Targeting both GD2 and B7-H3 using bispecific antibody improves tumor selectivity for GD2-positive tumors.

Objectives: Disialoganglioside 2 (GD2), overexpressed by cancers such as melanoma and neuroblastoma, is a tumor antigen for targeted therapy. The delivery of conventional IgG antibody technologies targeting GD2 is limited clinically by its co-expression on nerves that contributes to toxicity presenting as severe neuropathic pain. To improve the tumor selectivity of current GD2-targeting approaches, a next-generation bispecific antibody targeting GD2 and B7-H3 (CD276) was generated. Methods: Differential expression of human B7-H3 (hB7-H3) was transduced into GD2+ B78 murine melanoma cells and confirmed by flow cytometry. We assessed the avidity and selectivity of our GD2-B7-H3 targeting bispecific antibodies (INV34-6, INV33-2, and INV36-6) towards GD2+/hB7-H3- B78 cells relative to GD2+/hB7-H3+ B78 cells using flow cytometry and competition binding assays, comparing results an anti-GD2 antibody (dinutuximab, DINU). The bispecific antibodies, DINU, and a non-targeted bispecific control (bsAb CTRL) were conjugated with deferoxamine for radiolabeling with Zr-89 (t1/2 = 78.4 h). Using positron emission tomography (PET) studies, we evaluated the in vivo avidity and selectivity of the GD2-B7-H3 targeting bispecific compared to bsAb CTRL and DINU using GD2+/hB7-H3+ and GD2+/hB7-H3- B78 tumor models. Results: Flow cytometry and competition binding assays showed that INV34-6 bound with high avidity to GD2+/hB7-H3+ B78 cells with high avidity but not GD2+/hB7-H3+ B78 cells. In comparison, no selectivity between cell types was observed for DINU. PET in mice bearing the GD2+/hB7-H3- and GD2+/hB7-H3+ B78 murine tumor showed similar biodistribution in normal tissues for [89Zr]Zr-Df-INV34-6, [89Zr]Zr-Df-bsAb CTRL, and [89Zr]Zr-Df-DINU. Importantly, [89Zr]Zr-Df-INV34-6 tumor uptake was selective to GD2+/hB7-H3+ B78 over GD2+/hB7-H3- B78 tumors, and substantially higher to GD2+/hB7-H3+ B78 than the non-targeted [89Zr]Zr-Df-bsAb CTRL control. [89Zr]Zr-Df-DINU displayed similar uptake in both GD2+ tumor models, with uptake comparable to [89Zr]Zr-Df-INV34-6 in the GD2+/hB7-H3+ B78 model. Conclusion: The GD2-B7-H3 targeting bispecific antibodies successfully improved selectivity to cells expressing both antigens. This approach should address the severe toxicities associated with GD2-targeting therapies by reducing off-tumor GD2 binding in nerves. Continued improvements in bispecific antibody technologies will continue to transform the therapeutic biologics landscape.

Mechanistic Characterization of Cancer-associated Fibroblast Depletion via an Antibody-Drug Conjugate Targeting Fibroblast Activation Protein.

Cancer-associated fibroblasts (CAF) are a prominent cell type within the tumor microenvironment (TME) where they are known to promote cancer cell growth and survival, angiogenesis, drug resistance, and immunosuppression. The transmembrane prolyl protease fibroblast activation protein (FAP) is expressed on the surface of highly protumorigenic CAFs found in the stroma of nearly every cancer of epithelial origin. The widespread expression of FAP has made it an attractive therapeutic target based on the underlying hypothesis that eliminating protumorigenic CAFs will disrupt the cross-talk between components of TME resulting in cancer cell death and immune infiltration. This hypothesis, however, has never been directly proven. To eliminate FAP-expressing CAFs, we developed an antibody-drug conjugate using our anti-FAP antibody, huB12, coupled to a monomethyl auristatin E (huB12-MMAE) payload. After determining that huB12 was an effective targeting vector, we found that huB12-MMAE potently eliminated FAP-expressing cells as monocultures in vitro and significantly prolonged survival in vivo using a xenograft engineered to overexpress FAP. We investigated the effects of selectively eliminating CAFs using a layered, open microfluidic cell coculture platform, known as the Stacks. Analysis of mRNA and protein expression found that treatment with huB12-MMAE resulted in the increased secretion of the proinflammatory cytokines IL6 and IL8 by CAFs and an associated increase in expression of proinflammatory genes in cancer cells. We also detected increased secretion of CSF1, a cytokine involved in myeloid recruitment and differentiation. Our findings suggest that the mechanism of FAP-targeted therapies is through effects on the immune microenvironment and antitumor immune response. SIGNIFICANCE: The direct elimination of FAP-expressing CAFs disrupts the cross-talk with cancer cells leading to a proinflammatory response and alterations in the immune microenvironment and antitumor immune response.

