Non-invasive PD-L1 quantification using [18F]DK222-PET imaging in cancer immunotherapy

68Ga-Labeled Peptide for Noninvasive Quantifying Tumor Exposure of PD-L1 Therapeutics

PURPOSE

Targeting the programmed death protein 1/programmed death-ligand 1 (PD-1/PD-L1) immune checkpoint blockade therapy plays a critical role in cancer therapy. However, not all patients benefit from this approach, with PD-L1 expression levels being a significant contributing factor. Positron emission tomography (PET) imaging of PD-L1 offers a noninvasive, whole-body, and dynamic assessment of its expression. This study aims to develop a novel peptide-based PD-L1 tracer, [68Ga]HF12, to quantitatively evaluate PD-L1 expression in tumors, thereby offering clinical guidance.

METHODS

HF12 was successfully synthesized and radiolabeled with 68Ga to yield [68Ga]HF12. In vitro binding assays confirmed the specific binding affinity of HF12 for PD-L1 using CHO-hPD-L1 and CHO cell lines. Subsequent in vivo positron emission tomography (PET) imaging and biodistribution studies assessed [68Ga]HF12 for monitoring PD-L1 expression levels in tumor-bearing mice, including those subjected to immunotherapy. Furthermore, PD-L1 expression in tumor tissues was evaluated by using autoradiography, Western blotting, and immunohistochemical (IHC) analysis.

RESULTS

The synthesis of [68Ga]HF12 was successfully achieved with a radiochemical purity and yield exceeding 95%. Cellular uptake studies indicated that [68Ga]HF12 demonstrated both high specificity and significant uptake in PD-L1-positive CHO-hPD-L1 cells. Micro-PET imaging and biodistribution studies revealed that [68Ga]HF12 was preferentially accumulated in CHO-hPD-L1 tumors compared to PD-L1-negative CHO tumors. Treatment with Atezolizumab resulted in a significant reduction in [68Ga]HF12 uptake in CHO-hPD-L1 tumors relative to pretreatment levels, whereas no significant changes were observed in the phosphate-buffered saline (PBS) control group. Subsequent biodistribution studies, along with Western blotting and immunohistochemical analyses, confirmed that PD-L1 expression levels in tumors were reduced following immunotherapy, consistent with the results obtained from PET imaging.

CONCLUSIONS

[68Ga]HF12 was successfully synthesized as a radiotracer for noninvasive quantitative PET imaging of PD-L1 expression levels. This radiotracer exhibited the potential to quantify PD-L1 expression across various tumors, thereby facilitating the prediction of patient response to anti-PD-1 and anti-PD-L1 immunotherapies and monitoring therapeutic efficacy.

Current Biomarkers in Non-Small Cell Lung Cancer-The Molecular Pathologist's Perspective

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related mortality worldwide. Advances in tissue-based biomarkers have significantly enhanced diagnostic and therapeutic approaches in NSCLC, enabling precision medicine strategies. This review provides a comprehensive analysis of the molecular pathologist's practical approach to assessing NSCLC biomarkers across various specimen types (liquid biopsy, broncho-alveolar lavage, transbronchial biopsy/endobronchial ultrasound-guided biopsy, and surgical specimen), including challenges such as biological heterogeneity and preanalytical variability. We discuss the role of programmed death ligand 1 (PD-L1) immunohistochemistry in predicting immunotherapy response, the practice of histopathological tumor regression grading after neoadjuvant chemoimmunotherapy, and the application of DNA- and RNA-based techniques for detecting actionable molecular alterations. Finally, we emphasize the critical need for quality management to ensure the reliability and reproducibility of biomarker testing in NSCLC.

Peptide-based immuno-PET/CT monitoring of dynamic PD-L1 expression during glioblastoma radiotherapy

