89Zr-atezolizumab imaging as a non-invasive approach to assess clinical response to PD-L1 blockade in cancer

Granzyme B PET/CT Imaging Evaluates Early Response to Immunotherapy in Gastric Cancer

In several malignancies, only a limited number of patients respond to immune checkpoint inhibitors. Predicting and monitoring responses to these inhibitors represent an unmet clinical need. Here, we developed a PET/CT probe targeting granzyme B, [68Ga]Ga-NOTA-Gly-Gly-Gly-Ile-Glu-Pro-Asp-CHO (GSI), and aimed to investigate whether it can be used to monitor the effects of immune checkpoint inhibitors early in the course of therapy. Methods: Seventy-two patients with gastric cancer (stages III-IV) were recruited for [68Ga]Ga-DOTA-GSI PET/CT imaging after 2 or 3 cycles of the immunotherapy, and 40 patients were included in the final analysis. The SUVmax of primary tumors (SUVmax-t), SUVmax of metastatic lymph nodes (SUVmax-LN), and SUVmax of normal tissues (liver and blood pool) were measured, and their target-to-liver background ratio (TLR) and target-to-blood background ratio (TBR) were denoted for primary tumors as TLRtumor and TBRtumor and for metastatic lymph nodes as TLRLN and TBRLN, respectively. The treatment responses were assessed within 1 wk after full-course treatment according to RECIST version 1.1. Wilcoxon rank-sum tests were used to compare the PET/CT parameters between responders and nonresponders. Receiver operating characteristic curve analysis was used to assess the diagnostic efficacy of [68Ga]Ga-DOTA-GSI PET/CT parameters in identifying responders. Two-tailed P value of less than 0.05 was considered statistically significant. Results: We found that SUVmax-t, TLRtumor, TBRtumor, SUVmax-LN, and TBRLN were higher in responders than in nonresponders (2.49 ± 0.58 vs. 1.55 ± 0.48, P = 0.000; 2.24 ± 0.48 vs. 1.74 ± 0.67, P = 0.007; 1.38 ± 0.43 vs. 0.90 ± 0.23, P = 0.000; 2.24 ± 0.99 vs. 1.42 ± 0.55, P = 0.003; and 1.28 ± 0.68 vs. 0.83 ± 0.32, P = 0.012, respectively). According to receiver operating characteristic curve analysis, the area under the curve for SUVmax-t, TBRtumor, TLRtumor, SUVmax-LN, TLRLN, and TBRLN was 0.886, 0.866, 0.746, 0.772, 0.648, and 0.731, respectively. The threshold of SUVmax-t was 2.05, and its sensitivity and specificity were 81.0% and 84.2%, respectively. In addition, multivariate logistic regression indicated that TBRtumor was an independent predictor of treatment response (P = 0.03). Conclusion: Our results indicated that [68Ga]Ga-DOTA-GSI PET/CT is a promising tool for predicting early response to combined immunotherapy in gastric cancer patients.

68Ga-grazytracer PET for noninvasive assessment of response to immunotherapy in solid tumors and lymphomas: a phase 1/2 clinical trial

To tackle the clinical challenge of noninvasively assessing immunotherapy efficacy in patients, here we used positron emission tomography (PET) with 68Ga-grazytracer, which targets granzyme B, a crucial effector molecule secreted by activated CD8+ T cells. In this phase 1/2 clinical trial (NCT05000372) involving a diverse cohort of 24 patients with solid tumors and lymphomas who received immunotherapies, including immune checkpoint inhibitors (either alone or with chemotherapies) and chimeric antigen receptor-T cell therapy, we examined the in vivo behaviors of 68Ga-grazytracer. Primary endpoints were safety, biodistribution, granzyme B specificity, and the predictive utility of 68Ga-grazytracer, while secondary endpoint was the relationship between 68Ga-grazytracer uptake and tumor immune phenotype. 68Ga-grazytracer exhibited a safe profile and specifically targeted granzyme B in patients. 68Ga-grazytracer PET showed superior predictive value for short-term prognosis and progression-free survival than those of conventional assessment criteria, including RECIST 1.1 and PERCIST. Moreover, the uptake of 68Ga-grazytracer in tumors was significantly higher in those with a "non-desert" immune phenotype than those with an immune "desert" phenotype, thereby meeting the primary and secondary endpoints of this trial. Collectively, we successfully visualized CD8+ T cell effector function in humans using 68Ga-grazytracer PET, offering insights for enhancing immunotherapy assessment, patient stratification and treatment planning.

Targeted protein degradation combined with PET imaging reveals the role of host PD-L1 in determining anti-PD-1 therapy efficacy

PURPOSE

Immunohistochemical staining of programmed death-ligand 1 (PD-L1) in tumor biopsies acquired through invasive procedures is routinely employed in clinical practice to identify patients who are most likely to benefit from anti-programmed cell death protein 1 (PD-1) therapy. Nevertheless, PD-L1 expression is observed in various cellular subsets within tumors and their microenvironments, including tumor cells, dendritic cells, and macrophages. The impact of PD-L1 expression across these different cell types on the responsiveness to anti-PD-1 treatment is yet to be fully understood.

METHODS

We synthesized polymer-based lysosome-targeting chimeras (LYTACs) that incorporate both PD-L1-targeting motifs and liver cell-specific asialoglycoprotein receptor (ASGPR) recognition elements. Small-animal positron emission tomography (PET) imaging of PD-L1 expression was also conducted using a PD-L1-specific radiotracer 89Zr-αPD-L1/Fab.

RESULTS

The PD-L1 LYTAC platform was capable of specifically degrading PD-L1 expressed on liver cancer cells through the lysosomal degradation pathway via ASGPR without impacting the PD-L1 expression on host cells. When coupled with whole-body PD-L1 PET imaging, our studies revealed that host cell PD-L1, rather than tumor cell PD-L1, is pivotal in the antitumor response to anti-PD-1 therapy in a mouse model of liver cancer.

CONCLUSION

The LYTAC strategy, enhanced by PET imaging, has the potential to surmount the limitations of knockout mouse models and to provide a versatile approach for the selective degradation of target proteins in vivo. This could significantly aid in the investigation of the roles and mechanisms of protein functions associated with specific cell subsets in living subjects.

Comparative study of [18F]AlF-PAI-PDL1p and [68Ga]Ga-PAI-PDL1p as novel PD-L1 targeting PET probes for tumor imaging

PD-L1 is expressed in many tumors but rarely in normal tissues, therefore, it can be a target of PET imaging. In this work, we developed new peptide-based PET probes [18F]AlF-PAI-PDL1p and [68Ga]Ga-PAI-PDL1p with yields of 20-25 % and 40-55 %, respectively. [18F]AlF-PAI-PDL1p and [68Ga]Ga-PAI-PDL1p were synthesized within 30 min with high molar activities. [18F]AlF-PAI-PDL1p and [68Ga]Ga-PAI-PDL1p showed good stability in vivo and in vitro. In vitro cell studies showed [18F]AlF-PAI-PDL1p and [68Ga]Ga-PAI-PDL1p target PD-L1 specifically, with high uptake of 61.52 ± 4.39 and 19.29 ± 2.17 %ID/1 million cells in B16F10 cells at 60 min, respectively. Biodistribution results showed that both [18F]AlF-PAI-PDL1p and [68Ga]Ga-PAI-PDL1p had lower liver accumulation. In vivo PET imaging results showed that [18F]AlF-PAI-PDL1p had a high tumor uptake of 4.23 ± 0.81 %ID/g at 2 h and increased uptake of 6.60 ± 1.01 %ID/g at 12 h. [68Ga]Ga-PAI-PDL1p also showed high tumor uptake of 2.30 ± 0.20 %ID/g at 2 h and slightly increased uptake of 3.80 ± 0.26 %ID/g at 6 h. In conclusion, [18F]AlF-PAI-PDL1p and [68Ga]Ga-PAI-PDL1 seemed to be potential tracers for PET imaging of PD-L1 expression.

Molecular imaging supports the development of multispecific cancer antibodies

Multispecific antibodies are engineered antibody derivatives that can bind to two or more distinct epitopes or antigens. Unlike mixtures of monospecific antibodies, the binding properties of multispecific antibodies enable two specific molecules to be physically linked, a characteristic with important applications in cancer therapy. The field of multispecific antibodies is highly dynamic and expanding rapidly; to date, 15 multispecific antibodies have been approved for clinical use, of which 11 were approved for oncological indications, and more than 100 new antibodies are currently in clinical development. Nevertheless, substantial challenges limit the applications of multispecific antibodies in cancer therapy, particularly inefficient targeting of solid tumours and substantial adverse effects. Both PET and single photon emission CT imaging can reveal the biodistribution and complex pharmacology of radiolabelled multispecific antibodies. This Review summarizes the insights obtained from preclinical and clinical molecular imaging studies of multispecific antibodies, focusing on their structural properties, such as molecular weight, shape, target specificity, affinity and avidity. The opportunities associated with use of molecular imaging studies to support the clinical development of multispecific antibody therapies are also highlighted.

Spatiotemporal metabolomic approaches to the cancer-immunity panorama: a methodological perspective

Metabolic reprogramming drives the development of an immunosuppressive tumor microenvironment (TME) through various pathways, contributing to cancer progression and reducing the effectiveness of anticancer immunotherapy. However, our understanding of the metabolic landscape within the tumor-immune context has been limited by conventional metabolic measurements, which have not provided comprehensive insights into the spatiotemporal heterogeneity of metabolism within TME. The emergence of single-cell, spatial, and in vivo metabolomic technologies has now enabled detailed and unbiased analysis, revealing unprecedented spatiotemporal heterogeneity that is particularly valuable in the field of cancer immunology. This review summarizes the methodologies of metabolomics and metabolic regulomics that can be applied to the study of cancer-immunity across single-cell, spatial, and in vivo dimensions, and systematically assesses their benefits and limitations.

