive spheroids in collagen‐hyaluronic acid hydrogels with T cells, it is demonstrated that MoTEs resulted in ≈2.5‐fold greater cytotoxicity toward cancer spheroids than a PSMA targeting BiTE at longer 12‐day timepoints. MoTEsmay therefore prove beneficial for local therapies by extending the duration of action after single‐dose administration and establishing simple synthetic protocols to target various cancer antigens.

Development of Novel 111In/225Ac-Labeled Agent Targeting PSMA for Highly Efficient Cancer Radiotheranostics.

Prostate-specific membrane antigen (PSMA) is a promising target for metastatic castration-resistant prostate cancer. We previously reported the effectiveness of PSMA-DA1 as a PSMA-targeting radiotheranostic agent containing an albumin binder moiety. To further enhance tumor uptake, we newly designed PSMA-NAT-DA1 (PNT-DA1) by the introduction of a lipophilic linker into PSMA-DA1. The PSMA affinity of [111In]In-PNT-DA1 was increased (Kd = 8.20 nM) compared with that of [111In]In-PSMA-DA1 (Kd = 89.4 nM). [111In]In-PNT-DA1 showed markedly high tumor accumulation (131.6% injected dose/g at 48 h post-injection), and [111In]In-PNT-DA1 enabled the visualization of the tumor clearly at 24 h post-injection with SPECT/CT imaging. The administration of [225Ac]Ac-PNT-DA1 (2.5 kBq) led to shrinkage of the tumor without marked toxicity, and the antitumor effects of [225Ac]Ac-PNT-DA1 were superior to those of [225Ac]Ac-PSMA-DA1 and [225Ac]Ac-PSMA-617, which is the current gold standard for PSMA-targeting 225Ac-endoradiotherapy. These results suggest that the combination of [111In]In-PNT-DA1 and [225Ac]Ac-PNT-DA1 comprises a promising method of PSMA-targeting radiotheranostics.

Prostate-specific membrane antigen (PSMA) expression in patients with metastatic triple negative breast cancer: Initial results of the PRISMA study.

1025 Background: Radioligand therapy (RLT) targeting prostate-specific membrane antigen (PSMA) prolongs survival of patients (pts) with prostate cancer. Preliminary immunohistochemistry (IHC)-based studies suggest that PSMA is highly expressed in triple negative breast cancer (TNBC). The PRISMA study aims to assess PSMA expression in pts with metastatic TNBC (mTNBC) via positron-emission tomography/computed tomography (PET/CT) to evaluate the feasibility of PSMA-targeted RLT for TNBC. Methods: PRISMA is a prospective, single-center study that enrolled pts with progressive mTNBC and measurable disease on 18F-FDG PET/CT to undergo 68Ga-PSMA-11 PET/CT. TNBC definition (ASCO/CAP) was based on the IHC of the primary breast cancer (BC) or metastasis. Target lesions (TL) were defined as metastatic lesions ≥1.5 cm with significant uptake in 18FDG-PET/CT. The same TL regions were propagated to the 68Ga-PSMA-PET/CT. 68Ga-PSMA-11 maximum standard uptake value (SUVmax) was measured for each TL. PSMA patterns A and B were defined according to presence of a majority (pattern A) or a minority (pattern B) of positive TL on 68Ga-PSMA (ie. uptake greater than that of normal liver parenchyma). Mann-Whitney U test was used to assess differences in median SUVmax (mSUVmax) between subgroups. Results: Ten pts with progressive mTNBC were enrolled. One pt was excluded due to lack of TL on 18FDG-PET/CT. Median age was 48 years (range 36-68), median number of TL per patient was 8 (5-18). Five pts had a TNBC IHC since the initial BC diagnosis, while 4 had a switch to TNBC (4 with initial estrogen receptor [ER]-positive and 1 with HER2-positive BC). All evaluable pts had inter- and intra-organ heterogeneity in PSMA uptake in TL and 2 pts had some mismatch with FDG-positive and PSMA-negative TL. mSUVmax was 2.99 (range 1.7-6.3) in the overall population and was higher in pts with pattern A (5.1 vs 2.6 in patterns A and B, respectively, p = 0.03). mSUVmax was numerically higher in younger pts (5.0 vs 2.6 in pts &lt;50y and ≥50y, p = 0.28), PD-L1-positive (5.0 vs 2.7 in PD-L1-positive and -negative, p = 0.14), de novo metastatic disease (5.0 vs 2.9 in de novo and recurrent BC, p = 0.38) and those with ER-negative primary breast tumor (3.4 vs 3.0 in ER-negative and ER-positive primary BC, p = 0.9). Conclusions: A significant PSMA uptake was observed in a proportion of pts with mTNBC. Inclusion of additional pts and translational analyses will allow the identification of PSMA expression determinants. PSMA-targeted RLT may be considered as an innovative therapeutic strategy to be explored in selected pts with mTNBC. [Table: see text]

