Spatiotemporal Concurrent PARP Inhibitor Sensitization Based on Radiation-Responsive Nanovesicles for Lung Cancer Chemoradiotherapy.

The implementation of chemoradiation combinations has gained great momentum in clinical practices. However, the full utility of this paradigm is often restricted by the discordant tempos of action of chemotherapy and radiotherapy. Here, a gold nanoparticle-based radiation-responsive nanovesicle system loaded with cisplatin and veliparib, denoted as CV-Au NVs, is developed to augment the concurrent chemoradiation effect in a spatiotemporally controllable manner of drug release. Upon irradiation, the in situ generation of •OH induces the oxidation of polyphenylene sulfide from being hydrophobic to hydrophilic, resulting in the disintegration of the nanovesicles and the rapid release of the entrapped cisplatin and veliparib (the poly ADP-ribose polymerase (PARP) inhibitor). Cisplatin-induced DNA damage and the impairment of the DNA repair mechanism mediated by veliparib synergistically elicit potent pro-apoptotic effects. In vivo studies suggest that one-dose injection of the CV-Au NVs and one-time X-ray irradiation paradigm effectively inhibit tumor growth in the A549 lung cancer model. This study provides new insight into designing nanomedicine platforms in chemoradiation therapy from a vantage point of synergizing both chemotherapy and radiation therapy in a spatiotemporally concurrent manner.

First-in-human validation of enzymolysis clearance strategy for decreasing renal radioactivity using modified [68Ga]Ga-HER2 Affibody.

PURPOSE: Enzymolysis clearance strategy, characterized by releasing the non-reabsorbable radioactive fragment under the specific cleavage of enzymes, is confirmed to be a safe and effective way to reduce the renal radioactivity accumulation in mice. However, the effectiveness of this strategy in humans remains unknown. Human epidermal growth factor receptor 2 (HER2) is overexpressed in various types of tumors, and radiolabeled HER2 Affibody is believed to be an attractive tool for HER2-targeted theranostics. However, its wide application is limited by the high and persistent renal uptake. In this study, we intend to validate the effectiveness of enzymolysis clearance strategy in reducing renal accumulation by using a modified HER2 Affibody. MATERIALS AND METHODS: A new HER2 Affibody ligand, NOTA-MVK-ZHER2:2891, containing a cleavable Met-Val-Lys (MVK) linker was synthesized and labeled with 68Ga. The microPET imaging study was performed in SKOV-3 tumor mice to assess the uptakes of the control ligand and the MVK one in tumors and kidneys. Seven healthy volunteers were included for biodistribution and dosimetric studies with both the control and MVK ligands performed 1 week apart. Urine and blood samples from healthy volunteers were collected for in vivo metabolism study of the two ligands. Four HER2-positive and two HER2-negative patients were recruited for [68Ga]Ga-NOTA-MVK-ZHER2:2891 PET/CT imaging at 2 and 4 h post-injection (p.i.). RESULTS: [68Ga]Ga-NOTA-MVK-ZHER2:2891 was stable both in PBS and in mouse serum. MicroPET images showed that the tumor uptake of [68Ga]Ga-NOTA-MVK-ZHER2:2891 was comparable to that of [68Ga]Ga-NOTA-ZHER2:2891 at all the time points, while the kidney uptake was significantly reduced 40 min p.i. (P < 0.05). The biodistribution study in healthy volunteers showed that the kidney uptake of MVK ligand was significantly lower than that of the control ligand at 1 h p.i. (P < 0.05), with the SUVmean of 34.3 and 45.8, respectively, while the uptakes of the two ligands in the other organs showed negligible difference. The effective doses of the MVK ligand and the control one were 26.1 and 28.7 µSv/MBq, respectively. The enzymolysis fragment of [68Ga]Ga-NOTA-Met-OH was observed in the urine samples of healthy volunteers injected with the MVK ligand, indicating that the enzymolysis clearance strategy worked in humans. The PET/CT study of patients showed that the range of SUVmax of HER2-positive lesions was 9.4-21, while that of HER2-negative lesions was 2.7-6.2, which suggested that the MVK modification did not affect the ability of ZHER2:2891 structure to bind with HER2. CONCLUSION: We for the first time demonstrated that enzymolysis clearance strategy can effectively reduce renal radioactivity accumulation in humans. This strategy is expected to decrease renal radiation dose of peptide and small protein-based radiotracers, especially in the field of radionuclide therapy.

Effects of albumin and crystalloid priming strategies on red blood cell transfusions in on-pump cardiac surgery: a network meta-analysis.