Real-time, noninvasive programmed death-ligand 1 (PD-L1) testing using molecular imaging has enhanced our understanding of the immune environments of neoplasms and has served as a guide for immunotherapy. However, the utilization of radiotracers in the imaging of human brain tumors using positron emission tomography/computed tomography (PET/CT) remains limited. This investigation involved the synthesis of [18F]AlF-NOTA-PCP2, which is a novel peptide-based radiolabeled tracer that targets PD-L1, and evaluated its imaging capabilities in orthotopic glioblastoma (GBM) models. Using this tracer, we could noninvasively monitor radiation-induced PD-L1 changes in GBM. [18F]AlF-NOTA-PCP2 exhibited high radiochemical purity (>95%) and stability up to 4 h after synthesis. It demonstrated specific, high-affinity binding to PD-L1 in vitro and in vivo, with a dissociation constant of 0.24 nM. PET/CT imaging, integrated with contrast-enhanced magnetic resonance imaging, revealed significant accumulation of [18F]AlF-NOTA-PCP2 in orthotopic tumors, correlating with blood-brain barrier disruption. After radiotherapy (15 Gy), [18F]AlF-NOTA-PCP2 uptake in tumors increased from 9.51% ± 0.73% to 12.04% ± 1.43%, indicating enhanced PD-L1 expression consistent with immunohistochemistry findings. Fractionated radiation (5 Gy × 3) further amplified PD-L1 upregulation (13.9% ± 1.54% ID/cc) compared with a single dose (11.48% ± 1.05% ID/cc). Taken together, [18F]AlF-NOTA-PCP2 may be a valuable tool for noninvasively monitoring PD-L1 expression in brain tumors after radiotherapy.

Development and First-in-Human evaluation of a Site-Specific [18F]-Labeled PD-L1 nanobody PET radiotracer for noninvasive imaging in NSCLC

Immunohistochemistry (IHC) for PD-L1 detection is limited by its invasiveness and heterogeneity of tumors. To address these challenges, a new PD-L1-targeted nanobody-based immune-PET radiotracer [18F]AlF-APN09 was developed using the site-specific radiolabeling method with the complexing agent (Mal-RESCA) under mild conditions. [18F]AlF-APN09 was prepared at room temperature (pH 4.6-4.8) within 20 min with satisfactory radiochemical yields (45.8 ± 4.48 %, non-decay corrected), high radiochemical purity (>98 %) and moderate apparent molar activity (15-35 GBq/μmol), and remained stable in both PBS and 5 % HSA after 4 h (>90 %). Cell uptake studies indicated variable levels of surface PD-L1 expression in the following order: A549PD-L1 > H1975 > A549. In micro-PET/CT imaging, A549PD-L1 and H1975 tumors were distinctly visualized in a 6.0:1 and 3.2:1 ratios over PD-L1-negative A549 tumors in vivo. Ex vivo biodistribution studies showed tumor uptake values of 6.47 ± 1.06 %ID/g (A549PD-L1) and 2.27 ± 0.19 %ID/g (H1975), significantly higher than 0.90 ± 0.28 %ID/g in A549 tumors. The estimated effective radiation dose in humans was 8.65E-03 mSv/MBq, lower than that of conventional [18F]FDG. First-in-human imaging was conducted on a single resectable non-small cell lung cancer (NSCLC) subject without any adverse reactions. The radiotracer exhibited renal excretion with minimal hepatobiliary clearance. Tumor uptake reached SUVmax 4.20 at 2 h post-injection, demonstrating high contrast and rapid clearance. After PD-1 inhibitor immunotherapy and chemotherapy, the subject showed a therapeutic response and postoperative pathological specimens confirmed a major pathological response (MPR). These results suggest that we have successfully developed a new PD-L1-targeted nanobody PET tracer using the site-specific labeling method with the complexing agent (Mal-RESCA) within 20 min under mild conditions and [18F]AlF-APN09 is a promising noninvasive PET radiotracer for visualizing PD-L1 expression in tumors, offering rapid tumor targeting, excellent signal-to-noise ratios, and favorable clearance properties.

PD-L1 peptides in cancer immunoimaging and immunotherapy

The interaction between programmed death protein 1 (PD-1) and programmed death ligand 1 (PD-L1) constitutes a critical immune checkpoint pathway that leads to immune tolerance in cancer cells and impacts antitumor treatment. Monoclonal antibody blockade of the PD-L1 immunoinhibitory pathway has demonstrated significant and lasting clinical antitumor responses. Furthermore, PD-L1 serves as an important biomarker for predicting the effectiveness of immune checkpoint inhibitors (ICIs). To date, numerous studies based on monoclonal antibodies have been carried out to detect the expression levels of PD-L1 and predict the antitumor effectiveness of PD-L1 ICIs. However, due to the deficiencies of monoclonal antibodies, researches of PD-L1 peptides have received increasing attention. PD-L1 peptides present promising candidates due to their advantages, including reduced manufacturing costs, enhanced stability, decreased immunogenicity, faster clearance and improved tumor or organ penetration, thereby offering broad application prospects in cancer immunoimaging and immunotherapy. In this review, we analyze the existing evidence on PD-L1 peptides in cancer immunoimaging and immunotherapy. First, the design techniques of different types of PD-L1 targeting peptides and their strengths and weaknesses are briefly introduced. Second, the recent advancements in immunoimaging and the development trends in immunotherapy are summarized. Finally, the existing challenges and future directions in this field are comprehensively deliberated.

