Qualification of a flow cytometry-based method for the evaluation of in vitro cytotoxicity of GTA002 natural killer cell therapy

Background

Natural Killer (NK) cell-based therapies represent a ground-breaking opportunity for the treatment of solid tumors and hematological malignancies. NK cell manufacturing under good manufacturing practice (GMP) is complex and requires attentive assessment the product's safety and efficacy through quality control (QC). Release testing includes monitoring of in vitro cell expansion, differentiation, purity, phenotype, and cytotoxicity. As NK cells are biologically active products, the establishment of potency methods is particularly relevant; surrogate or improper assays can lead to rejection of qualifiable batches or to release of products that falsely meet potency specifications, potentially causing low efficacy during clinical trials. As cell-based therapeutics are highly heterogeneous, no universal guidelines for product characterization are available, and developers must invest significant effort in establishing and validating robust and fit-to-purpose assays. In this study, we describe the qualification procedure of a flow cytometry-based analytical method to assess in vitro potency of GTA002 NK cells, to be applied to oNKord®/inaleucel allogeneic off-the-shelf NK cell product from Glycostem Therapeutics, undergoing a Phase I/IIa clinical trial in acute myeloid leukemia (AML) patients (NCT04632316).

Methods

First, we established multi-color flow cytometry panels to quantitatively determine the count of effector (E) GTA002 cells and leukemia target (T) K562 cells alone and in co-culture at different E:T ratios (10:1, 3:1, 1:1). Effector potency was then qualitatively expressed as percentage of cytotoxicity. Next, we defined protocols for method qualification to assess the pivotal features of the assays, including accuracy, precision, linearity, range, specificity, robustness, and carryover; quantitative acceptance criteria were determined for all parameters. Results of the qualification procedure are reported and discussed against pre-defined acceptance criteria.

Results

Overall, our methods show robust performance across all parameters, ensuring QC-compliant assessment of NK cell potency as part of the release test panel for clinical batches. Notably, we identified relevant aspects to address when progressing towards method validation to support pivotal clinical studies.

Conclusions

This article provides a "case-study" of how analytical method development for cell therapeutics is planned and executed from early clinical stages, anticipating the need to establish robust procedures to overcome scientific and regulatory challenges during method validation.

Clinical Manufacturing of Regulatory T Cell Products For Adoptive Cell Therapy and Strategies to Improve Therapeutic Efficacy

Based on successes in preclinical animal transplant models, adoptive cell therapy (ACT) with regulatory T cells (Tregs) is a promising modality to induce allograft tolerance or reduce the use of immunosuppressive drugs to prevent rejection. Extensive work has been done in optimizing the best approach to manufacture Treg cell products for testing in transplant recipients. Collectively, clinical evaluations have demonstrated that large numbers of Tregs can be expanded ex vivo and infused safely. However, these trials have failed to induce robust drug-free tolerance and/or significantly reduce the level of immunosuppression needed to prevent solid organ transplant (SOTx) rejection. Improving Treg therapy effectiveness may require increasing Treg persistence or orchestrating Treg migration to secondary lymphatic tissues or places of inflammation. In this review, we describe current clinical Treg manufacturing methods used for clinical trials. We also highlight current strategies being implemented to improve delivered Treg ACT persistence and migration in preclinical studies.

Generation of a bank of clinical-grade, HLA-homozygous iPSC lines with high coverage of the Spanish population

BACKGROUND

Induced pluripotent stem cell (iPSC)-derived cell therapies are an interesting new area in the field of regenerative medicine. One of the approaches to decrease the costs of iPSC-derived therapies is the use of allogenic homozygous human leukocyte antigen (HLA)-matched donors to generate iPSC lines and to build a clinical-grade iPSC bank covering a high percentage of the Spanish population.

METHODS

The Spanish Stem Cell Transplantation Registry was screened for cord blood units (CBUs) homozygous for the most common HLA-A, HLA-B and HLA-DRB1 haplotypes. Seven donors were selected with haplotypes covering 21.37% of the haplotypes of the Spanish population. CD34-positive hematopoietic progenitors were isolated from the mononuclear cell fraction of frozen cord blood units from each donor by density gradient centrifugation and further by immune magnetic labeling and separation using purification columns. Purified CD34 + cells were reprogrammed to iPSCs by transduction with the CTS CytoTune-iPS 2.1 Sendai Reprogramming Kit.

