Quantitative evaluation of the improvement in the pharmacokinetics of a nucleic acid drug delivery system by dynamic PET imaging with (18)F-incorporated oligodeoxynucleotides

Ultrasound technology assisted colloidal nanocrystal synthesis and biomedical applications

Non-invasive and high spatiotemporal resolution mythologies for the diagnosis and treatment of disease in clinical medicine promote the development of modern medicine. Ultrasound (US) technology provides a non-invasive, real-time, and cost-effective clinical imaging modality, which plays a significant role in chemical synthesis and clinical translation, especially in in vivo imaging and cancer therapy. On the one hand, the US treatment is usually accompanied by cavitation, leading to high temperature and pressure, so-called "hot spot", playing a significant role in sonochemical-based colloidal synthesis. Compared with the classical nucleation synthetic method, the sonochemical synthesis strategy presents high efficiency for the fabrication of colloidal nanocrystals due to its fast nucleation and growth procedure. On the other hand, the US is attractive for in vivo and medical treatment, with applications increasing with the development of novel contrast agents, such as the micro and nano bubbles, which are widely used in neuromodulation, with which the US can breach the blood-brain barrier temporarily and safely, opening a new door to neuromodulation and therapy. In terms of cancer treatment, sonodynamic therapy and US-assisted synergetic therapy show great effects against cancer and sonodynamic immunotherapy present unparalleled potentiality compared with other synergetic therapies. Further development of ultrasound technology can revolutionize both chemical synthesis and clinical translation by improving efficiency, precision, and accessibility while reducing environmental impact and enhancing patient care. In this paper, we review the US-assisted sonochemical synthesis and biological applications, to promote the next generation US technology-assisted applications.

64Cu-labeling of small extracellular vesicle surfaces via a cross-bridged macrocyclic chelator for pharmacokinetic study by positron emission tomography imaging

We developed a method of labeling the surfaces of small extracellular vesicles (sEVs) with ⁶⁴Cu using a cross-bridged, macrocyclic chelator (CB-TE1A1P) and applied to pharmacokinetics study with positron emission tomography (PET). After incubation in 20% plasma for 10 min, approximately a half of the ⁶⁴Cu was desorbed from ⁶⁴Cu-labeled sEVs purified by phosphate-buffered saline wash, suggesting partly weak interaction without coordinating to CB-TE1A1P. After subsequent purification with albumin, ⁶⁴Cu desorption was greatly reduced, resulting in a radiochemical stability of 95.7%. Notably, labeling did not alter the physicochemical and biological properties of sEVs. After intravenous injection, ⁶⁴Cu-labeled sEVs rapidly disappeared from the systemic blood circulation and accumulated mainly in the liver and spleen of macrophage-competent mice. In macrophage-depleted mice, ⁶⁴Cu-labeled sEVs remained in the blood circulation for a longer period and gradually accumulated in the liver and spleen, suggesting mechanisms of hepatic and splenic accumulation other than macrophage-dependent phagocytosis. The comparison of tissue uptake clearance between macrophage-competent and macrophage-depleted mice suggests that macrophages contributed to 67% and 76% of sEV uptake in the liver and spleen, respectively. The application of this method in pharmacokinetics PET studies can be useful in preclinical and clinical research and the development of sEV treatment modalities.

Recent advances in lipid nanoparticles for delivery of nucleic acid, mRNA, and gene editing-based therapeutics

Lipid nanoparticles (LNPs) are becoming popular as a means of delivering therapeutics, including those based on nucleic acids and mRNA. The mRNA-based coronavirus disease 2019 vaccines are perfect examples to highlight the role played by drug delivery systems in advancing human health. The fundamentals of LNPs for the delivery of nucleic acid- and mRNA-based therapeutics, are well established. Thus, future research on LNPs will focus on addressing the following: expanding the scope of drug delivery to different constituents of the human body, expanding the number of diseases that can be targeted, and studying the change in the pharmacokinetics of LNPs under physiological and pathological conditions. This review article provides an overview of recent advances aimed at expanding the application of LNPs, focusing on the pharmacokinetics and advantages of LNPs. In addition, analytical techniques, library construction and screening, rational design, active targeting, and applicability to gene editing therapy have also been discussed.

Pharmacokinetic-pharmacodynamic modeling for hepatic delivery and efficacy of antisense oligonucleotides with lipophilic ligands in mice

Conjugation with lipophilic ligands such as cholesterol and α-tocopherol dramatically improves the delivery and efficacy of antisense oligonucleotides (ASOs) in the liver. To estimate the hepatic ASO concentration and the efficacy of ASOs conjugated with lipophilic ligands in mice, we constructed a pharmacokinetic-pharmacodynamic (PK-PD) model that consisted of a two-linear compartment model for the plasma and the hepatic ASO concentration, and two indirect response models for the hepatic apolipoprotein B (Apo-B) mRNA and plasma total cholesterol. The model provided a good fit of the hepatic ASO concentration although it showed an overprediction of Apo-B mRNA and an underprediction of the plasma total cholesterol within 2-fold at a later time after single intravenous administration of ASOs conjugated with lipophilic ligands. In addition, the model simulations indicated that the efficacy at a dose regimen of ASOs conjugated with lipophilic ligands (0.2 mg/kg, once a week) in mice was comparable to that at an effective dose of unchanged ASO (2.5 mg/kg, once a week). Although further studies are required to refine the parameters of the PK-PD model, this approach could be used to guide dose-ranging pharmacological studies for ASOs conjugated with lipophilic ligands in mice.