BACKGROUND: In on-pump cardiac surgery, the albumin priming strategy could maintain colloid osmotic pressure better than crystalloid solutions and reduce excessive perioperative fluid balance. However, a high-quality meta-analysis is required to compare the safety of these approaches in perioperative red blood cell (RBC) transfusions. Owing to limited direct evidence, we conducted a network meta-analysis (NMA) to increase the pool of studies and provide indirect evidence. METHODS: The pre-defined primary outcomes were intraoperative and the first 24 h postoperative RBC transfusion volume in units. The pre-defined secondary outcome was postoperative blood loss (the first 24 h). We reviewed all randomized controlled trials comparing albumin, crystalloid, and artificial colloid priming strategies. Studies that only displayed pre-defined outcomes could be included. A pairwise meta-analysis was performed on studies that directly compared the pre-defined outcomes between albumin and crystalloids. Additionally, a random-effects network meta-analysis (NMA) model was employed to generate indirect evidence for the pre-defined outcomes between albumin and crystalloids. RESULTS: The literature search identified 830 studies,10 of which were included in the final analysis. Direct meta-analysis indicated that crystalloid priming significantly decreased total perioperative RBC transfusions (MD: -0.68U; 95%CI: -1.26, -0.09U; P = 0.02) and intraoperative RBC transfusions (MD: -0.20U; 95%CI: -0.39, -0.01U; P = 0.03) compared to albumin. Postoperative RBC transfusions showed a decreasing trend in the crystalloid group; however, the difference was not statistically significant. (MD: -0.16U; 95%CI: -0.45, 0.14U; P = 0.30). After including indirect evidence, the NMA results continued to demonstrate a higher RBC receiving with the albumin priming strategy compared to crystalloids, although the differences did not reach statistical significance. For postoperative blood loss, direct evidence showed no significant differences between albumin and crystalloid priming strategies. However, NMA evidence displayed that albumin exist higher probability of reducing postoperative blood loss than crystalloid. CONCLUSION: Both direct and NMA evidence indicated that the albumin priming strategy resulted in more perioperative RBC transfusions than crystalloids. Considering the additional blood management burden, the application of an albumin-priming strategy in on-pump cardiac surgery still needs more consideration.

Head-to-Head Comparison of 68Ga-PSMA-11 with 68Ga-P137 in Patients with Suspected Prostate Cancer.

P137 is a novel oxalyldiaminopropionic acid-urea-based prostate-specific membrane antigen (PSMA) targeting agent. This study compared the uptake patterns of 68Ga-P137 and the FDA-approved PET tracer 68Ga-PSMA-11 for diagnosing prostate cancer (PCa). Sixteen patients suspected of PCa were scanned by 68Ga-PSMA-11 and 68Ga-P137 PET/CT, respectively, followed by prospective analysis. The tumor-to-background ratio was calculated using normal prostate tissue, blood pool, muscle, and urine as backgrounds. Pathology or follow-up results were used to analyze uptake patterns of benign/malignant lesions and various organs. Thirteen patients were diagnosed with PCa and three with benign prostate diseases (BPD). The number and location of primary lesions, lymph node metastasis (LNM) (n = 25), bone metastasis (n = 30), and liver metastasis (n = 3) detected by the two tracers were identical. Maximum standardized uptake value (SUVmax), tumor/normal prostate ratio, as well as semiquantitative miPSMA-ES and PRIMARY diagnostic scores (P all >0.05) showed similar uptake levels of primary lesions between 68Ga-P137 and 68Ga-PSMA-11. Compared to 68Ga-P137, the SUVmax of 68Ga-PSMA-11 was significantly higher for bone metastasis, LNM, and liver metastasis (14.9 ± 7.2 vs 9.1 ± 4.4, 14.4 ± 5.0 vs 7.5 ± 2.4, 13.9 ± 2.0 vs 8.8 ± 2.4, P all <0.05). One-hour postinjection, SUVmax of the duodenum (9.4 ± 2.1 vs 16.2 ± 6.1), kidney (19.4 ± 4.3 vs 45.6 ± 20.9), and urine (14.1 ± 7.1 vs 42.1 ± 25.9) were significantly lower for 68Ga-P137 than for 68Ga-PSMA-11 (P all <0.05), whereas the radioactivity accumulation of blood pool and muscle (3.9 ± 0.5 vs 1.6 ± 0.4, 1.0 ± 0.1 vs 0.6 ± 0.1, P all <0.05) of 68Ga-P137 was significantly higher than 68Ga-PSMA-11. The uptake level of 68Ga-P137 has no significant difference from that of 68Ga-PSMA-11 in prostate primary lesions, and their imaging performances are visually equivalent for both primary and metastatic lesions, despite a higher blood pool and muscle background and a lower uptake in metastatic lesions. Due to the lower urine excretion of 68Ga-P137, primary prostate lesions near the urine can potentially be displayed clearer than 68Ga-PSMA-11.

First-in-Humans PET Imaging of KRASG12C Mutation Status in Non-Small Cell Lung and Colorectal Cancer Patients Using [18F]PFPMD.

