68Ga-EMP-100 PET/CT-a novel ligand for visualizing c-MET expression in metastatic renal cell carcinoma-first in-human biodistribution and imaging results

Preclinical Evaluation of 68Ga-Labeled SL1 Aptamer for c-Met Targeted PET Imaging

Tyrosine protein kinase c-Met, encoded by the Met gene, is a membrane-associated receptor tyrosine kinase that is often aberrantly expressed in a wide range of tumors. The development of imaging probes specifically targeting c-Met is critical for improving cancer diagnostics. In this study, we successfully designed and fabricated an aptamer molecular imaging probe ([68Ga]Ga-NOTA-SL1) with high radiochemical purity (RCP), good stability in vitro, and high affinity for c-Met expressed tumors. As shown by the micro-PET/CT scanning, [68Ga]Ga-NOTA-SL1 efficiently imaged tumor models with varying c-Met expression. The quantitative analysis of micro-PET/CT showed tumor uptake of [68Ga]Ga-NOTA-SL1 in the HCC827 tumor models (30 min, 2.93 ± 0.64%ID/g; 60 min, 2.03 ± 0.67%ID/g; 90 min, 1.63 ± 0.61%ID/g), PC-9 tumor models (30 min, 2.1 ± 0.72%ID/g; 60 min, 1.7 ± 0.56%ID/g; 90 min, 1.33 ± 0.38%ID/g), and HCT116 tumor models (30 min, 1.4 ± 0.17%ID/g; 60 min, 1.23 ± 0.15%ID/g; 90 min, 0.97 ± 0.21%ID/g). The results of immunohistochemistry (IHC) further confirmed the targeting ability of [68Ga]Ga-NOTA-SL1 to c-Met from a molecular pathological perspective. The probe effectively imaged c-Met-positive tumors and demonstrated a favorable metabolism profile and targeting performance in non-small cell lung cancer (NSCLC) or colorectal cancer tumor models. Consequently, this probe shows promise as an imaging agent capable of providing valuable diagnostic insights into tumors with aberrant c-Met expression.

Evaluation of a Novel MET-Targeting Camelid-Derived Antibody in Head and Neck Cancer

In head and neck squamous cell carcinoma (HNSCC), the mesenchymal epithelial transition (MET) receptor drives cancer growth, proliferation, and metastasis. MET is known to be overexpressed in HNSCC and, therefore, is an appealing therapeutic target. In this study, we evaluated MET expression in patients with HNSCC and investigated the potential imaging application of a novel MET-binding single-domain camelid antibody using positron emission tomography/computed tomography (PET/CT) in a preclinical MET-expressing HNSCC model. Multiplex immunostaining for MET protein performed on a tissue microarray from 203 patients with HNSCC found 86% of patients to have MET expression, with 14% having high expression and 53% having low MET expression. Using The Cancer Genome Atlas (TCGA) database, high MET RNA expression was associated with worse progression-free survival and overall survival in patients with HPV-negative HSNCC. Utilizing flow cytometry and immunofluorescence, our novel camelid antibody fused to a human IgG Fc chain (1E7-Fc) showed high binding affinity and specificity to high MET-expressing Detroit 562 cells but not to low MET-expressing HNSCC cells. The efficacy and biodistribution of [89Zr]Zr-1E7-Fc as a PET imaging agent was then investigated in a MET-expressing head and neck xenograft model. [89Zr]Zr-1E7-Fc rapidly localized and showed high tumor uptake in Detroit 562 xenografts (8.4% ID/g at 72 h postinjection), with rapid clearance from the circulatory system (2.7 tumor-to-blood radioactivity ratio at 72 h postinjection). Our preclinical data suggest that the camelid antibody 1E7-Fc could be a potential theranostic agent for HNSCC. Further investigations are warranted to confirm these findings in patients and to evaluate 1E7-Fc as an imaging agent and platform to deliver radionuclide or drug therapy to MET-driven cancers.