Development of [177Lu]Lu-LNC1003 for radioligand therapy of prostate cancer with a moderate level of PSMA expression.

Evans blue as an albumin binder has been widely used to improve pharmacokinetics and enhance tumor uptake of radioligands, including prostate-specific membrane antigen (PSMA) targeting agents. The goal of this study is to develop an optimal Evans blue-modified radiotherapeutic agent that could maximize the absolute tumor uptake and tumor absorbed dose thus the therapeutic efficacy to allow treatment of tumors even with moderate level of PSMA expression. [177Lu]Lu-LNC1003 was synthesized based on PSMA-targeting agent and Evans blue. Binding affinity and PSMA targeting specificity were verified through cell uptake and competition binding assay in 22Rv1tumor model that has moderate level of PSMA expression. SPECT/CT imaging and biodistribution studies in 22Rv1 tumor-bearing mice were performed to evaluate the preclinical pharmacokinetics. Radioligand therapy studies were conducted to systematically assess the therapeutic effect of [177Lu]Lu-LNC1003. LNC1003 showed high binding affinity (IC50 = 10.77nM) to PSMA in vitro, which was comparable with that of PSMA-617 (IC50 = 27.49nM) and EB-PSMA-617 (IC50 = 7.91nM). SPECT imaging of [177Lu]Lu-LNC1003 demonstrated significantly improved tumor uptake and retention as compared with [177Lu]Lu-EB-PSMA and [177Lu]Lu-PSMA-617, making it suitable for prostate cancer therapy. Biodistribution studies further confirmed the remarkably higher tumor uptake of [177Lu]Lu-LNC1003 (138.87 ± 26.53%ID/g) over [177Lu]Lu-EB-PSMA-617 (29.89 ± 8.86%ID/g) and [177Lu]Lu-PSMA-617 (4.28 ± 0.25%ID/g) at 24h post-injection. Targeted radioligand therapy results showed noteworthy inhibition of 22Rv1 tumor growth after administration of a single dose of 18.5MBq [177Lu]Lu-LNC1003. There was no obvious antitumor effect after [177Lu]Lu-PSMA-617 treatment under the same condition. In this study, [177Lu]Lu-LNC1003 was successfully synthesized with high radiochemical purity and stability. High binding affinity and PSMA targeting specificity were identified in vitro and in vivo. With greatly enhanced tumor uptake and retention, [177Lu]Lu-LNC1003 has the potential to improve therapeutic efficacy using significantly lower dosages and less cycles of 177Lu that promises clinical translation to treat prostate cancer with various levels of PSMA expression.

Theranostics of Primary Prostate Cancer: Beyond PSMA and GRP-R.