Kirsten rat sarcoma (KRAS) mutations are an important marker for tumor-targeted therapy. In this study, we sought to develop a KRASG12C oncoprotein-targeted PET tracer and to evaluate its translational potential for noninvasive imaging of the KRASG12C mutation in non-small cell lung cancer (NSCLC) and colorectal cancer (CRC) patients. Methods: [18F]PFPMD was synthesized on the basis of AMG510 (sotorasib) by attaching a polyethylene glycol chain to the quinazolinone structure. The binding selectivity and imaging potential of [18F]PFPMD were verified by cellular uptake, internalization, and blocking (H358: KRASG12C mutation; A549: non-KRASG12C mutation) studies, as well as by a small-animal PET/CT imaging study on tumor-bearing mice. Five healthy volunteers were enrolled to assess the safety, biodistribution, and dosimetry of [18F]PFPMD. Subsequently, 14 NSCLC or CRC patients with or without the KRASG12C mutation underwent [18F]PFPMD and [18F]FDG PET/CT imaging. The SUVmax of tumor uptake of [18F]PFPMD was measured and compared between patients with and without the KRASG12C mutation. Results: [18F]PFPMD was obtained with a high radiochemical yield, radiochemical purity, and stability. The protein-binding assay showed that [18F]PFPMD selectively binds to the KRASG12C protein. [18F]PFPMD uptake was significantly higher in H358 than in A549 and was decreased by pretreatment with AMG510 (H358 vs. A549: 3.22% ± 0.28% vs. 2.50% ± 0.25%, P < 0.05; block: 2.06% ± 0.13%, P < 0.01). Similar results were observed in tumor-bearing mice on PET imaging (H358 vs. A549: 3.93% ± 0.24% vs. 2.47% ± 0.26% injected dose/g, P < 0.01; block: 2.89% ± 0.29% injected dose/g; P < 0.05). [18F]PFPMD was safe in humans and was excreted primarily by the gallbladder and intestines. The whole-body effective dose was comparable to that of [18F]FDG. The accumulation of [18F]PFPMD in KRASG12C mutation tumors was significantly higher than that in non-KRASG12C mutation tumors (SUVmax: 3.73 ± 0.58 vs. 2.39 ± 0.22, P < 0.01) in NSCLC and CRC patients. Conclusion: [18F]PFPMD is a safe and promising PET tracer for noninvasive screening of the KRASG12C mutation status in NSCLC and CRC patients.

68Ga-FAPI-04 PET for Surveillance of Anastomotic Recurrence in Postoperative Patients with Gastrointestinal Cancer: a Comparative Study with 18F-FDG PET.

PURPOSE: This study aims to compare the diagnostic efficacy of 68Ga-FAPI-04 PET and 18F-FDG PET for detecting anastomotic recurrence in postoperative patients with gastrointestinal cancer, and to characterize the signal pattern over time at surgical wounds on both PET imaging. METHODS: Gastrointestinal cancer patients who planned to 68Ga-FAPI-04 and 18F-FDG PET/CT imaging for postoperative surveillance were involved. The SUVmax at surgical wounds were assessed. Endoscopic pathology confirmed anastomotic recurrence or it was ruled out by imaging and clinical follow-up. The sensitivity, specificity, positive and negative predictive values (PPV and NPV), and accuracy of the two PET imaging in detecting anastomotic recurrence were compared. Relationships between tracer uptake at surgical wounds and postoperative time were also analyzed. RESULTS: Compared with non-recurrent patients, the recurrent patients exhibited a significantly higher anastomotic SUVmax on 68Ga-FAPI-04 PET (SUVmax: 9.92 ± 4.36 vs. 2.81 ± 1.86, P = 0.002). Sensitivity, specificity, PPV, NPV, and accuracy of detecting anastomotic recurrence were 100.0%, 87.3%, 41.7%, 100.0%, and 88.3% for 68Ga-FAPI-04 PET, and 60.0%, 81.8%, 23.1%, 95.7%, and 80.0% for 18F-FDG PET, respectively. Although 68Ga-FAPI-04 PET signal at surgical wounds showed a slight trend to decrease with time, no statistical difference was observed over months post-surgery (P > 0.05). CONCLUSIONS: Both tracers displayed high NPVs in identifying anastomotic recurrence with a higher sensitivity to 68Ga-FAPI-04. Tracer uptake at anastomotic sites does not decrease significantly over time, which results in low PPVs for both PET. Therefore, it is difficult to differentiate anastomotic recurrence from inflammation on either PET imaging.

PI-RADS-Based Segmented Threshold of PSMA-PET SUVmax Is Better than Traditional Fixed Threshold for Diagnosing Clinically Significant Prostate Cancer Especially for PI-RADS 3 Lesions.