Trends in cancer imaging

Molecular imaging of cancer is a collaborative endeavor, uniting scientists and physicians from diverse fields. Such collaboration is actively developing and translating cutting-edge molecular imaging approaches to enhance the diagnostic landscape of human malignancies. The advent of positron emission tomography (PET) and PET imaging tracers has realized non-invasive target annotation and tumor characterization at the molecular level. In surgical procedures, novel imaging techniques, such as fluorescence or Cherenkov luminescence, help identify tumors and enhance surgical precision. Simultaneously, progress in imaging equipment, innovative algorithms, and artificial intelligence has opened avenues for next-generation cancer screening and imaging, augmenting the efficiency and accuracy of cancer diagnosis. In this review, we provide a panorama of molecular cancer imaging and ongoing developments in the field.

Radiolabelling and preclinical characterisation of [89Zr]Zr-Df-ATG-101 bispecific to PD-L1/4-1BB

PURPOSE

ATG-101, a bispecific antibody that simultaneously targets the immune checkpoint PD-L1 and the costimulatory receptor 4-1BB, activates exhausted T cells upon PD-L1 crosslinking. Previous studies demonstrated promising anti-tumour efficacy of ATG-101 in preclinical models. Here, we labelled ATG-101 with 89Zr to confirm its tumour targeting effect and tissue biodistribution in a preclinical model. We also evaluated the use of immuno-PET to study tumour uptake of ATG-101 in vivo.

METHODS

ATG-101, anti-PD-L1, and an isotype control were conjugated with p-SCN-Deferoxamine (Df). The Df-conjugated antibodies were radiolabelled with 89Zr, and their radiochemical purity, immunoreactivity, and serum stability were assessed. We conducted PET/MRI and biodistribution studies on [89Zr]Zr-Df-ATG-101 in BALB/c nude mice bearing PD-L1-expressing MDA-MB-231 breast cancer xenografts for up to 10 days after intravenous administration of [89Zr]Zr-labelled antibodies. The specificity of [89Zr]Zr-Df-ATG-101 was evaluated through a competition study with unlabelled ATG-101 and anti-PD-L1 antibodies.

RESULTS

The Df-conjugation and [89Zr]Zr -radiolabelling did not affect the target binding of ATG-101. Biodistribution and imaging studies demonstrated biological similarity of [89Zr]Zr-Df-ATG-101 and [89Zr]Zr-Df-anti-PD-L1. Tumour uptake of [89Zr]Zr-Df-ATG-101 was clearly visualised using small-animal PET imaging up to 7 days post-injection. Competition studies confirmed the specificity of PD-L1 targeting in vivo.

CONCLUSION

[89Zr]Zr-Df-ATG-101 in vivo distribution is dependent on PD-L1 expression in the MDA-MB-231 xenograft model. Immuno-PET with [89Zr]Zr-Df-ATG-101 provides real-time information about ATG-101 distribution and tumour uptake in vivo. Our data support the use of [89Zr]Zr-Df-ATG-101 to assess tumour and tissue uptake of ATG-101.

Targeting tumour metabolism in melanoma to enhance response to immune checkpoint inhibition: A balancing act

Immune checkpoint inhibition has transformed the treatment landscape of advanced melanoma and long-term survival of patients is now possible. However, at least half of the patients do not benefit sufficiently. Metabolic reprogramming is a hallmark of cancer cells and may contribute to both tumour growth and immune evasion by the tumour. Preclinical studies have indeed demonstrated that modulating tumour metabolism can reduce tumour growth while improving the functionality of immune cells. Since metabolic pathways are commonly shared between immune and tumour cells, it is essential to understand how modulating tumour metabolism in patients influences the intricate balance of pro-and anti-tumour immune effects in the tumour microenvironment. The key question is whether modulating tumour metabolism can inhibit tumour cell growth as well as facilitate an anti-tumour immune response. Here, we review current knowledge on the effect of tumour metabolism on the immune response in melanoma. We summarise metabolic pathways in melanoma and non-cancerous cells in the tumour microenvironment and discuss models and techniques available to study the metabolic-immune interaction. Finally, we discuss clinical use of these techniques to improve our understanding of how metabolic interventions can tip the balance towards a favourable, immune permissive microenvironment in melanoma patients.

[18F]AlF-NOTA-PCP2: a novel PET/CT tracer for enhanced PD-L1 heterogeneity imaging and comparative analysis with [18F]AlF-NOTA-WL12 in glioblastoma xenografts

PURPOSE

The unsatisfactory efficacy of PD-L1 antibodies in glioblastoma (GBM) is largely due to the temporal and spatial heterogeneity of PD-L1 expression. Molecular imaging can enhance understanding of the tumor immune microenvironment and guide immunotherapy. However, highly sensitive imaging agents capable of effectively visualizing PD-L1 heterogeneity are limited. This study introduces a novel PET tracer, offering improved imaging of PD-L1 heterogeneity in GBM xenografts, with a comparative analysis to [18F]AlF-NOTA-WL12.

METHODS

[18F]AlF-NOTA-PCP2 was synthesized with high purity and its affinity for PD-L1 was characterized using surface plasmon resonance (SPR) and cell binding assays. Its specificity for PD-L1 was evaluated both in vitro using various cell lines and in vivo with GBM xenograft models in NOD/SCID mice. PET/CT imaging was conducted to evaluate the tracer's biodistribution, pharmacokinetics, and ability to quantify tumoral spatial heterogeneity of PD-L1 expression. A focused comparative analysis between [18F]AlF-NOTA-PCP2 and [18F]AlF-NOTA-WL12 was conducted, examining binding affinity, biodistribution, pharmacokinetics, and imaging effectiveness in GBM xenografts. Additionally, human radiation dosimetry estimates compared the safety profiles of both tracers.

RESULTS

[18F]AlF-NOTA-PCP2 demonstrated high radiochemical purity (> 95%) and a strong affinity for PD-L1, comparable to [18F]AlF-NOTA-WL12. In vitro and in vivo studies confirmed its specificity for PD-L1, with increased uptake in PD-L1 expressing cells and tumors. Toxicological profiles indicated no significant abnormalities in serum biochemical indicators or major organ tissues. MicroPET/CT imaging showed [18F]AlF-NOTA-PCP2's effectiveness in visualizing PD-L1 expression levels and spatial heterogeneity in GBM xenografts. Comparative studies revealed [18F]AlF-NOTA-PCP2's improved pharmacokinetic properties, including higher tumor-to-blood ratios and lower nonspecific liver uptake, as well as reduced radiation exposure compared to [18F]AlF-NOTA-WL12.

CONCLUSION

[18F]AlF-NOTA-PCP2 distinguishes itself as an exceptionally sensitive PET/CT tracer, adept at non-invasively and accurately quantifying PD-L1 expression and its spatial heterogeneity in tumors, especially in GBM. Its favorable pharmacokinetic properties, safety profile, and high affinity for PD-L1 highlight its potential for enhancing the precision of cancer immunotherapy and guiding individualized treatment strategies. While promising, its clinical translation, especially in brain imaging, necessitates further validation in clinical trials.

Preliminary Research of Radiolabeled Atezolizumab for the Noninvasive Evaluation of TNBC PD-L1 Expression In Vivo

Programmed death-ligand 1 (PD-L1) expression is related to the efficacy and prognosis in triple-negative breast cancer. This study employed an indirect labeling method to synthesize [125I]PI-Atezolizumab. The in vitro stability of [125I]PI-Atezolizumab was assessed through incubation in phosphate buffered saline and fetal bovine serum, revealing sustained stability. Specific binding of [125I]PI-Atezolizumab to MDA-MB-231 cells expressing humanized PD-L1 was assessed through in vitro incubation, yielding a Kd value comparable to that of Atezolizumab. This suggests that the labeling process did not compromise the affinity of the Atezolizumab to PD-L1. Subsequently, pharmacokinetic studies were conducted in normal mice and biodistribution experiments in tumor-bearing mice. A comparison of the biodistribution results between [125I]PI-Atezolizumab and 125I-labeled Atezolizumab indicated better in vivo stability for the former. Single photon emission computed tomography (SPECT)/CT imaging further confirmed the targeted specificity of [125I]PI-Atezolizumab for PD-L1 in MDA-MB-231 xenografts, which were validated by immunohistochemistry staining. This research underscores the utility of [125I]PI-Atezolizumab, prepared via indirect labeling, for monitoring PD-L1 in triple-negative breast cancer models.

Multispectral fluorescence imaging of EGFR and PD-L1 for precision detection of oral squamous cell carcinoma: a preclinical and clinical study

BACKGROUND

Early detection and treatment are effective methods for the management of oral squamous cell carcinoma (OSCC), which can be facilitated by the detection of tumor-specific OSCC biomarkers. The epidermal growth factor receptor (EGFR) and programmed death-ligand 1 (PD-L1) are important therapeutic targets for OSCC. Multispectral fluorescence molecular imaging (FMI) can facilitate the detection of tumor multitarget expression with high sensitivity and safety. Hence, we developed Nimotuzumab-ICG and Atezolizumab-Cy5.5 imaging probes, in combination with multispectral FMI, to sensitively and noninvasively identify EGFR and PD-L1 expression for the detection and comprehensive treatment of OSCC.

METHODS

The expression of EGFR and PD-L1 was analyzed using bioinformatics data sources and specimens. Nimotuzumab-ICG and Atezolizumab-Cy5.5 imaging probes were developed and tested on preclinical OSCC cell line and orthotopic OSCC mouse model, fresh OSCC patients' biopsied samples, and further clinical mouthwash trials were conducted in OSCC patients.

RESULTS

EGFR and PD-L1 were specifically expressed in human OSCC cell lines and tumor xenografts. Nimotuzumab-ICG and Atezolizumab-Cy5.5 imaging probes can specifically target to the tumor sites in an in situ human OSCC mouse model with good safety. The detection sensitivity and specificity of Nimotuzumab-ICG in patients were 96.4% and 100%, and 95.2% and 88.9% for Atezolizumab-Cy5.5.

CONCLUSIONS

EGFR and PD-L1 are highly expressed in OSCC, the combination of which is important for a precise prognosis of OSCC. EGFR and PD-L1 expression can be sensitively detected using the newly synthesized multispectral fluorescence imaging probes Nimotuzumab-ICG and Atezolizumab-Cy5.5, which can facilitate the sensitive and specific detection of OSCC and improve treatment outcomes.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR2100045738. Registered 23 April 2021, https://www.chictr.org.cn/bin/project/edit?pid=125220.