Recent Strategies for Targeted Brain Drug Delivery

Because the brain is the most important human organ, many brain disorders can cause severe symptoms. For example, glioma, one type of brain tumor, is progressive and lethal, while neurodegenerative diseases cause severe disability. Nevertheless, medical treatment for brain diseases remains unsatisfactory, and therefore innovative therapies are desired. However, the development of therapies to treat some cerebral diseases is difficult because the blood-brain barrier (BBB) or blood-brain tumor barrier prevents drugs from entering the brain. Hence, drug delivery system (DDS) strategies are required to deliver therapeutic agents to the brain. Recently, brain-targeted DDS have been developed, which increases the quality of therapy for cerebral disorders. This review gives an overview of recent brain-targeting DDS strategies. First, it describes strategies to cross the BBB. This includes BBB-crossing ligand modification or temporal BBB permeabilization. Strategies to avoid the BBB using local administration are also summarized. Intrabrain drug distribution is a crucial factor that directly determines the therapeutic effect, and thus it is important to evaluate drug distribution using optimal methods. We introduce some methods for evaluating drug distribution in the brain. Finally, applications of brain-targeted DDS for the treatment of brain tumors, Alzheimer's disease, Parkinson's disease, and stroke are explained.

Biosorption-based 64Cu-labeling of bacteria for pharmacokinetic positron-emission tomography

Biosorption-based bacterial ⁶⁴Cu-labeling and its application in pharmacokinetic positron-emission tomography (PET) were investigated. Both gram-positive and gram-negative bacteria were efficiently labeled with [⁶⁴Cu]Cu²⁺ ion in saline at room temperature within 5 min. The labeling ratio for Escherichia coli drastically decreased with trypsin pretreatment and the co-presence of excess Cu²⁺ ion, indicating the existence of specific Cu²⁺ binding sites on the E. coli cell surface. Washing with lysogeny broth medium was effective in purifying ⁶⁴Cu-labeled E. coli for kinetic study; the labeling stability was approximately 90% in serum for 15 min. According to dynamic PET imaging in colon-26 tumor-bearing mice, ⁶⁴Cu-labeled E. coli immediately disappeared from the blood circulation and primarily accumulated in the liver. In addition, transient pulmonary distribution was observed, being in a dose-dependently accelerated manner. Considering the simplicity and versatility of biosorption-based bacterial ⁶⁴Cu-labeling without genetic modification, the early-phase pharmacokinetic PET with ⁶⁴Cu-labeled bacteria is promising for assessing toxicological aspects of bacteria-mediated cancer therapy as well as a variety of bacterial pathogenicities in infectious diseases.

Review: PET imaging with macro- and middle-sized molecular probes

Recent progress in radiolabeling of macro- and middle-sized molecular probes has been extending possibilities to use PET molecular imaging for dynamic application to drug development and therapeutic evaluation. Theranostics concept also accelerated the use of macro- and middle-sized molecular probes for sharpening the contrast of proper target recognition even the cellular types/subtypes and proper selection of the patients who should be treated by the same molecules recognition. Here, brief summary of the present status of immuno-PET, and then further development of advanced technologies related to immuno-PET, peptidic PET probes, and nucleic acids PET probes are described.

Pharmacokinetic evaluation of liposomal nanoparticle-encapsulated nucleic acid drug: A combined study of dynamic PET imaging and LC/MS/MS analysis

In vivo biodistribution analyses, especially in tumors, of nucleic acids delivered with nanoparticles are important to develop drug delivery technologies for medical use. We previously developed wrapsome® (WS), an ~100 nm liposomal nanoparticle that can encapsulate siRNA, and reported that WS accumulates in tumors in vivo and inhibits their growth by an enhanced permeability and retention effect. In the present study, we evaluated the pharmacokinetics of nucleic acid-containing nanoparticles by combining dynamic positron emission tomography (PET) imaging and liquid chromatography-tandem mass spectrometry (LC/MS/MS) analysis. An 18-mer phosphorothioate oligodeoxynucleotide (ODN), trabedersen, was used as a model drug and was encapsulated in WS. Dynamic PET imaging and time-activity curve analysis of WS-encapsulated ⁶⁴Cu-labeled ODNs administered to mice with MIA PaCa-2 subcutaneous xenograft tumors showed tumor accumulation (~3% injected dose per gram (%ID/g)) and liver accumulation (~30 %ID/g) at 24 h. Under these conditions, LC/MS/MS analysis showed that the level of intact ODNs was 1.62 %ID/g in the tumor and 1.70 %ID/g in the liver. From these pharmacokinetic data, the intact/accumulated ODN ratios were calculated using the following equation: intact/accumulated ODN ratio (%) = %ID/g _{LC/MS/MS, tissue, mean}/%ID/g _{PET, tissue, mean} × 100. Interestingly, the ratios for the tumor and kidney were maintained at 20-50% over 48 h after administration of the WS-encapsulated form. In contrast, the ratio for the liver rapidly decreased at 24 h, showing the same pattern as that for naked ODN. These different patterns indicate that WS effectively protected the ODN in the tumor and kidney, but protected it less efficiently in the liver. A combined approach of dynamic PET imaging and LC/MS/MS analysis will assist the development of nanoparticle-encapsulated nucleic acid drugs, such as those using WSs, to determine their detailed pharmacokinetics.