OBJECTIVES: Our purpose was to compare the performance of prostate-specific membrane antigen (PSMA)-positron emission tomography (PET) traditional fixed threshold (FT) and newly established Prostate Imaging Reporting and Data System (PI-RADS)-based segmented threshold (ST) for diagnosing clinically significant prostate cancer (csPCa). METHODS: The study retrospectively included 218 patients who underwent multiparametric magnetic resonance imaging (mpMRI) and PSMA-PET examination for suspected prostate cancer (PCa) from January 2018 to November 2021. Lesions with Gleason score ≥ 3 + 4 were diagnosed as csPCa. In PSMA-PET maximum standardized uptake value (SUVmax), the FT for all the lesions and STs for lesions with different PI-RADS score for diagnosing csPCa were determined by receiver operating characteristic (ROC) curves analysis and compared with Z test. The McNemar test was used to compare sensitivity and specificity. RESULTS: Among the 218 patients, there were 113 csPCa and 105 non-csPCa. The PSMA-PET FT was SUVmax > 5.3 (area under the curve, AUC = 0.842) and STs for PI-RADS 3/4/5 were SUVmax > 4.2/5.7/6.0 (AUCs = 0.870/0.867/0.882), respectively. The AUC of PSMA-PET ST was higher than that of PSMA-PET FT (0.872 vs. 0.842), especially for PI-RADS 3 (0.870 vs. 0.653). Multimodality diagnostic criteria combining PSMA-PET ST and PI-RADS scores of mpMRI was established and its AUC was higher than that of PSMA-PET ST (0.893 vs. 0.872) and significantly higher than that of PSMA-PET FT (0.893 vs. 0.842) with an improvement in sensitivity (93% vs. 78%, p < 0.05) without significantly sacrificing specificity (86% vs. 91%, p > 0.05). CONCLUSIONS: For diagnosing csPCa, PI-RADS-based PSMA-PET segmented threshold achieved better performance than traditional fixed threshold, especially for PI-RADS 3 lesions. Multimodality diagnostic criteria demonstrated higher diagnostic performance than segmented threshold and significantly better than PSMA-PET fixed threshold for detecting csPCa.

Combined Probe Strategy to Increase the Enzymatic Digestion Rate and Accelerate the Renal Radioactivity Clearance of Peptide Radiotracers.

High and sustained renal radioactivity accumulation is a major challenge in peptide-based radionuclide imaging and therapy. However, neutral endopeptidase (NEP)-based enzymatic hydrolysis to release and excrete the radioactive fragments has been proven to be an effective and promising way to reduce renal accumulation. Despite the improvement, the effect is still far from being satisfactory. To further reduce kidney uptake, we studied the relationship between the enzymatic reaction rate and the substrate concentration and came up with a combined probe strategy. Model compounds Boc-MVK-Dde and Boc-MFK-Dde were used for an in vitro enzymatic digestion study. NOTA-Exendin 4 and NOTA-MVK-Exendin 4 were labeled with 64Cu for in vivo dose-dependent micro-positron emission tomography (PET) studies. Groups 1 and 2 were injected with 0.2 and 0.8 nmol of 64Cu-NOTA-Exendin 4, respectively. Groups 3-6 were injected with 0.2, 0.8, 1.0, and 1.4 nmol of 64Cu-NOTA-MVK-Exendin 4, respectively. Groups 7 and 8 were co-injected with 0.2 nmol of 64Cu-NOTA-MVK-Exendin 4 and NOTA-MVK-PEG5K (1.3 and 2.6 nmol). The radioactivity uptakes were determined and compared within and among the groups. The in vitro cleavage study for both Boc-MVK-Dde and Boc-MFK-Dde indicated that within a certain concentration range, the enzyme digestion rate increased with increasing substrate concentration. The microPET images showed that the renal clearance could be accelerated significantly by increasing the injection dose of 64Cu-NOTA-MVK-Exendin 4, with the kidney uptakes being 60.98, 43.01, and 16.10 % ID/g at 1 h for groups 3, 4 and 5, respectively. Unfortunately, the tumor uptakes were also significantly inhibited as the injected dose of the tracer increased. However, with the co-injection of NOTA-MVK-PEG5K, the renal accumulation was significantly decreased without hampering the tumor uptake. As a result, the tumor-to-kidney ratios were significantly improved, which were 1.93, 3.47, 1.74, and 3.38 times that of group 3 at 1, 4, 24, and 48 h, respectively. The enzymatic reaction rate of NEP is dependent on the concentration of the substrates both in vitro and in vivo. The combined probe strategy developed in this study can dramatically reduce the renal accumulation of a peptide radioligand without affecting the tumor uptake, which shows great potential in peptide-based radiotheranostics.

Unsymmetrical cyanine dye via in vivo hitchhiking endogenous albumin affords high-performance NIR-II/photoacoustic imaging and photothermal therapy.

Herein, an unprecedented synergistic strategy for the development of high-performance NIR-II fluorophore is proposed and validated. Based on an unsymmetrical cyanine dye design strategy, the NIR-II emissive dye NIC was successfully developed by replacing only one of the indoline donors of symmetrical cyanine dye ICG with a fully conjugated benz[c,d]indole donor. This minor structural change maximally maintains the high extinction coefficient advantage of cyanine dyes. NIC-ER with endogenous albumin-hitchhiking capability was constructed to further enhance its in vivo fluorescence brightness. In the presence of HSA (Human serum albumin), NIC-ER spontaneously resides in the albumin pocket, and a brilliant ~89-fold increase in fluorescence was observed. Due to its high molar absorptivity and moderate quantum yield, NIC-ER in HSA exhibits bright NIR-II emission with high photostability and significant Stokes shift (>110 nm). Moreover, NIC-ER was successfully employed for tumor-targeted NIR-II/PA imaging and efficient photothermal tumor elimination. Overall, our strategy may open up a new avenue for designing and constructing high-performance NIR-II fluorophores.