Synthesis and evaluation of anti-PD-L1-B11 antibody fragments for PET imaging of PD-L1 in breast cancer and melanoma tumor models

There is a critical need to non-invasively assess the PD-L1 expression in tumors as a predictive biomarker for determining the efficacy of anti-PD-1/PD-L1 immunotherapies. Non-invasive imaging modality like positron emission tomography (PET) can be a powerful tool to assess the PD-L1 expression in the whole body including multiple metastases as a patient selection criterion for the anti-PD-1/PD-L1 immunotherapy. In this study, we synthesized B11-nanobody, B11-scFv and B11-diabody fragments from the full-length anti-PD-L1 B11 IgG. Out of the three antibody fragments, B11-diabody showed higher nM affinity towards PD-L1 antigen as compared to B11-scFv and B11-nanobody. All three antibody fragments were successfully radiolabeled with 64Cu, a PET radioisotope. For radiolabeling, the antibody fragments were first conjugated with p-SCN-Bn-NOTA followed by chelation with 64Cu. All three radiolabeled antibody fragments were found to be stable in mouse and human sera for up to 24 h. Additionally, all three [64Cu]Cu-NOTA-B11-antibody fragments were evaluated in PD-L1 negative and human PD-L1 expressing cancer cells and subcutaneous tumor models. Based on the results, [64Cu]Cu-NOTA-B11-diabody has potential to be used as a PET imaging probe for assessing PD-L1 expression in tumors as early as 4 h post-injection, allowing faster assessment compared to the full length IgG based PET imaging probe.

Fluorescently labelled vedolizumab to visualise drug distribution and mucosal target cells in inflammatory bowel disease

OBJECTIVE

Improving patient selection and development of biological therapies such as vedolizumab in IBD requires a thorough understanding of the mechanism of action and target binding, thereby providing individualised treatment strategies. We aimed to visualise the macroscopic and microscopic distribution of intravenous injected fluorescently labelled vedolizumab, vedo-800CW, and identify its target cells using fluorescence molecular imaging (FMI).

DESIGN

Forty three FMI procedures were performed, which consisted of macroscopic in vivo assessment during endoscopy, followed by macroscopic and microscopic ex vivo imaging. In phase A, patients received an intravenous dose of 4.5 mg, 15 mg vedo-800CW or no tracer prior to endoscopy. In phase B, patients received 15 mg vedo-800CW preceded by an unlabelled (sub)therapeutic dose of vedolizumab.

RESULTS

FMI quantification showed a dose-dependent increase in vedo-800CW fluorescence intensity in inflamed tissues, with 15 mg (153.7 au (132.3-163.7)) as the most suitable tracer dose compared with 4.5 mg (55.3 au (33.6-78.2)) (p=0.0002). Moreover, the fluorescence signal decreased by 61% when vedo-800CW was administered after a therapeutic dose of unlabelled vedolizumab, suggesting target saturation in the inflamed tissue. Fluorescence microscopy and immunostaining showed that vedolizumab penetrated the inflamed mucosa and was associated with several immune cell types, most prominently with plasma cells.

CONCLUSION

These results indicate the potential of FMI to determine the local distribution of drugs in the inflamed target tissue and identify drug target cells, providing new insights into targeted agents for their use in IBD.

TRIAL REGISTRATION NUMBER

NCT04112212.

Construction of [89Zr]Zr-Labeled HuL13 for ImmunoPET Imaging of LAG-3 Checkpoint Expression on Tumor-Infiltrating T Cells

Lymphocyte activation gene 3 (LAG-3) has attracted much attention as a potentially valuable immune checkpoint. Individual identification of LAG-3 expression at screening and during treatment could improve the successful implementation of anti-LAG-3 therapies. HuL13 is a human IgG1 monoclonal antibody that binds to the LAG-3 receptor in T cells. Here, we used [89Zr]Zr-labeled HuL13 to delineate LAG-3+ T-cell infiltration into tumors via positron emission tomography (PET) imaging. A549/LAG-3 cells, which stably express LAG-3, were generated by infection with lentivirus. The uptake of [89Zr]Zr-DFO-HuL13 in A549/LAG-3 cells was greater than that in the negative control (A549/NC) cells at each time point. The equilibrium dissociation constant (Kd) of [89Zr]Zr-DFO-HuL13 for the LAG-3 receptor was 8.22 nM. PET imaging revealed significant uptake in the tumor areas of A549/LAG-3 tumor-bearing mice from 24 h after injection (SUVmax = 2.43 ± 0.06 at 24 h). As a proof of concept, PET imaging of the [89Zr]Zr-DFO-HuL13 tracer was further investigated in an MC38 tumor-bearing humanized LAG-3 mouse model. PET imaging revealed that the [89Zr]Zr-DFO-HuL13 tracer specifically targets human LAG-3 expressed on tumor-infiltrating lymphocytes (TILs). In addition to the tumors, the spleen was also noticeably visible. Tumor uptake of the [89Zr]Zr-DFO-HuL13 tracer was lower than its uptake in the spleen, but high uptake in the spleen could be reduced by coinjection of unlabeled antibodies. Coinjection of unlabeled antibodies increases tracer activity in the blood pool, thereby improving tumor uptake. Dosimetry evaluation of the healthy mouse models revealed that the highest absorbed radiation dose was in the spleen, followed by the liver and heart wall. In summary, these studies demonstrate the feasibility of using the [89Zr]Zr-DFO-HuL13 tracer for the detection of LAG-3 expression on TILs. Further clinical evaluation of the [89Zr]Zr-DFO-HuL13 tracer may be of significant help in the stratification and management of patients suitable for anti-LAG-3 therapy.

Carboxylesterase Activatable Molecular Probe for Personalized Treatment Guidance by Analyte-Induced Molecular Transformation

Accurate visualization of tumor microenvironment is of great significance for personalized medicine. Here, we develop a near-infrared (NIR) fluorescence/photoacoustic (FL/PA) dual-mode molecular probe (denoted as NIR-CE) for distinguishing tumors based on carboxylesterase (CE) level by an analyte-induced molecular transformation (AIMT) strategy. The recognition moiety for CE activity is the acetyl unit of NIR-CE, generating the pre-product, NIR-CE-OH, which undergoes spontaneous hydrogen atom exchange between the nitrogen atoms in the indole group and the phenol hydroxyl group, eventually transforming into NIR-CE-H. In cellular experiments and in vivo blind studies, the human hepatoma cells and tumors with high level of CE were successfully distinguished by both NIR FL and PA imaging. Our findings provide a new molecular imaging strategy for personalized treatment guidance.

ImmunoPET imaging of LAG-3 expression in tumor microenvironment with 68Ga-labelled cyclic peptides tracers: from bench to bedside

BACKGROUND

Lymphocyte activation gene 3 (LAG-3) has been considered as the next generation of immune checkpoint and a promising prognostic biomarker of immunotherapy. As with programmed cell death protein-1/programmed death-ligand 1 and cytotoxic T-lymphocyte antigen-4 inhibitors, positron emission tomography (PET) imaging strategies could benefit the development of clinical decision-making of LAG-3-related therapy. In this study, we developed and validated 68Ga-labeled cyclic peptides tracers for PET imaging of LAG-3 expression in bench-to-bedside studies.

METHODS

A series of LAG-3-targeted cyclic peptides were modified and radiolabeled with 68GaCl3 and evaluated their affinity and specificity, biodistribution, pharmacokinetics, and radiation dosimetry in vitro and in vivo. Furthermore, hu-PBL-SCID (PBL) mice models were constructed to validate the capacity of [68Ga]Ga-CC09-1 for mapping of LAG-3+ lymphocytes infiltrates using longitudinal PET imaging. Lastly, [68Ga]Ga-CC09-1 was translated into the first-in-human studies to assess its safety, biodistribution and potential for imaging of LAG-3 expression.

RESULTS

A series of cyclic peptides targeting LAG-3 were employed as lead compounds to design and develop 68Ga-labeled PET tracers. In vitro binding assays showed higher affinity and specificity of [68Ga]Ga-CC09-1 in Chinese hamster ovary-human LAG-3 cells and peripheral blood mononuclear cells. In vivo PET imaging demonstrated better imaging capacity of [68Ga]Ga-CC09-1 with a higher tumor uptake of 1.35±0.33 per cent injected dose per gram and tumor-to-muscle ratio of 17.18±3.20 at 60 min post-injection. Furthermore, [68Ga]Ga-CC09-1 could detect the LAG-3+ lymphocyte infiltrates in spleen, lung and salivary gland of PBL mice. In patients with melanoma and non-small cell lung cancer, primary lesions with modest tumor uptake were observed in [68Ga]Ga-CC09-1 PET, as compared with that of [18F]FDG PET. More importantly, [68Ga]Ga-CC09-1 delineated the heterogeneity of LAG-3 expression within large tumors.

CONCLUSION

These findings consolidated that [68Ga]Ga-CC09-1 is a promising PET tracer for quantifying the LAG-3 expression in tumor microenvironment, indicating its potential as a companion diagnostic for patients stratification and therapeutic response monitoring in anti-LAG-3 therapy.

Peptide-based PET tracer targeting LAG-3 for evaluating the efficacy of immunotherapy in melanoma

BACKGROUND

Lymphocyte activation gene 3 (LAG-3) is expressed on activated immune cells and has emerged as a promising target for immune checkpoints blockade. However, conflicting findings have been reported regarding the association between LAG-3 expression in tumors and patient prognosis, indicating the need for further investigation into the significance of LAG-3 expression levels in tumor therapies. In this study, 68Ga-NOTA-XH05, a novel peptide-based positron emission tomography (PET) tracer targeting LAG-3, was constructed to non-invasively detect LAG-3 expression in melanoma after CpG oligonucleotide (CpG) treatment and explore the relationship between LAG-3 expression and therapeutic effect.

