International Society for Extracellular Vesicles and International Society for Cell and Gene Therapy statement on extracellular vesicles from mesenchymal stromal cells and other cells: considerations for potential therapeutic agents to suppress coronavirus disease-19.

STATEMENT: The International Society for Cellular and Gene Therapies (ISCT) and the International Society for Extracellular Vesicles (ISEV) recognize the potential of extracellular vesicles (EVs, including exosomes) from mesenchymal stromal cells (MSCs) and possibly other cell sources as treatments for COVID-19. Research and trials in this area are encouraged. However, ISEV and ISCT do not currently endorse the use of EVs or exosomes for any purpose in COVID-19, including but not limited to reducing cytokine storm, exerting regenerative effects or delivering drugs, pending the generation of appropriate manufacturing and quality control provisions, pre-clinical safety and efficacy data, rational clinical trial design and proper regulatory oversight.

Concise Review: Developing Best-Practice Models for the Therapeutic Use of Extracellular Vesicles.

Growing interest in extracellular vesicles (EVs, including exosomes and microvesicles) as therapeutic entities, particularly in stem cell-related approaches, has underlined the need for standardization and coordination of development efforts. Members of the International Society for Extracellular Vesicles and the Society for Clinical Research and Translation of Extracellular Vesicles Singapore convened a Workshop on this topic to discuss the opportunities and challenges associated with development of EV-based therapeutics at the preclinical and clinical levels. This review outlines topic-specific action items that, if addressed, will enhance the development of best-practice models for EV therapies. Stem Cells Translational Medicine 2017;6:1730-1739.

Clinical Development and Commercialization of Advanced Therapy Medicinal Products in the European Union: How Are the Product Pipeline and Regulatory Framework Evolving?

The research and development of advanced therapy medicinal products (ATMPs) has been active in Europe and worldwide during recent years. Yet, the number of licensed products remains low. The main expected legal change in the near future in the European Union (EU) concerns the regulation on clinical trials (536/2014), which will come into force in 2018. With this new framework, a more harmonized and swift process for approval of clinical trials is anticipated, which is expected to support the entry of new innovations into the EU market. A survey on ATMPs in clinical trials during 2010-2015 in the EU was conducted in order to study the trends of ATMP development since the earlier survey published in 2012. According to the results, the number of clinical trials using ATMPs is slowly increasing in the EU. Yet, the focus is still in early development, and the projects are mainly carried out by small and medium-sized enterprises, academia, and hospitals. Oncology is the main area of clinical development. Yet, the balance between cell-based products and gene therapy medicinal products in this area may be changing in the future due to the new T-cell technologies. Many limitations and challenges are identified for ATMP development, requiring proportionate regulatory requirements. On the other hand, for such a novel field, the developers should be active in considering possible constraints and actively engage with authorities to look for solutions. This article provides up to-date information on forthcoming regulatory improvements and discusses the main challenges hampering the commercialization of ATMPs in the EU.

Manufacturing, characterization and control of cell-based medicinal products: challenging paradigms toward commercial use.

During the past decade, a large number of cell-based medicinal products have been tested in clinical trials for the treatment of various diseases and tissue defects. However, licensed products and those approaching marketing authorization are still few. One major area of challenge is the manufacturing and quality development of these complex products, for which significant manipulation of cells might be required. While the paradigms of quality, safety and efficacy must apply also to these innovative products, their demonstration may be demanding. Demonstration of comparability between production processes and batches may be difficult for cell-based medicinal products. Thus, the development should be built around a well-controlled manufacturing process and a qualified product to guarantee reproducible data from nonclinical and clinical studies.

Applying extracellular vesicles based therapeutics in clinical trials - an ISEV position paper.

Extracellular vesicles (EVs), such as exosomes and microvesicles, are released by different cell types and participate in physiological and pathophysiological processes. EVs mediate intercellular communication as cell-derived extracellular signalling organelles that transmit specific information from their cell of origin to their target cells. As a result of these properties, EVs of defined cell types may serve as novel tools for various therapeutic approaches, including (a) anti-tumour therapy, (b) pathogen vaccination, (c) immune-modulatory and regenerative therapies and (d) drug delivery. The translation of EVs into clinical therapies requires the categorization of EV-based therapeutics in compliance with existing regulatory frameworks. As the classification defines subsequent requirements for manufacturing, quality control and clinical investigation, it is of major importance to define whether EVs are considered the active drug components or primarily serve as drug delivery vehicles. For an effective and particularly safe translation of EV-based therapies into clinical practice, a high level of cooperation between researchers, clinicians and competent authorities is essential. In this position statement, basic and clinical scientists, as members of the International Society for Extracellular Vesicles (ISEV) and of the European Cooperation in Science and Technology (COST) program of the European Union, namely European Network on Microvesicles and Exosomes in Health and Disease (ME-HaD), summarize recent developments and the current knowledge of EV-based therapies. Aspects of safety and regulatory requirements that must be considered for pharmaceutical manufacturing and clinical application are highlighted. Production and quality control processes are discussed. Strategies to promote the therapeutic application of EVs in future clinical studies are addressed.

Challenges with advanced therapy medicinal products and how to meet them.

