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

PURPOSE: Programmed cell death protein ligand 1 (PD-L1) is a crucial biomarker for immunotherapy. However, nearly 70% of patients do not respond to PD-L1 immune checkpoint therapy. Accurate monitoring of PD-L1 expression and quantification of target binding during treatment are essential. In this study, a series of small-molecule radiotracers were developed to assess PD-L1 expression and direct immunotherapy. METHODS: Radiotracers of [68Ga]Ga-D-PMED, [68Ga]Ga-D-PEG-PMED, and [68Ga]Ga-D-pep-PMED were designed based on a 2-methyl-3-biphenyl methanol scaffold and successfully synthesized. Cellular experiments and molecular docking assays were performed to determine their specificity for PD-L1. PD-L1 status was investigated via positron emission tomography (PET) imaging in MC38 tumor models. PET imaging of [68Ga]Ga-D-pep-PMED was performed to noninvasively quantify PD-L1 blocking using an anti-mouse PD-L1 antibody (PD-L1 mAb). RESULTS: The radiosyntheses of [68Ga]Ga-D-PMED, [68Ga]Ga-D-PEG-PMED, and [68Ga]Ga-D-pep-PMED were achieved with radiochemical yields of 87 ± 6%, 82 ± 4%, and 79 ± 9%, respectively. In vitro competition assays demonstrated their high affinities (the IC50 values of [68Ga]Ga-D-PMED, [68Ga]Ga-D-PEG-PMED, and [68Ga]Ga-D-pep-PMED were 90.66 ± 1.24, 160.8 ± 1.35, and 51.6 ± 1.32 nM, respectively). At 120 min postinjection (p.i.) of the radiotracers, MC38 tumors displayed optimized tumor-to-muscle ratios for all radioligands. Owing to its hydrophilic modification, [68Ga]Ga-D-pep-PMED had the highest target-to-nontarget (T/NT) ratio of approximately 6.2 ± 1.2. Interestingly, the tumor/liver ratio was hardly affected by different concentrations of the inhibitor BMS202. We then evaluated the impacts of dose and time on accessible PD-L1 levels in the tumor during anti-mouse PD-L1 antibody treatment. The tumor uptake of [68Ga]Ga-D-pep-PMED significantly decreased with increasing PD-L1 mAb dose. Moreover, after 8 days of treatment with a single antibody, the uptake of [68Ga]Ga-D-pep-PMED in the tumor significantly increased but remained lower than that in the saline group. CONCLUSION: PET imaging with [68Ga]Ga-D-pep-PMED, a small-molecule radiotracer, is a promising tool for evaluating PD-L1 expression and quantifying the target blockade of PD-L1 to assist in the development of effective therapeutic regimens.

Development of radiotracers for riboflavin transporter 3 imaging in diseases-A brief overview.

Riboflavin (RF, vitamin B2) plays a key role in metabolic oxidation-reduction reactions, especially in the mitochondrial reprogramming of energy metabolism. Riboflavin transporter 3 (RFVT3) is a vital section of the mitochondrial network and involved in riboflavin homeostasis and production of adenosine triphosphate (ATP). The abnormal expression of RFVT3 is closely associated with the occurrence and progression of multiple diseases. Therefore, it is vital to understand the riboflavin internalization pathway under pathological conditions by addressing the abnormal expression of RFVT3, which could be a highly valuable biomarker for the early diagnosis and effective therapy of various diseases.

Development of 18F-Labeled Acridone Analogue for Tumor Imaging via Stimulator of Interferon Genes Targeting.