[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.

Amplification of Cerenkov luminescence using semiconducting polymers for cancer theranostics.

The therapeutic efficacy of photodynamic therapy is limited by the ability of light to penetrate tissues. Due to this limitation, Cerenkov luminescence (CL) from radionuclides has recently been proposed as an alternative light source in a strategy referred to as Cerenkov radiation induced therapy (CRIT). Semiconducting polymer nanoparticles (SPNs) have ideal optical properties, such as large absorption cross-sections and broad absorbance, which can be utilized to harness the relatively weak CL produced by radionuclides. SPNs can be doped with photosensitizers and have nearly 100% energy transfer efficiency by multiple energy transfer mechanisms. Herein, we investigated an optimized photosensitizer doped SPN as a nanosystem to harness and amplify CL for cancer theranostics. We found that semiconducting polymers significantly amplified CL energy transfer efficiency. Bimodal PET and optical imaging studies showed high tumor uptake and retention of the optimized SPNs when administered intravenously or intratumorally. Lastly, we found that photosensitizer doped SPNs have excellent potential as a cancer theranostics nanosystem in an in vivo tumor therapy study. Our study shows that SPNs are ideally suited to harness and amplify CL for cancer theranostics, which may provide a significant advancement for CRIT that are unabated by tissue penetration limits.

Nanoparticle-Reinforced Tough Hydrogel as a Versatile Platform for Pharmaceutical Drug Delivery: Preparation and in Vitro Characterization.

Natural polymer-based hydrogels are excellent for encapsulating hydrophilic drugs, but they are mechanically weak and degrade easily. In this communication, we exploit the electrostatic interaction between nanosilicates (nSi) and gelatin methacrylate (GelMA) to form a mechanically tough nanocomposite hydrogel for pharmaceutical drug delivery. These hydrogels, prepared at subzero temperatures to form cryogels, displayed macroporous structures, which favors cell infiltration. The designed tough cryogel also showed a slower rate of degradation. Furthermore, we encapsulated the small molecule metformin and sustained the drug release under physiological conditions. Cryogel-loaded metformin reduced the effect of endothelial cell injury caused by nutrient deprivation in vitro. Finally, we hypothesize that this versatile nanocomposite material will find use in diverse biomedical applications.

Multimodal imaging demonstrates enhanced tumor exposure of PEGylated FUD peptide in breast cancer.

In breast cancer, the extracellular matrix (ECM) undergoes remodeling and changes the tumor microenvironment to support tumor progression and metastasis. Fibronectin (FN) assembly is an important step in the regulation of the tumor microenvironment since the FN matrix precedes the deposition of various other ECM proteins, controls immune cell infiltration, and serves as a reservoir for cytokines and growth factors. Therefore, FN is an attractive target for breast cancer therapy and imaging. Functional Upstream Domain (FUD) is a 6-kDa peptide targeting the N-terminal 70-kDa domain of FN, which is critical for fibrillogenesis. FUD has previously been shown to function as an anti-fibrotic peptide both in vitro and in vivo. In this work, we conjugated the FUD peptide with 20-kDa of PEG (PEG-FUD) and demonstrated its improved tumor exposure compared to non-PEGylated FUD in a murine breast cancer model via multiple imaging modalities. Importantly, PEG-FUD peptide retained a nanomolar binding affinity for FN and maintained in vitro plasma stability for up to 48 h. Cy5-labeled PEG-FUD bound to exogenous or endogenous FN assembled by fibroblasts. The in vivo fluorescence imaging with Cy5-labeled FUD and FUD conjugates demonstrated that PEGylation of the FUD peptide enhanced blood exposure after subcutaneous (SC) injection and significantly increased accumulation of FUD peptide in 4T1 mammary tumors. Intravital microscopy confirmed that Cy5-labeled PEG-FUD deposited mostly in the extravascular region of the tumor microenvironment after SC administration. Lastly, positron emission tomography/computed tomography imaging showed that 64Cu-labeled PEG-FUD preferentially accumulated in the 4T1 tumors with improved tumor uptake compared to 64Cu-labeled FUD (48 h: 1.35 ± 0.05 vs. 0.59 ± 0.03 %IA/g, P < 0.001) when injected intravenously (IV). The results indicate that PEG-FUD targets 4T1 breast cancer with enhanced tumor retention compared to non-PEGylated FUD, and biodistribution profiles of PEG-FUD after SC and IV injection may guide the optimization of PEG-FUD as a therapeutic and/or imaging agent for use in vivo.