68Ga-Labeled GX1 Dimer: A Novel Probe for PET/Cerenkov Imaging Targeting Gastric Cancer.

PURPOSE: To synthesize the dimer of GX1 and identify whether its affinity and targeting are better than those of GX1. To prepare 68Ga-DOTA-KEK-(GX1)2 and to apply it to PET and Cerenkov imaging of gastric cancer. METHODS: 68Ga-DOTA-KEK-(GX1)2 was prepared, and the labeling yield and stability were determined. Its specificity and affinity were verified using an in vitro cell binding assay and competitive inhibition test, cell immunofluorescence, and cell uptake and efflux study. Its tumor-targeting ability was determined by nano PET/CT and Cerenkov imaging, standardized uptake value (SUV), signal-to-background ratio (SBR) quantification, and a biodistribution study in tumor-bearing nude mice. RESULTS: 68Ga-DOTA-KEK-(GX1)2 was successfully prepared, and the labeling yield was more than 97%. It existed stably for 90 min in serum. The binding of 68Ga-DOTA-KEK-(GX1)2 to cocultured HUVECs (Co-HUVECs) was higher than that to human umbilical vein endothelial cells (HUVECs), BGC823 cells, and GES cells. It was also higher than that of 68Ga-DOTA-GX1, indicating that the dimer did improve the specificity and affinity of GX1. The binding of KEK-(GX1)2 to Co-HUVECs was significantly higher than that of GX1. Additionally, the uptake of 68Ga-DOTA-KEK-(GX1)2 by Co-HUVECs was higher than that of 68Ga-DOTA-GX1 and reached a maximum at 60 min. Nano PET/CT and Cerenkov imaging showed that the tumor imaging of the nude mice injected with 68Ga-DOTA-KEK-(GX1)2 was clear, and the SUV and SBR value of the tumor sites were significantly higher than those of the nude mice injected with 68Ga-DOTA-GX1, indicating that the probe had better targeting in vivo. Finally, the biodistribution showed quantitatively that when organs such as the kidney and liver metabolized rapidly, the radioactivity of the tumor site of the nude mice injected with 68Ga-DOTA-KEK-(GX1)2 decreased relatively slowly. At the same time, the percentage of injected dose per gram (%ID/g) of the tumor site was higher than that of other normal organs except the liver and kidney at 60 min, which indicated that the tumor had good absorption of the probe. CONCLUSION: GX1 was modified successfully, and the in vivo and in vitro properties of the GX1 dimer were significantly better than those of GX1. The imaging probe, 68Ga-DOTA-KEK-(GX1)2, was successfully prepared, which provides a candidate probe for PET and Cerenkov diagnosis of gastric cancer.

Optimization of Enzymolysis Clearance Strategy To Enhance Renal Clearance of Radioligands.

The kidney is the main dose-limiting organ in radioligand therapy (RLT), and there is an urgent need for reducing renal radioactivity accumulation. According to the enzymolysis clearance strategy, the first objective of this study is to test whether enzymolysis efficiency can be improved by introducing a hydrophobic amino acid with a bulkier side chain to the second position of the cleavable sequence, and the second objective is to screen an optimal sequence to minimize the renal uptake. Four exendin 4 (Ex4) peptide analogues with different cleavable sequences were synthesized and labeled with 68Ga. Both in vitro and in vivo metabolism studies were performed using either the model compounds or the complete probes. The in vitro stabilities of the tracers were evaluated in PBS and mouse serum. The microPET images were acquired in the INS-1 tumor model at different time points, and the radioactivity uptakes of the probes in tumors and kidneys were determined and compared. All the probes were stable in both PBS and mouse serum for at least 1 h. The in vitro cleavage study for both model compounds and intact probes showed enzymolysis efficiency in the following order: MWK > MFK > MVK > MGK. The in vivo metabolism study confirmed that a fragment of 68Ga-NOTA-Met-OH appeared in both kidney and urine samples for all analogues with MVK, MFK, and MWK sequences. The microPET images showed that the tumor uptakes of all the modified probes were comparable to those of the control, while the kidney uptakes were significantly reduced by inserting the MWK, MFK, or MVK linker. The tumor-to-kidney ratios at 0.5, 1, and 2 h time points showed the following order: 68Ga-NOTA-MWK-Ex4 > 68Ga-NOTA-MFK-Ex4 > 68Ga-NOTA-MVK-Ex4. In this study, based on the enzymolysis clearance strategy and the preference of the enzyme, different sequences were designed and compared both in vitro and in vivo. The results indicated that the larger the steric hindrance of the second hydrophobic amino acid side chain, the more effective the enzymatic hydrolysis, with enzymolysis efficiency in the following order: MWK > MFK > MVK > MGK. MWK appears to be the most effective sequence in reducing renal radioactivity accumulation of exendin 4 peptide derivatives.

