89Zr-pembrolizumab biodistribution is influenced by PD-1-mediated uptake in lymphoid organs

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.

New Long-Acting [89Zr]Zr-DFO GLP-1 PET Tracers with Increased Molar Activity and Reduced Kidney Accumulation

Positron emission tomography (PET) imaging is used in drug development to noninvasively measure biodistribution and receptor occupancy. Ideally, PET tracers retain target binding and biodistribution properties of the investigated drug. Previously, we developed a zirconium-89 PET tracer based on a long-circulating glucagon-like peptide 1 receptor agonist (GLP-1RA) using desferrioxamine (DFO) as a chelator. Here, we aimed to develop an improved zirconium-89-labeled GLP-1RA with increased molar activity to increase the uptake in low receptor density tissues, such as brain. Furthermore, we aimed at reducing tracer accumulation in the kidneys. Introducing up to four additional Zr-DFOs resulted in higher molar activity and stability, while retaining potency. Branched placement of DFOs was especially beneficial. Tracers with either two or four DFOs had similar biodistribution as the tracer with one DFO in vivo, albeit increased kidney and liver uptake. Reduced kidney accumulation was achieved by introducing an enzymatically cleavable Met-Val-Lys (MVK) linker motif between the chelator and the peptide.

Evaluation of 89Zr-Labeled Anti-PD-L1 Monoclonal Antibodies Using DFO and Novel HOPO Analogues as Chelating Agents for Immuno-PET

Programmed death ligand 1 (PD-L1) is a type 1 transmembrane immunosuppressive protein that is expressed on a wide range of cell types, including cancer cells. Anti-PD-L1 antibodies have revolutionized cancer therapy and have led to improved outcomes for subsets of cancer patients, including triple-negative breast cancer (TNBC) patients. As a result, PET imaging of PD-L1 protein expression in cancer patients has been explored for noninvasive detection of PD-L1 expressing tumors as well as monitoring response to anti-PD-L1 immune checkpoint therapy. Previous studies have indicated that the in vivo stability and in vivo target detection of antibody-based radio-conjugates can be dramatically affected by the chelator used. These reports demonstrated that the chelator HOPO diminishes ⁸⁹Zr de-chelation compared to DFO. Herein, we report an improved HOPO synthesis and evaluated a series of novel analogues for thermal stability, serum stability, PD-L1-specific binding using the BT-549 TNBC cell line, PET imaging in vivo, as well as biodistribution of ⁸⁹Zr-labeled anti-PD-L1 antibodies in BT-549 xenograft murine models. A new chelator, C5HOPO, demonstrated high stability in vitro and afforded effective PD-L1 targeting in vivovia immuno-PET. These results demonstrated that an improved HOPO chelator is an effective chelating agent that can be utilized to image therapeutically relevant targets in vivo.

Image-based response assessment during immunotherapy in skin cancer

Immune-checkpoint inhibitors and further immunotherapeutic treatment strategies have significantly extended therapy options for melanoma and other skin cancer entities over the last decade. In the context of a broader application of immunotherapeutic approaches, sufficient ways to monitor the course of the disease during therapy are required. Immunotherapies are based on different ways of modulating the immune system. This leads to complex clinical response patterns including pseudoprogression and others, requiring an adaptation of conventional diagnostic imaging tools or the introduction of novel technologies. In this review, current non-invasive imaging approaches for response assessment during immunotherapies in skin cancers as well as their limitations are discussed. To overcome present hurdles, promising alternatives to better address novel imaging features during immunotherapy are depicted giving an outlook on what can be expected in the future.

Positron emission tomography molecular imaging to monitor anti-tumor systemic response for immune checkpoint inhibitor therapy

Immune checkpoint inhibitors (ICIs) achieve a milestone in cancer treatment. Despite the great success of ICI, ICI therapy still faces a big challenge due to heterogeneity of tumor, and therapeutic response is complicated by possible immune-related adverse events (irAEs). Therefore, it is critical to assess the systemic immune response elicited by ICI therapy to guide subsequent treatment regimens. Positron emission tomography (PET) molecular imaging is an optimal approach in cancer diagnosis, treatment effect evaluation, follow-up, and prognosis prediction. PET imaging can monitor metabolic changes of immunocytes and specifically identify immuno-biomarkers to reflect systemic immune responses. Here, we briefly review the application of PET molecular imaging to date of systemic immune responses following ICI therapy and the associated rationale.