RESULTS

The iPSCs generated from the 7 donors were expanded, characterized, banked and registered. Master cell banks (MCBs) and working cell banks (WCBs) from the iPSCs of each donor were produced under GMP conditions in qualified clean rooms.

CONCLUSIONS

Here, we present the first clinical-grade, iPSC haplobank in Spain made from CD34 + cells from seven cord blood units homozygous for the most common HLA-A, HLA-B and HLA-DRB1 haplotypes within the Spanish population. We describe their generation by transduction with Sendai viral vectors and their GMP-compliant expansion and banking. These haplolines will constitute starting materials for advanced therapy medicinal product development (ATMP).

Virus-Specific T Cells From Cryopreserved Blood During an Emergent Virus Outbreak for a Potential Off-the-Shelf Therapy

During the first outbreak of an emergent virus, methods need to be developed to rapidly establish suitable therapies for patients with high risk of severe disease caused by the pathogen. Considering the importance of the T-cell response in controlling viral infections, adoptive cell therapy with virus-specific T cells has been used as a safe and effective antiviral prophylaxis and treatment for immunocompromised patients. The main objective of this study was to establish an effective and safe method to cryostore whole blood as starting material and to adapt a T-cell activation and expansion protocol to generate an off-the-shelf antiviral therapeutic option. Additionally, we studied how memory T-cell phenotype, clonality based on T-cell receptor, and antigen specificity could condition characteristics of the final expanded T-cell product. Twenty-nine healthy blood donors were selected from a database of convalescent plasma donors with a confirmed history of SARS-CoV-2 infection. Blood was processed using a fully automated, clinical-grade, and 2-step closed system. Eight cryopreserved bags were advanced to the second phase of the protocol to obtain purified mononucleated cells. We adapted the T-cell activation and expansion protocol, without specialized antigen-presenting cells or presenting molecular structures, in a G-Rex culture system with IL-2, IL-7, and IL-15 cytokine stimulation. The adapted protocol successfully activated and expanded virus-specific T cells to generate a T-cell therapeutic product. We observed no major impact of post-symptom onset time of donation on the initial memory T-cell phenotype or clonotypes resulting in minor differences in the final expanded T-cell product. We showed that antigen competition in the expansion of T-cell clones affected the T-cell clonality based on the T-cell receptor β repertoire. We demonstrated that good manufacturing practice of blood preprocessing and cryopreserving is a successful procedure to obtain an initial cell source able to activate and expand without a specialized antigen-presenting agent. Our 2-step blood processing allowed recruitment of the cell donors independently of the expansion cell protocol timing, facilitating donor, staff, and facility needs. Moreover, the resulting virus-specific T cells could be also banked for further use, notably maintaining viability and antigen specificity after cryopreservation.

Manufacturing and validation of Good Manufacturing Practice-compliant regulatory dendritic cells for infusion into organ transplant recipients

BACKGROUND AIMS

Regulatory (or "tolerogenic") dendritic cells (DCregs) are a highly promising, innovative cell therapy for the induction or restoration of antigen-specific tolerance in immune-mediated inflammatory disorders. These conditions include organ allograft rejection, graft-versus-host disease following bone marrow transplantation and various autoimmune disorders. DCregs generated for adoptive transfer have potential to reduce patients' dependence on non-specific immunosuppressive drugs that can induce serious side effects and enhance the risk of infection and certain types of cancer. Here, our aim was to provide a detailed account of our experience manufacturing and validating comparatively large numbers of Good Manufacturing Practice-grade DCregs for systemic (intravenous) infusion into 28 organ (liver) transplant recipients and to discuss factors that influence the satisfaction of release criteria and attainment of target cell numbers.

RESULTS

DCregs were generated in granulocyte-macrophage colony stimulating factor and interleukin (IL)-4 from elutriated monocyte fractions isolated from non-mobilized leukapheresis products of consenting healthy adult prospective liver transplant donors. Vitamin D3 was added on day 0 and 4 and IL-10 on day 4 during the 7-day culture period. Release and post-release criteria included cell viability, purity, phenotype, sterility and functional assessment. The overall conversion rate of monocytes to DCregs was 28 ± 8.2%, with 94 ± 5.1% product viability. The mean cell surface T-cell co-inhibitory to co-stimulatory molecule (programmed death ligand-1:CD86) mean fluorescence intensity ratio was 3.9 ± 2.2, and the mean ratio of anti-inflammatory:pro-inflammatory cytokine product (IL-10:IL-12p70) secreted upon CD40 ligation was 60 ± 63 (median = 40). The mean total number of DCregs generated from a single leukapheresis product (n = 25 donors) and from two leukapheresis products (n = 3 donors) was 489 ± 223 × 10⁶ (n = 28). The mean total number of DCregs infused was 5.9 ± 2.8 × 10⁶ per kg body weight. DCreg numbers within a target cell range of 2.5-10 × 10⁶/kg were achieved for 25 of 27 (92.6%) of products generated.