Development and Preclinical Evaluation of Radiolabeled Covalent G12C-Specific Inhibitors for Direct Imaging of the Oncogenic KRAS Mutant.

Although KRAS has been an important target for many cancers, direct inhibition of oncogenic RAS remains challenging. Until recently, covalent KRAS G12C-specific inhibitors have been developed and progressed to the clinics. Nevertheless, not all patients benefit from these covalent inhibitors. At present, identification of candidates for this treatment requires tissue biopsies and gene sequencing, which are invasive, time-consuming, and could be of insufficient quality and limited predictive value owing to tumor heterogeneity. The use of noninvasive molecular imaging techniques such as PET and SPECT for spying KRAS G12C mutation in tumors provide a promising strategy for circumventing these hurdles. In the present study, based on the covalent G12C-specific inhibitor ARS-1620, we sought to develop radiolabeled small molecules for direct imaging of the KRAS mutation status in tumors. [131I]I-ARS-1620 and [18F]F-ARS-1620 were successfully prepared with high radiochemical yield, radiochemical purity, and molar activity. In vitro and in vivo studies have demonstrated the affinity, specificity, and capacity of [131I]I-ARS-1620 for direct imaging of the oncogenic KRAS G12C mutant. This initial attempt allows us to directly screen the KRAS G12C mutant for the first time in vivo.

Biphasic synthesis of biodegradable urchin-like mesoporous organosilica nanoparticles for enhanced cellular internalization and precision cascaded therapy.

It is widely accepted that a small particle size and rough surface can enhance tumor tissue accumulation and tumor cellular uptake of nanoparticles, respectively. Herein, sub-50 nm urchin-inspired disulfide bond-bridged mesoporous organosilica nanoparticles (UMONs) featured with a spiky surface and glutathione (GSH)-responsive biodegradability were successfully synthesized by a facile one-pot biphasic synthesis strategy for enhanced cellular internalization and tumor accumulation. l-Arginine (LA) is encapsulated into the mesopores of UMONs, whose outer surface is capped with the gatekeeper of ultrasmall gold nanoparticles, i.e., UMONs-LA-Au. On the one hand, the mild acidity-activated uncapping of ultrasmall gold can realize a tumor microenvironment (TME)-responsive release of LA. On the other hand, the unique natural glucose oxidase (GOx)-mimicking catalytic activity of ultrasmall gold can catalyze the decomposition of intratumoral glucose to produce acidic hydrogen peroxide (H2O2) and gluconic acid. Remarkably, these products can not only further facilitate the release of LA, but also catalyze the LA-H2O2 reaction for an increased nitric oxide (NO) yield, which realizes synergistic catalysis-enhanced NO gas therapy for tumor eradication. The judiciously fabricated UMONs-LA-Au present a paradigm of TME-responsive nanoplatforms for both enhanced cellular uptake and tumor-specific precision cascaded therapy, which broadens the range of practical biomedical applications and holds a significant promise for the clinical translation of silica-based nanotheranostics.

188Re-labeled GX1 dimer as a novel dual-functional probe targeting TGM2 for imaging and antiangiogenic therapy of gastric cancer.

PURPOSE: The GX1 peptide (CGNSNPKSC) can specifically bind to TGM2 and possesses the ability to target the blood vessels of gastric cancer. This study intends to develop an integrated dual-functional probe with higher affinity, specificity and targeting and to characterize it in vivo and in vitro. METHODS: The dimer and tetramer of GX1 were prepared using cross-linked PEG and labeled with 99mTc. The best targeting probe [PEG-(GX1)2] was selected by gamma camera imaging in nude mouse models of gastric cancer. 188Re-PEG-(GX1)2 was prepared and characterized through cell binding analysis and competitive inhibition experiments, gamma camera imaging, MTT analysis and flow cytometry, BLI, immunohistochemistry, HE staining and biochemical analysis. RESULTS: PEG-(GX1)2 bound specifically to Co-HUVEC with higher affinity than GX1. 188Re-PEG-(GX1)2 had better ability to target gastric cancer in tumor-bearing nude mice and higher T/H ratios than 188Re-GX1. 188Re-PEG-(GX1)2 inhibited the growth of Co-HUVEC and induced apoptosis, and its effects were more robust than those of 188Re-GX1. BLI showed that 188Re-PEG-(GX1)2 inhibited tumor proliferation in vivo with a stronger effect than 188Re-GX1. Compared with 188Re-GX1, 188Re-PEG-(GX1)2 suppressed tumor angiogenesis and tumor cell proliferation and induced tumor cell apoptosis in vivo. The 188Re-PEG-(GX1)2 group did not cause visible changes in liver and kidney morphology and function in vivo. CONCLUSION: The dimer of GX1 was synthesized by using cross-linked PEG, and then 188Re-PEG-(GX1)2 was prepared. This radiopharmaceutical played both diagnostic and therapeutic functions, and gamma camera imaging could be utilized to detect the distribution of drugs in vivo during treatment. Through a series of experiments in vitro and in vivo, the feasibility of the drug was confirmed, and these results laid the foundation for the subsequent development and application of GX1.