A Novel Dextran-Based Dual Drug Conjugate Targeted Tumors with High Biodistribution Ratio of Tumors to Normal Tissues

PURPOSE

Most chemotherapeutic agents possess poor water solubility and show more significant accumulations in normal tissues than in tumor tissues, resulting in serious side effects. To this end, a novel dextran-based dual drug delivery system with high biodistribution ratio of tumors to normal tissues was developed.

METHODS

A bi-functionalized dextran was developed, and several negatively charged dextran-based dual conjugates containing two different types of drugs, docetaxel and docosahexaenoic acid (DTX and DHA, respectively) were synthesized. The structures of these conjugates were characterized using nuclear magnetic resonance and liquid chromatography/mass spectrometry (¹H-NMR and LC/MS, respectively) analysis. Cell growth inhibition, apoptosis, cell cycle distribution, and cellular uptake were measured in vitro. Drug biodistribution and pharmacokinetics were investigated in mice bearing 4T1 tumors using LC/MS analysis. Drug biodistribution was also explored by in vivo imaging. The effects of these conjugates on tumor growth were evaluated in three mice models.

RESULTS

The dextran-docosahexaenoic acid (DHA)- docetaxel (DTX) conjugates caused a significant enhancement of DTX water solubility and improvement in pharmacokinetic characteristics. The optimized dextran-DHA-DTX conjugate A treatment produced a 2.1- to 15.5-fold increase in intra-tumoral DTX amounts for up to 96 h compared to parent DTX treatment. Meanwhile, the concentrations of DTX released from conjugate A in normal tissues were much lower than those of the parent DTX. This study demonstrated that DHA could lead to an improvement in the efficacy of the conjugates and that the conjugate with the shortest linker displayed more activity than conjugates with longer linkers. Moreover, conjugate A completely eradicated all MCF-7 xenograft tumors without causing any obvious side effects and totally outperformed both the conventional DTX formulation and Abraxane in mice.

CONCLUSION

These dextran-based dual drug conjugates may represent an innovative tumor targeting drug delivery system that can selectively deliver anticancer agents to tumors.

ImmunoPET: Antibody-Based PET Imaging in Solid Tumors

Immuno-positron emission tomography (immunoPET) is a molecular imaging modality combining the high sensitivity of PET with the specific targeting ability of monoclonal antibodies. Various radioimmunotracers have been successfully developed to target a broad spectrum of molecules expressed by malignant cells or tumor microenvironments. Only a few are translated into clinical studies and barely into clinical practices. Some drawbacks include slow radioimmunotracer kinetics, high physiologic uptake in lymphoid organs, and heterogeneous activity in tumoral lesions. Measures are taken to overcome the disadvantages, and new tracers are being developed. In this review, we aim to mention the fundamental components of immunoPET imaging, explore the groundbreaking success achieved using this new technique, and review different radioimmunotracers employed in various solid tumors to elaborate on this relatively new imaging modality.

Application of molecular imaging in immune checkpoints therapy: From response assessment to prognosis prediction

Recently, immune checkpoint therapy (ICT) represented by programmed cell death1 (PD-1) and its major ligands, programmed death ligand 1 (PD-L1), has achieved significant success. Detection of PD-L1 by immunohistochemistry (IHC) is a classic method to guide the treatment of ICT patients. However, PD-L1 expression in the tumor microenvironment is highly complex. Thus, PD-L1 IHC is inadequate to fully understand the relevance of PD-L1 levels in the whole body and their dynamics to improve therapeutic outcomes. Intriguingly, numerous studies have revealed that molecular imaging technologies could potentially meet this need. Therefore, the purpose of this narrative review is to summarize the preclinical and clinical application of ICT guided by molecular imaging technology, and to explore the future opportunities and practical difficulties of these innovations.

