Mitigation of supply chain challenges in cell therapy manufacturing: perspectives from the cord blood alliance.

Cellular therapies rely on highly specialized supply chains that often depend on single source providers. Public cord blood banks (CBB) manufacturing the first cell therapy to be highly regulated by the FDA and related international agencies are a prime example of being subject to this phenomenon. In addition to banking unrelated donor cord blood units for transplantation, CBBs also source and characterize starting materials for supply to allogeneic cell therapy developers that often employ customized technologies offered by just a small number of manufacturers. As such, these supply chains are especially sensitive to even minor changes which often result in potential major impacts. Regulations can shape supply chain efficiencies, both directly via the definition of restricted technology and process requirements and indirectly by steering strategic business decisions of critical supply or service providers. We present 3 current supply chain issues with different root causes that are swaying efficiencies in cord blood banking and beyond. Specifically, the shortage of Hespan, a common supplement used in cord blood processing, the decision by the provider to stop supporting medical device marking of the Sepax system broadly used in cord blood banking, and a new European ruling on phasing out plasticizers that are critical for providing flexibility to cord blood collection bags, are all threatening downstream supply chain issues for the biologics field. We discuss overcoming these hurdles through the prism of unified mitigation strategies, defined, and implemented by multi-factorial teams and stakeholders, to negotiate resolutions with providers and regulators alike.

The fulfilled promise and unmet potential of umbilical cord blood.

PURPOSE OF REVIEW: Here, we review classic and emerging uses of umbilical cord blood and highlight strategies to improve its utility, focusing on selection of the appropriate units and cell types for the intended applications. RECENT LITERATURE: Recent studies have shown advancements in cord blood cell utility in a variety of cellular therapies and have made strides in elucidating manners to select the best units for therapy and target new ways to improve the various cell subpopulations for their respective applications. SUMMARY: Umbilical cord blood is a proven source of cells for hematopoietic cell transplantation and research and is an important potential source for additional cellular therapies. However, cord blood utility is limited by low "doses" of potent cells that can be obtained from individual units, a limitation that is specific to cord blood as a donor source. In addition to traditional CD34 + progenitor cells, cord blood lymphocytes are being pursued as therapeutic entities with their own unique properties and characteristics. Thus, selection of ideal units depends on the intended therapeutic entity and target, and identification of differential potency parameters is critical to drive effective banking strategies accommodating successful clinical use of cord blood in broader cell therapy settings.

Insights into highly engraftable hematopoietic cells from 27-year cryopreserved umbilical cord blood.

Umbilical cord blood transplantation is a life-saving treatment for malignant and non-malignant hematologic disorders. It remains unclear how long cryopreserved units remain functional, and the length of cryopreservation is often used as a criterion to exclude older units. We demonstrate that long-term cryopreserved cord blood retains similar numbers of hematopoietic stem and progenitor cells compared with fresh and recently cryopreserved cord blood units. Long-term cryopreserved units contain highly functional cells, yielding robust engraftment in mouse transplantation models. We also leverage differences between units to examine gene programs associated with better engraftment. Transcriptomic analyses reveal that gene programs associated with lineage determination and oxidative stress are enriched in high engrafting cord blood, revealing potential molecular markers to be used as potency markers for cord blood unit selection regardless of length of cryopreservation. In summary, cord blood units cryopreserved for extended periods retain engrafting potential and can potentially be used for patient treatment.

UM171 Expansion of Cord Blood Improves Donor Availability and HLA Matching For All Patients, Including Minorities.