First, we prospectively performed neurotensin receptor-1 (NTS1) IHC in a series of patients receiving both [68Ga]Ga-PSMA-617 and [68Ga]Ga-RM2 before prostatectomy. In this series, PSMA and GRP-R IHC were also available (n = 16). Next, we aimed at confirming the PSMA/GRP-R/NTS1 expression profile by retrospective autoradiography (n = 46) using a specific radiopharmaceuticals study and also aimed to decipher the expression of less-investigated targets such as NTS2, SST2 and CXCR4. In the IHC study, all samples with negative PSMA staining (two patients with ISUP 2 and one with ISUP 3) were strongly positive for NTS1 staining. No samples were negative for all three stains-for PSMA, GRP-R or NTS1. In the autoradiography study, binding of [111In]In-PSMA-617 was high in all ISUP groups. However, some samples did not bind or bound weakly to [111In]In-PSMA-617 (9%). In these cases, binding of [111n]In-JMV 6659 and [111In]In-JMV 7488 towards NTS1 and NTS2 was high. Targeting PSMA and NTS1/NTS2 could allow for the detection of all intraprostatic lesions.

Molecular Design of 68Ga- and 89Zr-Labeled Anticalin Radioligands for PET-Imaging of PSMA-Positive Tumors.

Anticalin proteins directed against the prostate-specific membrane antigen (PSMA), optionally having tailored plasma half-life using PASylation technology, show promise as radioligands for PET-imaging of xenograft tumors in mice. To investigate their suitability, the short-circulating unmodified Anticalin was labeled with 68Ga (τ1/2 = 68 min), using the NODAGA chelator, whereas the half-life extended PASylated Anticalin was labeled with 89Zr (τ1/2 = 78 h), using either the linear chelator deferoxamine (Dfo) or a cyclic derivative, fusarinine C (FsC). Different PSMA targeting Anticalin versions (optionally carrying the PASylation sequence) were produced carrying a single exposed N- or C-terminal Cys residue and site-specifically conjugated with the different radiochelators via maleimide chemistry. These protein conjugates were labeled with radioisotopes having distinct physical half-lives and, subsequently, applied for PET-imaging of subcutaneous LNCaP xenograft tumors in CB17 SCID mice. Uptake of the protein tracers into tumor versus healthy tissues was assessed by segmentation of PET data as well as biodistribution analyses. PET-imaging with both the 68Ga-labeled plain Anticalin and the 89Zr-labeled PASylated Anticalin allowed clear delineation of the xenograft tumor. The radioligand A3A5.1-PAS(200)-FsC·89Zr, having an extended plasma half-life, led to a higher tumor uptake 24 h p.i. compared to the 68Ga·NODAGA-Anticalin imaged 60 min p.i. (2.5% ID/g vs 1.2% ID/g). Pronounced demetallation was observed for the 89Zr·Dfo-labeled PASylated Anticalin, which was ∼50% lower in the case of the cyclic radiochelator FsC (p < 0.0001). Adjusting the plasma half-life of Anticalin radioligands using PASylation technology is a viable approach to increase radioisotope accumulation within the tumor. Furthermore, 89Zr-ImmunoPET-imaging using the FsC radiochelator is superior to that using Dfo. Our strategy for the half-life adjustment of a tumor-targeting Anticalin to match the physical half-life of the applied radioisotope illustrates the potential of small binding proteins as an alternative to antibodies for PET-imaging.

Comparative assessment of 18F-PSMA-1007 biodistribution at 60 and 120 minutes after administration by PET/CT in prostate cancer patients