Development of Radiotracers for Imaging of the PD-1/PD-L1 Axis

Immune checkpoint inhibitor (ICI) therapy has emerged as a major treatment option for a variety of cancers. Among the immune checkpoints addressed, the programmed death receptor 1 (PD-1) and its ligand PD-L1 are the key targets for an ICI. PD-L1 has especially been proven to be a reproducible biomarker allowing for therapy decisions and monitoring therapy success. However, the expression of PD-L1 is not only heterogeneous among and within tumor lesions, but the expression is very dynamic and changes over time. Immunohistochemistry, which is the standard diagnostic tool, can only inadequately address these challenges. On the other hand, molecular imaging techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) provide the advantage of a whole-body scan and therefore fully address the issue of the heterogeneous expression of checkpoints over time. Here, we provide an overview of existing PET, SPECT, and optical imaging (OI) (radio)tracers for the imaging of the upregulation levels of PD-1 and PD-L1. We summarize the preclinical and clinical data of the different molecule classes of radiotracers and discuss their respective advantages and disadvantages. At the end, we show possible future directions for developing new radiotracers for the imaging of PD-1/PD-L1 status in cancer patients.

Immuno-PET imaging of PD-L1 expression in patient-derived lung cancer xenografts with [68Ga]Ga-NOTA-Nb109

Background

Accurate evaluation of programmed death-ligand 1 (PD-L1) expression levels in cancer patients may be useful in the identification of potential candidates for anti-programmed death-1/PD-L1 (anti-PD-1/PD-L1) immune checkpoint therapy to improve the response rate of immune checkpoint blockade therapy. This study evaluated the feasibility of the nanobody-based positron emission tomography (PET) tracer [68Ga]Ga-NOTA-Nb109 for immuno-PET imaging of PD-L1 in lung cancer patient-derived xenograft (PDX).

Methods

We constructed 2 PDXs of lung adenocarcinoma (ADC) and lung squamous cell carcinoma (SCC) and used them for immuno-PET imaging. A 2-hour dynamic PET scanning was performed on the samples and the in vivo biodistribution and metabolism of [68Ga]Ga-NOTA-Nb109 were investigated using region of interest (ROI) analysis. The ex vivo biodistribution of [68Ga]Ga-NOTA-Nb109 in the 2 PDXs was investigated by static PET scanning. In addition, tumor PD-L1 expression in the 2 PDXs was evaluated by autoradiography, western blot, and immunohistochemical (IHC) analysis.

Results

Noninvasive PET imaging showed that [68Ga]Ga-NOTA-Nb109 can accurately and sensitively assess the PD-L1 expression in non-small cell lung cancer (NSCLC) PDX models. The maximum [68Ga]Ga-NOTA-Nb109 uptake by the ADC PDX LU6424 and the SCC PDX LU6437 were 3.13%±0.35% and 2.60%±0.32% injected dose per milliliter of tissue volume (ID/mL), respectively, at 20 min post injection. In vivo and ex vivo biodistribution analysis showed that [68Ga]Ga-NOTA-Nb109 was rapidly cleared through renal excretion and an enhanced signal-to-noise ratio (SNR) was achieved. Ex vivo PD-L1 expression analysis showed good agreement with in vivo PET imaging results.

Conclusions

This study demonstrated that [68Ga]Ga-NOTA-Nb109 could be applied with PET imaging to noninvasively and accurately monitor PD-L1 expression in vivo for screening patients who may be responsive to immunotherapy and to guide the development of appropriate treatment strategies for such patients.

Immuno-Imaging (PET/SPECT)-Quo Vadis?

The use of immunotherapy has revolutionized the treatment regimen of certain cancer types, but response assessment has become a difficult task with conventional methods such as CT/MRT or FDG PET-CT and the classical response criteria such as RECIST or PERCIST which have been developed for chemotherapeutic treatment. Plenty of new tracers have been published to improve the assessment of treatment response and to stratify the patient population. We gathered the information on published tracers (in total, 106 individual SPECT/PET tracers were identified) and performed a descriptor-based analysis; in this way, we classify the tracers with regard to target choice, developability (probability to progress from preclinical stage into the clinic), translatability (probability to be widely applied in the 'real world'), and (assumed) diagnostic quality. In our analysis, we show that most tracers are targeting PD-L1, PD-1, CTLA-4, and CD8 receptors by using antibodies or their fragments. Another finding is that plenty of tracers possess only minor iterations regarding chelators and nuclides instead of approaching the problem in a new innovative way. Based on the data, we suggest an orthogonal approach by targeting intracellular targets with PET-activatable small molecules that are currently underrepresented.