CONCLUSIONS

High-purity DCregs meeting a range of quality criteria were readily generated from circulating blood monocytes under Good Manufacturing Practice conditions to meet target cell numbers for infusion into prospective organ transplant recipients.

NMR as powerful technology for non-invasively monitoring cell health and expansion during bioprocessing

Over the last decades, the success of advanced cell therapies and the increasing production volumes of vaccines, proteins or viral vectors have raised the need of robust cell-based manufacturing processes for ensuring product quality and satisfying GMP requirements. The cultivation process of cells needs to be highly controlled for improved productivity, reduced variability and optimized bioprocesses. Cell cultures can be easily monitored using different technologies, which could deliver direct or indirect assessment of the cells' viability. Among these techniques, Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful technology which permits the evaluation and the identification of key endogenous metabolites. NMR can provide information on the cell metabolic pathways, on the bioprocesses and is also capable to quickly test for impurities. In this study, NMR was successfully used as a technology for monitoring cell viability and expansion in different supports for cell growth (including bioreactors), in order to predict the bioprocess output and for the early identification of key metabolites linked to cell starvation. This investigation will allow the timely control of culture conditions and favour the optimization of the bioprocesses. This article is protected by copyright. All rights reserved.

Public Cord Blood Banks as a source of starting material for clinical grade HLA-homozygous induced pluripotent stem cells

BACKGROUND

The increasing number of clinical trials for induced pluripotent stem cell (iPSC)-derived cell therapy products makes the production on clinical grade iPSC more and more relevant and necessary. Cord blood banks are an ideal source of young, HLA-typed and virus screened starting material to produce HLA-homozygous iPSC lines for wide immune-compatibility allogenic cell therapy approaches. The production of such clinical grade iPSC lines (haplolines) involves particular attention to all steps since donor informed consent, cell procurement and a GMP-compliant cell isolation process.

METHODS

Homozygous cord blood units were identified and quality verified before recontacting donors for informed consent. CD34+ cells were purified from the mononuclear fraction isolated in a cell processor, by magnetic microbeads labelling and separation columns.

RESULTS

We obtained a median recovery of 20.0% of the collected pre-freezing CD34+, with a final product median viability of 99.1% and median purity of 83.5% of the post-thawed purified CD34+ population.

CONCLUSIONS

Here we describe our own experience, from unit selection and donor reconsenting, in generating a CD34+ cell product as a starting material to produce HLA-homozygous iPSC following a cost-effective and clinical grade-compliant procedure. These CD34+ cells are the basis for the Spanish bank of haplolines envisioned to serve as a source of cell products for clinical research and therapy.

GMP Manufacturing and IND-Enabling Studies of a Recombinant Hyperimmune Globulin Targeting SARS-CoV-2

Conventionally, hyperimmune globulin drugs manufactured from pooled immunoglobulins from vaccinated or convalescent donors have been used in treating infections where no treatment is available. This is especially important where multi-epitope neutralization is required to prevent the development of immune-evading viral mutants that can emerge upon treatment with monoclonal antibodies. Using microfluidics, flow sorting, and a targeted integration cell line, a first-in-class recombinant hyperimmune globulin therapeutic against SARS-CoV-2 (GIGA-2050) was generated. Using processes similar to conventional monoclonal antibody manufacturing, GIGA-2050, comprising 12,500 antibodies, was scaled-up for clinical manufacturing and multiple development/tox lots were assessed for consistency. Antibody sequence diversity, cell growth, productivity, and product quality were assessed across different manufacturing sites and production scales. GIGA-2050 was purified and tested for good laboratory procedures (GLP) toxicology, pharmacokinetics, and in vivo efficacy against natural SARS-CoV-2 infection in mice. The GIGA-2050 master cell bank was highly stable, producing material at consistent yield and product quality up to >70 generations. Good manufacturing practices (GMP) and development batches of GIGA-2050 showed consistent product quality, impurity clearance, potency, and protection in an in vivo efficacy model. Nonhuman primate toxicology and pharmacokinetics studies suggest that GIGA-2050 is safe and has a half-life similar to other recombinant human IgG1 antibodies. These results supported a successful investigational new drug application for GIGA-2050. This study demonstrates that a new class of drugs, recombinant hyperimmune globulins, can be manufactured consistently at the clinical scale and presents a new approach to treating infectious diseases that targets multiple epitopes of a virus.