PD-1 and PD-L1 Expression in Endometrial Cancer: A Systematic Review of the Literature

Background/Objectives: Cancer immunotherapy through the use of PD-1/PD-L1 inhibitors have shown significant promise in endometrial carcinoma (EC), particularly in tumors with microsatellite instability (MSI) or mismatch repair deficiency (dMMR), present in approximately 30% of cases. This review evaluated PD-L1 and PD-1 expression as potential biomarkers for immunotherapy response in EC, focusing on their relationship with MSI status. Methods: A systematic review, adhering to PRISMA guidelines, analyzed studies from MEDLINE and Embase until February 2023 on PD-1/PD-L1 expression in EC stratified by MSI status, including diverse study designs but excluding conference abstracts, with independent screening, data extraction, and additional reference checks to ensure comprehensive coverage. Results: A systematic analysis of 10 studies found that PD-L1 expression was more frequently expressed in MSI tumors (49%) compared to microsatellite-stable tumors (MSS) (33.5%), while PD-1 was expressed in 58% of MSI cases and 48% of MSS cases. Despite these findings, the prognostic value of PD-L1/PD-1 remains uncertain, with conflicting results regarding their association with survival outcomes. PD-L1 expression varied across molecular subtypes, being highest in POLE-mutated tumors (76.56%) and serous carcinomas (73%). Differences in PD-L1 expression between primary and metastatic sites were also noted, complicating its use as a biomarker. Conclusions: The assessment of PD-L1 expression in EC could represent a valuable option for selecting patients who may benefit from immune checkpoint inhibitors (ICI), including those in the MSS cohort, thereby ensuring a more tailored and personalized treatment strategy.

CRISPR/Cas9-mediated knockout strategies for enhancing immunotherapy in breast cancer

Breast cancer, a prevalent disease with significant mortality rates, often presents treatment challenges due to its complex genetic makeup. This review explores the potential of combining Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) gene knockout strategies with immunotherapeutic approaches to enhance breast cancer treatment. The CRISPR/Cas9 system, renowned for its precision in inducing genetic alterations, can target and eliminate specific cancer cells, thereby minimizing off-target effects. Concurrently, immunotherapy, which leverages the immune system's power to combat cancer, has shown promise in treating breast cancer. By integrating these two strategies, we can potentially augment the effectiveness of immunotherapies by knocking out genes that enable cancer cells to evade the immune system. However, safety considerations, such as off-target effects and immune responses, necessitate careful evaluation. Current research endeavors aim to optimize these strategies and ascertain the most effective methods to stimulate the immune response. This review provides novel insights into the integration of CRISPR/Cas9-mediated knockout strategies and immunotherapy, a promising avenue that could revolutionize breast cancer treatment as our understanding of the immune system's interplay with cancer deepens.

A PD-L1-Targeted Probe Cy5.5-A11 for In Vivo Imaging of Multiple Tumors

PD-L1 is an immune checkpoint molecule mediating cancer immune escape, and its expression level in the tumor has been used as a biomarker to predict response to immune checkpoint inhibitor (ICI) therapy. Our previous study reveals that an 11 amino acid-long ANXA1-derived peptide (named A11) binds and degrades the PD-L1 protein in multiple cancers and is a potential peptide for cancer diagnosis and treatment. Near-infrared fluorescence (NIF) optical imaging of tumors offers a noninvasive method for detecting cancer and monitoring therapeutic responses. In this study, an NIF dye Cy5.5 was conjugated with A11 peptide to develop a novel PD-L1-targeted probe for molecular imaging of tumors and monitor the dynamic changes in PD-L1 expression in tumors. In vitro imaging studies showed that intense fluorescence was observed in triple-negative breast cancer MDA-MB-231, nonsmall cell lung cancer H460, and melanoma A375 cells incubated with Cy5.5-A11, and the cellular uptake of Cy5.5-A11 was efficiently inhibited by coincubation with unlabeled A11 or knockdown of cellular PD-L1 by shRNA. In vivo imaging studies showed accumulation of Cy5.5-A11 in the MDA-MB-231, H460, and A375 xenografts with good contrast from 0.5 to 24 h after intravenous injection, indicating that Cy5.5-A11 possesses the strong ability for in vivo tumor imaging. Moreover, the fluorescent signal of A11-Cy5.5 in the xenografts was successfully blocked by coinjection of unlabeled A11 peptide or knockdown of cellular PD-L1 by shRNA, indicating the specificity of Cy5.5-A11 targeting PD-L1 in tumor imaging. Our data demonstrate that Cy5.5-A11 is a novel tool for tumor imaging of PD-L1, which has the potential for detecting cancer and predicting ICI therapeutic responses.

