In vivo tracking of [89Zr]Zr-labeled engineered extracellular vesicles by PET reveals organ-specific biodistribution based upon the route of administration.

Extracellular vesicles (EVs) have garnered increasing interest as delivery vehicles for multiple classes of therapeutics based on their role as mediators in an important, natural intercellular communication system. We recently described a platform to allow the design, production and in vivo study of human EVs with specific properties (drug or tropism modifiers). This article seeks to compare and expand upon historical biodistribution and kinetic data by comparing systemically and compartmentally administered labeled engineered EVs using in vivo and ex vivo techniques. METHODS: EVs were surface-labeled to high radiochemical purity and specific activity with 89Zirconium deferoxamine ([89Zr]Zr-DFO) and/or cy7-scrambled antisense oligonucleotide (Cy7-ExoASOscr), or luminally loaded with GFP for in vivo tracking in rodents and non-human primates (NHPs). Positron Emission Tomography (PET) and subsequent immunohistochemistry (IHC) and autoradiography (ARG) cross-validation enabled assessment of the anatomical and cellular distribution of labeled EVs both spatially and temporally. RESULTS: Over time, systemic administration of engineered EVs distributed preferentially to the liver and spleen (Intravenous, IV), gastrointestinal tract and lymph nodes (Intraperitoneal, IP) and local/regional lymph nodes (Subcutaneous, SC). Immunostaining of dissected organs displaying PET signal revealed co-localization of an EV marker (PTGFRN) with a subset of macrophage markers (CD206, F4/80, IBA1). Compartmental dosing into NHP cerebrospinal fluid (CSF) resulted in a heterogenous distribution of labeled EVs depending upon whether the route was intrathecal (ITH), intracisterna magna (ICM) or intracerebroventricular (ICV), compared to the homogeneous distribution observed in rodents. Thus anatomically, ITH administration in NHP revealed meningeal distribution along the neuraxis to the base of the skull. In contrast ICM and ICV dosing resulted in meningeal distribution around the skull and to the cervical and thoracic spinal column. Further characterization using IHC shows uptake in a subset of meningeal macrophages. CONCLUSIONS: The present studies provide a comprehensive assessment of the fate of robustly and reproducibly labeled engineered EVs across several mammalian species. The in vivo distribution was observed to be both spatially and temporally dependent upon the route of administration providing insight into potential targeting opportunities for engineered EVs carrying a therapeutic payload.

Computed Tomographic Characterization of Traumastem-A New Oxidized Cellulose Hemostatic Agent.

Oxidized regenerated cellulose (ORC) is a commonly used surgical hemostatic agent. When retained at the surgical site, it is frequently misdiagnosed on postoperative computed tomography (CT) images as an abscess or a recurrent tumor. Oxidized nonregenerated cellulose (ONC) is a new, more effective version of ORC. It is more effective because of its unorganized fiber structure and greater material density, which may also alter its appearance on CT images relative to ORC. This image report compares the CT characteristics of ONC and ORC. A rabbit's bilateral femoral arteries were punctured to model peripheral vascular surgery. ORC was used to treat 1 of the femoral artery punctures and ONC to treat the contralateral puncture. Noncontrast CT imaging was performed immediately following surgery (day 0) and on postoperative day 14. On day 0, both ORC and ONC were isoattenuating relative to muscle and hyperattenuating to fat, although ONC appears more homogenous. On day 14, neither ORC nor ONC was clearly identifiable. Thus, postoperative retention of ONC can obscure immediate postoperative CT interpretation and, similar to ORC, lead to an erroneous diagnosis of an abscess. By day 14, ONC retention may not obscure CT interpretation. In noncontrast CT imaging, ONC appears more homogeneous than ORC, but is otherwise indistinguishable. The greater homogeneity of ONC may be caused by the unorganized fiber structure or greater material density. Intraoperative use of ONC should be clinically investigated before radiographically diagnosing a postoperative abscess or recurrent tumor.

Durable pharmacological responses from the peptide ShK-186, a specific Kv1.3 channel inhibitor that suppresses T cell mediators of autoimmune disease.

The Kv1.3 channel is a recognized target for pharmaceutical development to treat autoimmune diseases and organ rejection. ShK-186, a specific peptide inhibitor of Kv1.3, has shown promise in animal models of multiple sclerosis and rheumatoid arthritis. Here, we describe the pharmacokinetic-pharmacodynamic relationship for ShK-186 in rats and monkeys. The pharmacokinetic profile of ShK-186 was evaluated with a validated high-performance liquid chromatography-tandem mass spectrometry method to measure the peptide's concentration in plasma. These results were compared with single-photon emission computed tomography/computed tomography data collected with an ¹¹¹In-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-conjugate of ShK-186 to assess whole-blood pharmacokinetic parameters as well as the peptide's absorption, distribution, and excretion. Analysis of these data support a model wherein ShK-186 is absorbed slowly from the injection site, resulting in blood concentrations above the Kv1.3 channel-blocking IC50 value for up to 7 days in monkeys. Pharmacodynamic studies on human peripheral blood mononuclear cells showed that brief exposure to ShK-186 resulted in sustained suppression of cytokine responses and may contribute to prolonged drug effects. In delayed-type hypersensitivity, chronic relapsing-remitting experimental autoimmune encephalomyelitis, and pristane-induced arthritis rat models, a single dose of ShK-186 every 2 to 5 days was as effective as daily administration. ShK-186's slow distribution from the injection site and its long residence time on the Kv1.3 channel contribute to the prolonged therapeutic effect of ShK-186 in animal models of autoimmune disease.