The stimulator of interferon genes (STING) is a pivotal protein in the production of STING-dependent type I interferon, which has the potential to enhance tumor rejection. The visualization of STING in the tumor microenvironment is valuable for STING-related treatments, but few STING imaging probes have been reported to date. In this study, we developed a novel 18F-labeled agent ([18F]F-CRI1) with an acridone core structure for the positron emission tomography (PET) imaging of STING in CT26 tumors. The probe was successfully prepared with a nanomolar STING binding affinity of Kd = 40.62 nM. [18F]F-CRI1 accumulated quickly in the tumor sites and its uptake reached a maximum of 3.02 ± 0.42% ID/g after 1 h i.v. injection. The specificity of [18F]F-CRI1 was confirmed both in in vitro cell uptake and in vivo PET imaging by blocking studies. Our findings suggest that [18F]F-CRI1 may be a potential agent for visualizing STING in the tumor microenvironment.

Development of a novel radiofluorinated riboflavin probe for riboflavin receptor-targeting PET imaging.

Riboflavin receptor 3 (RFVT3) is a key protein in energetic metabolism reprogramming and is overexpressed in multiple cancers involved in malignant proliferation, angiogenesis, chemotherapy resistance, and immunosuppression. To enable non-invasive real-time quantification of RFVT3 in tumors, we sought to develop a suitable PET probe that would allow specific and selective RFVT3 imaging in vivo. A novel radiofluorinated riboflavin probe (18F-RFTA) based on riboflavin was synthesized and characterized in terms of radiochemical purity, hydrophilicity, binding affinity, and stability. Positron emission tomography (PET) imaging of 18F-RFTA was performed in U87MG tumor-bearing mice. Immunohistochemistry staining was carried out to determine the expression of RFVT3 in U87MG tumors. 18F-RFTA was characterized by high radiochemical purity and RFVT3 binding affinity, and remarkable stability in vitro and in vivo. Small-animal PET imaging with 18F-RFTA revealed significantly higher uptake in RFVT3-expressing U87MG tumors than in muscle. In conclusion, we have developed the first radiofluorinated riboflavin-based PET probe that is suitable for imaging RFVT3-positive tumors. The new target/probe system can be leveraged for extensive use in the diagnosis and treatment of RFVT3 overexpressing diseases, such as oncologic, cardiovascular, and neurodegenerative diseases.

MicroSPECT Imaging-Guided Treatment of Idiopathic Pulmonary Fibrosis in Mice with a Vimentin-Targeting 99mTc-Labeled N-Acetylglucosamine-Polyethyleneimine.

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic disease with poor prognosis. Evidence has shown that vimentin is a key regulator of lung fibrogenesis. 99mTc-labeled N-acetylglucosamine-polyethyleneimine (NAG-PEI), a vimentin-targeting radiotracer, was used for the early diagnosis of IPF, and NAG-PEI was also used as a therapeutic small interfering RNA (siRNA) delivery vector for the treatment of IPF in this study. Single-photon emission-computed tomography (SPECT) imaging of bleomycin (BM)- and silica-induced IPF mice with 99mTc-labeled NAG-PEI was performed to visualize pulmonary fibrosis and monitor the treatment efficiency of siRNA-loaded NAG-PEI, lipopolysaccharide (LPS, a tolerogenic adjuvant), or zymosan (ZYM, an immunostimulant). The lung uptakes of 99mTc-NAG-PEI in the BM- and silica-induced IPF mice were clearly and directly correlated with IPF progression. The lung uptake of 99mTc-NAG-PEI in the NAG-PEI/TGF-ß1-siRNA treatment group or LPS treatment group was evidently lower than that in the control group, while the lung uptake of 99mTc-NAG-PEI was significantly higher in the ZYM treatment group compared to that in the control group. These results demonstrate that NAG-PEI is a potent MicroSPECT imaging-guided theranostic platform for IPF diagnosis and therapy.

Radioiodinated Portable Albumin Binder as a Versatile Agent for in Vivo Imaging with Single-Photon Emission Computed Tomography.