Use of Upadacitinib to Treat a Severe Flare-Up of Rheumatoid Arthritis During Anti-PD-1 Immune Checkpoint Inhibitor Therapy for Stage IV Squamous Cell Carcinoma of the Lung

Background: Immune checkpoint inhibitor (ICI) therapy is becoming the standard of care for the treatment of advanced non-small-cell lung cancer. However, T-cell activation by ICIs frequently induces a flare-up of preexisting autoimmune diseases such as rheumatoid arthritis (RA). Janus kinase (JAK) inhibitors are increasingly used in the treatment of RA, but they could interfere with the efficacy of ICIs by inhibiting interferon signaling. Case Report: Here, we describe a case in which upadacitinib, a JAK1-selective inhibitor, was used to manage a severe RA flare-up occurring during ICI therapy with pembrolizumab, an anti-programmed cell death protein-1 antibody. A 54-year-old man with RA was diagnosed with grade IV lung squamous cell carcinoma. The patient had maintained RA remission for 4 years at the time of lung cancer diagnosis. After seven cycles of pembrolizumab therapy, the size of the primary tumor was markedly reduced, but a severe RA flare-up and organizing pneumonia (OP)-like pulmonary lesions occurred. Considering the severity of the flare-up, pembrolizumab was discontinued. Upadacitinib induced swift recovery from the RA flare-up and OP. Eleven months after the last pembrolizumab use, almost all metastatic lesions in the body had disappeared. We did not observe recurrence of lung cancer for more than 1 year during upadacitinib therapy. Conclusions: Upadacitinib could be a safe and effective option to treat severe RA flare-ups occurring during anti-PD-1 ICI therapy.

Remote Control of Energy Transformation-Based Cancer Imaging and Therapy

Cancer treatment requires precise tumor-specific targeting at specific sites that allows for high-resolution diagnostic imaging and long-term patient-tailorable cancer therapy; while, minimizing side effects largely arising from non-targetability. This can be realized by harnessing exogenous remote stimuli, such as tissue-penetrative ultrasound, magnetic field, light, and radiation, that enable local activation for cancer imaging and therapy in deep tumors. A myriad of nanomedicines can be efficiently activated when the energy of such remote stimuli can be transformed into another type of energy. This review discusses the remote control of energy transformation for targetable, efficient, and long-term cancer imaging and therapy. Such ultrasonic, magnetic, photonic, radiative, and radioactive energy can be transformed into mechanical, thermal, chemical, and radiative energy to enable a variety of cancer imaging and treatment modalities. The current review article describes multimodal energy transformation where a serial cascade or multiple types of energy transformation occur. This review includes not only mechanical, chemical, hyperthermia, and radiation therapy but also emerging thermoelectric, pyroelectric, and piezoelectric therapies for cancer treatment. It also illustrates ultrasound, magnetic resonance, fluorescence, computed tomography, photoluminescence, and photoacoustic imaging-guided cancer therapies. It highlights afterglow imaging that can eliminate autofluorescence for sustained signal emission after the excitation.

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.