Accelerating clinical-scale production of BCMA CAR T cells with defined maturation stages

The advent of CAR T cells targeting CD19 or BCMA on B cell neoplasm demonstrated remarkable efficacy, but rapid relapses and primary refractoriness remains challenging. A leading cause of CAR T cell failure is their lack of expansion and limited persistence. Long-lived, self-renewing multipotent T memory stem cells (T_SCM) and T central memory cells (T_CM) likely sustain superior tumor regression, but their low frequencies in blood from cancer patients impose a major hurdle for clinical CAR T production. We designed a clinically compliant protocol for generating BCMA CAR T cells starting with increased T_SCM/T_CM cell input. A CliniMACS Prodigy process was combined with flow cytometry-based enrichment of CD62L⁺CD95⁺ T cells. Although starting with only 15% of standard T cell input, the selected T_SCM/T_CM material was efficiently activated and transduced with a BCMA CAR-encoding retrovirus. Cultivation in the presence of IL-7/IL-15 enabled the harvest of CAR T cells containing an increased CD4⁺ T_SCM fraction and 70% T_SCM cells amongst CD8⁺. Strong cell proliferation yielded cell numbers sufficient for clinical application, while effector functions were maintained. Together, adaptation of a standard CliniMACS Prodigy protocol to low input numbers resulted in efficient retroviral transduction with a high CAR T cell yield.

Scaling up and scaling out: Advances and challenges in manufacturing engineered T cell therapies

Engineered T cell therapies such as CAR-T cells and TCR-T cells have generated impressive patient responses in previously incurable diseases. In the past few years there have been a number of technical innovations that enable robust clinical manufacturing in functionally closed and often automated systems. Here we describe the latest technology used to manufacture CAR- and TCR-engineered T cells in the clinic, including cell purification, transduction/transfection, expansion and harvest. To help compare the different systems available, we present three case studies of engineered T cells manufactured for phase I clinical trials at the NIH Clinical Center (CD30 CAR-T cells for lymphoma, CD19/CD22 bispecific CAR-T cells for B cell malignancies, and E7 TCR T cells for human papilloma virus-associated cancers). Continued improvement in cell manufacturing technology will help enable world-wide implementation of engineered T cell therapies.

Current Perspectives on "Off-The-Shelf" Allogeneic NK and CAR-NK Cell Therapies

Natural killer cells (NK cells) are the first line of the innate immune defense system, primarily located in peripheral circulation and lymphoid tissues. They kill virally infected and malignant cells through a balancing play of inhibitory and stimulatory receptors. In pre-clinical investigational studies, NK cells show promising anti-tumor effects and are used in adoptive transfer of activated and expanded cells, ex-vivo. NK cells express co-stimulatory molecules that are attractive targets for the immunotherapy of cancers. Recent clinical trials are investigating the use of CAR-NK for different cancers to determine the efficiency. Herein, we review NK cell therapy approaches (NK cell preparation from tissue sources, ways of expansion ex-vivo for "off-the-shelf" allogeneic cell-doses for therapies, and how different vector delivery systems are used to engineer NK cells with CARs) for cancer immunotherapy.

GMP Tiered Cell Banking of Non-enzymatically Isolated Dermal Progenitor Fibroblasts for Allogenic Regenerative Medicine

Non-enzymatically isolated primary dermal progenitor fibroblasts derived from fetal organ donations are ideal cell types for allogenic musculoskeletal regenerative therapeutic applications. These cell types are differentiated, highly proliferative in standard in vitro culture conditions and extremely stable throughout their defined lifespans. Technical simplicity, robustness of bioprocessing and relatively small therapeutic dose requirements enable pragmatic and efficient production of clinical progenitor fibroblast lots under cGMP standards. Herein we describe optimized and standardized monolayer culture expansion protocols using dermal progenitor fibroblasts isolated under a Fetal Transplantation Program for the establishment of GMP tiered Master, Working and End of Production cryopreserved Cell Banks. Safety, stability and quality parameters are assessed through stringent testing of progeny biological materials, in view of clinical application to human patients suffering from diverse cutaneous chronic and acute affections. These methods and approaches, coupled to adequate cell source optimization, enable the obtention of a virtually limitless source of highly consistent and safe biological therapeutic material to be used for innovative regenerative medicine applications.