Cord blood (CB) stem cell transplantation offers a greater tolerance to HLA mismatches compared to adult-derived stem cell transplants (i.e., bone marrow or peripheral blood stem cells). Indeed, 4/6 or 5/8 HLA-matched CB transplantations are regularly performed for patients lacking a matched unrelated donor. Unfortunately, most banked CB units contain a stem cell dose that is too small to treat adult patients, resulting in only 4% to 5% of available CB units offering an adequate cell dose for prompt engraftment for adult patients. Ex vivo stem cell expansion appears to be an attractive strategy to circumvent this cell dose issue, while also enabling the selection of better HLA-matched CB units. In this study, we retrospectively performed HLA matching simulations to assess how the minimal cell content requirements associated with UM171 CB expansion may improve usability of existing CB unit inventories and donor availability for patients of different races and ethnicities. We analyzed a dataset of 58,971 adults for whom a donor search was initiated through the National Marrow Donor Program Be The Match registry against 142,942 CB units from major U.S. public CB banks listed on the Be The Match registry. Our results show that by enabling selection of smaller CB units, UM171-expanded CB transplantation increases donor availability from 72% to 84% for all patients compared to single unmanipulated CB transplantation. Furthermore, the low cell dose criteria for UM171-expanded CB also increases donor availability compared to double CB transplantation, while enabling better HLA matching between donor and recipient. UM171 expanded CB appears particularly beneficial for racial and ethnic minority patients as CB availability increases from 53% to 78% for African Americans, from 66% to 85% for Hispanics, and from 68% to 84% for Asians and Pacific Islanders, compared to single unmanipulated CB transplantation. In addition, UM171 expansion dramatically improves usability of CB units currently in inventories, as only 4.3% and 0.6% of banked CBs have sufficient cell doses for a 70 kg and 100 kg patient, respectively. UM171 raises this proportion to 53.8% and 20.2%, respectively, making CB banks potentially more cost effective. In conclusion, UM171 expansion allows the use of smaller CB units while also improving access to transplantation for racial and ethnic minorities.

IFN-γ and PPARδ influence the efficacy and retention of multipotent adult progenitor cells in graft vs host disease.

Cell-based therapy for the treatment of inflammatory disorders has focused on the application of mesenchymal stromal cells (MSCs) and multipotent adult progenitor cells (MAPCs). Despite the recent positive findings in industry-sponsored clinical trials of MSCs and MAPCs for graft vs host disease (GvHD), cell therapy is efficacious in some but not all patients, highlighting the need to identify strategies to enhance cell-based therapeutic efficacy. Here, we demonstrate the capacity for interferon (IFN)-γ licensing to enhance human MAPC efficacy and retention following early administration in a humanized mouse model of acute GvHD (aGvHD). Activation of the nuclear receptor peroxisome proliferator-activated receptor delta (PPARδ) negatively influenced the retention and efficacy of human MAPCs as well as IFN-γ-licensed MAPCs in the aGvHD model. PPARδ antagonism significantly enhanced the efficacy of human MAPCs when administered early in the humanized aGvHD model. COX-2 expression in human MAPC was significantly decreased in IFN-γ licensed MAPCs exposed to a PPARδ agonist. Importantly, MAPC exposure to the PPARδ antagonist in the presence of a COX-2 inhibitor indomethacin before administration significantly reduced the efficacy of PPARδ antagonized MAPCs in the aGvHD humanized mouse model. This is the first study to demonstrate the importance of PPARδ in human MAPC efficacy in vivo and highlights the importance of understanding the disease microenvironment in which cell-based therapies are to be administered. In particular, the presence of PPARδ ligands may negatively influence MAPC or MSC therapeutic efficacy.

Mesenchymal stromal cell mitochondrial transfer to human induced T-regulatory cells mediates FOXP3 stability.

The key obstacle to clinical application of human inducible regulatory T cells (iTreg) as an adoptive cell therapy in autoimmune disorders is loss of FOXP3 expression in an inflammatory milieu. Here we report human iTreg co-cultured with bone marrow-derived mesenchymal stromal cells (MSCs) during short-term ex vivo expansion enhances the stability of iTreg FOXP3 expression and suppressive function in vitro and in vivo, and further that a key mechanism of action is MSC mitochondrial (mt) transfer via tunneling nanotubules (TNT). MSC mt transfer is driven by mitochondrial metabolic function (CD39/CD73 signaling) in proliferating iTreg and promotes iTreg expression of FOXP3 stabilizing factors BACH2 and SENP3. These results elucidate cellular and molecular mechanisms underlying human MSC mt transfer to proliferating cells. MSC mt transfer stabilizes FOXP3 expression in iTregs, thereby enhancing and sustaining their suppressive function in inflammatory conditions in vitro and in vivo.