CD38-Specific Gallium-68 Labeled Peptide Radiotracer Enables Pharmacodynamic Monitoring in Multiple Myeloma with PET

The limited availability of molecularly targeted low-molecular-weight imaging agents for monitoring multiple myeloma (MM)-targeted therapies has been a significant challenge in the field. In response, a first-in-class peptide-based radiotracer, [68Ga]Ga-AJ206, is developed that can be seamlessly integrated into the standard clinical workflow and is specifically designed to noninvasively quantify CD38 levels and pharmacodynamics by positron emission tomography (PET). A bicyclic peptide, AJ206, is synthesized and exhibits high affinity to CD38 (KD: 19.1 ± 0.99 × 10-9 m) by surface plasmon resonance. Further, [68Ga]Ga-AJ206-PET shows high contrast within 60 min and suitable absorbed dose estimates for clinical use. Additionally, [68Ga]Ga-AJ206 detects CD38 expression in cell line-derived xenografts, patient-derived xenografts (PDXs), and disseminated disease models in a manner consistent with flow cytometry and immunohistochemistry findings. Moreover, [68Ga]Ga-AJ206-PET successfully quantifies CD38 pharmacodynamics in PDXs, revealing increased CD38 expression in the tumor following all-trans retinoic acid (ATRA) therapy. In conclusion, [68Ga]Ga-AJ206 exhibits the salient features required for clinical translation, providing CD38-specific high-contrast images in multiple models of MM. [68Ga]Ga-AJ206-PET could be useful for quantifying total CD38 levels and pharmacodynamics during therapy to evaluate approved and new therapies in MM and other diseases with CD38 involvement.

Anti-metastatic effects of AGS-30 on breast cancer through the inhibition of M2-like macrophage polarization

AGS-30, a new andrographolide derivative, showed significant anticancer and anti-angiogenic characteristics. However, its role in controlling macrophage polarization and tumor immune response is unknown. Thus, the main goals of this study are to investigate how AGS-30 regulates macrophage polarization and how it suppresses breast cancer metastasis. AGS-30 inhibited IL-4 and IL-13-induced RAW 264.7 and THP-1 macrophages into M2-like phenotype. However, AGS-30 did not affect the LPS and IFN-γ-induced polarization of M1-like macrophages. AGS-30 reduced the mRNA expressions of CD206, Arg-1, Fizz-1, Ym-1, VEGF, IL-10, MMP2, and MMP9 in M2-like macrophages in a concentration-dependent manner. In contrast, andrographolide treatment at 5 μM did not affect M1-like and M2-like macrophage polarization. The conditioned medium from M2-like macrophages increased 4T1 breast cancer cell migration and invasion, whereas AGS-30 inhibited these effects. In the 4T1 breast tumor xenograft mice, the tumor volume and weight were reduced without affecting body weight after receiving AGS-30. AGS-30 treatment also reduced lung and liver metastasis, with reduced STAT6, CD31, VEGF, and Ki67 protein expressions. Moreover, the tumors had considerably fewer M2-like macrophages and Arg-1 expression, but the proportion of M1-like macrophages and iNOS expression increased after AGS-30 treatment. Same results were found in the tail vein metastasis model. In conclusion, this study shows that AGS-30 inhibits breast cancer growth and metastasis, probably through inhibiting M2-like macrophage polarization. Our findings suggest that AGS-30 may be a potential immunotherapeutic alternative for metastatic breast cancer.

Comparison of Tumor Non-specific and PD-L1 Specific Imaging by Near-Infrared Fluorescence/Cerenkov Luminescence Dual-Modality In-situ Imaging

Background

Labeled antibodies are excellent imaging agents in oncology to non-invasively visualize cancer-related antigens expression levels. However, tumor tracer uptake (TTU) of specific antibodies in-vivo may be inferior to non-specific IgG in some cases.

Objectives

To explore factors affecting labeled antibody visualization by PD-L1 specific and non-specific imaging of nude mouse tumors.

Methods

TTU was observed in RKO model on Cerenkov luminescence (CL) and near-infrared fluorescence (NIRF) imaging of radionuclide 131I or NIRF dyes labeled Atezolizumab and IgG. A mixture of NIRF dyes labeled Atezolizumab and 131I-labeled IgG was injected, and TTU was observed in the RKO and HCT8 model by NIRF/CL dual-modality in-situ imaging. TTU were observed by 131I-labeled Atezolizumab and IgG in-vitro distribution.

Results

Labeled IgG concentrated more in tumors than Atezolizumab. NIRF/CL imaging in 24 to 168 h showed that TTU gradually decreased over time, which decreased more slowly on CL imaging compared to NIRF imaging. The distribution data in-vitro showed that TTU of 131I-labeled IgG was higher than that of 131I-labeled Atezolizumab at any time point.

Conclusion

Non-specific IgG may not be suitable as a control for Atezolizumab in comparing tumor PD-L1 expression in nude mice via labeled antibody optical imaging under certain circumstances.