[68 Ga]Ga-FAPI-46 PET for non-invasive detection of pulmonary fibrosis disease activity.

PURPOSE: The lack of effective molecular biomarkers to monitor idiopathic pulmonary fibrosis (IPF) activity or treatment response remains an unmet clinical need. Herein, we determined the utility of fibroblast activation protein inhibitor for positron emission tomography (FAPI PET) imaging in a mouse model of pulmonary fibrosis. METHODS: Pulmonary fibrosis was induced by intratracheal administration of bleomycin (1 U/kg) while intratracheal saline was administered to control mice. Subgroups from each cohort (n = 3-5) underwent dynamic 1 h PET/CT after intravenously injecting FAPI-46 radiolabeled with gallium-68 ([68 Ga]Ga-FAPI-46) at 7 days and 14 days following disease induction. Animals were sacrificed following imaging for ex vivo gamma counting and histologic correlation. [68 Ga]Ga-FAPI-46 uptake was quantified and reported as percent injected activity per cc (%IA/cc) or percent injected activity (%IA). Lung CT density in Hounsfield units (HU) was also correlated with histologic examinations of lung fibrosis. RESULTS: CT only detected differences in the fibrotic response at 14 days post-bleomycin administration. [68 Ga]Ga-FAPI-46 lung uptake was significantly higher in the bleomycin group than in control subjects at 7 days and 14 days. Significantly (P = 0.0012) increased [68 Ga]Ga-FAPI-46 lung uptake in the bleomycin groups at 14 days (1.01 ± 0.12%IA/cc) vs. 7 days (0.33 ± 0.09%IA/cc) at 60 min post-injection of the tracer was observed. These findings were consistent with an increase in both fibrinogenesis and FAP expression as seen in histology. CONCLUSION: CT was unable to assess disease activity in a murine model of IPF. Conversely, FAPI PET detected both the presence and activity of lung fibrogenesis, making it a promising tool for assessing early disease activity and evaluating the efficacy of therapeutic interventions in lung fibrosis patients.

CD38-Targeted Theranostics of Lymphoma with 89Zr/177Lu-Labeled Daratumumab.

Lymphoma is a heterogeneous disease with varying clinical manifestations and outcomes. Many subtypes of lymphoma, such as Burkitt's lymphoma and diffuse large B cell lymphoma, are highly aggressive with dismal prognosis even after conventional chemotherapy and radiotherapy. As such, exploring specific biomarkers for lymphoma is of high clinical significance. Herein, a potential marker, CD38, is investigated for differentiating lymphoma. A CD38-targeting monoclonal antibody (mAb, daratumumab) is then radiolabeled with Zr-89 and Lu-177 for theranostic applications. As the diagnostic component, the Zr-89-labeled mAb is highly specific in delineating CD38-positive lymphoma via positron emission tomography (PET) imaging, while the Lu-177-labeled mAb serves well as the therapeutic component to suppress tumor growth after a one-time administration. These results strongly suggest that CD38 is a lymphoma-specific marker and prove that 89Zr/177Lu-labeled daratumumab facilitates immunoPET imaging and radioimmunotherapy of lymphoma in preclinical models. Further clinical evaluation and translation of this CD38-targeted theranostics may be of significant help in lymphoma patient stratification and management.

Ultrasmall Porous Silica Nanoparticles with Enhanced Pharmacokinetics for Cancer Theranostics.