In this study, radioiodinated 4-( p-iodophenyl)butyric acid ([131I]IBA) was synthesized and evaluated as a portable albumin-binder for potential applications in single photon emission computed tomography imaging of blood pool, tumor, and lymph node with significantly improved pharmacokinetic properties. The [131I]IBA was prepared under the catalyst of Cu2O/1,10-phenanthroline. After that, the albumin-binding capability of [131I]IBA was tested in vitro, ex vivo, and in vivo, respectively. [131I]IBA was obtained with very high radiolabeling yield (>99%) and good radiochemical purity (>98%) within 10 min. It binds to albumin effectively with high affinity (IC50= 46.5 µM) and has good stability. The results of biodistribution indicated that the [131I]IBA was mainly accumulated in blood with good retention (10.51 ± 2.58%ID/g at 30 min p.i. and 4.63 ± 0.17%ID/g at 4 h p.i.). In the SPECT imaging of mice models with [131I]IBA, blood pool, lymph node, and tumors could be imaged clearly with high target-to-background ratio. Overall, the radioiodinated albumin binder of [131I]IBA with long blood half-life and excellent stability could be used to decorate diversified albumin-binding radioligands and developed as a versatile theranostic agent.

Radioiodinated progesterone derivative for progesterone receptor targeting with enhanced nucleus uptake via phenylboronic acid conjugation.

A novel 131 I-radiolabeled probe with aromatic boronate motif (131 I-EIPBA) was designed to target progesterone receptor (PR)-positive breast cancer with enhanced nucleus uptake. Acetylene progesterone was conjugated with pegylated phenylboronic acid via click reaction and radiolabeled with 131 I to afford 131 I-EIPBA. Meanwhile, 131 I-EIPB without boronate was prepared as control agent. After determination of the lipophilicity and stability of these tracers, in vitro cell uptake studies and in vivo biodistribution in rats were performed to verify the enhanced nucleus uptake and PR targeting ability of 131 I-EIPBA. 131 I-EIPBA was obtained with moderate radiochemical yield (40.35 ± 3.52%) and high radiochemical purity (>98%). As expected, the high binding affinity (39.58 nM) of 131 I-EIPBA for PR was determined by cell binding assay. The internalization ratio of 131 I-EIPBA was remarkably higher than that of 131 I-EIPB in PR-positive MCF-7 cells. Furthermore, the enhanced nucleus uptake of 131 I-EIPBA (0.59 ± 0.02%) was found to be significantly higher than that of 131 I-EIPB (0.13 ± 0.01%) in MCF-7 cells. A novel 131 I-EIPBA compound was developed for PR targeting with improved cellular nucleus uptake. Furthermore, the introduction of aromatic boronate motif provides a worthwhile strategy for enhancing the nuclear receptor targeting of tracers.

Radioiodinated Pentixather for SPECT Imaging of Expression of the Chemokine Receptor CXCR4 in Rat Myocardial-Infarction-Reperfusion Models.

The purpose of this study is to develop a specific CXCR4-targeting radioiodinated agent (125I- or 131I-pentixather) for single-photon-emission-computed-tomography (SPECT) imaging of CXCR4 expression in myocardial-infarction-reperfusion (MI/R) rat models. After SPECT-CT imaging with 125I-pentixather at 4, 12, and 36 h and 3 and 7 days after MI/R, the models were validated by ex vivo autoradiography, TTC staining, and immunohistochemistry and in vivo echocardiography and classical 99mTc-MIBI perfusion imaging. The SPECT-CT images showed that the infarcted myocardium (IM) could be visualized with high quality as early as 4 h and reached the maximum at 3 days after MI/R and that CXCR4 upregulation was still visible at 7 days after MI/R. In the biodistribution study, high uptakes in the IM (0.99 ± 0.13, 1.52 ± 0.29, 1.75 ± 0.22, 1.94 ± 0.27, and 0.61 ± 0.14% ID/g at 4, 12, and 36 h and 3 and 7 days after MI/R, respectively) were observed that were much higher than that of normal myocardium. The highest uptake was reached at 3 days after MI/R, which agreed well with the SPECT results. In addition, the radioactivity uptakes of the IM in both the biodistribution and SPECT imaging could be blocked effectively by excess amounts of AMD3465, indicating the high specificity of radioiodinated pentixather to CXCR4. On the basis of its promising properties, 125I-pentixather may serve as a powerful CXCR4-expression diagnostic probe for evaluating lesions and monitoring therapy responses in patients with cardiovascular diseases.