METHODS

The tracer 68Ga-NOTA-XH05 was identified by high-performance liquid chromatography after being prepared and purified. Cell uptake and blocking essays were performed to verify the specificity of the tracer in vitro. The expression of LAG-3 in B16-F10 subcutaneous tumors was monitored by flow cytometry, and its correlation with the tracer uptake was analyzed to evaluate the tracer specificity. PET imaging and biodistribution studies were conducted after CpG treatment of unilateral or bilateral B16-F10 subcutaneous tumor models to assess the ability of 68Ga-NOTA-XH05 in monitoring immunotherapy efficacy and the abscopal effect of CpG.

RESULTS

Following purification, 68Ga-NOTA-XH05 exhibited high radiochemical purity and specificity. Flow cytometry analysis revealed a positive correlation between LAG-3 expression in tumors and the uptake of 68Ga-NOTA-XH05. In B16-F10 bearing mice treated with CpG, PET imaging using 68Ga-NOTA-XH05 demonstrated a higher tumor to blood ratio (TBR) compared with the control group. Furthermore, TBR values obtained from CpG-treated mice allowed for differentiation between responders and non-responders. In a bilateral subcutaneous tumor model where only right-sided tumors were treated with intratumoral injection of CpG, TBR values of left-sided tumors were significantly higher than those in the control group, indicating that 68Ga-NOTA-XH05 could effectively monitor the systemic effect of local CpG injection.

CONCLUSION

Our findings highlight the detection capability of 68Ga-NOTA-XH05 in assessing LAG-3 expression levels within tumors and evaluating response to immunotherapy, thereby suggesting promising clinical translational prospects.

Illuminating immunotherapy response via precision T cell-targeted PET imaging

Traditionally, immunotherapy agent selection and treatment strategies are guided by biopsy-based histological information. However, biopsies are limited in that they are invasive, provide static information regarding the tumor immune microenvironment, and only sample a small part of one tumor site. The tumor microenvironment is dynamic and heterogenous. As a result, the immune milieu at one site may be distinct from other metastatic sites. These factors make identifying which patients are likely to respond to different immunotherapies and which harbor intrinsic resistance mechanisms difficult to identify based on a biopsy alone. As such, there is significant interest in alternative methodologies that better characterize the tumor immune microenvironment and monitor immunotherapy response. PET imaging potentially offers a non-invasive way to characterize the tumor immune microenvironment at the primary tumor and metastases and allow for longitudinal characterization. Herein, we review pre-clinically and clinically tested T cell-targeted PET radiopharmaceuticals, as T cells have been the dominant immunotherapy target, and their utility in both evaluating response to immunotherapy and in understanding the systemic immune response to treatment with immunotherapeutics.

Current status and progress of PD-L1 detection: guiding immunotherapy for non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related deaths and represents a substantial disease burden worldwide. Immune checkpoint inhibitors combined with chemotherapy are the standard first-line therapy for advanced NSCLC without driver mutations. Programmed death-ligand 1 (PD-L1) is currently the only approved immunotherapy marker. PD-L1 detection methods are diverse and have developed rapidly in recent years, such as improved immunohistochemical detection methods, the application of liquid biopsy in PD-L1 detection, genetic testing, radionuclide imaging, and the use of machine learning methods to construct PD-L1 prediction models. This review focuses on the detection methods and challenges of PD-L1 from different sources, and discusses the influencing factors of PD-L1 detection and the value of combined biomarkers. Provide support for clinical screening of immunotherapy-advantage groups and formulation of personalized treatment decisions.

Multimodal Imaging Approach for Tumor Treatment Response Evaluation in the Era of Immunotherapy

ABSTRACT

Immunotherapy is likely the most remarkable advancement in lung cancer treatment during the past decade. Although immunotherapy provides substantial benefits, their therapeutic responses differ from those of conventional chemotherapy and targeted therapy, and some patients present unique immunotherapy response patterns that cannot be judged under the current measurement standards. Therefore, the response monitoring of immunotherapy can be challenging, such as the differentiation between real response and pseudo-response. This review outlines the various tumor response patterns to immunotherapy and discusses methods for quantifying computed tomography (CT) and 18F-fluorodeoxyglucose positron emission tomography (PET) in the field of lung cancer. Emerging technologies in magnetic resonance imaging (MRI) and non-FDG PET tracers are also explored. With immunotherapy responses, the role for imaging is essential in both anatomical radiological responses (CT/MRI) and molecular changes (PET imaging). Multiple aspects must be considered when assessing treatment responses using CT and PET. Finally, we introduce multimodal approaches that integrate imaging and nonimaging data, and we discuss future directions for the assessment and prediction of lung cancer responses to immunotherapy.

Bench-to-bedside imaging in brain metastases: a road to precision oncology

Radiology has seen tremendous evolution in the last few decades. At the same time, oncology has made great strides in diagnosing and treating cancer. Distant metastases of neoplasms are being encountered more often in light of longer patient survival due to better therapeutic strategies and diagnostic methods. Brain metastasis (BM) is a dismal manifestation of systemic cancer. In the present scenario, magnetic resonance imaging (MRI), computed tomography (CT) and positron emission tomography (PET) are playing a big role in providing molecular information about cancer. Lately, molecular imaging has emerged as a stirring arena of dynamic imaging techniques that have enabled clinicians and scientists to noninvasively visualize and understand biological processes at the cellular and molecular levels. This knowledge has impacted etiopathogenesis, detection, personalized treatment, drug development, and our understanding of carcinogenesis. This article offers insight into the molecular biology underlying brain metastasis, its pathogenesis, imaging protocols, and algorithms. It also discusses disease-specific molecular imaging features, focusing on common tumors that spread to the brain, such as lung, breast, colorectal cancer, melanoma, and renal cell carcinoma. Additionally, it covers various targeted treatment options, criteria for assessing treatment response, and the role of artificial intelligence in diagnosing, managing, and predicting prognosis for patients with brain metastases.

Non-operative management after immune checkpoint inhibitors for early-stage, dMMR/MSI-H gastrointestinal cancers

Surgery is a standard treatment for early-stage gastrointestinal cancers, often preceded by neoadjuvant chemo(radio)therapy or followed by adjuvant therapy. While leading to cure in a proportion of patients, it has some drawbacks such as intra/post-operative complications, mutilation and life-long functional sequelae. Further to the unprecedented efficacy data from studies of immune checkpoint inhibitors for advanced mismatch repair deficient/microsatellite instable (dMMR/MSI-H) tumours, a strong interest has recently emerged for the investigation of such agents in the neoadjuvant setting. Although limited by the exploratory design and small sample size, trials of neoadjuvant immune checkpoint inhibitors for early-stage dMMR/MSI-H gastrointestinal cancers have consistently reported complete response rates ranging from 70 % to 100 %. As a result, the question has arisen as to whether surgery is still needed or organ-preserving strategies should be offered to this especially immuno-sensitive population. In this article, we discuss the available evidence for neoadjuvant immune checkpoint inhibitors in dMMR/MSI-H gastrointestinal cancers and analyse opportunities and challenges to the implementation of non-operative management approaches in this setting.

Exploring the predictive potential of programmed death ligand 1 expression in healthy organs and lymph nodes as measured by 18F-BMS986-192 PET: pooled analysis of data from four solid tumor types

INTRODUCTION

Immune checkpoint inhibitors (ICIs) can elicit anticancer immune responses, but predictive biomarkers are needed. We measured programmed death ligand 1 (PD-L1) expression in organs and lymph nodes using 18F-BMS-986192 positron emission tomography (PET)-imaging and looked for correlations with response and immune-related adverse events.

METHODS

Four 18F-BMS-986192 PET studies in patients with melanoma, lung, pancreatic and oral cancer, receiving ICI treatment, were combined. Imaging data (organ standardized uptake value (SUV)mean, lymph node SUVmax) and clinical data (response to treatment and incidence of immune-related adverse events) were extracted.

RESULTS

Baseline PD-L1 uptake in the spleen was on average higher in non-responding patients than in responders (spleen SUVmean 16.1±4.4 vs 12.5±3.4, p=0.02). This effect was strongest in lung cancer, and not observed in oral cancer. In the oral cancer cohort, benign tumor-draining lymph nodes (TDLNs) had higher PD-L1 uptake (SUVmax 3.3 IQR 2.5-3.9) compared with non-TDLNs (SUVmax 1.8, IQR 1.4-2.8 p=0.04). Furthermore, in the same cohort non-responders showed an increase in PD-L1 uptake in benign TDLNs on-treatment with ICIs (+15%), while for responders the PD-L1 uptake decreased (-11%). PD-L1 uptake did not predict immune-related adverse events, though elevated thyroid uptake on-treatment correlated with pre-existing thyroid disease or toxicity.

CONCLUSION

PD-L1 PET uptake in the spleen is a potential negative predictor of response to ICIs. On-treatment with ICIs, PD-L1 uptake in benign TDLNs increases in non-responders, while it decreases in responders, potentially indicating a mechanism for resistance to ICIs in patients with oral cancer.

Novel PET tracers in breast cancer for treatment optimization: clinical utility and future perspectives

PURPOSE OF REVIEW

There is a critical need for timely and accurate decisions in breast cancer management. This narrative review aims to clarify the potential role of novel PET tracers in optimizing treatment strategies for different breast cancer subtypes.

RECENT FINDINGS

2-deoxy-2-[18F]-fluoro-D-glucose PET/computed tomography (FDG PET/CT) has a pivotal role in response assessment in metastatic breast cancer, despite its limitations in certain histological and molecular subtypes. Further PET radiopharmaceuticals have been proposed to address these clinical needing.

SUMMARY

FES PET/CT demonstrates its usefulness in assessing ER expression and predicting response to therapy in luminal breast cancer, with implications for treatment optimization and monitoring. In HER2-positive and HER2-low breast cancer, HER2-targeted PET tracers show potential in assessing HER2 status, while their accuracy in predicting response to targeted therapies is still debated. PARP-targeted PET imaging holds potential for selecting patients for PARP inhibitors treatments, particularly in triple-negative breast cancer (TNBC), where imaging tools are crucial due to the absence of specific targets. Immunotherapy and antibody-drug conjugates (ADCs) are emerging treatment options for TNBC, and PET imaging targeting immune checkpoints could aid in treatment selection and response monitoring. The dynamic role of PET/CT imaging in tailoring breast cancer treatments requires further multidisciplinary research to validate the clinical utility of targeted tracers.