ImmunoPET: harnessing antibodies for imaging immune cells

Dramatic, but uneven, progress in the development of immunotherapies for cancer has created a need for better diagnostic technologies including innovative non-invasive imaging approaches. This review discusses challenges and opportunities for molecular imaging in immuno-oncology and focuses on the unique role that antibodies can fill. ImmunoPET has been implemented for detection of immune cell subsets, activation and inhibitory biomarkers, tracking adoptively transferred cellular therapeutics, and many additional applications in preclinical models. Parallel progress in radionuclide availability and infrastructure supporting biopharmaceutical manufacturing has accelerated clinical translation. ImmunoPET is poised to provide key information on prognosis, patient selection, and monitoring immune responses to therapy in cancer and beyond.

Shining Damaged Hearts: Immunotherapy-Related Cardiotoxicity in the Spotlight of Nuclear Cardiology

The emerging use of immunotherapies in cancer treatment increases the risk of immunotherapy-related cardiotoxicity. In contrast to conventional chemotherapy, these novel therapies have expanded the forms and presentations of cardiovascular damage to a broad spectrum from asymptomatic changes to fulminant short- and long-term complications in terms of cardiomyopathy, arrythmia, and vascular disease. In cancer patients and, particularly, cancer patients undergoing (immune-)therapy, cardio-oncological monitoring is a complex interplay between pretherapeutic risk assessment, identification of impending cardiotoxicity, and post-therapeutic surveillance. For these purposes, the cardio-oncologist can revert to a broad spectrum of nuclear cardiological diagnostic workup. The most promising commonly used nuclear medicine imaging techniques in relation to immunotherapy will be discussed in this review article with a special focus on the continuous development of highly specific molecular markers and steadily improving methods of image generation. The review closes with an outlook on possible new developments of molecular imaging and advanced image evaluation techniques in this exciting and increasingly growing field of immunotherapy-related cardiotoxicity.

Radiolabeled Antibodies for Cancer Imaging and Therapy

Simple Summary

Monoclonal antibodies (mAbs) have the ability to specifically target tumor-cell antigens. This unique property has led to their use in the delivery of radioisotopes to tumor sites (scintigraphic imaging and radioimmunotherapy (RIT)). The choice of the radionuclide depends on its unique physical properties and intended use. Using radiolabeled mAbs with imaging techniques provides critical data that are essential for predicting side effects and determining an optimal antibody dose and treatment schedule. While RIT has been successful in the management of hematological malignancies, the treatment of solid tumors remains challenging. Various strategies are being investigated to improve the efficacy of RIT in solid tumors.

Abstract

Radioimmunoconjugates consist of a monoclonal antibody (mAb) linked to a radionuclide. Radioimmunoconjugates as theranostics tools have been in development with success, particularly in hematological malignancies, leading to approval by the US Food and Drug Administration (FDA) for the treatment of non-Hodgkin’s lymphoma. Radioimmunotherapy (RIT) allows for reduced toxicity compared to conventional radiation therapy and enhances the efficacy of mAbs. In addition, using radiolabeled mAbs with imaging methods provides critical information on the pharmacokinetics and pharmacodynamics of therapeutic agents with direct relevance to the optimization of the dose and dosing schedule, real-time antigen quantitation, antigen heterogeneity, and dynamic antigen changes. All of these parameters are critical in predicting treatment responses and identifying patients who are most likely to benefit from treatment. Historically, RITs have been less effective in solid tumors; however, several strategies are being investigated to improve their therapeutic index, including targeting patients with minimal disease burden; using pre-targeting strategies, newer radionuclides, and improved labeling techniques; and using combined modalities and locoregional application. This review provides an overview of the radiolabeled intact antibodies currently in clinical use and those in development.