Theranostic nanoparticles hold the potential to greatly improve cancer management by providing personalized medicine. Although many theranostic nanoconstructs have been successful in preclinical studies, clinical translation is still hampered by their limited targeting capability and lack of successful therapeutic efficacy. We report the use of novel ultrasmall porous silica nanoparticles (UPSN) with enhanced in vivo pharmacokinetics such as high target tissue accumulation (12% ID/g in the tumor) and evasion from the reticuloendothelial system (RES) organs. Herein, UPSN is conjugated with the isotopic pair 90/86Y, enabling both noninvasive imaging as well as internal radiotherapy. In vivo PET imaging demonstrates prolonged blood circulation and excellent tumor contrast with 86Y-DOTA-UPSN. Tumor-to-muscle and tumor-to-liver uptake values were significantly high (12.4 ± 1.7 and 1.5 ± 0.5, respectively), unprecedented for inorganic nanomaterials. 90Y-DOTA-UPSN significantly inhibits tumor growth and increases overall survival, indicating the promise of UPSN for future clinical translation as a cancer theranostic agent.

Noninvasive Evaluation of CD20 Expression Using 64Cu-Labeled F(ab')2 Fragments of Obinutuzumab in Lymphoma.

CD20-overexpressed non-Hodgkin lymphoma typically indicates progressive malignancy. Obinutuzumab is a next-generation Food and Drug Administration-approved humanized monoclonal antibody that targets CD20. Previous studies with 89Zr-labeled obinutuzumab have successfully imaged CD20 in vivo. However, delayed tumor uptake and increased radioactive exposure caused by long blood circulation limit its clinical translation. This study aimed to develop 64Cu-labeled F(ab')2 fragments of obinutuzumab for imaging CD20 in lymphoma xenograft tumor models. Methods: F(ab')2 fragments were produced from obinutuzumab using an IgG-degrading enzyme of Streptococcus pyogenes (IdeS) enzyme and purified with protein A beads. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and high-performance liquid chromatography were performed to evaluate the products and their stability. F(ab')2 products were conjugated with p-SCN-Bn-NOTA (NOTA) for 64Cu radiolabeling. Western blotting was performed to screen the CD20 expression levels of lymphoma cells. Enzyme-linked immunosorbent assay, flow cytometry, and confocal imaging were used to test the binding affinity in vitro. Serial PET imaging and biodistribution studies in subcutaneous lymphoma-bearing mice were performed using 64Cu-NOTA-F(ab')2-obinutuzumab or 64Cu-NOTA-F(ab')2-IgG. Results: F(ab')2-obinutuzumab and F(ab')2-IgG produced by the IdeS digestion system were confirmed with sodium dodecyl sulfate polyacrylamide gel electrophoresis and high-performance liquid chromatography. The radiochemical purity of 64Cu-labeled F(ab')2 fragments was no less than 98%, and the specific activity was 56.3 ± 7.9 MBq/mg (n = 6). Among the 5 lymphoma cell lines, Ramos showed the strongest expression of CD20, and CLL-155 showed the lowest, as confirmed by enzyme-linked immunosorbent assay, flow cytometry, and confocal imaging. PET imaging revealed rapid and sustained tumor uptake of 64Cu-NOTA-F(ab')2-obinutuzumab in Ramos tumor-bearing mice. The peak tumor uptake (9.08 ± 1.67 percentage injected dose per gram of tissue [%ID/g]) in the Ramos model was significantly higher than that in the CCL-155 model (2.78 ± 0.62 %ID/g) or the 64Cu-NOTA-F(ab')2-IgG control (1.93 ± 0.26 %ID/g, n = 4, P < 0.001). The tumor-to-blood and tumor-to-muscle ratios were 7.3 ± 1.6 and 21.9 ± 9.0, respectively, at 48 h after injection in the 64Cu-NOTA-F(ab')2-obinutuzumab group. Of the measured off-target organs, the kidneys showed the highest uptake. Ex vivo immunofluorescent staining verified the differential CD20 expression in the Ramos and CCL-155 tumor models. Conclusion: This study demonstrated that 64Cu-NOTA-F(ab')2-obinutuzumab had a rapid and sustained tumor uptake in CD20-positive lymphoma with high contrast, which could enable noninvasive evaluation of CD20 levels in the clinic.