Recent advancements in new tracers from first-in-human studies

Recent advancements in the development of positron emission tomography (PET) tracers have significantly enhanced our ability to image neuroinflammatory processes and neurotransmitter systems, which are vital for understanding and treating neurodegenerative and psychiatric disorders. Similarly, innovative tracers in oncology provide detailed images of the metabolic and molecular characteristics of tumors, which are crucial for tailoring targeted therapies and monitoring responses, including radiotherapy. Notable advancements include programmed death ligand 1 (PD-L1)-targeting agents for lung cancer, prostate-specific membrane antigen-based tracers for prostate cancer, chemokine receptor-targeting agents for hematological malignancies, human epidermal growth factor receptor 2 (HER2)-targeting tracers for various cancers, Claudin 18 based tracers for epithelial tumors, glutamine tracers for colorectal cancer, and ascorbic acid analogs for assessing cancer metabolism and therapy efficacy. Additionally, novel tracers have been developed for non-neurological and non-oncological applications, including adrenal imaging, amyloidosis, and human immunodeficiency virus (HIV) infection. This overview focuses on the newly developed tracers, particularly those used in neurology and oncology.

First-in-human validation of a DROP-IN β-probe for robotic radioguided surgery: defining optimal signal-to-background discrimination algorithm

PURPOSE

In radioguided surgery (RGS), radiopharmaceuticals are used to generate preoperative roadmaps (e.g., PET/CT) and to facilitate intraoperative tracing of tracer avid lesions. Within RGS, there is a push toward the use of receptor-targeted radiopharmaceuticals, a trend that also has to align with the surgical move toward minimal invasive robotic surgery. Building on our initial ex vivo evaluation, this study investigates the clinical translation of a DROP-IN β probe in robotic PSMA-guided prostate cancer surgery.

METHODS

A clinical-grade DROP-IN β probe was developed to support the detection of PET radioisotopes (e.g., 68 Ga). The prototype was evaluated in 7 primary prostate cancer patients, having at least 1 lymph node metastases visible on PSMA-PET. Patients were scheduled for radical prostatectomy combined with extended pelvic lymph node dissection. At the beginning of surgery, patients were injected with 1.1 MBq/kg of [68Ga]Ga-PSMA. The β probe was used to trace PSMA-expressing lymph nodes in vivo. To support intraoperative decision-making, a statistical software algorithm was defined and optimized on this dataset to help the surgeon discriminate between probe signals coming from tumors and healthy tissue.

RESULTS

The DROP-IN β probe helped provide the surgeon with autonomous and highly maneuverable tracer detection. A total of 66 samples (i.e., lymph node specimens) were analyzed in vivo, of which 31 (47%) were found to be malignant. After optimization of the signal cutoff algorithm, we found a probe detection rate of 78% of the PSMA-PET-positive samples, a sensitivity of 76%, and a specificity of 93%, as compared to pathologic evaluation.

CONCLUSION

This study shows the first-in-human use of a DROP-IN β probe, supporting the integration of β radio guidance and robotic surgery. The achieved competitive sensitivity and specificity help open the world of robotic RGS to a whole new range of radiopharmaceuticals.

Development of an Engineered Single-Domain Antibody for Targeting MET in Non-Small Cell Lung Cancer

The Mesenchymal Epithelial Transition (MET) receptor tyrosine kinase is upregulated or mutated in 5% of non-small-cell lung cancer (NSCLC) patients and overexpressed in multiple other cancers. We sought to develop a novel single-domain camelid antibody with high affinity for MET that could be used to deliver conjugated payloads to MET expressing cancers. From a naïve camelid variable-heavy-heavy (VHH) domain phage display library, we identified a VHH clone termed 1E7 that displayed high affinity for human MET and was cross-reactive with MET across multiple species. When expressed as a bivalent human Fc fusion protein, 1E7-Fc was found to selectively bind to EBC-1 (MET amplified) and UW-Lung 21 (MET exon 14 mutated) cell lines by flow cytometry and immunofluorescence imaging. Next, we investigated the ability of [89Zr]Zr-1E7-Fc to detect MET expression in vivo by PET/CT imaging. [89Zr]Zr-1E7-Fc demonstrated rapid localization and high tumor uptake in both xenografts with a %ID/g of 6.4 and 5.8 for EBC-1 and UW-Lung 21 at 24 h, respectively. At the 24 h time point, clearance from secondary and nontarget tissues was also observed. Altogether, our data suggest that 1E7-Fc represents a platform technology that can be employed to potentially both image and treat MET-altered NSCLC.