Highly Efficient and Stable Strain-Release Radioiodination for Thiol Chemoselective Bioconjugation.

We report a novel thiol selective radioiodination method based on strain-release reaction. A new heterobifunctional radioiodination agent which has very good thiol selectivity and excellent stability with high radiolabeling yield was synthesized, characterized, and applied successfully for thiol-contained peptide labeling.

Synthesis and Preclinical Evaluation of Radioiodinated Hypericin Dicarboxylic Acid as a Necrosis Avid Agent in Rat Models of Induced Hepatic, Muscular, and Myocardial Necroses.

Myocardial infarction (MI) leads to substantial morbidity and mortality around the world. Accurate assessment of myocardial viability is essential to assist therapies and improve patient outcomes. (131)I-hypericin dicarboxylic acid ((131)I-HDA) was synthesized and evaluated as a potential diagnostic agent for earlier assessment of myocardium viability compared to its preceding counterpart (131)I-hypericin ((131)I-Hyp) with strong hydrophobic property, long plasma half-life, and high uptake in mononuclear phagocyte system (MPS). Herein, HDA was synthesized and characterized, and self-aggregation constant Kα was analyzed by spectrophotometry. Plasma half-life was determined in healthy rats by γ-counting. (131)I-HDA and (131)I-Hyp were prepared with iodogen as oxidant. In vitro necrosis avidity of (131)I-HDA and (131)I-Hyp was evaluated in necrotic cells induced by hyperthermia. Biodistribution was determined in rat models of induced necrosis using γ-counting, autoradiography, and histopathology. Earlier imaging of necrotic myocardium to assess myocardial viability was performed in rat models of reperfused myocardium infarction using single photon emission computed tomography/computed tomography (SPECT/CT). As a result, the self-aggregation constant Kα of HDA was lower than that of Hyp (105602 vs 194644, p < 0.01). (131)I-HDA displayed a shorter blood half-life compared with (131)I-Hyp (9.21 vs 31.20 h, p < 0.01). The necrotic-viable ratio in cells was higher with (131)I-HDA relative to that with (131)I-Hyp (5.48 vs 4.63, p < 0.05). (131)I-HDA showed a higher necrotic-viable myocardium ratio (7.32 vs 3.20, p < 0.01), necrotic myocardium-blood ratio (3.34 vs 1.74, p < 0.05), and necrotic myocardium-lung ratio (3.09 vs 0.61, p < 0.01) compared with (131)I-Hyp. (131)I-HDA achieved imaging of necrotic myocardium at 6 h postinjection (p.i.) with SPECT/CT, earlier than what (131)I-Hyp did. Therefore, (131)I-HDA may serve as a promising necrosis-avid diagnostic agent for earlier imaging of necrotic myocardium compared with (131)I-Hyp. This may support further development of radiopharmaceuticals ((123)I and (99m)Tc) based on HDA for SPECT/CT of necrotic myocardium.

Synthesis and Evaluation of 131I-Skyrin as a Necrosis Avid Agent for Potential Targeted Radionuclide Therapy of Solid Tumors.

An innovative anticancer approach targeted to necrotic tissues, which serves as a noncancerous and generic anchor, may present a breakthrough. Necrosis avid agents with a flat conjugate aromatic structure selectively accumulate in necrotic tissues, but they easily form aggregates that undesirably distribute to normal tissues. In this study, skyrin, a dianthraquinone compound with smaller and distorted π-cores and thus decreased aggregates as compared with hypericin (Hyp), was designed to target necrosis for tumor therapy. Aggregation studies of skyrin by UV/vis spectroscopy showed a smaller self-association constant with skyrin than with Hyp. Skyrin was labeled by iodine-131 with a radiochemical purity of 98% and exhibited good stability in rat serum for 72 h. In vitro cell uptake studies showed significant difference in the uptake of 131I-skyrin by necrotic cells compared to normal cells (P < 0.05). Compared in rats with liver and muscle necrosis, radiobiodistribution, whole-body autoradiography, and SPECT/CT studies revealed higher accumulation of 131I-skyrin in necrotic liver and muscle (p < 0.05), but lower uptake in normal organs, relative to that of 131I-Hyp. In mice bearing H22 tumor xenografts treated with combretastatin A4 disodium phosphate, the highest uptake of 131I-skyrin was found in necrotic tumor. In conclusion, 131I-skyrin appears a promising agent with reduced accumulation in nontarget organs for targeted radionuclide therapy of solid tumors.