Advanced therapy medicinal products (ATMPs), which include gene therapy medicinal products, somatic cell therapy medicinal products and tissue-engineered products, are at the cutting edge of innovation and offer a major hope for various diseases for which there are limited or no therapeutic options. They have therefore been subject to considerable interest and debate. Following the European regulation on ATMPs, a consolidated regulatory framework for these innovative medicines has recently been established. Central to this framework is the Committee for Advanced Therapies (CAT) at the European Medicines Agency (EMA), comprising a multidisciplinary scientific expert committee, representing all EU member states and European Free Trade Association countries, as well as patient and medical associations. In this article, the CAT discusses some of the typical issues raised by developers of ATMPs, and highlights the opportunities for such companies and research groups to approach the EMA and the CAT as a regulatory advisor during development.

Dual role of SLP-76 in mediating T cell receptor-induced activation of phospholipase C-gamma1.

Phospholipase C-gamma1 (PLC-gamma1) activation depends on a heterotrimeric complex of adaptor proteins composed of LAT, Gads, and SLP-76. Upon T cell receptor stimulation, a portion of PLC-gamma1 is recruited to a detergent-resistant membrane fraction known as the glycosphingolipid-enriched membrane microdomains (GEMs), or lipid rafts, to which LAT is constitutively localized. In addition to LAT, PLC-gamma1 GEM recruitment depended on SLP-76, and, in particular, required the Gads-binding domain of SLP-76. The N-terminal tyrosine phosphorylation sites and P-I region of SLP-76 were not required for PLC-gamma1 GEM recruitment, but were required for PLC-gamma1 phosphorylation at Tyr(783). Thus, GEM recruitment can be insufficient for full activation of PLC-gamma1 in the absence of a second SLP-76-mediated event. Indeed, a GEM-targeted derivative of PLC-gamma1 depended on SLP-76 for T cell receptor-induced phosphorylation at Tyr783 and subsequent NFAT activation. On a biochemical level, SLP-76 inducibly associated with both Vav and catalytically active ITK, which efficiently phosphorylated a PLC-gamma1 fragment at Tyr783 in vitro. Both associations were disrupted upon mutation of the N-terminal tyrosine phosphorylation sites of SLP-76. The P-I region deletion disrupted Vav association and reduced SLP-76-associated kinase activity. A smaller deletion within the P-I region, which does not impair PLC-gamma1 activation, did not impair the association with Vav, but reduced SLP-76-associated kinase activity. These results provide new insight into the multiple roles of SLP-76 and the functional importance of its interactions with other signaling proteins.

Surface expression of Fc epsilon RI on Langerhans' cells of clinically uninvolved skin is associated with disease activity in atopic dermatitis, allergic asthma, and rhinitis.

BACKGROUND: Fc epsilon RI expressed on the surface of human epidermal Langerhans' cells facilitates uptake of IgE-associated allergens and plays a pivotal role in the pathogenesis of atopic dermatitis. Seminal results from studies investigating Langerhans' cell Fc epsilon RI in skin biopsy sections or epidermal cell suspensions demonstrate the highest receptor expression in lesional skin of patients with active atopic dermatitis. OBJECTIVE: We sought to investigate and localize Fc epsilon RI expression on Langerhans' cells within a minimally disturbed tissue environment in clinically uninvolved skin and to compare receptor expression between healthy donors and patients with atopic dermatitis or other allergic diseases. METHODS: Intact epidermal sheets from skin suction blisters, immunofluorescently stained with Langerhans' cell markers and anti-Fc epsilon RI alpha (mAbs 15E5 and 22E7) or anti-IgE, were examined by means of confocal microscopy. Samples incubated with anti-Fc epsilon RI alpha before or after cell fixation-permeabilization were compared to discriminate between cytoplasmic and membrane localization. RESULTS: Cytoplasmic Fc epsilon RI alpha chain was found in Langerhans' cells from all donors, irrespective of atopic status. Surface Fc epsilon RI-bound IgE was detected in the skin of individuals with active atopic dermatitis and in the skin of those with active asthma or rhinitis. No surface Fc epsilon RI was expressed in the skin of patients with a clinical history of atopic dermatitis, asthma, or rhinitis whose disease was in remission or in the skin of nonatopic individuals. CONCLUSION: In clinically uninvolved skin, Langerhans' cell-surface Fc epsilon RI expression is not only linked to atopic dermatitis but is also generally associated with allergic disease. This supports the concept of a systemic regulatory mechanism associated with active allergic disease, which is further aggravated by local inflammation in atopic skin lesions.

Investigation of early events in Fc epsilon RI-mediated signaling using a detailed mathematical model.

Aggregation of Fc epsilon RI on mast cells and basophils leads to autophosphorylation and increased activity of the cytosolic protein tyrosine kinase Syk. We investigated the roles of the Src kinase Lyn, the immunoreceptor tyrosine-based activation motifs (ITAMs) on the beta and gamma subunits of Fc epsilon RI, and Syk itself in the activation of Syk. Our approach was to build a detailed mathematical model of reactions involving Fc epsilon RI, Lyn, Syk, and a bivalent ligand that aggregates Fc(epsilon)RI. We applied the model to experiments in which covalently cross-linked IgE dimers stimulate rat basophilic leukemia cells. The model makes it possible to test the consistency of mechanistic assumptions with data that alone provide limited mechanistic insight. For example, the model helps sort out mechanisms that jointly control dephosphorylation of receptor subunits. In addition, interpreted in the context of the model, experimentally observed differences between the beta- and gamma-chains with respect to levels of phosphorylation and rates of dephosphorylation indicate that most cellular Syk, but only a small fraction of Lyn, is available to interact with receptors. We also show that although the beta ITAM acts to amplify signaling in experimental systems where its role has been investigated, there are conditions under which the beta ITAM will act as an inhibitor.