Human Hematopoietic Stem, Progenitor, and Immune Cells Respond Ex Vivo to SARS-CoV-2 Spike Protein.

Despite evidence that SARS-CoV-2 infection is systemic in nature, there is little known about the effects that SARS-CoV-2 infection or exposure has on many host cell types, including primitive and mature hematopoietic cells. The hematopoietic system is responsible for giving rise to the very immune cells that defend against viral infection and is a source of hematopoietic stem cells (HSCs) and progenitor cells (HPCs) which are used for hematopoietic cell transplantation (HCT) to treat hematologic disorders, thus there is a strong need to understand how exposure to the virus may affect hematopoietic cell functions. We examined the expression of ACE2, to which SARS-CoV-2 Spike (S) protein binds to facilitate viral entry, in cord blood derived HSCs/HPCs and in peripheral blood derived immune cell subtypes. ACE2 is expressed in low numbers of immune cells, higher numbers of HPCs, and up to 65% of rigorously defined HSCs. We also examined effects of exposing HSCs/HPCs and immune cells to SARS-CoV-2 S protein ex vivo. HSCs and HPCs expand less effectively and have less functional colony forming capacity when grown with S protein, while peripheral blood monocytes upregulate CD14 expression and show distinct changes in size and granularity. That these effects are induced by recombinant S protein alone and not the infectious viral particle suggests that simple exposure to SARS-CoV-2 may impact HSCs/HPCs and immune cells via S protein interactions with the cells, regardless of whether they can be infected. These data have implications for immune response to SARS-CoV-2 and for HCT. Graphical Abstract • Human HSCs, HPCs, and immune cells express ACE2 on the cell surface, making them potentially susceptible to SARS-CoV-2 infection. • SARS-CoV-2 S protein, which binds to ACE2, induces defects in the colony forming capacity of human HPC and inhibits the expansion of HSC/HPC subpopulations ex vivo. These effects can be at least partially neutralized by treatment with SARS-CoV-2 targeting antibody, recombinant human ACE2, or Angiotensin1-7. • S protein also induces aberrant morphological changes in peripheral blood derived monocytes ex vivo. • Thus, there are many different manners in which SARS-CoV-2 virus may impact the functional hematopoietic system, which has important implications for hematological manifestations of COVID-19 (i.e. thrombocytopenia and lymphopenia), immune response, and hematopoietic stem cell transplant in the era of COVID-19.

Foxp3 expression in induced T regulatory cells derived from human umbilical cord blood vs. adult peripheral blood.

Foxp3 is essential for T regulatory cell (Treg) function. Broad complex-Tramtrack-Bric-a-brac domain (BTB) and Cap'n'collar (CNC) homology 1, transcription factor 2 (BACH2) stabilizes Treg immune homeostasis in murine studies. However, little is known regarding what role, if any, BACH2 may have in Foxp3 regulation in human-induced Treg (iTreg). We examined Foxp3 expression and regulation comparing iTreg differentiated from umbilical cord blood (UCB) vs. adult blood (AB) naive CD4+ T-cells. Foxp3 expression was higher in UCB vs. AB-derived iTreg, and was sustained during 21-day expansion in vitro. The number of Foxp3+ iTreg generated from UCB vs. AB naive CD4+ T-cells was higher in iTreg differentiation conditions. In addition, UCB iTreg were more potent in suppressing T-cell proliferation compared to AB iTreg. Naive UCB CD4+ T-cells highly expressed BACH2 protein compared to AB. Putative transcriptional BACH2 binding sites were identified at the Foxp3 promoter, using BACH2 consensus sequence. Cross-linking chromatin immunoprecipitation (ChIP) showed that BACH2 binds to the Foxp3 proximal promoter in UCB iTreg, but not AB iTreg. BACH2 was transcriptionally active, as shRNA-mediated BACH2 knockdown resulted in reduction of Foxp3 gene transcription in UCB CD4+ T-cells. In summary, BACH2 serves to stabilize robust Foxp3 expression in UCB CD4+ T-cell-derived iTreg.