Probing immune infiltration dynamics in cancer by in vivo imaging

Cancer immunotherapies typically aim to stimulate the accumulation and activity of cytotoxic T-cells or pro-inflammatory antigen-presenting cells, reduce immunosuppressive myeloid cells or regulatory T-cells, or elicit some combination of effects thereof. Notwithstanding the encouraging results, immunotherapies such as PD-1/PD-L1-targeted immune checkpoint blockade act heterogeneously across individual patients. It remains challenging to predict and monitor individual responses, especially across multiple sites of metastasis or sites of potential toxicity. To address this need, in vivo imaging of both adaptive and innate immune cell populations has emerged as a tool to quantify spatial leukocyte accumulation in tumors non-invasively. Here we review recent progress in the translational development of probes for in vivo leukocyte imaging, focusing on complementary perspectives provided by imaging of T-cells, phagocytic macrophages, and their responses to therapy.

89Zr Immuno-PET Imaging of Tumor PD-1 Reveals That PMA Upregulates Lymphoma PD-1 through NFκB and JNK Signaling

Immune therapy of T-cell lymphoma requires assessment of tumor-expressed programmed cell death protein-1 (PD-1). Herein, we developed an immuno-PET technique that quantitatively images and monitors regulation of PD-1 expression on T-cell lymphomas. Methods. Anti-PD-1 IgG underwent sulfhydryl moiety-specific conjugation with maleimide-deferoxamine and 89Zr labeling. Binding assays and Western blotting were performed in EL4 murine T-cell lymphoma cells. In vivo pharmacokinetics, biodistribution, and PET were performed in mice. Results. 89Zr-PD-1 IgG binding to EL4 cells was completely blocked by cold antibodies, confirming excellent target specificity. Following intravenous injection into mice, 89Zr-PD-1 IgG showed biexponential blood clearance and relatively low normal organ uptake after five days. PET/CT and biodistribution demonstrated high EL4 tumor uptake that was suppressed by cold antibodies. In EL4 cells, phorbol 12-myristate 13-acetate (PMA) increased 89Zr-PD-1 IgG binding ( $305.5\pm 30.6$ %) and dose-dependent augmentation of PD-1 expression ( $15.8\pm 3.8-\text{fold}$ of controls by 200 ng/ml). FACS showed strong PD-1 expression on all EL4 cells and positive but weaker expression on $41.6\pm 2.1$ % of the mouse spleen lymphocytes. PMA stimulation led to $2.7\pm 0.3$ -fold increase in the proportion of the strongest PD-1 expressing EL4 cells but failed to influence that of PD-1+ mouse lymphocytes. In mice, PMA treatment increased 89Zr-PD-1 IgG uptake in EL4 lymphomas from $6.6\pm 1.6$ to $13.9\pm 3.6$ %ID/g ( $P=0.01$ ), and tumor uptake closely correlated with PD-1 level ( $r=0.771$ , $P<0.001$ ). On immunohistochemistry of tumor sections, infiltrating CD8α+ T lymphocytes constituted a small fraction of tumor cells. The entire tumor section showed strong PD-1 staining that was even stronger for PMA-treated mice. Investigation of involved signaling revealed that PMA increased EL4 cell and tumor HIF-1α accumulation and NFκB and JNK activation. Conclusion. 89Zr-PD-1 IgG offered high-contrast PET imaging of tumor PD-1 in mice. This was found to mostly represent binding to EL4 tumor cells, although infiltrating T lymphocytes may also have contributed. PD-1 expression on T-cell lymphomas was upregulated by PMA stimulation, and this was reliably monitored by 89Zr-PD-1 IgG PET. This technique may thus be useful for understanding the mechanisms of PD-1 regulation in lymphomas of living subjects.

89Zr-pembrolizumab imaging as a non-invasive approach to assess clinical response to PD-1 blockade in cancer

BACKGROUND

Programmed cell death protein-1 (PD-1) antibody treatment is standard of care for melanoma and non-small cell lung cancer (NSCLC). Accurately predicting which patients will benefit is currently not possible. Tumor uptake and biodistribution of the PD-1 antibody might play a role. Therefore, we performed a positron emission tomography (PET) imaging study with zirconium-89 (⁸⁹Zr) labeled pembrolizumab before PD-1 antibody treatment.