Internally Responsive Nanomaterials for Activatable Multimodal Imaging of Cancer.

Advances in technology and nanomedicine have led to the development of nanoparticles that can be activated for multimodal imaging of cancer, where a stimulus induces a material modification that enhances image contrast. Multimodal imaging using nanomaterials with this capability can combine the advantages and overcome the limitations of any single imaging modality. When designed with stimuli-responsive abilities, the target-to-background ratio of multimodal imaging nanoprobes increases because specific stimuli in the tumor enhance the signal. Several aspects of the tumor microenvironment can be exploited as an internal stimulus response for multimodal imaging applications, such as the pH gradient, redox processes, overproduction of various enzymes, or combinations of these. In this review, design strategies are discussed and an overview of the recent developments of internally responsive multimodal nanomaterials is provided. Properly implementing this approach improves noninvasive cancer diagnosis and staging as well as provides a method to monitor drug delivery and treatment response.

Nanomedicines for Renal Management: From Imaging to Treatment.

Nanomedicine has benefited from recent advances in chemistry and biomedical engineering to produce nanoscale materials as theranostic agents. Well-designed nanomaterials may present optimal biological properties, influencing circulation, retention, and excretion for imaging and treatment of various diseases. As the understanding of nanomedicine pharmacokinetics expands continuously, efficient renal clearance of nanomedicines can significantly increase the signal-to-background ratio for precision diagnosis and lower potential toxicity for improved treatment. Studies on nanomaterial-kidney interactions have led to many novel findings on the underlying principles of nanomaterial renal clearance, targeting, and accumulation. In return, the optimized nanomedicines confer significant benefits to the detection and treatment of kidney dysfunction.In this Account, we present an overview of recent progress in the development of nanomaterials for kidney theranostics, aiming to speed up translation and expand possible applications. We start by introducing biological structures of the kidney and their influence on renal targeting, retention, and clearance. Several key factors regarding renal accumulation and excretion, including nanomaterial types, sizes, and shapes, surface charges, and chemical modifications, are identified and discussed. Next, we highlight our recent efforts investigating kidney-interacting nanomaterials and introduce representative nanomedicines for imaging and treatment of kidney diseases. Multiple renal-clearable and renal-accumulating nanomedicines were devised for kidney function imaging. By employing renal-clearable nanomedicines, including gold nanoparticles, porphyrin polymers, DNA frameworks, and polyoxometalate clusters, we were able to noninvasively evaluate split renal function in healthy and diseased mice. Further engineering of renal-accumulating nanosystems has shifted attention from renal diagnosis to precision kidney protection. Many biocompatible nanomedicines, such as DNA origami, selenium-doped carbon quantum dots, melanin nanoparticles, and black phosphorus have all played essential roles in diminishing excessive reactive oxygen species for kidney treatment and protection. Finally, we discuss the challenges and perspectives of nanomaterials for renal care, their future clinical translation, and how they may affect the current landscape of clinical practices. We believe that this Account updates our current understanding of nanomaterial-kidney interactions for further design and control of nanomedicines for specific kidney diagnosis and treatment. This timely Account will generate broad interest in integrating nanotechnology and nanomaterial-biological interaction for state-of-the-art theranostics of renal diseases.

PET imaging of macrophages in cardiovascular diseases.

Cardiovascular diseases (CVDs) have been the leading cause of death in United States. While tremendous progress has been made for treating CVDs over the year, the high prevalence and substantial medical costs requires the necessity for novel methods for the early diagnosis and treatment monitoring of CVDs. Macrophages are a promising target due to its crucial role in the progress of CVDs (atherosclerosis, myocardial infarction and inflammatory cardiomyopathies). Positron emission tomography (PET) is a noninvasive imaging technique with high sensitivity and provides quantitive functional information of the macrophages in CVDs. Although 18F-FDG can be taken up by active macrophages, the PET imaging tracer is non-specific and susceptible to blood glucose levels. Thus, developing more specific PET tracers will help us understand the role of macrophages in CVDs. Moreover, macrophage-targeted PET imaging will further improve the diagnosis, treatment monitoring, and outcome prediction for patients with CVDs. In this review, we summarize various targets-based tracers for the PET imaging of macrophages in CVDs and highlight research gaps to advise future directions.