Automatic Stem Cell Detection in Microscopic Whole Mouse Cryo-Imaging.

With its single cell sensitivity over volumes as large as or larger than a mouse, cryo-imaging enables imaging of stem cell biodistribution, homing, engraftment, and molecular mechanisms. We developed and evaluated a highly automated software tool to detect fluorescently labeled stem cells within very large ( âˆ¼ 200 GB) cryo-imaging datasets. Cell detection steps are: preprocess, remove immaterial regions, spatially filter to create features, identify candidate pixels, classify pixels using bagging decision trees, segment cell patches, and perform 3D labeling. There are options for analysis and visualization. To train the classifier, we created synthetic images by placing realistic digital cell models onto cryo-images of control mice devoid of cells. Very good cell detection results were (precision=98.49%, recall=99.97%) for synthetic cryo-images, (precision=97.81%, recall=97.71%) for manually evaluated, actual cryo-images, and false positives in control mice. An α-multiplier applied to features allows one to correct for experimental variations in cell brightness due to labeling. On dim cells (37% of standard brightness), with correction, we improved recall (49.26%→ 99.36%) without a significant drop in precision (99.99%→ 99.75%) . With tail vein injection, multipotent adult progenitor cells in a graft-versus-host-disease model in the first days post injection were predominantly found in lung, liver, spleen, and bone marrow. Distribution was not simply related to blood flow. The lung contained clusters of cells while other tissues contained single cells. Our methods provided stem cell distribution anywhere in mouse with single cell sensitivity. Methods should provide a rational means of evaluating dosing, delivery methods, cell enhancements, and mechanisms for therapeutic cells.

Solution-Phase Crosstalk and Regulatory Interactions Between Multipotent Adult Progenitor Cells and Peripheral Blood Mononuclear Cells.

UNLABELLED: Multipotent adult progenitor cells (MAPCs) are adult adherent stromal stem cells currently being assessed in clinical trials for acute graft versus host disease with demonstrated immunomodulatory capabilities and the potential to ameliorate detrimental autoimmune and inflammation-related processes. Anti-CD3/anti-CD28 (3/28) activation of T cells within the peripheral blood mononuclear cell (PBMC) compartment was performed in the presence or absence of MAPCs. Liquid chromatography-coupled tandem mass spectrometry was used to characterize the differential secretion of proteins, and transcriptional profiling was used to monitor mRNA expression changes in both cell populations. Overall, 239 secreted and/or ectodomain-shed proteins were detected in the secretomes of PBMCs and MAPCs. In addition, 3/28 activation of PBMCs induced differential expression of 2,925 genes, and 22% of these transcripts were differentially expressed on exposure to MAPCs in Transwell. MAPCs exposed to 3/28-activated PBMCs showed differential expression of 1,247 MAPC genes. Crosstalk was demonstrated by reciprocal transcriptional regulation. Secretome proteins and transcriptional signatures were used to predict molecular activities by which MAPCs could dampen local and systemic inflammatory responses. These data support the hypothesis that MAPCs block PBMC proliferation via cell cycle arrest coupled to metabolic stress in the form of tryptophan depletion, resulting in GCN2 kinase activation, downstream signaling, and inhibition of cyclin D1 translation. These data also provide a plausible explanation for the immune privilege reported with administration of donor MAPCs. Although most components of the major histocompatibility complex class II antigen presentation pathway were markedly transcriptionally upregulated, cell surface expression of human leukocyte antigen-DR is minimal on MAPCs exposed to 3/28-activated PBMCs. SIGNIFICANCE: This study documents experiments quantifying solution-phase crosstalk between multipotent adult progenitor cells (MAPCs) and peripheral blood mononuclear cells. The secretome and transcriptional changes quantified suggest mechanisms by which MAPCs are hypothesized to provide both local and systemic immunoregulation of inflammation. The potential impact of these studies includes development of a robust experimental framework to be used for preclinical evaluation of the specific mechanisms by which beneficial effects are obtained after treatment of patients with MAPCs.

