Ralf Sanzenbacher

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.

Regulation of activation-induced cell death of mature T-lymphocyte populations

Abstract Resting mature T lymphocytes are activated when triggered via their antigen-specific T-cell receptor (TCR) to elicit an appropriate immune response. In contrast, preactivated T cells may undergo activation-induced cell death (AICD) in response to the same signals. Along with cell death induced by growth factor deprivation, AICD followed by the elimination of useless or potentially harmful cells preserves homeostasis, leads to the termination of cellular immune responses and ensures peripheral tolerance. T-cell apoptosis and AICD are controlled by survival cytokines such as interleukin-2 (IL-2) and by death factors such as tumor necrosis factor (TNF) and CD95 ligand (CD95L). In AICD-sensitive T cells, stimulation upregulates expression of one or several death factors, which in turn engage specific death receptors on the same or a neighboring cell. Death receptors are activated by oligomerization to rapidly assemble a number of adapter proteins and enzymes to result in an irreversible activation of proteases and nucleases that culminates in cell death by apoptosis. Increased knowledge of the molecular mechanisms that regulate AICD of lymphocytes opens new immunotherapeutic perspectives for the treatment of certain autoimmune diseases, and has implications in other areas such as transplantation medicine and AIDS research.

Standardization of Good Manufacturing Practice-compliant production of bone marrow-derived human mesenchymal stromal cells for immunotherapeutic applications.

BACKGROUND AIMS Human mesenchymal stem or stromal cells (MSCs) represent a potential resource not only for regenerative medicine but also for immunomodulatory cell therapies. The application of different MSC culture protocols has significantly hampered the comparability of experimental and clinical data from different laboratories and has posed a major obstacle for multicenter clinical trials. Manufacturing of cell products for clinical application in the European Community must be conducted in compliance with Good Manufacturing Practice and requires a manufacturing license. In Germany, the Paul-Ehrlich-Institut as the Federal Authority for Vaccines and Biomedicines is critically involved in the approval process. METHODS This report summarizes a consensus meeting between researchers, clinicians and regulatory experts on standard quality requirements for MSC production. RESULTS The strategy for quality control testing depends on the products cell composition, the manufacturing process and the indication and target patient population. Important quality criteria in this sense are, among others, the immunophenotype of the cells, composition of the culture medium and the risk for malignant transformation, as well as aging and the immunosuppressive potential of the manufactured MSCs. CONCLUSIONS This position paper intends to provide relevant information to interested parties regarding these criteria to foster the development of scientifically valid and harmonized quality standards and to support approval of MSC-based investigational medicinal products.

Identification of interaction partners of the cytosolic polyproline region of CD95 ligand (CD178) 1

The CD95/Fas/Apo‐1 ligand (CD95L, CD178) induces apoptosis through the death receptor CD95. CD95L was also described as a co‐stimulatory receptor for T‐cell activation in mice in vivo. The molecular basis for the bidirectional signaling capacity and directed expression of CD95L is unknown. In the present study we identify proteins that precipitate from T‐cell lysates with constructs containing fragments of the CD95L cytosolic tail. The determined peptide mass fingerprints correspond to Grb2, actin, β‐tubulin, formin binding protein 17 (FBP17) and PACSIN2. Grb2 had been identified as a putative mediator of T‐cell receptor‐to‐CD95L signaling before. FBP17 and PACSIN2 may be associated with expression and trafficking of CD95L. When overexpressed, CD95L co‐precipitates with FBP17 and PACSIN. Protein–protein interactions are mediated via Src homology 3 (SH3) domain binding to the polyproline region of CD95L and can be abolished by mutation or deletion of the respective SH3 domain.

Differential Regulation of Activation-Induced Cell Death in Individual Human T Cell Clones

Background: Restimulation of T lymphocytes via the TCR/CD3 complex can result in CD95/CD95L-dependent activation-induced cell death (AICD). Although the correlation of AICD sensitivity to the T helper 1 phenotype was confirmed in different studies, the underlying mechanism is still debated. Thus, it has been suggested that in Th2 cells, AICD resistance is controlled by a TCR-induced upregulation of the CD95-associated inhibitory phosphatase, FAP-1. We and others demonstrated that AICD resistance is associated with a reduced surface expression of CD95L upon restimulation. Methods: Utilizing RT-PCR, Western blotting and flow cytometry, we analyzed time-dependent changes in levels of CD95L mRNA, cytosolic protein and surface expression in five long-term human T cell clones and polarized helper populations. Results: We confirm that the inducible CD95L surface expression is lower or absent in all tested AICD-resistant clones as compared to sensitive cells. It is of interest that striking differences with respect to the activation-dependent inducibility of CD95L mRNA expression in individual resistant clones were observed. In addition, alterations in the expression of the inhibitory phosphatase FAP-1 or TCR-dependent changes in CD95 sensitivity in AICD-resistant clones could be ruled out as a mechanism for AICD resistance of human T cell clones. Conclusions: (1) The data presented strongly support the previous notion that AICD resistance of human T cell clones is mainly regulated by a differential expression of CD95L. (2) Differential expression of CD95L on individual resistant clones results from a lack of mRNA induction in one set and from a markedly decreased surface expression of translated protein in another set of clones.

Microbial safety of cell based medicinal products--what can we learn from cellular blood components?