Molecular engineering of a high quantum yield NIR-II molecular fluorophore with aggregation-induced emission (AIE) characteristics for in vivo imaging.

NIR-II biological imaging (1000-1700 nm) has shown promise for deep tissue penetration, high spatial resolution, and low background noise. Among all the NIR-II probes, organic probes particularly attract huge attention due to their excellent stability and biocompatibility, which have the most potential for clinical translation. However, most previously reported organic NIR-II fluorescent agents often suffer from low quantum yields in aqueous solution. Herein, we developed a novel D-π-A-π-D-type NIR II chromophore XA1 with AIE characteristics based on a new design strategy for NIR-II AIE fluorophores. Owing to their intrinsic aggregation-induced emission enhancement nature, the formulated XA1 NPs show a high fluorescence quantum yield up to 14.8%, which is higher than those of most previously reported organic NIR-II fluorophores. Based on the XA1 NPs, noninvasive imaging of limb and cerebral vessels is achieved with a high signal-to-background ratio and deep penetration. Furthermore, the XA1 NPs can be used as good contrast agents for high resolution imaging of blood vessels of tumors and precise detection of tumors based on the EPR mechanism. Collectively, our work demonstrated a novel strategy for designing and manufacturing NIR-II fluorophores with AIE characteristics and proved that XA1 NPs are highly promising NIR-II probes for biomedical imaging under physiological and pathological conditions.

Smart Nanovesicle-Mediated Immunogenic Cell Death through Tumor Microenvironment Modulation for Effective Photodynamic Immunotherapy.

Combination therapy that could better balance immune activation and suppressive signals holds great potential in cancer immunotherapy. Herein, we serendipitously found that the pH-responsive nanovesicles (pRNVs) self-assembled from block copolymer polyethylene glycol-b-cationic polypeptide can not only serve as a nanocarrier but also cause immunogenic cell death (ICD) through preapoptotic exposure of calreticulin. After coencapsulation of a photosensitizer, 2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-a (HPPH) and an indoleamine 2,3-dioxygenase inhibitor, indoximod (IND), pRNVs/HPPH/IND at a single low dose elicited significant antitumor efficacy and abscopal effect following laser irradiation in a B16F10 melanoma tumor model. Treatment efficacy attributes to three key factors: (i) singlet oxygen generation by HPPH-mediated photodynamic therapy (PDT); (ii) increased dendritic cell (DC) recruitment and immune response provocation after ICD induced by pRNVs and PDT; and (iii) tumor microenvironment modulation by IND via enhancing P-S6K phosphorylation for CD8+ T cell development. This study exploited the nanocarrier to induce ICD for the host's immunity activation. The "all-in-one" smart nanovesicles allow the design of multifunctional materials to strengthen cancer immunotherapy efficacy.

Tumor Microenvironment-Activated Ultrasensitive Nanoprobes for Specific Detection of Intratumoral Glutathione by Ratiometric Photoacoustic Imaging.

Glutathione (GSH), one of the most significant reducing species in vivo, plays important roles in a variety of diseases and cellular functions. Precise quantification of GSH via advanced noninvasive photoacoustic imaging (PAI) is of vital significance for the early diagnosis and prompt treatment of GSH-related deep-seated diseases, which stresses the need for custom-design of GSH-sensitive PAI probes with changeable near-infrared spectroscopy (NIR) absorption. In this work, a novel intelligent tumor microenvironment-activated ratiometric PAI nanoprobe is first developed with the intention of specific ultrasensitive detection of intratumoral GSH by overcoming the limitations of previously reported fluorescent or PA imaging sensors. This special ratiometric PAI nanoprobe (CR-POM) is synthesized through the self-assembly of croconaine (CR) dye and molybdenum-based polyoxometalate (POM) clusters with opposite NIR absorbance change in response to GSH. The resulting amplified ratiometric absorbance (Ab866/Ab700), the relatively low limit of detection value (0.51 mM), and the unique acidity-activated self-aggregation contribute to the prolonged intratumoral retention and enhanced tumor accumulation of CR-POM for accurate quantification of intratumoral GSH (0.5-10 mM). Featuring the additional merit of 64Cu radiolabeling for whole-body positron-emission tomography imaging, the smartly designed CR-POM nanoprobe will open new horizons for real-time noninvasive monitoring of biodistribution and simultaneous accurate quantification of GSH levels, especially in tumor and other GSH-related pathophysiological processes.

In situ polymerization on nanoscale metal-organic frameworks for enhanced physiological stability and stimulus-responsive intracellular drug delivery.