PD-L1 has a heterogeneous and dynamic expression in gastric cancer with implications for immunoPET

Introduction

This study aimed to investigate the dynamics of programmed death-ligand 1 (PD-L1) expression, spatial heterogeneity, and binding affinity of FDA-approved anti-PD-L1 antibodies (avelumab and atezolizumab) in gastric cancer. Additionally, we determined how PD-L1 glycosylation impacts antibody accumulation in gastric cancer cells.

Methods

Dynamic PD-L1 expression was examined in NCIN87 gastric cancer cells. Comparative binding studies of avelumab and atezolizumab were conducted in gastric cancer models, both in vitro and in vivo. Antibody uptake in tumors was visualized through positron emission tomography (PET) imaging. PD-L1 glycosylation status was determined via Western blot analyses before and after PNGase F treatment.

Results

Consistent findings revealed time-dependent PD-L1 induction in NCIN87 gastric cancer cells and spatial heterogeneity in tumors, as shown by PET imaging and immunofluorescence. Avelumab displayed superior binding affinity to NCIN87 cells compared to atezolizumab, confirmed by in vivo PET imaging and ex vivo biodistribution analyses. Notably, PD-L1 glycosylation at approximately 50 kDa was observed, with PNGase F treatment inducing a shift to 35 kDa in molecular weight. Tissue samples from patient-derived xenografts (PDXs) validated the presence of both glycosylated and deglycosylated PD-L1 (degPD-L1) forms in gastric cancer. Immunofluorescence microscopy and binding assays demonstrated enhanced avelumab binding post-deglycosylation.

Discussion

This study provides an understanding of dynamic and spatially heterogeneous PD-L1 expression in gastric cancer. Anti-PD-L1 immunoPET was able to visualize gastric tumors, and PD-L1 glycosylation has significant implications for antibody recognition. These insights contribute to demonstrating the complexities of PD-L1 in gastric cancer, holding relevance for refining PD-L1 imaging-based approaches.

Navigating the landscape of PD-1/PD-L1 imaging tracers: from challenges to opportunities

Immunotherapy targeted to immune checkpoint inhibitors, such as the program cell death receptor (PD-1) and its ligand (PD-L1), has revolutionized cancer treatment. However, it is now well-known that PD-1/PD-L1 immunotherapy response is inconsistent among patients. The current challenge is to customize treatment regimens per patient, which could be possible if the PD-1/PD-L1 expression and dynamic landscape are known. With positron emission tomography (PET) imaging, it is possible to image these immune targets non-invasively and system-wide during therapy. A successful PET imaging tracer should meet specific criteria concerning target affinity, specificity, clearance rate and target-specific uptake, to name a few. The structural profile of such a tracer will define its properties and can be used to optimize tracers in development and design new ones. Currently, a range of PD-1/PD-L1-targeting PET tracers are available from different molecular categories that have shown impressive preclinical and clinical results, each with its own advantages and disadvantages. This review will provide an overview of current PET tracers targeting the PD-1/PD-L1 axis. Antibody, peptide, and antibody fragment tracers will be discussed with respect to their molecular characteristics and binding properties and ways to optimize them.

Total Body PET-CT Protocols in Oncology

Recently developed long axial field of view (LAFOV) PET-CT scanners, including total body scanners, are already in use in a few centers worldwide. These systems have some major advantages over standard axial field of view (SAFOV) PET-CT scanners, mainly due to up to 20 times higher sensitivity and therefore improved lesion detectability. Other advantages are the reduction of the PET acquisition time for a static whole-body measurement, the reduction of the administered radiotracer dose, and the ability to perform delayed scans with good image quality, which is important for imaging radionuclides with long half-lives and pharmaceuticals with long biodistribution times, such as 89Zr-labeled antibodies. The reduction of the applied tracer dose leads to less radiation exposure and may facilitate longitudinal studies, especially in oncological patients, for the evaluation of therapy. The reduction in acquisition time for a static whole body (WB) study allows a markedly higher patient throughput. Furthermore, LAFOV PET-CT scanners enable for the first-time WB dynamic PET scanning and WB parametric imaging with an improved image quality due to increased sensitivity and time resolution. WB tracer kinetics is of particular interest for the characterization of novel radiopharmaceuticals and for a better biological characterization of cancer diseases, as well as for a more accurate assessment of the response to new targeted therapies. Further technological developments based on artificial intelligence (AI) approaches are underway and may in the future allow CT-less attenuation correction or ultralow dose CT for attenuation correction as well as segmentation algorithms for the evaluation of total metabolic tumor volume. The aim of this review is to present dedicated PET acquisition protocols for oncological studies with LAFOV scanners, including static and dynamic acquisition as well as parametric scans, and to present literature data to date on this topic.

Recent advances and impending challenges for the radiopharmaceutical sciences in oncology

This paper is the first of a Series on theranostics that summarises the current landscape of the radiopharmaceutical sciences as they pertain to oncology. In this Series paper, we describe exciting developments in radiochemistry and the production of radionuclides, the development and translation of theranostics, and the application of artificial intelligence to our field. These developments are catalysing growth in the use of radiopharmaceuticals to the benefit of patients worldwide. We also highlight some of the key issues to be addressed in the coming years to realise the full potential of radiopharmaceuticals to treat cancer.

Clinical significance of 18F-FDG-PET/CT for detection of incidental pre-malignant and malignant colonic lesions: correlation with colonoscopic and histopathological results

BACKGROUND

Incidental colorectal fluorodeoxyglucose (FDG) uptake, observed during positron emission tomography/computed tomography (PET/CT) scans, attracts particular attention due to its potential to represent both benign and pre-malignant/malignant lesions. Early detection and excision of these lesions are crucial for preventing cancer development and reducing mortality. This research aims to evaluate the correlation between incidental colorectal FDG uptake on PET/CT with colonoscopic and histopathological results.

METHODS

Retrospective analysis was performed on data from all patients who underwent PET/CT between December 2019 and December 2023 in our hospital. The study included 79 patients with incidental colonic FDG uptake who underwent endoscopy. Patient characteristics, imaging parameters, and the corresponding colonoscopy and histopathological results were studied. A comparative analysis was performed among the findings from each of these modalities. The optimal cut-off value of SUVmax for 18F-FDG PET/CT diagnosis of premalignant and malignant lesions was determined by receiver operating characteristic (ROC) curves. The area under the curve (AUC) of SUVmax and the combined parameters of SUVmax and colonic wall thickening (CWT) were analyzed.

RESULTS

Among the 79 patients with incidental colorectal FDG uptake, histopathology revealed malignancy in 22 (27.9%) patients and premalignant polyps in 22 (27.9%) patients. Compared to patients with benign lesions, patients with premalignant and malignant lesions were more likely to undergo a PET/CT scan for primary evaluation (p = 0.013), and more likely to have focal GIT uptake (p = 0.001) and CWT (p = 0.001). A ROC curve analysis was made and assesed a cut-off value of 7.66 SUVmax (sensitivity: 64.9% and specificity: 82.4%) to distinguish premalignant and malignant lesions from benign lesions. The AUCs of the SUVmax and the combined parameters of SUVmax and CWT were 0.758 and 0.832 respectively.

CONCLUSION

For patients undergo PET/CT for primary evaluation, imaging features of colorectal focal FDG uptake and CWT were more closely associated with premalignant and malignant lesions. The SUVmax helps determine benign and premalignant/malignant lesions of the colorectum. Moreover, the combination of SUVmax and CWT parameters have higher accuracy in estimating premalignant and malignant lesions than SUVmax.

Imageable Brachytherapy with Chelator-Free Radiolabeling Hydrogel

Brachytherapy stands as an essential clinical approach for combating locally advanced tumors. Here, an injectable brachytherapy hydrogel is developed for the treatment of both local and metastatic tumor. Fe-tannins nanoparticles are efficiently and stably radiolabeled with clinical used therapeutic radionuclides (such as 131I, 90Y, 177Lu, and 225Ac) without a chelator, and then chemically cross-linked with 4-armPEG-SH to form brachytherapy hydrogel. Upon intratumoral administration, magnetic resonance imaging (MRI) signal from ferric ions embedded within the hydrogel directly correlates with the retention dosage of radionuclides, which can real-time monitor radionuclides emitting short-range rays in vivo without penetration limitation during brachytherapy. The hydrogel's design ensures the long-term tumor retention of therapeutic radionuclides, leading to the effective eradication of local tumor. Furthermore, the radiolabeled hydrogel is integrated with an adjuvant to synergize with immune checkpoint blocking therapy, thereby activating potent anti-tumor immune responses and inhibiting metastatic tumor growth. Therefore, this work presents an imageable brachytherapy hydrogel for real-time monitoring therapeutic process, and expands the indications of brachytherapy from treatment of localized tumors to metastatic tumors.

Cancer Immunotherapy and Medical Imaging Research Trends from 2003 to 2023: A Bibliometric Analysis

Purpose

With the rapid development of immunotherapy, cancer treatment has entered a new phase. Medical imaging, as a primary diagnostic method, is closely related to cancer immunotherapy. However, until now, there has been no systematic bibliometric analysis of the state of this field. Therefore, the main purpose of this article is to clarify the past research trajectory, summarize current research hotspots, reveal dynamic scientific developments, and explore future research directions.

Patients and Methods

A comprehensive search was conducted on the Web of Science Core Collection (WoSCC) database to identify publications related to immunotherapy specifically for the medical imaging of carcinoma. The search spanned the period from the year 2003 to 2023. Several analytical tools were employed. These included CiteSpace (6.2.4), and the Microsoft Office Excel (2016).