PATIENTS AND METHODS

Patients with advanced or metastatic melanoma or NSCLC received 37 MBq (1 mCi) ⁸⁹Zr-pembrolizumab (∼2.5 mg antibody) intravenously plus 2.5 or 7.5 mg unlabeled pembrolizumab. After that, up to 3 PET scans were performed on days 2, 4, and 7. Next, PD-1 antibody treatment was initiated. ⁸⁹Zr-pembrolizumab tumor uptake was calculated as maximum standardized uptake value (SUV_max) and expressed as geometric mean. Normal organ uptake was calculated as SUV_mean, and expressed as a mean. Tumor response was assessed according to (i)RECIST v1.1.

RESULTS

Eighteen patients, 11 with melanoma and seven with NSCLC, were included. The optimal dose was 5 mg pembrolizumab, and the optimal time-point for PET scanning was day 7. The tumor SUV_max did not differ between melanoma and NSCLC (4.9 and 6.5, P = 0.49). Tumor ⁸⁹Zr-pembrolizumab uptake correlated with tumor response (Ptrend = 0.014) and progression-free (P = 0.0025) and overall survival (P = 0.026). ⁸⁹Zr-pembrolizumab uptake at 5 mg was highest in the spleen with mean SUV_mean 5.8 (±SD 1.8). There was also ⁸⁹Zr-pembrolizumab uptake in Waldeyer's ring, normal lymph nodes, and at sites of inflammation.

CONCLUSION

⁸⁹Zr-pembrolizumab uptake in tumor lesions correlated with treatment response and patient survival. ⁸⁹Zr-pembrolizumab also showed uptake in lymphoid tissues and at sites of inflammation.

Negative prognostic implications of splenomegaly in nivolumab-treated advanced or recurrent pancreatic adenocarcinoma

Immune checkpoint inhibitors have limited efficacy in the treatment of pancreatic ductal adenocarcinoma (PDAC). We investigated prognostic markers for nivolumab-based therapy in advanced or recurrent PDAC. Consecutive patients receiving nivolumab-based therapy at our institution between 2015 and 2020 were evaluated. Overall survival (OS) was analyzed through univariate and multivariate analyses. Spleen volume was estimated from the width, thickness, and length of the spleen. A total of 45 patients were identified. Biweekly nivolumab was administered as monotherapy (n = 5) or in combination with chemotherapy or targeted therapy (n = 40). Among 31 evaluable patients, the response and disease control rates were 7% and 36%, respectively. The baseline median spleen volume was 267 (110–674) mL. Patients with spleens ≥267 mL had significantly shorter median OS (1.9 months, 95% confidence interval [CI], 1.0–2.7) than did those with smaller spleens (8.2 months, 95% CI, 5.6–10.8; P = .003). In the multivariate analysis, spleen volume of <267 mL, ≤2 lines of prior chemotherapy, ECOG performance status of 0–2, add-on nivolumab with stable disease after prior therapy, concomitant or sequential cell therapy, high lymphocyte count, and total bilirubin <1 mg/dL were independent favorable prognostic factors for OS. In the control groups of patients receiving gemcitabine-based chemotherapy (n = 142) or FOLFIRINOX regimen (n = 24), spleen volume exhibited no prognostic significance. In heavily pretreated PDAC, a large spleen may predict poor OS following nivolumab-based immunotherapy. Studies with larger cohorts should confirm the prognostic value of spleen volume.

Prognostic value of inflammatory response biomarkers using peripheral blood and [18F]-FDG PET/CT in advanced NSCLC patients treated with first-line chemo- or immunotherapy

OBJECTIVES

We aimed to compare the prognostic value of inflammatory biomarkers extracted from pretreatment peripheral blood and [18F]-FDG PET for estimating outcomes in non-small cell lung cancer (NSCLC) patients treated with first-line immunotherapy (IT) or chemotherapy (CT).