MicroPET Imaging of Riboflavin Transporter 3 Expression in Myocardial Infarction/Reperfusion Rat Models with Radiofluorinated Riboflavin.

Riboflavin transporter 3 (RFVT3) represents a potential cardioprotective biotarget in energetic metabolism reprogramming after myocardial infarction/reperfusion (MI/R). This study investigated the feasibility of noninvasive real-time quantification of RFVT3 expression after MI/R with an radiolabeled probe 18F-RFTA in a preclinical rat model of MI/R. The tracer 18F-RFTA was radio-synthesized manually and characterized on the subjects of radiolabeling yield, radiochemical purity, and stability in vivo. MI/R and sham-operated rat models were confirmed by cardiac magnetic resonance imaging (cMRI) and single-photon-emission computed tomography (SPECT) myocardial perfusion imaging (MPI) with technetium-99m sestamibi (99mTc-MIBI). Positron emission tomography (PET) imaging of MI/R and sham-operated rat models were conducted with 18F-RFTA. Ex vivo autoradiography and RFVT3 immunohistochemical (IHC) staining were conducted to verify the RFVT3 expression in infarcted and normal myocardium. 18F-RFTA injection was prepared with high radiochemical purity (>95%) and kept stable in vitro and in vivo. 18F-RFTA PET revealed significant uptake in the infarcted myocardium at 8 h after reperfusion, as confirmed by lower 99mTc-MIBI perfusion and decreased intensity of cMRI. Conversely, there were only the tiniest uptakes in the normal myocardium and blocked infarcted myocardium, which was further corroborated by ex vivo autoradiography. The RFVT3 expression was further confirmed by IHC staining in the infarcted and normal myocardium. We first demonstrate the feasibility of imaging RFVT3 in infarcted myocardium. 18F-RFTA is an encouraging PET probe for imaging cardioprotective biotarget RFVT3 in mitochondrial energetic metabolism reprogramming after myocardial infarction. Noninvasive imaging of cardioprotective biotarget RFVT3 has potential value in the diagnosis and therapy of patients with MI.

Development of Preladenant-Based Radiotracers for Imaging A2AR in Tumors.

Activation of the adenosine 2A receptor (A2AR) can lead to tumor immunosuppression, which results in poor prognosis of immunotherapy. The aim of this study was to design novel 18F-labeled probes ([18F]F-PFP2 and [18F]F-PFP4) to visualize A2AR in the tumor. The uptake of radioprobes in A2AR-negative 4T1 breast tumor was lower than that of A2AR-positive B16F10 melanoma at 1 h p.i. (1.22 ± 0.36% ID/g vs 2.80 ± 0.72% ID/g), 2 h p.i. (1.09 ± 0.20% ID/g vs 2.93 ± 0.76% ID/g) and 3 h p.i. (0.89 ± 0.27% ID/g vs 2.73 ± 0.58% ID/g), respectively. B16F10 lung metastasis models were employed to expand the application scenarios, observing significantly higher uptake of [18F]F-PFP2 in metastatic lesions compared to normal lung tissue (5.55 ± 2.18% ID/g vs 1.89 ± 0.65% ID/g, tumor/lung ratio ∼3). It is given that [18F]F-PFP2 might lay the foundation for establishing an A2AR-targeted imaging evaluation system for tumors, which will provide more precise guidance for personalized treatment.