Abstract Today, sterility of established parenteral drugs including biologicals, such as plasma derived products, is practically guaranteed. Bacterially contaminated products are extremely rare exceptions owing to the efficiency of the manufacturing processes in the pharmaceutical industry. In contrast, the manufacturing processes of cell based medicinal products or tissue preparations show much less defined conditions. The sterility of source materials cannot be guaranteed in many cases. As a rule, these source materials cannot be sterilised, as it holds true for the final products. Furthermore, the established methods for sterility testing are not applicable for cell preparations. Sterility of a restricted sample does not guarantee sterility of the whole preparation. Thus, small amounts of residual bacteria in the product can be overlooked and can grow up to enormous numbers during storage and shipping of cell based medicinal products. Considering these problems, there are some parallels in the warranty of microbial safety of cellular blood components. Therefore, the experiences collected in transfusion medicine in the past decade can be successfully used in the production of cell based medicinal products. Comparable to the situation regarding cellular blood components, there is a need for new principles in rapid bacteria detection. Clin Chem Lab Med 2008;46:963–5.

Accelerating Patients’ Access to Advanced Therapies in the EU

Pharmaceutical developers are continuously searching for potential drug development targets.1 The time frame to develop and bring a new drug to the market may take 15 years, on average, starting from concept to final marketing, and the cost is likely around a billion dollars. Although technological advances, such as high-throughput identification of agents, have expedited the process of finding new drug targets,2 and a steady increase in new therapy concepts can be noted, many malignancies, for instance, still cannot be efficiently tackled or cured.

Regulation of Clinical Trials with Advanced Therapy Medicinal Products in Germany

In the European Union, clinical trials for Advanced Therapy Medicinal Products are regulated at the national level, in contrast to the situation for a Marketing Authorisation Application, in which a centralised procedure is foreseen for these medicinal products. Although based on a common understanding regarding the regulatory requirement to be fulfilled before conduct of a clinical trial with an Advanced Therapy Investigational Medicinal Product, the procedures and partly the scientific requirements for approval of a clinical trial application differ between the European Union Member States. This chapter will thus give an overview about the path to be followed for a clinical trial application and the subsequent approval process for an Advanced Therapy Investigational Medicinal Product in Germany and will describe the role of the stakeholders that are involved. In addition, important aspects of manufacturing, quality control and non-clinical testing of Advanced Therapy Medicinal Products in the clinical development phase are discussed. Finally, current and future approaches for harmonisation of clinical trial authorisation between European Union Member States are summarised.

SIVagm containing the SHIV89.6P envelope gene replicates poorly and is non-pathogenic.

SIVagm does not induce disease in its African green monkey (AGM) host. In comparison, the hybrid simian-human immunodeficiency virus SHIV89.6P that carries the HIV env gene induces disease in rhesus macaques more rapidly than the SIVmac parent virus. To address the possibility that this enhancement of disease by HIV env would also occur when present in SIVagm, a full-length SIVagm/89.6Penv chimeric lentivirus genome (termed SHIV-MP) was constructed. SHIV-MP replicated similarly to SIVagm in simian peripheral blood mononuclear cells (PBMCs). In inoculated AGMs, rhesus macaques and pig-tailed (PT) macaques the absolute number of CD4(+) T lymphocytes remained at normal levels. The peak levels of productively infected cells in SHIV-MP-infected monkeys ranged from 10(1) to 10(2) per 10(6) PBMCs, while in SIVagm infected macaques the levels were 10-100-fold higher. The env gene of SHIV89.6P therefore appears insufficient to confer acute pathogenicity to a non-pathogenic primate lentivirus due to poor in vivo replication.

[Strategic considerations on the design and choice of animal models for non-clinical investigations of cell-based medicinal products].

For the development of medicinal products animal models are still indispensable to demonstrate efficacy and safety prior to first use in humans. Advanced therapy medicinal products (ATMP), which include cell-based medicinal products (CBMP), differ in their pharmacology and toxicology compared to conventional pharmaceuticals, and thus, require an adapted regime for non-clinical development. Developers are, therefore, challenged to develop particular individual concepts and to reconcile these with regulatory agencies. Guidelines issued by the European Medicines Agency (EMA), the U.S. Food and Drug Administration (FDA) and other sources can provide direction.The published approaches for non-clinical testing of efficacy document that homologous animal models where the therapeutic effect is investigated in a disease-relevant animal model utilizing cells derived from the same species are commonly used. The challenge is that the selected model should reflect the human disease in all critical features and that the cells should be comparable to the investigated human medicinal product in terms of quality and biological activity. This is not achievable in all cases. In these cases, alternative methods may provide supplemental information. To demonstrate the scientific proof-of-concept (PoC), small animal models such as mice or rats are preferred. During the subsequent product development phase, large animal models (i.e. sheep, minipigs, dogs) must be considered, as they may better reflect the anatomical or physiological situation in humans. In addition to efficacy, those models may also be suitable to prove some safety aspects of ATMP (e.g. regarding dose finding, local tolerance, or undesired interactions and effects of the administered cells in the target tissue). In contrast, for evaluation of the two prominent endpoints for characterizing the safety of ATMP (i.e. biodistribution, tumorigenicity) heterologous small animal models, especially immunodeficient mouse strains, are favourable due to their tolerance to the human cell therapy product. The execution of non-clinical studies under the principles of good laboratory practice (GLP) increases the acceptance of the results by authorities and the scientific community.