Development of a novel 18F-labeled small molecule probe for PET imaging of mesenchymal epithelial transition receptor expression

The mesenchymal epithelial transition factor (c-Met) is frequently overexpressed in numerous cancers and has served as a validated anticancer target. Inter- and intra-tumor heterogeneity of c-Met, however, challenges the use of anti-MET therapies, highlighting an urgent need to develop an alternative tool for visualizing whole-body c-Met expression quantitatively and noninvasively. Here we firstly reported an 18F labeled, small-molecule quinine compound-based PET probe, 1-(4-(5-amino-7-(trifluoromethyl) quinolin-3-yl) piperazin-1-yl)-2-(fluoro-[18F]) propan-1-one, herein referred as [18F]-AZC.

METHODS

[18F]-AZC was synthesized via a one-step substitution reaction and characterized by radiochemistry methods. [18F]-AZC specificity and affinity toward c-Met were assessed by cell uptake assay, with or without cold compound [19F]-AZC or commercial c-Met inhibitor blocking. MicroPET/CT imaging and biodistribution studies were conducted in subcutaneous murine xenografts of glioma. Additionally, [18F]-AZC was then further evaluated in orthotopic glioma xenografts, by microPET/CT imaging accompanied with MRI and autoradiography for co-registration of the tumor. Immunofluorescence staining was also carried out to qualitatively evaluate the c-Met expression in tumor tissue, co-localizes with H&E staining.

RESULTS

This probe shows easy radiosynthesis, high stability in vitro and in vivo, high targeting affinity, and favorable lipophilicity and brain transport coefficient. [18F]-AZC demonstrates excellent tumor imaging properties in vivo and can delineate c-Met positive glioma specifically at 1 h after intravenous injection of the probe. Moreover, favorable correlation was observed between the [18F]-AZC accumulation and the amount of c-Met expression in tumor.

CONCLUSION

This novel imaging probe could be applied as a valuable tool for management of anti-c-Met therapies in patients in the future.

Fully automated radiolabeling of [68Ga]Ga-EMP100 targeting c-MET for PET-CT clinical imaging

BACKGROUND

c-MET is a transmembrane receptor involved in many biological processes and contributes to cell proliferation and migration during cancer invasion process. Its expression is measured by immunehistochemistry on tissue biopsy in clinic, although this technique has its limitations. PET-CT could allow in vivo mapping of lesions expressing c-MET, providing whole-body detection. A number of radiopharmaceuticals are under development for this purpose but are not yet in routine clinical use. EMP100 is a cyclic oligopeptide bound to a DOTA chelator, with nanomolar affinity for c-MET. The aim of this project was to develop an automated method for radiolabelling the radiopharmaceutical [68Ga]Ga-EMP100.

RESULTS

The main results showed an optimal pH range between 3.25 and 3.75 for the complexation reaction and a stabilisation of the temperature at 90 °C, resulting in an almost complete incorporation of gallium-68 after 10 min of heating. In these experiments, 90 µg of EMP-100 peptide were initially used and then lower amounts (30, 50, 75 µg) were explored to determine the minimum required for sufficient synthesis yield. Radiolysis impurities were identified by radio-HPLC and ascorbic acid and ethanol were used to improve the purity of the compound. Three batches of [68Ga]Ga-EMP100 were then prepared according to the optimised parameters and all met the established specifications. Finally, the stability of [68Ga]Ga-EMP100 was assessed at room temperature over 3 h with satisfactory results in terms of appearance, pH, radiochemical purity and sterility.