MATERIALS AND METHODS

In this retrospective multicenter study, we evaluated 111 patients with advanced NSCLC who underwent baseline [18F]-FDG PET/CT before IT or CT between 2016 and 2019. Several blood inflammatory indices were evaluated: derived neutrophil-to-lymphocyte ratio (dNLR), platelet-to-lymphocyte ratio (PLR), C-reactive protein (CRP) and systemic immune-inflammation index (SII). FDG-PET inflammatory parameters were extracted from lymphoid tissues (BLR and SLR: bone marrow or spleen-to-Liver SUVmax ratios). Association with survival and relationships between parameters were evaluated using Cox prediction models and Spearman's correlation respectively.

RESULTS

Overall, 90 patients were included (IT:CT) (51:39pts). Median PFS was 8.6:6.6 months and median OS was not reached:21.2 months. In the IT cohort, high dNLR (>3), high SII (≥1,270) and high SLR (0.77) were independent statistically significant prognostic factors for one-year progression-free survival (1y-PFS) and two-year overall survival (2y-OS) on multivariable analysis. In the CT cohort, high BLR (≥0.80) and high dNLR (>3) were associated with shorter 1y-PFS (HR 2.2, 95% CI 1.0-4.9) and 2y-OS (HR 3.4, 95CI 1.1-10.3) respectively, on multivariable analysis. Finally, BLR significantly but moderately correlated with most blood-based inflammatory indices (CRP, PLR and SII) while SLR was only associated with CRP (p < 0.01 for all).

CONCLUSION

In advanced NSCLC patients undergoing first-line IT or CT, pretreatment blood and inflammatory factors evaluating the spleen or bone marrow on [18F]-FDG PET/CT provided prognostic information for 1y-PFS and 2y-OS. These biomarkers should be further evaluated for potential clinical application.

Don't overlook spleen glucose metabolism on [18F]-FDG PET/CT for cancer drug discovery and development

Fluorine-18-fluorodeoxyglucose ([18F]-FDG) positron emission tomography/computed tomography (PET/CT) is a useful tool that assesses glucose metabolism in tumor cells to help guide management of cancer patients. However, the clinical relevance of glucose metabolism in healthy tissues, including hematopoietic tissues such as the spleen, has been potentially overlooked. Recent studies suggested that spleen glucose metabolism could improve the management of different cancers. Overall, the current literature includes 1,157 patients, with a wide range of tumor types. The prognostic and/or predictive value of spleen metabolism have been demonstrated in a broad spectrum of therapies including surgery and systemic cancer therapies. Most of these studies showed that high spleen glucose metabolism at baseline is associated with a poor outcome while treatment-induce change in spleen glucose metabolism is a multi-faceted surrogate of cancer-related inflammation, which correlates with immunosuppressive tumor microenvironment as well as with immune activation. In this systematic review, we seek to unravel the prognostic/predictive significance of spleen glucose metabolism on [18F]-FDG PET/CT and discuss how it could potentially guide cancer patient management in the future.

First-in-human study of 89Zr-pembrolizumab PET/CT in patients with advanced stage non-small-cell lung cancer

Background: Tumor programmed-death ligand-1 (PD-L1) proportion score is the current method to select non-small-cell lung cancer (NSCLC) patients for single agent treatment with pembrolizumab, a programmed cell death-1 (PD-1) monoclonal antibody. However, not all patients respond to therapy. Better understanding of in vivo drug behavior may help to select patients that benefit most. Methods: NSCLC patients eligible for pembrolizumab monotherapy as first or later line therapy were enrolled. Patients received two injections of ⁸⁹Zr-pembrolizumab; one without a preceding dose of pembrolizumab and one with 200 mg pembrolizumab, directly prior to tracer injection. Up to four PET/CT scans were obtained after tracer injection. Post-imaging acquisition, patients were treated with 200 mg pembrolizumab, every three weeks. Tumor uptake and tracer biodistribution were visually assessed and quantified as standardized uptake value (SUV). Tumor tracer uptake was correlated with PD-1 and PD-L1 expression and response to pembrolizumab treatment. Results: Twelve NSCLC patients were included. One patient experienced grade 3 myalgia after tracer injection. ⁸⁹Zr-pembrolizumab was observed in the blood pool, liver and spleen. Tracer uptake was visualized in 47,2% of 72 tumor lesions measuring ≥20 mm long axis diameter, and substantial uptake heterogeneity was observed within and between patients. Uptake was higher in patients with response to pembrolizumab treatment (n = 3) compared to patients without a response (n = 9), although this was not statistically significant (median SUVpeak 11.4 vs 5.7, P = 0.066). No significant correlations were found with PD-L1 or PD-1 immunohistochemistry. Conclusion: ⁸⁹Zr-pembrolizumab injection was safe with only one grade 3 adverse event, possibly immune related, out of 12 patients. ⁸⁹Zr-pembrolizumab tumor uptake was higher in patients with response to pembrolizumab treatment, but did not correlate with PD-L1 or PD-1 immunohistochemistry.