Recent advances and applications of microspheres and nanoparticles in transarterial chemoembolization for hepatocellular carcinoma.

Transarterial chemoembolization (TACE) is a recommended treatment for patients suffering from intermediate and advanced hepatocellular carcinoma (HCC). As compared to the conventional TACE, drug-eluting bead TACE demonstrates several advantages in terms of survival, treatment response, and adverse effects. The selection of embolic agents is critical to the success of TACE. Many studies have been performed on the modification of the structure, size, homogeneity, biocompatibility, and biodegradability of embolic agents. Continuing efforts are focused on efficient loading of versatile chemotherapeutics, controlled sizes for sufficient occlusion, real-time detection intra- and post-procedure, and multimodality imaging-guided precise treatment. Here, we summarize recent advances and applications of microspheres and nanoparticles in TACE for HCC. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Molecular Imaging of Tumor Microenvironment to Assess the Effects of Locoregional Treatment for Hepatocellular Carcinoma.

Liver cancer is one of the leading causes of cancer deaths worldwide. Among all primary liver cancers, hepatocellular carcinoma (HCC) is the most common type, representing 75%-85% of all primary liver cancer cases. Median survival following diagnosis of HCC is approximately 6 to 20 months due to late diagnosis in its course and few effective treatment options. Interventional therapy with minimal invasiveness is recognized as a promising treatment for HCC. However, due to the heterogeneity of HCC and the complexity of the tumor microenvironment, the long-term efficacy of treatment for HCC remains a challenge in the clinic. Tumor microenvironment, including factors such as hypoxia, angiogenesis, low extracellular pH, interstitial fluid pressure, aerobic glycolysis, and various immune responses, has emerged as a key contributor to tumor residual and progression after locoregional treatment for HCC. New approaches to noninvasively assess the treatment response and assist in the clinical decision-making process are therefore urgently needed. Molecular imaging tools enabling such an assessment may significantly advance clinical practice by allowing real-time optimization of treatment protocols for the individual patient. This review discusses recent advances in the application of molecular imaging technologies for noninvasively assessing changes occurring in the microenvironment of HCC after locoregional treatment.

Micro-SPECT Imaging of Acute Ischemic Stroke with Radioiodinated Riboflavin in Rat MCAO Models via Riboflavin Transporter Targeting.

Riboflavin transporter-3 (RFVT3) is a recently discovered and novel biomarker for the theranostics of nervous system diseases. RFVT3 is significantly overexpressed in cerebral injury after ischemic stroke. Herein, we first reported an RFVT3-targeted tracer 131I-riboflavin (131I-RFLA) for SPECT imaging of ischemic stroke in vivo. 131I-RFLA was radiosynthesized by the iodogen-coating method. 131I-RFLA possessed a radiochemical yield of 69.2 ± 3.7% and greater than 95% radiochemical purity. The representative SPECT/CT images using 131I-RFLA demonstrated the conspicuously increased tracer uptake in the cerebral injury by comparison with the contralateral normal brain at 1 h and 3 and 7 d after stroke. Ex vivo autoradiography demonstrated that the ratio of infarcted to normal brain uptake was 3.63 and it was decreased to 1.98 after blocking, which reconfirmed the results of SPECT images. Importantly, a significant correlation was identified between RFVT3 expression and brain injury by H&E and immunohistochemistry staining. Therefore, RFVT3 is a new and potential biomarker for the early diagnosis of ischemic stroke. In addition, 131I-RFLA is a promising SPECT tracer for imaging RFVT3-related ischemic cerebral injury in vivo.

Radioiodinated Ethinylestradiol Derivatives for Estrogen Receptor Targeting Breast Cancer Imaging.