CONCLUSIONS

For the automated synthesis of [68Ga]Ga-EMP100, the parameters of pH, temperature, precursor peptide content and the use of adjuvants for impurity management were efficiently optimised, resulting in the production of three compliant and stable batches according to the principles of good manufacturing practice. [68Ga]Ga-EMP100 was successfully synthesised and is now available for clinical development in PET-CT imaging.

Multimodality imaging of Xp11.2 translocation/TFE3 gene fusion associated with renal cell carcinoma: a case report

Background

Xp11.2 translocation/TFE3 gene fusion associated with renal cell carcinoma (Xp11.2 RCC) exhibits unique biological characteristics and is associated with an increased incidence of tumor thrombosis, lymph node metastasis, and advanced disease stages. Multimodality imaging, including US, contrast-enhanced CT, multi-parametric MRI, and 18F-FDG PET/CT plays a crucial role in the preoperative diagnosis and differentiation of renal tumors.

Case report

A 15-year-old female presented with lumbar pain worsened, and developed persistent painless hematuria. The CT attenuation values of the scan without contrast, corticomedullary phase, nephrographic phase, and delayed phases were 35 HU, 83 HU, 82 HU, and 75 HU, respectively. The solid component of the mass displayed heterogeneous marked enhancement. Furthermore, MRU indicated that the lesion involved the cortical medulla and infringed on the renal sinus fat. The lesion appeared isosignal in T1WI, slightly low signal in T2WI, and slightly high signal in DWI. The degree of enhancement in the three phases of enhancement scan was lower than that in the renal parenchyma, and hemorrhage and necrosis were observed within the internal part of the lesion. To further clarify the staging, the patient underwent 18F-FDG PET/CT. PET/CT images showed multiple irregular occupancies in the right kidney with unclear borders, showing a heterogeneous increase in 18F-FDG uptake, with SUVmax values ranging from 2.3 to 5.2 in the routine imaging phase (60 min post-injection), compared to SUVmax values ranging from 2.8 to 6.9 in the delayed imaging phase (160 min post-injection). Additionally, multiple enlarged and fused lymph nodes were observed in the medial part of the right kidney and the retroperitoneum, exhibiting a heterogeneous increase in 18F-FDG uptake, with SUVmax values ranging from 4.1 to 8.7 in the routine imaging phase, compared to SUVmax values ranging from 4.4 to 9.1 in the delayed imaging phase. The postoperative pathology, immunohistochemistry, and molecular analysis of histiocytes were consistent with a diagnosis of Xp11.2 RCC. One month after surgery, enhanced-CT examination of the patient revealed lung metastasis, peritoneal metastasis, and multiple lymph node metastases throughout the body, with an overall survival of 16 months.

Conclusion

Xp11.2 RCC exhibits unique biological characteristics and is associated with an increased incidence of tumor thrombosis, lymph node metastasis, and advanced disease stages. Long-term follow-up is essential to monitor the likelihood of recurrence and metastasis. 18F-FDG PET/CT examination can comprehensively visualize the lesion's location and extent, providing a basis for clinical tumor staging and aiding in treatment monitoring and follow-up. To address the limitations of FDG, the utilization of specific tracers designed for RCC or tracers that are not excreted via the urinary system would be ideal. Further advancements in molecular imaging technologies and the development of novel tracers hold great promise in advancing the diagnosis and management of RCC, ultimately contributing to better patient outcomes and overall disease management.

Evaluation of [18F]AlF-EMP-105 for Molecular Imaging of C-Met

C-Met is a receptor tyrosine kinase that is overexpressed in a range of different cancer types, and has been identified as a potential biomarker for cancer imaging and therapy. Previously, a ⁶⁸Ga-labelled peptide, [⁶⁸Ga]Ga-EMP-100, has shown promise for imaging c-Met in renal cell carcinoma in humans. Herein, we report the synthesis and preliminary biological evaluation of an [¹⁸F]AlF-labelled analogue, [¹⁸F]AlF-EMP-105, for c-Met imaging by positron emission tomography. EMP-105 was radiolabelled using the aluminium-[¹⁸F]fluoride method with 46 ± 2% RCY and >95% RCP in 35-40 min. In vitro evaluation showed that [¹⁸F]AlF-EMP-105 has a high specificity for c-Met-expressing cells. Radioactive metabolite analysis at 5 and 30 min post-injection revealed that [¹⁸F]AlF-EMP-105 has good blood stability, but undergoes transformation-transchelation, defluorination or demetallation-in the liver and kidneys. PET imaging in non-tumour-bearing mice showed high radioactive accumulation in the kidneys, bladder and urine, demonstrating that the tracer is cleared predominantly as [¹⁸F]fluoride by the renal system. With its high specificity for c-Met expressing cells, [¹⁸F]AlF-EMP-105 shows promise as a potential diagnostic tool for imaging cancer.