Single and multiple dose MultiStem (multipotent adult progenitor cell) therapy prophylaxis of acute graft-versus-host disease in myeloablative allogeneic hematopoietic cell transplantation: a phase 1 trial.

We conducted a multicenter, phase 1 dose escalation study evaluating the safety of the allogeneic multipotent adult progenitor cell (MAPC, MultiStem, Athersys, Inc., Cleveland, OH) stromal product administered as an adjunct therapy to 36 patients after myeloablative allogeneic hematopoietic cell transplantation (HCT). Patients received increasing doses of MAPC (1, 5, or 10 million cells per kilogram recipient weight) as a single i.v. dose on day +2 after HCT (n = 18), or once weekly for up to 5 doses (1 or 5 million cells per kilogram; n = 18). Infusional and regimen-related toxicities were assessed for 30 days after the last MAPC dose. Of 36 allogeneic HCT donors (17 related and 19 unrelated), 35 were 6/6 HLA matched. MAPC infusions were well tolerated without associated infusional toxicity, graft failure, or increased incidence of infection. Median times to neutrophil (n = 36) and platelet (n = 31) engraftment were 15 (range, 11 to 25) and 16 (range, 11 to 41) days, respectively. The overall cumulative incidences of grades II to IV and III and IV acute graft-versus-host disease (GVHD) at day 100 were 37% and 14%, respectively (n = 36). In the group that received the highest single MAPC dose (10 million cells/kg), day 100 incidence of grade II to IV GVHD was 11.1% (1 of 9) with no observed cases of grade III and IV GVHD. We found no evidence for MHC class II allogeneic antibody induction, although some patients showed an increase in serum anticlass I titers compared with baseline. MAPC contribution to blood chimerism was negligible. These phase I data support the safety of stromal stem cell therapy and suggest that MAPC should be tested prospectively as a novel therapeutic option for GVHD prophylaxis after HCT.

Culturing protocols for human multipotent adult stem cells.

Culture procedures are presented that support the initiation and controlled expansion of the multipotent adult progenitor cell (MAPC) population within the human bone marrow derived multipotent mesenchymal stromal cell compartment. Culture procedures or conditions and characterization assays that maintain and survey the distinctive primitive MAPC properties are discussed in the context of cell culturing platforms that facilitate controlled expansion of clinical grade human MAPC product to levels required for mid to late stage clinical testing.

Human multipotent adult progenitor cells transcriptionally regulate fucosyltransferase VII.

BACKGROUND AIMS: Targeted recruitment of leukocytes to sites of inflammation is a crucial event in normal host defense against pathogens, and attachment to and rolling on activated endothelial cells is a prerequisite first step for eventual leukocyte extravasation into sites of inflammation. These key events are mediated by interactions between glycosylated ligands expressed on leukocytes and selectins expressed on activated endothelium. Cell surface expression of selectin ligands on leukocytes is regulated by the rate-limiting enzyme fucosyltransferase VII (Fut7), and in its absence extravasation of leukocytes is severely inhibited. Multipotent adult progenitor cells (MAPCs) are an adherent cell population isolated from adult bone marrow. Intravenous administration of MAPCs provided functional improvement in multiple pre-clinical models of injury or disease, but the mechanisms by which these outcomes were achieved remain poorly understood. METHODS: In vitro cell analysis studies including fluorescence-activated cell sorting, messenger RNA analysis, T-cell proliferation assays and endothelial cell binding assays were performed. RESULTS: The in vitro cell analysis studies characterized the ability of MAPCs to secrete factors that transcriptionally attenuate expression of Fut7 in T cells, blocking the terminal fucosylation event in the biosynthesis of selectin ligands and reducing T-cell binding to endothelial cells. CONCLUSIONS: This study presents the first example of a distinct regulatory mechanism involving transcriptional down-regulation of Fut7 by MAPCs that could modulate the trafficking behavior of T cells in vivo.

Concise review: guidance in developing commercializable autologous/patient-specific cell therapy manufacturing.