Selenium-Doped Carbon Quantum Dots Act as Broad-Spectrum Antioxidants for Acute Kidney Injury Management.

The manifestation of acute kidney injury (AKI) is associated with poor patient outcomes, with treatment options limited to hydration or renal replacement therapies. The onset of AKI is often associated with a surfeit of reactive oxygen species. Here, it is shown that selenium-doped carbon quantum dots (SeCQDs) have broad-spectrum antioxidant properties and prominent renal accumulation in both healthy and AKI mice. Due to these properties, SeCQDs treat or prevent two clinically relevant cases of AKI induced in murine models by either rhabdomyolysis or cisplatin using only 1 or 50 µg per mouse, respectively. The attenuation of AKI in both models is confirmed by blood serum measurements, kidney tissue staining, and relevant biomarkers. The therapeutic efficacy of SeCQDs exceeds amifostine, a drug approved by the Food and Drug Administration that also acts by scavenging free radicals. The findings indicate that SeCQDs show great potential as a treatment option for AKI and possibly other ROS-related diseases.

86/90Y-Labeled Monoclonal Antibody Targeting Tissue Factor for Pancreatic Cancer Theranostics.

Pancreatic cancer is highly aggressive, with a median survival time of less than 6 months and a 5-year overall survival rate of around 7%. The poor prognosis of PaCa is largely due to its advanced stage at diagnosis and the lack of efficient therapeutic options. Thus, the development of an efficient, multifunctional PaCa theranostic system is urgently needed. Overexpression of tissue factor (TF) has been associated with increased tumor growth, angiogenesis, and metastasis in many malignancies, including pancreatic cancer. Herein, we propose the use of a TF-targeted monoclonal antibody (ALT836) conjugated with the pair 86/90Y as a theranostic agent against pancreatic cancer. For methods, serial PET imaging with 86Y-DTPA-ALT836 was conducted to map the biodistribution the tracer in BXPC-3 tumor-bearing mice. 90Y-DTPA-ALT836 was employed as a therapeutic agent that also allowed tumor burden monitoring through Cherenkov luminescence imaging. The results were that the uptake of 86Y-DTPA-ALT836 in BXPC-3 xenograft tumors was high and increased over time up to 48 h postinjection (p.i.), corroborated through ex vivo biodistribution studies and further confirmed by Cherenkov luminescence Imaging. In therapeutic studies, 90Y-DTPA-ALT836 was found to slow tumor growth relative to the control groups and had significantly smaller (p < 0.05) tumor volumes 1 day p.i. Histological analysis of ex vivo tissues revealed significant damage to the treated tumors. The conclusion is that the use of the 86/90Y theranostic pair allows PET imaging with excellent tumor-to-background contrast and treatment of TF-expressing pancreatic tumors with promising therapeutic outcomes.

ImmunoPET: Concept, Design, and Applications.

Immuno-positron emission tomography (immunoPET) is a paradigm-shifting molecular imaging modality combining the superior targeting specificity of monoclonal antibody (mAb) and the inherent sensitivity of PET technique. A variety of radionuclides and mAbs have been exploited to develop immunoPET probes, which has been driven by the development and optimization of radiochemistry and conjugation strategies. In addition, tumor-targeting vectors with a short circulation time (e.g., Nanobody) or with an enhanced binding affinity (e.g., bispecific antibody) are being used to design novel immunoPET probes. Accordingly, several immunoPET probes, such as 89Zr-Df-pertuzumab and 89Zr-atezolizumab, have been successfully translated for clinical use. By noninvasively and dynamically revealing the expression of heterogeneous tumor antigens, immunoPET imaging is gradually changing the theranostic landscape of several types of malignancies. ImmunoPET is the method of choice for imaging specific tumor markers, immune cells, immune checkpoints, and inflammatory processes. Furthermore, the integration of immunoPET imaging in antibody drug development is of substantial significance because it provides pivotal information regarding antibody targeting abilities and distribution profiles. Herein, we present the latest immunoPET imaging strategies and their preclinical and clinical applications. We also emphasize current conjugation strategies that can be leveraged to develop next-generation immunoPET probes. Lastly, we discuss practical considerations to tune the development and translation of immunoPET imaging strategies.

HER2-targeted multimodal imaging of anaplastic thyroid cancer.