Treatment patterns and prognosis of patients with inoperable stage III NSCLC after completion of concurrent chemoradiotherapy ± immune checkpoint inhibition: a decade-long single-center historical analysis

PURPOSE

To investigate the impact of treatment time and patterns in inoperable stage III non-small cell lung cancer (NSCLC) following concurrent chemoradiotherapy (cCRT) ± immune checkpoint inhibitors (ICIs).

METHODS

Patients were stratified by treatment year: A (2011-2014), B (2015-2017) and C (2018-2020). Tumor- and treatment-related characteristics regarding locoregional recurrence-free survival (LRRFS), progression-free survival (PFS) and overall survival (OS) were investigated.

RESULTS

One hundred and thirty-six consecutive patients were analyzed. All patients completed thoracic radiotherapy (TRT) to a total dose ≥ 60.0 Gy; 36 (26%) patients received ICI. Median PFS in subgroups A, B and C was 8.0, 8.2 and 26.3 months (p = 0.007). Median OS was 19.9 months, 23.4 months and not reached (NR), respectively. In group C, median LRRFS and PFS were 27.2 vs. NR; and 14.2 vs. 26.3 months in patients treated with and without ICI. On multivariate analysis planning target volume (PTV) ≥ 700 cc was a negative prognosticator of LRRFS (HR 2.194; p = 0.001), PFS (HR 1.522; p = 0.042) and OS (HR 2.883; p = 0.001); ICI was a predictor of LRRFS (HR 0.497; p = 0.062), PFS (HR 0.571; p = 0.071) and OS (HR 0.447; p = 0.1). In the non-ICI cohort, multivariate analyses revealed PTV ≥ 700 cc (p = 0.047) and a maximum standardized uptake value (SUVmax) ≥ 13.75 (p = 0.012) were predictors of PFS; PTV ≥ 700 cc (p = 0.017), SUVmax ≥ 13.75 (p = 0.002) and a total lung V20 ≥ 30% (V20 ≥ 30) (p < 0.05) were predictors of OS.

CONCLUSIONS

Patients treated after 2018 had improved survival regardless of ICI use. Implementation of ICI resulted in further significant increase of all tested survival endpoints. PTV ≥ 700 cc and ICI were only prognosticators for LRRFS, PFS and OS in the analyzed cohort.

Targeting the cMET pathway to enhance immunotherapeutic approaches for mUM patients

The liver is the most preferential initial site of metastasis for uveal melanoma (mUM), and this preference is associated with rapid mortality in mUM patients. Despite the significant clinical benefits of Immune checkpoint inhibitors (ICIs) in metastatic cutaneous melanoma patients, ICIs have shown little to no benefit in mUM patients. A potential reason for this inefficiency of ICI could be partly devoted to the involvement of the liver itself, thanks to its rich source of growth factors and immunosuppressive microenvironment. Uveal melanoma cells show increased expression of a transmembrane protein called cMET, which is known as the sole receptor for the Hepatocyte growth factor (HGF). Hyperactivation of cMET by HGF contributes to mUM development, and the liver, being the major source of HGF, may partially explain the metastasis of uveal melanoma cells to the liver. In addition, cMET/HGF signaling has also been shown to mediate resistance to ICI treatment, directly and indirectly, involving tumor and immune cell populations. Therefore, targeting the cMET/HGF interaction may enhance the efficacy of immunotherapeutic regimes for mUM patients. Hence in this minireview, we will discuss the rationale for combining cMET inhibitors/antibodies with leading immune checkpoint inhibitors for treating mUM. We will also briefly highlight the challenges and opportunities in targeting cMET in mUM.