Swiss Fetal Transplantation Program and Non-enzymatically Isolated Primary Progenitor Cell Types for Regenerative Medicine

Primary progenitor cell types adequately isolated from fetal tissue samples present considerable therapeutic potential for a wide range of applications within allogeneic musculoskeletal regenerative medicine. Progenitor cells are inherently differentiated and extremely stable in standard bioprocessing conditions and can be culture-expanded to establish extensive and robust cryopreserved cell banks. Stringent processing conditions and exhaustive traceability are prerequisites for establishing a cell source admissible for further cGMP biobanking and clinical-grade production lot manufacture. Transplantation programs are ideal platforms for the establishment of primary progenitor cell sources to be used for manufacture of cell therapies or cell-based products. Well-defined and regulated procurement and processing of fetal biopsies after voluntary pregnancy interruptions ensure traceability and safety of progeny materials and therapeutic products derived therefrom. We describe herein the workflows and specifications devised under the Swiss Fetal Progenitor Cell Transplantation Program in order to traceably isolate primary progenitor cell types in vitro and to constitute Parental Cell Banks fit for subsequent industrial-scale cGMP processing. When properly devised, derived, and maintained, such cell sources established after a single organ donation can furnish sufficient progeny materials for years of development in translational musculoskeletal regenerative medicine.

Progenitor Biological Bandages: An Authentic Swiss Tool for Safe Therapeutic Management of Burns, Ulcers, and Donor Site Grafts

Clinical experience gathered over two decades around therapeutic use of primary human dermal progenitor fibroblasts in burn patient populations has been at the forefront of regenerative medicine in Switzerland. Relative technical simplicity, ease of extensive serial multitiered banking, and high stability are major advantages of such cell types, assorted to ease of safety and traceability demonstration. Stringent optimization of cell source selection and standardization of biobanking protocols enables the safe and efficient harnessing of the considerable allogenic therapeutic potential yielded by primary progenitor cells. Swiss legal and regulatory requirements have led to the procurement of fetal tissues within a devised Fetal Progenitor Cell Transplantation Program in the Lausanne University Hospital. Proprietary nonenzymatic isolation of primary musculoskeletal cell types and subsequent establishment of progeny tiered cell banks under cGMP standards have enabled safe and effective management of acute and chronic cutaneous affections in various patient populations. Direct off-the-freezer seeding of viable dermal progenitor fibroblasts on a CE marked equine collagen scaffold is the current standard for delivery of the therapeutic biological materials to patients suffering from extensive and deep burns. Diversification in the clinical indications and delivery methods for these progenitor cells has produced excellent results for treatment of persistent ulcers, autograft donor site wounds, or chronic cutaneous affections such as eczema. Herein we describe the standard operating procedures for preparation and therapeutic deployment of the progenitor biological bandages within our translational musculoskeletal regenerative medicine program, as they are routinely used as adjuvants in our Burn Center to treat critically ailing patients.

A non-affinity purification process for GMP production of prefusion-closed HIV-1 envelope trimers from clades A and C for clinical evaluation