Results

By searching the database, a total of 704 English articles published between 2003 and 2023 were obtained. We have observed a rapid increase in the number of publications since 2018. The two most active countries are the United States (n=265) and China (n=170). Pittock, Sean J and Abu-sbeih, Hamzah are very concerned about the relationship between cancer immunotherapy and medical images and have published more academic papers (n = 5; n = 4). Among the top 10 co-cited authors, Topalian Sl (n=43) cited ranked first, followed by Graus F (n=40) cited. According to clustering, timeline, and burst word analysis, the results show that the current research focus is on "MRI", "deep learning", "tumor microenvironment" and so on.

Conclusion

Medical imaging and cancer immunotherapy are hot topics. The United States is the country with the most publications and the greatest influence in this field, followed by China. "MRI", "PET/PET-CT", "deep learning", "immune-related adverse events" and "tumor microenvironment" are currently hot research topics and potential targets.

Favorable impact of PD1/PD-L1 antagonists on bone remodeling: an exploratory prospective clinical study and ex vivo validation

BACKGROUND

Skeletal morbidity in patients with cancer has a major impact on the quality of life, and preserving bone health while improving outcomes is an important goal of modern antitumor treatment strategies. Despite their widespread use in early disease stages, the effects of immune checkpoint inhibitors (ICIs) on the skeleton are still poorly defined. Here, we initiated a comprehensive investigation of the impact of ICIs on bone health by longitudinal assessment of bone turnover markers in patients with cancer and by validation in a novel bioengineered 3D model of bone remodeling.

METHODS

An exploratory longitudinal study was conducted to assess serum markers of bone resorption (C-terminal telopeptide, CTX) and formation (procollagen type I N-terminal propeptide, PINP, and osteocalcin, OCN) before each ICI application (programmed cell death 1 (PD1) inhibitor or programmed death-ligand 1 (PD-L1) inhibitor) for 6 months or until disease progression in patients with advanced cancer and no evidence of bone metastases. To validate the in vivo results, we evaluated osteoclast (OC) and osteoblast (OB) differentiation on treatment with ICIs. In addition, their effect on bone remodeling was assessed by immunohistochemistry, confocal microscopy, and proteomics analysis in a dynamic 3D bone model.

RESULTS

During the first month of treatment, CTX levels decreased sharply but transiently. In contrast, we observed a delayed increase of serum levels of PINP and OCN after 4 months of therapy. In vitro, ICIs impaired the maturation of preosteoclasts by inhibiting STAT3/NFATc1 signaling but not JNK, ERK, and AKT while lacking any direct effect on osteogenesis. However, using our bioengineered 3D bone model, which enables the simultaneous differentiation of OB and OC precursor cells, we confirmed the uncoupling of the OC/OB activity on exposure to ICIs by demonstrating impaired OC maturation along with increased OB differentiation.

CONCLUSION

Our study indicates that the inhibition of the PD1/PD-L1 signaling axis interferes with bone turnover and may exert a protective effect on bone by indirectly promoting osteogenesis.

Development of small-molecular-based radiotracers for PET imaging of PD-L1 expression and guiding the PD-L1 therapeutics

PURPOSE

Programmed cell death protein ligand 1 (PD-L1) is a crucial biomarker for immunotherapy. However, nearly 70% of patients do not respond to PD-L1 immune checkpoint therapy. Accurate monitoring of PD-L1 expression and quantification of target binding during treatment are essential. In this study, a series of small-molecule radiotracers were developed to assess PD-L1 expression and direct immunotherapy.

METHODS

Radiotracers of [68Ga]Ga-D-PMED, [68Ga]Ga-D-PEG-PMED, and [68Ga]Ga-D-pep-PMED were designed based on a 2-methyl-3-biphenyl methanol scaffold and successfully synthesized. Cellular experiments and molecular docking assays were performed to determine their specificity for PD-L1. PD-L1 status was investigated via positron emission tomography (PET) imaging in MC38 tumor models. PET imaging of [68Ga]Ga-D-pep-PMED was performed to noninvasively quantify PD-L1 blocking using an anti-mouse PD-L1 antibody (PD-L1 mAb).

RESULTS

The radiosyntheses of [68Ga]Ga-D-PMED, [68Ga]Ga-D-PEG-PMED, and [68Ga]Ga-D-pep-PMED were achieved with radiochemical yields of 87 ± 6%, 82 ± 4%, and 79 ± 9%, respectively. In vitro competition assays demonstrated their high affinities (the IC50 values of [68Ga]Ga-D-PMED, [68Ga]Ga-D-PEG-PMED, and [68Ga]Ga-D-pep-PMED were 90.66 ± 1.24, 160.8 ± 1.35, and 51.6 ± 1.32 nM, respectively). At 120 min postinjection (p.i.) of the radiotracers, MC38 tumors displayed optimized tumor-to-muscle ratios for all radioligands. Owing to its hydrophilic modification, [68Ga]Ga-D-pep-PMED had the highest target-to-nontarget (T/NT) ratio of approximately 6.2 ± 1.2. Interestingly, the tumor/liver ratio was hardly affected by different concentrations of the inhibitor BMS202. We then evaluated the impacts of dose and time on accessible PD-L1 levels in the tumor during anti-mouse PD-L1 antibody treatment. The tumor uptake of [68Ga]Ga-D-pep-PMED significantly decreased with increasing PD-L1 mAb dose. Moreover, after 8 days of treatment with a single antibody, the uptake of [68Ga]Ga-D-pep-PMED in the tumor significantly increased but remained lower than that in the saline group.

CONCLUSION

PET imaging with [68Ga]Ga-D-pep-PMED, a small-molecule radiotracer, is a promising tool for evaluating PD-L1 expression and quantifying the target blockade of PD-L1 to assist in the development of effective therapeutic regimens.

ImmunoPET imaging of Trop2 in patients with solid tumours

Accurately predicting and selecting patients who can benefit from targeted or immunotherapy is crucial for precision therapy. Trophoblast cell surface antigen 2 (Trop2) has been extensively investigated as a pan-cancer biomarker expressed in various tumours and plays a crucial role in tumorigenesis through multiple signalling pathways. Our laboratory successfully developed two 68Ga-labelled nanobody tracers that can rapidly and specifically target Trop2. Of the two tracers, [68Ga]Ga-NOTA-T4, demonstrated excellent pharmacokinetics in preclinical mouse models and a beagle dog. Moreover, [68Ga]Ga-NOTA-T4 immuno-positron emission tomography (immunoPET) allowed noninvasive visualisation of Trop2 heterogeneous and differential expression in preclinical solid tumour models and ten patients with solid tumours. [68Ga]Ga-NOTA-T4 immunoPET could facilitate clinical decision-making through patient stratification and response monitoring during Trop2-targeted therapies.

18F-BMS-986229 PET to Assess Programmed-Death Ligand 1 Status in Gastroesophageal Cancer

Anti-programmed death 1 (PD-1) inhibitors are the standard of care for advanced gastroesophageal cancer. Although recommendations and approval by regulatory agencies are often based on programmed death ligand 1 (PD-L1) expression, pathologic assessments of PD-L1 status have several limitations. Single-site biopsies do not adequately capture disease heterogeneity within individual tumor lesions or among several lesions within the same patient, the PD-L1 combined positive score is a dynamic biomarker subject to evolution throughout a patient's disease course, and repeated biopsies are invasive and not always feasible. Methods: This was a prospective pilot study of the PD-L1-targeting radiotracer, 18F-BMS-986229, with PET imaging (PD-L1 PET) in patients with gastroesophageal cancer. Patients were administered the 18F-BMS-986229 radiotracer intravenously at a dose of 370 MBq over 1-2 min and underwent whole-body PET/CT imaging 60 min later. The primary objective of this study was to evaluate the safety and feasibility of 18F-BMS-986229. The trial is registered with ClinicalTrials.gov (NCT04161781). Results: Between February 3, 2020, and February 2, 2022, 10 patients with gastroesophageal adenocarcinoma underwent PD-L1 PET. There were no adverse events associated with the 18F-BMS-986229 tracer, and imaging did not result in treatment delays; the primary endpoint was achieved. Radiographic evaluation of PD-L1 expression was concordant with pathologic assessment in 88% of biopsied lesions, and 18F-BMS-986229 uptake on PET imaging correlated with pathologic evaluation by the combined positive score (Spearman rank correlation coefficient, 0.64). Seventy-one percent of patients with 18F-BMS-986229 accumulation on PET imaging also had lesions without 18F-BMS-986229 uptake, highlighting the intrapatient heterogeneity of PD-L1 expression. Patients treated with frontline programmed death 1 inhibitors who had 18F-BMS-986229 accumulation in any lesions on PET imaging had longer progression-free survival than patients without tracer accumulation in any lesions (median progression-free survival, 28.4 vs. 9.9 mo), though the small sample size prevents any definitive conclusions. Conclusion: PD-L1 PET imaging was safe, feasible, and concordant with pathologic evaluation and offers a potential noninvasive tool to assess PD-L1 expression.

PET/CT in Inflammatory and Auto-immune Disorders: Focus on Several Key Molecular Concepts, FDG, and Radiolabeled Probe Perspectives

Chronic immune diseases mainly include autoimmune and inflammatory diseases. Managing chronic inflammatory and autoimmune diseases has become a significant public health concern, and therapeutic advancements over the past 50 years have been substantial. As therapeutic tools continue to multiply, the challenge now lies in providing each patient with personalized care tailored to the specifics of their condition, ushering in the era of personalized medicine. Precise and holistic imaging is essential in this context to comprehensively map the inflammatory processes in each patient, identify prognostic factors, and monitor treatment responses and complications. Imaging of patients with inflammatory and autoimmune diseases must provide a comprehensive view of the body, enabling the whole-body mapping of systemic involvement. It should identify key cellular players in the pathology, involving both innate immunity (dendritic cells, macrophages), adaptive immunity (lymphocytes), and microenvironmental cells (stromal cells, tissue cells). As a highly sensitive imaging tool with vectorized molecular probe capabilities, PET/CT can be of high relevance in the management of numerous inflammatory and autoimmune diseases. Relying on key molecular concepts of immunity, the clinical usefulness of FDG-PET/CT in several relevant inflammatory and immune-inflammatory conditions, validated or emerging, will be discussed in this review, together with radiolabeled probe perspectives.