Metal-organic framework (MOF) nanoparticles have shown great potential as carrier platforms in theranostic applications. However, their poor physiological stability in phosphate-based media has limited their biological applications. Here, we studied the dissociation of MOF nanoparticles under physiological conditions, both in vitro and in vivo, and developed an in situ polymerization strategy on MOF nanoparticles for enhanced stability under physiological conditions and stimulus-responsive intracellular drug release. With polymer wrapped on the surface serving as a shield, the nanoscale MOFs were protected from decomposition by phosphate ions or acid and prevented the loaded cargos from leaking. An in vivo positron emission tomography (PET) study of 64Cu-labelled porphyrinic MOF indicated prolonged circulation time of the in situ polymerized MOF nanoparticles and greater tumor accumulation than unmodified MOF nanoparticles. With enhanced stability, cargos loaded into MOF nanoparticles or prodrugs conjugated on the surface can be efficiently delivered and released upon stimulus-responsive cleavage.

Improving the Theranostic Potential of Exendin 4 by Reducing the Renal Radioactivity through Brush Border Membrane Enzyme-Mediated Degradation.

As highly expressed in insulinomas, the glucagon-like peptide-1 receptor (GLP-1R) is believed to be an attractive target for diagnosis, localization, and treatment with radiolabeled exendin 4. However, the high and persistent radioactivity accumulation of exendin 4 in the kidneys limits accurate diagnosis and safe, as well as effective, radiotherapy in insulinomas. In this study, we intend to reduce the renal accumulation of radiolabeled exendin 4 through degradation mediated by brush border membrane enzymes. A new exendin 4 ligand NOTA-MVK-Cys40-Leu14-Exendin 4 containing Met-Val-Lys (MVK) linker between the peptide and 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) chelator was synthesized and labeled with 68Ga. The in vitro mouse serum stability and cell binding affinity of the tracer were evaluated. Initial in vitro cleavage of the linker was determined by incubation of a model compound Boc-MVK-Dde with brush border membrane vesicles (BBMVs) with and without the inhibitor of neutral endopeptidase (NEP). Further cleavage studies were performed with the full structure of NOTA-MVK-Cys40-Leu14-Exendin 4. Kidney and urine samples were collected in the in vivo metabolism study after intravenous injection of 68Ga-NOTA-MVK-Cys40-Leu14-Exendin 4. The microPET images were acquired in INS-1 tumor model at different time points; the radioactivity uptake of 68Ga-NOTA-MVK-Cys40-Leu14-Exendin 4 in tumor and kidneys were determined and compared with the control radiotracer without MVK linker. 68Ga-NOTA-MVK-Cys40-Leu14-Exendin 4 was stable in mouse serum. The MVK modification did not affect the affinity of NOTA-MVK-Cys40-Leu14-Exendin 4 toward GLP-1R. The in vitro cleavage study and in vivo metabolism study confirmed that the MVK sequence can be recognized by BBM enzymes and cleaved at the amide bond between Met and Val, thus releasing the small fragment containing Met. MicroPET images showed that the tumor uptake of 68Ga-NOTA-MVK-Cys40-Leu14-Exendin 4 was comparable to that of the control, while the kidney uptake was significantly reduced. As a result, more favorable tumor to kidney ratios were achieved. In this study, a novel exendin 4 analogue, NOTA-MVK-Cys40-Leu14-Exendin 4, was successfully synthesized and labeled with 68Ga. With the cleavable MVK sequence, this ligand could be cleaved by the enzymes on kidneys, and releasing the fragment of 68Ga-NOTA-Met-OH, which will rapidly excrete from urine. As the high and consistent renal radioactivity accumulation could be significantly reduced, NOTA-MVK-Cys40-Leu14-Exendin 4 shows great potential in the diagnosis and radiotherapy for insulinoma.

A Logic-Gated Modular Nanovesicle Enables Programmable Drug Release for On-Demand Chemotherapy.

It remains a major challenge to achieve precise on-demand drug release. Here, we developed a modular nanomedicine integrated with logic-gated system enabling programmable drug release for on-demand chemotherapy. Methods: We employed two different logical AND gates consisting of four interrelated moieties to construct the nanovesicles, denoted as v-A-CED2, containing oxidation-responsive nanovesicles (v), radical generators (A), and Edman linker conjugated prodrugs (CED2). The first AND logic gate is connected in parallel by mild hyperthermia ( I ) and acidic pH ( II ), which executes NIR laser triggered prodrug-to-drug transformation through Edman degradation. Meanwhile, the mild hyperthermia effect triggers alkyl radical generation ( III ) which contributes to internal oxidation and degradation of nanovesicles ( IV ). The second AND logic gate is therefore formed by the combination of I-IV to achieve programmable drug release by a single stimulus input NIR laser. The biodistribution of the nanovesicles was monitored by positron emission tomography (PET), photoacoustic, and fluorescence imaging. Results: The developed modular nanovesicles exhibited high tumor accumulation and effective anticancer effects both in vitro and in vivo. Conclusions: This study provides a novel paradigm of logic-gated programmable drug release system by a modular nanovesicle, which may shed light on innovation of anticancer agents and strategies.