Metastable glycosylated immunogens present challenges for GMP manufacturing. The HIV-1 envelope (Env) glycoprotein trimer is covered by N-linked glycan comprising half its mass and requires both trimer assembly and subunit cleavage to fold into a prefusion-closed conformation. This conformation, the vaccine-desired antigenic state, is both metastable to structural rearrangement and labile to subunit dissociation. Prior reported GMP manufacturing for a soluble trimer stabilized in a near-native state by disulfide (SOS) and Ile-to-Pro (IP) mutations has employed affinity methods based on antibody 2G12, which recognizes only ~30% of circulating HIV strains. Here, we develop a scalable manufacturing process based on commercially available, non-affinity resins, and we apply the process to current GMP (cGMP) production of trimers from clades A and C, which have been found to boost cross-clade neutralizing responses in vaccine-test species. The clade A trimer, which we named "BG505 DS-SOSIP.664", contained an engineered disulfide (201C-433C; DS) within gp120, which further stabilized this trimer in a prefusion-closed conformation resistant to CD4-induced triggering. BG505 DS-SOSIP.664 was expressed in a CHO-DG44 stable cell line and purified with initial and final tangential flow filtration steps, three commercially available resin-based chromatography steps, and two orthogonal viral clearance steps. The non-affinity purification enabled efficient scale-up, with a 250 L-scale cGMP run yielding 9.6 g of purified BG505 DS-SOSIP.664. Antigenic analysis indicated retention of a prefusion-closed conformation, including recognition by apex-directed and fusion peptide-directed antibodies. The developed manufacturing process was suitable for 50 L-scale production of a second prefusion-stabilized Env trimer vaccine candidate, ConC-FP8v2 RnS-3mut-2G-SOSIP.664, yielding 7.8 g of this consensus clade C trimer. The successful process development and purification scale-up of HIV-1 Env trimers from different clades by using commercially available materials provide experimental demonstration for cGMP manufacturing of trimeric HIV-Env vaccine immunogens, in an antigenically desired conformation, without the use of costly affinity resins.

Acceleration of Translational Mesenchymal Stromal Cell Therapy Through Consistent Quality GMP Manufacturing

Human mesenchymal stromal cell (hMSC) therapy has been gaining immense interest in regenerative medicine and quite recently for its immunomodulatory properties in COVID-19 treatment. Currently, the use of hMSCs for various diseases is being investigated in >900 clinical trials. Despite the huge effort, setting up consistent and robust scalable manufacturing to meet regulatory compliance across various global regions remains a nagging challenge. This is in part due to a lack of definitive consensus for quality control checkpoint assays starting from cell isolation to expansion and final release criterion of clinical grade hMSCs. In this review, we highlight the bottlenecks associated with hMSC-based therapies and propose solutions for consistent GMP manufacturing of hMSCs starting from raw materials selection, closed and modular systems of manufacturing, characterization, functional testing, quality control, and safety testing for release criteria. We also discuss the standard regulatory compliances adopted by current clinical trials to broaden our view on the expectations across different jurisdictions worldwide.

Process development and safety evaluation of ABCB5+ limbal stem cells as advanced-therapy medicinal product to treat limbal stem cell deficiency

Background

While therapeutic success of the limbal tissue or cell transplantation to treat severe cases of limbal stem cell (LSC) deficiency (LSCD) strongly depends on the percentage of LSCs within the transplanted cells, prospective LSC enrichment has been hampered by the intranuclear localization of the previously reported LSC marker p63. The recent identification of the ATP-binding cassette transporter ABCB5 as a plasma membrane-spanning marker of LSCs that are capable of restoring the cornea and the development of an antibody directed against an extracellular loop of the ABCB5 molecule stimulated us to develop a novel treatment strategy based on the utilization of in vitro expanded allogeneic ABCB5⁺ LSCs derived from human cadaveric limbal tissue.

Methods

We developed and validated a Good Manufacturing Practice- and European Pharmacopeia-conform production and quality-control process, by which ABCB5⁺ LSCs are derived from human corneal rims, expanded ex vivo, isolated as homogenous cell population, and manufactured as an advanced-therapy medicinal product (ATMP). This product was tested in a preclinical study program investigating the cells’ engraftment potential, biodistribution behavior, and safety.

Results

ABCB5⁺ LSCs were reliably expanded and manufactured as an ATMP that contains comparably high percentages of cells expressing transcription factors critical for LSC stemness maintenance (p63) and corneal epithelial differentiation (PAX6). Preclinical studies confirmed local engraftment potential of the cells and gave no signals of toxicity and tumorgenicity. These findings were sufficient for the product to be approved by the German Paul Ehrlich Institute and the U.S. Food & Drug Administration to be tested in an international multicenter phase I/IIa clinical trial (NCT03549299) to evaluate the safety and therapeutic efficacy in patients with LSCD.

Conclusion

Building upon these data in conjunction with the previously shown cornea-restoring capacity of human ABCB5⁺ LSCs in animal models of LSCD, we provide an advanced allogeneic LSC-based treatment strategy that shows promise for replenishment of the patient’s LSC pool, recreation of a functional barrier against invading conjunctival cells and restoration of a transparent, avascular cornea.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02272-2.