Clinical management of anaplastic thyroid cancer (ATC) is very challenging due to its dedifferentiation and aggressiveness. We aim to develop HER2-targeted multimodal imaging approaches and assess the diagnostic efficacies of these molecular imaging probes in preclinical ATC models. Flow cytometry was used to detect HER2 expression status in thyroid cancer cell lines. We then developed a HER2-specific immunoPET imaging probe 89Zr-Df-pertuzumab by radiolabeling a HER-2 specific monoclonal antibody (mAb) pertuzumab with 89Zr (t1/2=78.4 h) and a fluorescent imaging probe IRDye 800CW-pertuzumab. The diagnostic efficacies of the probes were assessed in subcutaneous and orthotopic ATC models, followed by ex vivo biodistribution profile and immunofluorescence staining studies. HER2 was highly expressed on the surface of all the four primary thyroid cancer cell lines examined, which included two ATC cell lines (i.e., 8505C and THJ-16T). PET imaging with 89Zr-Df-pertuzumab clearly visualized all the subcutaneous ATCs with a peak tumor uptake of 20.23±6.44 %ID/g (n=3), whereas the highest tumor uptake of the nonspecific probe 89Zr-Df-IgG in subcutaneous ATC models was 6.30±0.95 %ID/g (n=3). More importantly, 89Zr-Df-pertuzumab PET imaging strategy readily delineated all the orthotopic ATCs with a peak tumor uptake of 24.93±8.53 %ID/g (n=3). We also suggested that Cerenkov luminescence imaging (CLI) using 89Zr-Df-pertuzumab and fluorescence imaging using IRDye 800CW-pertuzumab are useful tools for image-guided removal of ATCs. We demonstrate that HER2 is a promising biomarker for ATC, and multimodal imaging using 89Zr-Df-pertuzumab and IRDye 800CW-pertuzumab is useful for identifying HER2-postive ATCs.

A "Missile-Detonation" Strategy to Precisely Supply and Efficiently Amplify Cerenkov Radiation Energy for Cancer Theranostics.

Cerenkov radiation (CR) from radionuclides can act as a built-in light source for cancer theranostics, opening a new horizon in biomedical applications. However, considerably low tumor-targeting efficiency of existing radionuclides and radionuclide-based nanomedicines limits the efficacy of CR-induced theranostics (CRIT). It remains a challenge to precisely and efficiently supply CR energy to the tumor site. Here, a "missile-detonation" strategy is reported, in which a high dose of p-SCN-Bn-deferoxamine-porphyrin-PEG nanocomplex (Df-PPN) is first adminstered as a CR energy receiver/missile to passively target to tumor, and then a low dose of the 89 Zr-labeled Df-PPN is administrated as a CR energy donor/detonator, which can be visualized and quantified by Cerenkov energy transfer imaging, positron-emission tomography, and fluorescence imaging. Based on homologous properties, the colocalization of Df-PPN and 89 Zr-Df-PPN in the tumor site is maximized and efficient CR energy transfer is enabled, which maximizes the tumor-targeted CRIT efficacy in an optimal spatiotemporal setting while also reducing adverse off-target effects from CRIT. This precise and efficient CRIT strategy causes significant tumor vascular damage and inhibited tumor growth.

Smart H2S-Triggered/Therapeutic System (SHTS)-Based Nanomedicine.

Hydrogen sulfide (H2S) is of vital importance in several biological and physical processes. The significance of H2S-specific detection and monitoring is emphasized by its elevated levels in various diseases such as cancer. Nanotechnology enhances the performance of chemical sensing nanoprobes due to the enhanced efficiency and sensitivity. Recently, extensive research efforts have been dedicated to developing novel smart H2S-triggered/therapeutic system (SHTS) nanoplatforms for H2S-activated sensing, imaging, and therapy. Herein, the latest SHTS-based nanomaterials are summarized and discussed in detail. In addition, therapeutic strategies mediated by endogenous H2S as a trigger or exogenous H2S delivery are also included. A comprehensive understanding of the current status of SHTS-based strategies will greatly facilitate innovation in this field. Lastly, the challenges and key issues related to the design and development of SHTS-based nanomaterials (e.g., morphology, surface modification, therapeutic strategies, appropriate application, and selection of nanomaterials) are outlined.