Cell therapy is poised to play an enormous role in regenerative medicine. However, little guidance is being made available to academic and industrial entities in the start-up phase. In this technical review, members of the International Society for Cell Therapy provide guidance in developing commercializable autologous and patient-specific manufacturing strategies from the perspective of process development. Special emphasis is placed on providing guidance to small academic or biotech researchers as to what simple questions can be addressed or answered at the bench in order to make their cell therapy products more feasible for commercial-scale production. We discuss the processes that are required for scale-out at the manufacturing level, and how many questions can be addressed at the bench level. The goal of this review is to provide guidance in the form of topics that can be addressed early in the process of development to better the chances of the product being successful for future commercialization.

Dissection of the human multipotent adult progenitor cell secretome by proteomic analysis.

Multipotent adult progenitor cells (MAPCs) are adult adherent stromal stem cells currently being assessed in acute graft versus host disease clinical trials with demonstrated immunomodulatory capabilities and the potential to ameliorate detrimental autoimmune and inflammation-related processes. Our previous studies documented that MAPCs secrete factors that play a role in regulating T-cell activity. Here we expand our studies using a proteomics approach to characterize and quantify MAPC secretome components secreted over 72 hours in vitro under steady-state conditions and in the presence of the inflammatory triggers interferon-γ and lipopolysaccharide, or a tolerogenic CD74 ligand, RTL1000. MAPCs differentially responded to each of the tested stimuli, secreting molecules that regulate the biological activity of the extracellular matrix (ECM), including proteins that make up the ECM itself, proteins that regulate its construction/deconstruction, and proteins that serve to attach and detach growth factors from ECM components for redistribution upon appropriate stimulation. MAPCs secreted a wide array of proteases, some detectable in their zymogen forms. MAPCs also secreted protease inhibitors that would regulate protease activity. MAPCs secreted chemokines and cytokines that could provide molecular guidance cues to various cell types, including neutrophils, macrophages, and T cells. In addition, MAPCs secreted factors involved in maintenance of a homeostatic environment, regulating such diverse programs as innate immunity, angiogenesis/angiostasis, targeted delivery of growth factors, and the matrix-metalloprotease cascade.

Heart grafts tolerized through third-party multipotent adult progenitor cells can be retransplanted to secondary hosts with no immunosuppression.

Multipotent adult progenitor cells (MAPCs) are an adherent stem cell population that belongs to the mesenchymal-type progenitor cell family. Although MAPCs are emerging as candidate agents for immunomodulation after solid organ transplantation, their value requires further validation in a clinically relevant cell therapy model using an organ donor- and organ recipient-independent, third-party cell product. We report that stable allograft survival can be achieved following third-party MAPC infusion in a rat model of fully allogeneic, heterotopic heart transplantation. Furthermore, long-term accepted heart grafts recovered from MAPC-treated animals can be successfully retransplanted to naïve animals without additional immunosuppression. This prolongation of MAPC-mediated allograft acceptance depends upon a myeloid cell population since depletion of macrophages by clodronate abrogates the tolerogenic MAPC effect. We also show that MAPC-mediated allograft acceptance differs mechanistically from drug-induced tolerance regarding marker gene expression, T regulatory cell induction, retransplantability, and macrophage dependence. MAPC-based immunomodulation represents a promising pathway for clinical immunotherapy that has led us to initiate a phase I clinical trial for testing safety and feasibility of third-party MAPC therapy after liver transplantation.

Human multipotent adult progenitor cells are nonimmunogenic and exert potent immunomodulatory effects on alloreactive T-cell responses.