Case report: The effect of second-line vebreltinib treatment on a patient with advanced NSCLC harboring the MET exon 14 skipping mutation after tepotinib treatment

Background

Highly selective type Ib mesenchymal-epithelial transition gene (MET) tyrosine kinase inhibitors (TKIs) are the standard-of-care (SOC) therapy for previously untreated non-small cell lung cancer (NSCLC) harboring MET exon 14 (METex14) skipping mutations. However, there are rare reports describing effective regimens for patients who fail SOC without identifying resistant mutations or tissue transformation.

Case report

We report the first case of a 74-year-old woman with lung adenocarcinoma (cT1cNxM0) harboring METex14 splice region mutation, which was identified by a next-generation sequencing (NGS)-based assay. The patient was administered two treatments, including first-line tepotinib and second-line vebreltinib. The patient achieved progression-free survival (PFS) of 7.6 months, and then disease progression of tepotinib was observed. A re-biopsy was performed for NGS, which revealed the same mutations as before, with no new gene mutations detected. The woman received subsequent vebreltinib therapy and experienced durable clinical benefits. In the first 6.8 months, chest computed tomography demonstrated stable disease. Then, she achieved partial response (PR). The durable PR lasted for more than 13 months, and the PFS is currently over 20 months, exceeding the prior treatment.

Conclusion

This case highlights the importance of considering re-biopsy and reanalysis of genetic profiles in NSCLC patients harboring METex14 skipping mutations after progressive disease in MET TKI treatment. This raises the possibility that vebreltinib may have long-term survival benefits for patients without mutations conferring resistance (funded by Beijing Pearl Biotechnology Co., Ltd; ClinicalTrials.gov number, NCT04258033).

Noninvasive Stratification of Colon Cancer by Multiplex PET Imaging

PURPOSE

The current approach for molecular subtyping of colon cancer relies on gene expression profiling, which is invasive and has limited ability to reveal dynamics and spatial heterogeneity. Molecular imaging techniques, such as PET, present a noninvasive alternative for visualizing biological information from tumors. However, the factors influencing PET imaging phenotype, the suitable PET radiotracers for differentiating tumor subtypes, and the relationship between PET phenotypes and tumor genotype or gene expression-based subtyping remain unknown.

EXPERIMENTAL DESIGN

In this study, we conducted 126 PET scans using four different metabolic PET tracers, [18F]fluorodeoxy-D-glucose ([18F]FDG), O-(2-[18F]fluoroethyl)-l-tyrosine ([18F]FET), 3'-deoxy-3'-[18F]fluorothymidine ([18F]FLT), and [11C]acetate ([11C]ACE), using a spectrum of five preclinical colon cancer models with varying genetics (BMT, AKPN, AK, AKPT, KPN), at three sites (subcutaneous, orthograft, autochthonous) and at two tumor stages (primary vs. metastatic).

RESULTS

The results demonstrate that imaging signatures are influenced by genotype, tumor environment, and stage. PET imaging signatures exhibited significant heterogeneity, with each cancer model displaying distinct radiotracer profiles. Oncogenic Kras and Apc loss showed the most distinctive imaging features, with [18F]FLT and [18F]FET being particularly effective, respectively. The tissue environment notably impacted [18F]FDG uptake, and in a metastatic model, [18F]FET demonstrated higher uptake.

CONCLUSIONS

By examining factors contributing to PET-imaging phenotype, this study establishes the feasibility of noninvasive molecular stratification using multiplex radiotracer PET. It lays the foundation for further exploration of PET-based subtyping in human cancer, thereby facilitating noninvasive molecular diagnosis.

[64Cu]Cu-PEG-FUD peptide for noninvasive and sensitive detection of murine pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease resulting in irreversible scarring within the lungs. However, the lack of biomarkers that enable real-time assessment of disease activity remains a challenge in providing efficient clinical decision-making and optimal patient care in IPF. Fibronectin (FN) is highly expressed in fibroblastic foci of the IPF lung where active extracellular matrix (ECM) deposition occurs. Functional upstream domain (FUD) tightly binds the N-terminal 70-kilodalton domain of FN that is crucial for FN assembly. In this study, we first demonstrate the capacity of PEGylated FUD (PEG-FUD) to target FN deposition in human IPF tissue ex vivo. We subsequently radiolabeled PEG-FUD with 64Cu and monitored its spatiotemporal biodistribution via μPET/CT imaging in mice using the bleomycin-induced model of pulmonary injury and fibrosis. We demonstrated [64Cu]Cu-PEG-FUD uptake 3 and 11 days following bleomycin treatment, suggesting that radiolabeled PEG-FUD holds promise as an imaging probe in aiding the assessment of fibrotic lung disease activity.

Preclinical development of novel PD-L1 tracers and first-in-human study of [68Ga]Ga-NOTA-RW102 in patients with lung cancers

BACKGROUND

The programmed cell death protein-1 (PD-1)/programmed death receptor ligand 1 (PD-L1) axis critically facilitates cancer cells' immune evasion. Antibody therapeutics targeting the PD-1/PD-L1 axis have shown remarkable efficacy in various tumors. Immuno-positron emission tomography (ImmunoPET) imaging of PD-L1 expression may help reshape solid tumors' immunotherapy landscape.

METHODS

By immunizing an alpaca with recombinant human PD-L1, three clones of the variable domain of the heavy chain of heavy-chain only antibody (VHH) were screened, and RW102 with high binding affinity was selected for further studies. ABDRW102, a VHH derivative, was further engineered by fusing RW102 with the albumin binder ABD035. Based on the two targeting vectors, four PD-L1-specific tracers ([68Ga]Ga-NOTA-RW102, [68Ga]Ga-NOTA-ABDRW102, [64Cu]Cu-NOTA-ABDRW102, and [89Zr]Zr-DFO-ABDRW102) with different circulation times were developed. The diagnostic efficacies were thoroughly evaluated in preclinical solid tumor models, followed by a first-in-human translational investigation of [68Ga]Ga-NOTA-RW102 in patients with non-small cell lung cancer (NSCLC).

RESULTS

While RW102 has a high binding affinity to PD-L1 with an excellent KD value of 15.29 pM, ABDRW102 simultaneously binds to human PD-L1 and human serum albumin with an excellent KD value of 3.71 pM and 3.38 pM, respectively. Radiotracers derived from RW102 and ABDRW102 have different in vivo circulation times. In preclinical studies, [68Ga]Ga-NOTA-RW102 immunoPET imaging allowed same-day annotation of differential PD-L1 expression with specificity, while [64Cu]Cu-NOTA-ABDRW102 and [89Zr]Zr-DFO-ABDRW102 enabled longitudinal visualization of PD-L1. More importantly, a pilot clinical trial shows the safety and diagnostic value of [68Ga]Ga-NOTA-RW102 immunoPET imaging in patients with NSCLCs and its potential to predict immune-related adverse effects following PD-L1-targeted immunotherapies.

CONCLUSIONS

We developed and validated a series of PD-L1-targeted tracers. Initial preclinical and clinical evidence indicates that immunoPET imaging with [68Ga]Ga-NOTA-RW102 holds promise in visualizing differential PD-L1 expression, selecting patients for PD-L1-targeted immunotherapies, and monitoring immune-related adverse effects in patients receiving PD-L1-targeted treatments.

TRIAL REGISTRATION NUMBER

NCT06165874.

Noninvasive Evaluation of Tumoral PD-L1 Using a Novel 99mTc-Labeled Nanobody Tracer with Rapid Renal Clearance

The expression level of PD-L1 in tumor tissue is considered one of the effective biomarkers to guide PD-1/PD-L1 therapy. Quantifying whole-body PD-L1 expression by SPECT imaging may help in selecting patients that potentially respond to PD-1/PD-L1 therapy. Nanobody is the smallest antibody fragment with antigen-binding ability that is well suited for radionuclide imaging. Nevertheless, high retention of radioactivity in the kidney may limit its clinical translation. The present study aimed to screen, design, and prepare a nanobody-based SPECT probe with rapid renal clearance to evaluate the PD-L1 expression level in vivo noninvasively. A phage library was constructed by immunizing alpaca with recombinant human PD-L1 protein, and 17 anti-PD-L1 nanobodies were screened by the phage display technique. After sequence alignment and flow cytometry analysis, APN09 was selected as the candidate nanobody, and a GGGC chelator was attached to its C-terminus for 99mTc labeling to prepare a SPECT imaging probe. The affinity and specificity of 99mTc-APN09 were evaluated by protein and cell-binding experiments, and SPECT imaging and biodistribution were performed in a mouse model with bilateral transplantation of A549 and A549PD-L1 tumors. The ability of 99mTc-APN09 to quantify the PD-L1 expression level in vivo was validated in tumor models with different PD-L1 expression levels. 99mTc-APN09 had a radiochemical purity higher than 99% and a binding equilibrium dissociation constant of 21.44 ± 1.65 nM with hPD-L1, showing high affinity. SPECT imaging results showed that 99mTc-APN09 could efficiently detect PD-L1-positive tumors within 0.5 h, and the quantitative results of SPECT were well correlated with the expression level of PD-L1 in cell lines. SPECT imaging and biodistribution results also showed that 99mTc-APN09 was rapidly cleared from the kidney in 2 h postinjection. 99mTc-APN09 was a simple and stable tool for visualizing PD-L1 expression in the whole body. In addition, due to its significant reduction in renal retention, it has better prospects for clinical translation.

An Interventional Radiologist's Guide to Lung Cancer

Lung cancer continues to be the third leading cause of cancer and the leading cause of cancer deaths. As the field of interventional oncology continues to grow, interventional radiologists are increasingly treating lung cancer patients. Involvement begins with tissue diagnosis for which biomarkers and immunohistochemistry are used to guide selective and advanced medical therapies. An interventional radiologist must be aware of the rationale behind tissue diagnosis and techniques to minimize biopsy complications. Staging is an important part of tumor board conversations and drives treatment pathways. Surgical therapy remains the gold standard for early-stage disease but with an aging population the need for less invasive treatments such as radiation therapy and ablation continue to grow. The interventionalist must be aware of the indications, techniques, and pre- and posttherapy managements for percutaneous ablation. Endovascular therapy is broadly divided into therapeutic treatment of lung cancer, which is gaining traction, and treatment of lung cancer complications such as hemoptysis. This review aims to provide a good basis for interventional radiologists treating lung cancer patients.