The current status and future prospects for molecular imaging-guided precision surgery

Molecular imaging technologies are increasingly used to diagnose, monitor, and guide treatment of i.e., cancer. In this review, the current status and future prospects of the use of molecular imaging as an instrument to help realize precision surgery is addressed with focus on the main components that form the conceptual basis of intraoperative molecular imaging. Paramount for successful interventions is the relevance and accessibility of surgical targets. In addition, selection of the correct combination of imaging agents and modalities is critical to visualize both microscopic and bulk disease sites with high affinity and specificity. In this context developments within engineering/imaging physics continue to drive the growth of image-guided surgery. Particularly important herein is enhancement of sensitivity through improved contrast and spatial resolution, features that are critical if sites of cancer involvement are not to be overlooked during surgery. By facilitating the connection between surgical planning and surgical execution, digital surgery technologies such as computer-aided visualization nicely complement these technologies. The complexity of image guidance, combined with the plurality of technologies that are becoming available, also drives the need for evaluation mechanisms that can objectively score the impact that technologies exert on the performance of healthcare professionals and outcome improvement for patients.

Recent progress in the imaging of c-Met aberrant cancers with positron emission tomography

Tyrosine-protein kinase Met-also known as c-Met or HGFR-is a membrane receptor protein with associated tyrosine kinase activity physiologically stimulated by its natural ligand, the hepatocyte growth factor (HGF), and is involved in different ways in cancer progression and tumourigenesis. Targeting c-Met with pharmaceuticals has been preclinically proved to have significant benefits for cancer treatment. Recently, evaluating the protein status during and before c-Met targeted therapy has been shown of relevant importance by different studies, demonstrating that there is a correlation between the status (e.g., aberrant activation and overexpression) of the HGFR with therapy response and clinical prognosis. Currently, clinical imaging based on positron emission tomography (PET) appears as one of the most promising tools for the in vivo real-time scanning of irregular alterations of the tyrosine-protein kinase Met and for the diagnosis of c-Met related cancers. In this study, we review the recent progress in the imaging of c-Met aberrant cancers with PET. Particular attention is directed on the development of PET probes with a range of different sizes (HGF, antibodies, anticalines, peptides, and small molecules), and radiolabeled with different radionuclides. The goal of this review is to report all the preclinical imaging studies based on PET imaging reported until now for in vivo diagnosis of c-Met in oncology to support the design of novel and more effective PET probes for in vivo evaluation of c-Met.

Role of PSMA-ligands imaging in Renal Cell Carcinoma management: current status and future perspectives

Background

Renal masses detection is continually increasing worldwide, with Renal Cell Carcinoma (RCC) accounting for approximately 90% of all renal cancers and remaining one of the most aggressive urological malignancies. Despite improvements in cancer management, accurate diagnosis and treatment strategy of RCC by computed tomography (CT) and magnetic resonance imaging (MRI) are still challenging. Prostate-Specific Membrane Antigen (PSMA) is known to be highly expressed on the endothelial cells of the neovasculature of several solid tumors other than prostate cancer, including RCC. In this context, recent preliminary studies reported a promising role for positron emission tomography (PET)/CT with radiolabeled molecules targeting PSMA, in alternative to fluorodeoxyglucose (FDG) in RCC patients.

Purpose

The aim of our review is to provide an updated overview of current evidences and major limitations regarding the use of PSMA PET/CT in RCC.

Methods

A literature search, up to 31 December 2021, was performed using the following electronic databases: PubMed, SCOPUS, Web of Science, and Google Scholar.

Results

The findings of this review suggest that PSMA PET/CT could represent a valid imaging option for diagnosis, staging, and therapy response evaluation in RCC, particularly in clear cell RCC.

Conclusions

Further studies are needed for this “relatively” new imaging modality to consolidate its indications, timing, and practical procedures.