Two novel PEGylated ethinylestradiol (PEG = poly(ethylene glycol)) estrogen receptor (ER) targeting probes [131I]EITE and [131I]MITE were synthesized and evaluated. Both probes had a nanomolar binding affinity to the ER receptor (36.47 nM for [131I]EITE and 61.83 nM for [131I]MITE). They showed high uptake in ER-positive MCF-7 cells and tumors, which could be significantly blocked by a coinjection of excess estradiol. Their ER specificities were further demonstrated by the low uptake in ER-negative MDA-MB-231 cells and tumors. The maximum tumor-to-muscle (T/M) ratios reach to 6.59 for [131I]EITE at 1 h postinjection (p.i.) and to 3.69 for [131I]MITE at 2 h p.i. in MCF-7 tumors. Among these two probes, [131I]EITE showed a faster tumor accumulation and a higher T/M ratio indicating it could be a better candidate for the potential diagnosis of ER-positive breast cancers.

Exploring Solvent Effects in the Radiosynthesis of 18F-Labeled Thymidine Analogues toward Clinical Translation for Positron Emission Tomography Imaging.

Thymidine analogues, 5-substituted 2'-deoxy-2'-[18F]fluoro-arabinofuranosyluracil derivatives, are promising positron emission tomography (PET) tracers being evaluated for noninvasive imaging of cancer cell proliferation and/or reporter gene expression. We report the radiosynthesis of 2'-deoxy-2'-[18F]fluoro-5-methyl-1-ß-d-arabinofuranosyluracil ([18F]FMAU) and other 2'-deoxy-2'-[18F]fluoro-5-substituted-1-ß-d-arabinofuranosyluracil analogues using 1,4-dioxane to replace the currently used 1,2-dichloroethane. Compared to 1,2-dichloroethane, 1,4-dioxane is analyzed as a better solvent in terms of radiochemical yield and toxicity concern. The use of a less toxic solvent allows for the translation of the improved approach to clinical production. The new radiolabeling method can be applied to an extensive range of uses for 18F-labeling of other nucleoside analogues.

Supramolecular nanosubstrate-mediated delivery system enables CRISPR-Cas9 knockin of hemoglobin beta gene for hemoglobinopathies.

Leveraging the endogenous homology-directed repair (HDR) pathway, the CRISPR-Cas9 gene-editing system can be applied to knock in a therapeutic gene at a designated site in the genome, offering a general therapeutic solution for treating genetic diseases such as hemoglobinopathies. Here, a combined supramolecular nanoparticle (SMNP)/supramolecular nanosubstrate-mediated delivery (SNSMD) strategy is used to facilitate CRISPR-Cas9 knockin of the hemoglobin beta (HBB) gene into the adeno-associated virus integration site 1 (AAVS1) safe-harbor site of an engineered K562 3.21 cell line harboring the sickle cell disease mutation. Through stepwise treatments of the two SMNP vectors encapsulating a Cas9•single-guide RNA (sgRNA) complex and an HBB/green fluorescent protein (GFP)-encoding plasmid, CRISPR-Cas9 knockin was successfully achieved via HDR. Last, the HBB/GFP-knockin K562 3.21 cells were introduced into mice via intraperitoneal injection to show their in vivo proliferative potential. This proof-of-concept demonstration paves the way for general gene therapeutic solutions for treating hemoglobinopathies.

Small molecules as theranostic agents in cancer immunology.

With further research into the molecular mechanisms and roles linking immune suppression and restraint of (pre)malignancies, immunotherapies have revolutionized clinical strategies in the treatment of cancer. However, nearly 70% of patients who received immune checkpoint therapeutics showed no response. Complementary and/or synergistic effects may occur when extracellular checkpoint antibody blockades combine with small molecules targeting intracellular signal pathways up/downstream of immune checkpoints or regulating the innate and adaptive immune response. After radiolabeling with radionuclides, small molecules can also be used for estimating treatment efficacy of immune checkpoint blockades. This review not only highlights some significant intracellular pathways and immune-related targets such as the kynurenine pathway, purinergic signaling, the kinase signaling axis, chemokines, etc., but also summarizes some attractive and potentially immunosuppression-related small molecule agents, which may be synergistic with extracellular immune checkpoint blockade. In addition, opportunities for small molecule-based theranostics in cancer immunology will be discussed.