Drug delivery system of therapeutic oligonucleotides

Therapeutic oligonucleotides are promising technologies. Nevertheless, improvement of their efficacy is an important issue. Introducing this drug delivery system (DDS) makes for a great enhancement for delivery of oligonucleotides to targeted tissue or cells. The strategy of DDS for therapeutic oligonucleotides is divided into four categories, A) single piece of oligonucleotide, B) oligonucleotide-ligand conjugate, C) oligonucleotide-polymer conjugate, and D) nanoparticle. In this review we will describe those basic concepts, especially for the technology of conjugating ligand. In addition, we developed a new technology, heteroduplex oligonucleotide (HDO), binding ligand-molecule to antisense oligonucleotide indirectly. We also outline α-tocopherol (a natural isomer of vitamin E) conjugated HDO.

Non-invasive and invasive imaging of vulnerable coronary plaque

Vulnerable plaque is characterized by a large necrotic core and an overlying thin fibrous cap. Non-invasive imaging modalities such as computed tomography angiography (CTA) and magnetic resonance imaging (MRI) allow for the assessment of morphological plaque characteristics, while positron emission tomography (PET) enables the detection of metabolic activity within the atherosclerotic lesions. Invasive imaging modalities such as intravascular ultrasound (IVUS), optical-coherence tomography (OCT), and intravascular MRI (IV-MRI) display plaques at a high spatial resolution. Near-infrared spectroscopy (NIRS) allows for the detection of chemical components of atherosclerotic plaques. In this review, we describe state-of-the-art non-invasive and invasive imaging modalities and stress the combination of their advantages to identify vulnerable plaque features.

Evaluation of the effects of chemically different linkers on hepatic accumulations, cell tropism and gene silencing ability of cholesterol-conjugated antisense oligonucleotides

Cholesterol conjugation of oligonucleotides is an attractive way to deliver the oligonucleotides specifically to the liver. However cholesterol-conjugated antisense oligonucleotides (ASOs) mainly accumulate in non-parenchymal cells (NPCs) such as Kupffer cells. In this study, to increase the hepatic accumulation of cholesterol-conjugated ASOs, we prepared a variety of linkers for cholesterol conjugation to anti-Pcsk9 ASOs and examined their effects on pharmacological parameters. Hepatic accumulation of ASO was dramatically increased with cholesterol conjugation. The increase in hepatic accumulation depended largely on the linker chemistry of each cholesterol-conjugated ASO. In addition to hepatic accumulation, the cell tropism of each cholesterol-conjugated ASO tended to depend on their linker. Although a linker bearing a disulfide bond accumulated mainly in NPCs, hexamethylene succinimide linker accumulated mainly in hepatocytes. To estimate the benefits of releasing ASO from the conjugated cholesterol in hepatocyte, we designed another linker based on hexamethylene succinimide, which has a phosphodiester bond between the linker and the ASO. The cholesterol-conjugated ASO bearing such a phosphodiester bond showed a significantly improved Pcsk9 mRNA inhibitory effect compared to its counterpart, cholesterol-conjugated ASO with a phosphorothioate bond, while the hepatic accumulation of both cholesterol-conjugated ASOs was comparable, indicating the effectiveness of removing the conjugated cholesterol for ASO activity. In toxicity analysis, some of the linkers induced lethal toxicities when they were injected at high concentrations (>600μM). These toxicities were attributed to decreased platelet levels in the blood, suggesting an interaction between cholesterol-conjugated ASO and platelets. Our findings may provide a guideline for the design of molecule-conjugated ASOs.

Gene therapy and imaging in preclinical and clinical oncology: recent developments in therapy and theranostics

In the case of disseminated cancer, current treatment options reach their limit. Gene theranostics emerge as an innovative route in the treatment and diagnosis of cancer and might pave the way towards development of an efficacious treatment of currently incurable cancer. Various gene vectors have been developed to realize tumor-specific nucleic acid delivery and are considered crucial for the successful application of cancer gene therapy. By adding reporter genes and imaging agents, these systems gain an additional diagnostic function, thereby advancing the theranostic paradigm into cancer gene therapy. Numerous preclinical studies have demonstrated the feasibility of combined tumor gene therapy and diagnostic imaging, and clinical trials in human and veterinary oncology have been executed with partly encouraging results.