Mesothelin/CD3 half-life extended bispecific T-cell engager molecule shows specific tumor uptake and distributes to mesothelin and CD3 expressing tissues

BiTE ® (bispecific T-cell engager) molecules exert antitumor activity by binding one arm to CD3 on cytotoxic T-cells and the other arm to a tumor-associated antigen. We generated a fully mouse cross-reactive mesothelin (MSLN)-targeted BiTE molecule that is genetically fused to a Fc-domain for half-life extension, and evaluated biodistribution and tumor targeting of a zirconium-89 (89Zr)-labeled MSLN HLE BiTE molecule in 4T1 breast cancer bearing syngeneic mice with positron emission tomography (PET). Biodistribution of 50 µg 89Zr-MLSN HLE BiTE was studied over time by PET imaging in BALB/c mice and revealed uptake in tumor and lymphoid tissues with an elimination half-life of 63.4 hours. Compared to a non-targeting 89Zr-control HLE BiTE, the 89Zr-MLSN HLE BiTE showed a 2-fold higher tumor uptake and higher uptake in lymphoid tissues. Uptake in the tumor colocalized with mesothelin expression, while uptake in the spleen colocalized with CD3 expression. Evaluation of the effect of protein doses on the biodistribution and tumor targeting of 89Zr-MSLN HLE BiTE revealed for all dose groups that uptake in the spleen was faster than in the tumor (day 1 vs day 5). The lowest dose of 10 µg 89Zr-MSLN HLE BiTE had higher spleen uptake and faster blood clearance compared to higher doses of 50 µg and 200 µg. 89Zr-MSLN HLE BiTE tumor uptake was similar at all doses. Conclusion: The MSLN HLE BiTE showed specific tumor uptake and both arms contributed to the biodistribution profile. These findings support the potential for clinical translation of HLE BiTE molecules.

The Future of Cancer Diagnosis, Treatment and Surveillance: A Systemic Review on Immunotherapy and Immuno-PET Radiotracers

Immunotherapy is an effective therapeutic option for several cancers. In the last years, the introduction of checkpoint inhibitors (ICIs) has shifted the therapeutic landscape in oncology and improved patient prognosis in a variety of neoplastic diseases. However, to date, the selection of the best patients eligible for these therapies, as well as the response assessment is still challenging. Patients are mainly stratified using an immunohistochemical analysis of the expression of antigens on biopsy specimens, such as PD-L1 and PD-1, on tumor cells, on peritumoral immune cells and/or in the tumor microenvironment (TME). Recently, the use and development of imaging biomarkers able to assess in-vivo cancer-related processes are becoming more important. Today, positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) is used routinely to evaluate tumor metabolism, and also to predict and monitor response to immunotherapy. Although highly sensitive, FDG-PET in general is rather unspecific. Novel radiopharmaceuticals (immuno-PET radiotracers), able to identify specific immune system targets, are under investigation in pre-clinical and clinical settings to better highlight all the mechanisms involved in immunotherapy. In this review, we will provide an overview of the main new immuno-PET radiotracers in development. We will also review the main players (immune cells, tumor cells and molecular targets) involved in immunotherapy. Furthermore, we report current applications and the evidence of using [18F]FDG PET in immunotherapy, including the use of artificial intelligence (AI).