The role of radiotherapy in tumor immunity and the potential of PET/CT in detecting the expression of PD-1/PD-L1

Upregulation of PD-1/PD-L1 allows cancer cells to escape from host immune systems by functionally inactivating T-cell immune surveillance. Clinical blockade strategies have resulted in an increased prevalence of patients with late-stage cancers. However, many cancer patients had limited or no response to current immunotherapeutic strategies. Therefore, how to improve the sensitivity of immunotherapy has become the focus of attention of many scholars. Radiotherapy plays a role in the recruitment of T cells in the tumor microenvironment, increases CD4 + and CD8 + T cells, and increases PD-L1 expression, resulting in the synergistically enhanced antitumor effect of irradiation and PD-L1 blockade. Radiotherapy can cause changes in tumor metabolism, especially glucose metabolism. Tumor glycolysis and tumor immune evasion are interdependent, glycolytic activity enhances PD-L1 expression on tumor cells and thus promotes anti-PD-L1 immunotherapy response. Therefore, the mechanism of radiotherapy affecting tumor immunity may be partly through intervention of tumor glucose metabolism. Furthermore, some authors had found that the uptake of 2'-deoxy-2'-[18F]fluoro-D-glucose(18F-FDG) was correlated with PD-1/PD-L1 expression. Positron emission tomography/computed tomography (PET/CT) is a non-invasive detection method for PD-1/PD-L1 expression and has several potential advantages over immunohistochemical (IHC), PET/CT can dynamically reflect the expression of PD-1/PD-L1 inside the tumor and further guide clinical treatment.

Synthesis and preclinical evaluation of a novel molecular probe [18F]AlF-NOTA-PEG2-Asp2-PDL1P for PET imaging of PD-L1 positive tumor

Immunotherapy has brought great benefits to cancer patients, but only some patients benefit from it. Noninvasive, real-time and dynamic monitoring of the effectiveness of immunotherapy through PET imaging may provide assistance for the treatment plan of immunotherapy. In this study, we designed and synthesized a new targeted PD-L1 peptide NOTA-PEG2-Asp2-PDL1P, which was labeled with nuclide 18F to obtain a new imaging agent [18F]AlF-NOTA-PEG2-Asp2-PDL1P. The total radiochemical yield of [18F]AlF-NOTA-PEG2-Asp2-PDL1P was 13.7 % (Uncorrected radiochemical yield, n > 5). [18F]AlF-NOTA-PEG2-Asp2-PDL1P achieved high radiochemical purity (>95 %) with a molar activity more than 51.2 GBq/μmol. [18F]AlF-NOTA-PEG2-Asp2-PDL1P exhibited good hydrophilicity and had good stability both in vivo and in vitro, it can specifically targets B16F10 tumor with PD-L1 expression, and had a relatively high retention in tumor, a relatively fast clearance in vivo and a higher tumor-to-non-target ratio, all of which could make [18F]AlF-NOTA-PEG2-Asp2-PDL1P a potential tracer for PD-L1 prediction before clinical immunotherapy.

PET/Computed Tomography Transformation of Oncology: Immunotherapy Assessment

Immunotherapy approaches have changed the treatment landscape in a variety of malignancies with a high anti-tumor response. Immunotherapy may be associated with novel response and progression patterns that pose a substantial challenge to the conventional criteria for assessing treatment response, including response evaluation criteria in solid tumors (RECIST) 1.1. In addition to the morphologic details provided by computed tomography (CT) and MRI, hybrid molecular imaging emerges as a comprehensive imaging modality with the capacity to interrogate pathophysiological mechanisms like glucose metabolism. This review highlights the current status of 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography/computed tomography (18F-FDG PET/CT) in prognostication, response monitoring, and identifying immune-related adverse events. Furthermore, it investigates the potential role of novel immuno-PET tracers that could complement the utilization of 18F-FDG PET/CT by imaging the specific pathways involved in immunotherapeutic strategies.

Radionuclide-Labeled Antisilencing Function 1a Inhibitory Peptides for Tumor Identification and Individualized Therapy

Immune checkpoint blockade (ICB) therapy is promising to revolutionize cancer regimens, but the low response rate and the lack of a suitable patient stratification method have impeded universal profit to cancer patients. Noninvasive positron emission tomography (PET) imaging in the whole body, upon coupling with specific biomarkers closely related to the immune response, could provide spatiotemporal information to prescribe cancer therapy. Herein, we demonstrate that antisilencing function 1a (ASF1a) could serve as a biomarker target to delineate tumor immune microenvironments by immune PET (iPET). The iPET radiotracer (68Ga-AP1) is designed to target ASF1a in tumors and predict immune response, and the signal intensity predicts anti-PD-1 (αPD-1) therapy response in a negative correlation manner. The ICB-resistant tumors with a high level of ASF1a as revealed by iPET (ASF1aHigh-iPET) are prescribed to be treated by either the combined 177Lu-labeled AP1 and αPD-1 or the standalone α particle-emitting 225Ac-labeled AP1, both achieving enhanced therapeutic efficacy and prolonged survival time. Our study not only replenishes the iPET arsenal for immune-related response evaluation by designing a reliable biomarker and a facile radiotracer but also provides optional therapeutic strategies for ICB-resistant tumors with versatile radionuclide-labeled AP1 peptides, which is promising for real-time clinical diagnosis and individualized therapy planning simultaneously.

Development and In Vivo Evaluation of Small-Molecule Ligands for Positron Emission Tomography of Immune Checkpoint Modulation Targeting Programmed Cell Death 1 Ligand 1

A substantial portion of patients do not benefit from programmed cell death protein 1/programmed cell death 1 ligand 1 (PD-1/PD-L1) checkpoint inhibition therapies, necessitating a deeper understanding of predictive biomarkers. Immunohistochemistry (IHC) has played a pivotal role in assessing PD-L1 expression, but small-molecule positron emission tomography (PET) tracers could offer a promising avenue to address IHC-associated limitations, i.e., invasiveness and PD-L1 expression heterogeneity. PET tracers would allow for improved quantification of PD-L1 through noninvasive whole-body imaging, thereby enhancing patient stratification. Here, a large series of PD-L1 targeting small molecules were synthesized, leveraging advantageous substructures to achieve exceptionally low nanomolar affinities. Compound 5c emerged as a promising candidate (IC50 = 10.2 nM) and underwent successful carbon-11 radiolabeling. However, a lack of in vivo tracer uptake in xenografts and notable accumulation in excretory organs was observed, underscoring the challenges encountered in small-molecule PD-L1 PET tracer development. The findings, including structure-activity relationships and in vivo biodistribution data, stand to illuminate the path forward for refining small-molecule PD-L1 PET tracers.

Biodistribution and pharmacokinetics of [89Zr]-anti-VEGF mAbs using PET in glioblastoma rat models

INTRODUCTION

Glioblastomas present intensive angiogenesis, thus anti-Vascular Endothelial Growth Factor (VEGF) antibodies (mAbs) have been proposed as promising therapies. However, the results of clinical trials reported moderate toxicity and limited effectiveness. This study evaluates the in vivo pharmacokinetics and biodistribution of these mAbs in a growing model of glioblastoma in rats using Positron Emission Tomography (PET).

MATERIAL

&Methods: mAbs were radiolabeled with zirconium-89. Four days after the model induction, animals were injected with 2.33 ± 1.3 MBq of [89Zr]-DFO-bevacizumab (n = 8) or 2.35 ± 0.26 MBq of [89Zr]-DFO-aflibercept (n = 6). PETs were performed at 0H, 48H, 168H, 240H, and 336H post-injection. Tumor induction was confirmed using [18F]-Fluorodeoxyglucose-PET and immunohistochemistry. Radiotracer uptake was estimated in all pre-defined Volumes-of-Interest.

RESULTS

Anti-VEGF mAbs showed 100 % Radiochemical-Purity. [89Zr]-DFO-bevacizumab showed a significantly higher bioavailability in whole-blood. A significant increase in the tumor uptake was detectable at 168H PET with [89Zr]-DFO-bevacizumab meanwhile with [89Zr]-DFO-aflibercept it was only detectable at 336H. [89Zr]-DFO-bevacizumab tumor uptake was significantly higher than that of [89Zr]-DFO-aflibercept in all the scans. Tumor induction was confirmed in all animal models.

CONCLUSION

MAbs detect VEGF-expression in glioblastoma models. Tumors were earlier targeted by Bevacizumab. The lower blood availability of aflibercept resulted in a lower tumor uptake than bevacizumab in all the scans.

PET Imaging of Peptide Probe Al[18F]F-NOTA-PCP1 for Monitoring the Engagement of PD-L1 Antibodies in Tumors

Immune checkpoint inhibitors (ICIs) are a powerful treatment modality for various types of cancer. The effectiveness of ICIs is intimately connected to the binding status of antibodies to receptors. However, validated means to accurately evaluate target specificity and predict antibody efficacy in vivo are lacking. A novel peptide-based probe called Al[18F]F-NOTA-PCP1 was developed and validated for its specificity to PD-L1 in A549, U87MG, GL261, and GL261-iPDL1 cell lines, as well as in xenograft models. Then the probe was used in PET/CT scans to determine the binding status of PD-L1 antibodies (atezolizumab, avelumab, and durvalumab) in U87MG xenograft model mice. Moreover, Al[18F]F-NOTA-PCP1 was used to evaluate the impact of different treatment times and doses. Al[18F]F-NOTA-PCP1 PET/CT can be used to evaluate the interaction between PD-L1 and antibodies to determine the effectiveness of immunotherapy. By quantifying target engagement, the probe has the potential to predict the efficacy of immunotherapy and optimize the dose and treatment schedules for PD-L1 immunotherapy. This imaging agent could be a valuable tool in guiding personalized treatment strategies and improving cancer patient outcomes.