INTRODUCTION: Positron emission tomography combined with computed tomography (PET/CT) with prostate-specific membrane antigen-targeted (PSMA) radiopharmaceuticals is a valuable method for prostate cancer (PCa) imaging. Both 68Ga- and 18F-labelled PSMA ligands are used in clinical practice now, for example, 18F-PSMA-1007. Currently there is no consensus on time interval between 18F-PSMA-1007 administration and scanning start that served as the basis for this study. OBJECTIVE: The aim of this study was to determinate the optimal time interval between 18F-PSMA-1007 administration and scanning start at PET/CT in PCa patients. MATERIALS AND METHODS: This prospective analysis included the results of 18F-PSMA-1007 PET/CT of 26 patients with PCa (mean age — 69.1±7.1 years, mean PSA value — 3.9 (0.5; 10) ng/ml), 4 patients — at primary staging, 10 patients — with therapy assessment and 12 patients — with biochemical recurrence. The PET/CT scanning was performed at 60 and 120 minutes after 18F-PSMA-1007 administration with subsequent measurement and comparison of the pathological and physiological uptake. TBR value (Tumor-to-Background Ratio) was calculated for the pathological uptake in the prostate or prostate bed and lymph nodes lesions relative to the physiological uptake in urinary bladder and abdominal aortic blood pool respectively. Statistics: Statistical analysis was carried out using the software SPSS Statistics 28 to analyse the significance of the differences in median SUVmax (for pathological 18F-PSMA-1007 uptake), SUVmean (for physiological 18F-PSMA-1007 uptake) and TBR between two stages of scanning. RESULTS: There was a significant decrease of physiological 18F-PSMA-1007 uptake from median SUVmean 1.5 (1.0; 1.73) to 0.9 (0.5; 0.9), p&lt;0.001 in the abdominal aortic blood pool, 2.6 (1.3; 3.6) to 1.7 (1.1; 2.8), p&lt;0.05 in the urinary bladder, 0.4 (0.35; 0.44) to 0.33 (0.3; 0.37), p&lt;0.05 in the right gluteus medius muscle in the second scan. Moreover, there was a significant increase of physiological 18F-PSMA-1007 uptake from median SUVmean 8.9±2.8 to 10.3±3.4, p&lt;0.001 in the liver, 7.5±3.5 to 8.3±3.8, p&lt;0,001 in the spleen, 9.8±3.7 to 11.6±4.3, p&lt;0.001 in the right parotid salivary gland. Uptake in the bone marrow remained stable with median SUVmean 1 (0.8; 1.3), p=0.917. There was a significant increase of pathological uptake from median SUVmax 4.6 (2.7; 7.7) to 5.25 (3.2; 9.0), p&lt;0.001 in 76 lesions without appearance of new lesions in the second scan at 120 minutes. Mean TBR value also significantly increased for the ratios «prostate or prostate bed/urinary bladder» from 1.7 (1.1; 4.7) to 3.6 (2.1; 9.5), p&lt;0.05 and «lymph node/aortic blood pool»: per-lesion analysis from 2.8 (2.5; 5.2) to 6.2 (5; 10.1), p&lt;0.001 and per-patient analysis from 4,6 (2.7; 5.5) to 9.8 (4.9; 12.1), p&lt;0.05. DISCUSSION: It’s not justified to use time interval in 120 minutes routinely because of the lack of new lesions in the second scan, irrational spending of the department resources and time of medical staff. However, there was an increase in the TBR values indicating the higher quality of images in the second scan at 120 minutes. CONCLUSION: Due to the lack of clinical benefits of the 120 minutes interval and the associated time cost, a 60 minutes interval between 18F-PSMA-1007 administration and the start of a PET/CT scan in PCa patients is more optimal, however, delayed scan is justified in cases of obtaining unclear results.

Quantitative assessment of PSMA PET response to therapy in castration-sensitive prostate cancer using an automated imaging platform for disease identification and measurement

RationaleProstate cancer treatment response may be automatically quantified using a molecular imaging analysis platform targeting prostate-specific membrane antigen (PSMA).MethodsA retrospective analysis of patients with castration-sensitive prostate cancer who underwent PSMA-targeted molecular imaging prior to and 3 months or more after treatment was conducted. Disease burden was analyzed with aPROMISE, an artificial intelligence imaging platform that automatically quantifies PSMA-positive lesions. The calculated PSMA scores for prostate/bed, nodal, and osseous disease sites were compared with prostate-specific antigen (PSA) values.ResultsOf 30 eligible patients, the median decline in prostate/bed, nodal, and osseous disease PSMA scores were 100% (range 52–100%), 100% (range − 87–100%), and 100% (range − 21–100%), respectively. PSMA score decline was significantly associated with PSA decline.ConclusionChanges in aPROMISE PSMA scores are associated with changes in PSA and may quantify treatment response.