Multipotent adult progenitor cells (MAPCs) are bone marrow-derived nonhematopoietic stem cells with a broad differentiation potential and extensive expansion capacity. A comparative study between human mesenchymal stem cells (hMSCs) and human MAPCs (hMAPCs) has shown that hMAPCs have clearly distinct phenotypical and functional characteristics from hMSCs. In particular, hMAPCs express lower levels of MHC class I than hMSCs and cannot only differentiate into typical mesenchymal cell types but can also differentiate in vitro and in vivo into functional endothelial cells. The use of hMSCs as cellular immunomodulatory stem cell products gained much interest since their immunomodulatory capacities in vitro became evident over the last decade. Currently, the clinical grade stem cell product of hMAPCs is already used in clinical trials to prevent graft-versus-host disease (GVHD), as well as for the treatment of acute myocardial infarct, ischemic stroke, and Crohn's disease. Therefore, we studied the immune phenotype, immunogenicity, and immunosuppressive effect of hMAPCs in vitro. We demonstrated that hMAPCs are nonimmunogenic for T-cell proliferation and cytokine production. In addition, hMAPCs exert strong immunosuppressive effects on T-cell alloreactivity and on T-cell proliferation induced by mitogens and recall antigens. This immunomodulatory effect was not MHC restricted, which makes off-the-shelf use promising. The immunosuppressive effect of hMAPCs is partially mediated via soluble factors and dependent on indoleamine 2,3-dioxygenase (IDO) activity. At last, we isolated hMAPCs, the clinical grade stem cell product of hMAPCs, named MultiStem, and hMSCs from one single donor and observed that both the immunogenicity and the immunosuppressive capacities of all three stem cell products are comparable in vitro. In conclusion, hMAPCs have potent immunomodulatory properties in vitro and can serve as a valuable cell source for the clinical use of immunomodulatory cellular stem cell product.

Potency assay development for cellular therapy products: an ISCT review of the requirements and experiences in the industry.

The evaluation of potency plays a key role in defining the quality of cellular therapy products (CTPs). Potency can be defined as a quantitative measure of relevant biologic function based on the attributes that are linked to relevant biologic properties. To achieve an adequate assessment of CTP potency, appropriate in vitro or in vivo laboratory assays and properly controlled clinical data need to be created. The primary objective of a potency assay is to provide a mechanism by which the manufacturing process and the final product for batch release are scrutinized for quality, consistency and stability. A potency assay also provides the basis for comparability assessment after process changes, such as scale-up, site transfer and new starting materials (e.g., a new donor). Potency assays should be in place for early clinical development, and validated assays are required for pivotal clinical trials. Potency is based on the individual characteristics of each individual CTP, and the adequacy of potency assays will be evaluated on a case-by-case basis by regulatory agencies. We provide an overview of the expectations and challenges in development of potency assays specific for CTPs; several real-life experiences from the cellular therapy industry are presented as illustrations. The key observation and message is that aggressive early investment in a solid potency evaluation strategy can greatly enhance eventual CTP deployment because it can mitigate the risk of costly product failure in late-stage development.

Application of MultiStem(®) Allogeneic Cells for Immunomodulatory Therapy: Clinical Progress and Pre-Clinical Challenges in Prophylaxis for Graft Versus Host Disease.

The last decade has seen much progress in adjunctive cell therapy for immune disorders. Both corporate and institutional Phase III studies have been run using mesenchymal stromal cells (MSC) for treatment of Graft versus Host Disease (GvHD), and product approval has been achieved for treatment of pediatric GvHD in Canada and New Zealand (Prochymal(®); Osiris Therapeutics). This effectiveness has prompted the prophylactic use of adherent stem cells at the time of allogeneic hematopoietic stem cell transplantation (HSCT) to prevent occurrence of GvHD and possibly provide stromal support for hematopoietic recovery. The MultiStem(®) product is an adult adherent stem cell product derived from bone marrow which has significant clinical exposure. MultiStem cells are currently in phase II clinical studies for treatment of ischemic stroke and ulcerative colitis, with Phase I studies completed in acute myocardial infarction and for GvHD prophylaxis in allogeneic HSCT, demonstrating that MultiStem administration was well tolerated while the incidence and severity of GvHD was reduced. In advancing this clinical approach, it is important to recognize that alternate models exist based on clinical manufacturing strategies. Corporate sponsors exploit the universal donor properties of adherent stem cells and manufacture at large scale, with many products obtained from one or limited donors and used across many patients. In Europe, institutional sponsors often produce allogeneic product in a patient designated context. For this approach, disposable bioreactors producing <10 products/donor in a closed system manner are very well suited. In this review, the use of adherent stem cells for GvHD prophylaxis is summarized and the suitability of disposable bioreactors for MultiStem production is presented, with an emphasis on quality control parameters, which are critical with a multiple donor approach for manufacturing.