Process data of allogeneic ex vivo-expanded ABCB5+ mesenchymal stromal cells for human use: off-the-shelf GMP-manufactured donor-independent ATMP

BACKGROUND

Human dermal mesenchymal stromal cells (MSCs) expressing the ATP-binding cassette (ABC) efflux transporter ABCB5 represent an easily accessible MSC population that, based on preclinical and first-in-human data, holds significant promise to treat a broad spectrum of conditions associated not only with skin-related but also systemic inflammatory and/or degenerative processes.

METHODS

We have developed a validated Good Manufacturing Practice-compliant expansion and manufacturing process by which ABCB5⁺ MSCs derived from surgical discard skin tissues are processed to an advanced-therapy medicinal product (ATMP) for clinical use. Enrichment for ABCB5⁺ MSCs is achieved in a three-step process involving plastic adherence selection, expansion in a highly efficient MSC-selecting medium, and immunomagnetic isolation of the ABCB5⁺ cells from the mixed culture.

RESULTS

Product Quality Review data covering 324 cell expansions, 728 ABCB5⁺ MSC isolations, 66 ABCB5⁺ MSC batches, and 85 final drug products reveal high process robustness and reproducible, reliable quality of the manufactured cell therapy product.

CONCLUSION

We have successfully established an expansion and manufacturing process that enables the generation of homogenous ABCB5⁺ MSC populations of proven biological activity manufactured as a standardized, donor-independent, highly pure, and highly functional off-the-shelf available ATMP, which is currently tested in multiple clinical trials.

Ex vivo-expanded highly pure ABCB5+ mesenchymal stromal cells as Good Manufacturing Practice-compliant autologous advanced therapy medicinal product for clinical use: process validation and first in-human data

Background aim:

Mesenchymal stromal cells (MSCs) hold promise for the treatment of tissue damage and injury. However, MSCs comprise multiple subpopulations with diverse properties, which could explain inconsistent therapeutic outcomes seen among therapeutic attempts. Recently, the adenosine triphosphate-binding cassette transporter ABCB5 has been shown to identify a novel dermal immunomodulatory MSC subpopulation.

Methods:

The authors have established a validated Good Manufacturing Practice (GMP)-compliant expansion and manufacturing process by which ABCB5⁺ MSCs can be isolated from skin tissue and processed to generate a highly functional homogeneous cell population manufactured as an advanced therapy medicinal product (ATMP). This product has been approved by the German competent regulatory authority to be tested in a clinical trial to treat therapy-resistant chronic venous ulcers.

Results:

As of now, 12 wounds in nine patients have been treated with 5 × 10⁵ autologous ABCB5⁺ MSCs per cm² wound area, eliciting a median wound size reduction of 63% (range, 32–100%) at 12 weeks and early relief of pain.

Conclusions:

The authors describe here their GMP- and European Pharmacopoeia-compliant production and quality control process, report on a pre-clinical dose selection study and present the first in-human results. Together, these data substantiate the idea that ABCB5⁺ MSCs manufactured as ATMPs could deliver a clinically relevant wound closure strategy for patients with chronic therapy-resistant wounds.

COVID-19 vaccine development during pandemic: gap analysis, opportunities, and impact on future emerging infectious disease development strategies

The world remains cautiously optimistic about a COVID-19 vaccine that is relatively safe and efficacious and that offers sufficient long-lasting protection/immunity by neutralizing the virus infectivity. However, key technical hurdles pertaining to antigen-adjuvant formulation, delivery, and manufacturing challenges of lipid nanoparticles (LNPs) for mRNA vaccines and stability of formulations need to be addressed for successful product development and stockpiling. In addition, the dosage form, the dosage level and regimen for eliciting a protective immune response remain to be established. The high dependence of global supply chains and demand-supply to sourcing quality raw materials, glassware and other supplies, along with the stress on existing production capacities and platform-specific manufacturing challenges could impede vaccine development and access. This article provides critical analysis of vaccine development processes and unit operations that can derail the pandemic response, and also extends to other emerging infectious disease development efforts - issues that take on added significance given the global mandate for an accelerated and at-risk development path to tackle the COVID-19 pandemic.

Overcoming Challenges in Process Development of Cellular Therapies

PURPOSE OF THE REVIEW

Cellular therapy using chimeric antigen receptor (CAR) T cells as a treatment option for patients with lymphoma and leukemia has proven to be remarkably efficacious. This success has sparked the development of new cellular therapy products for numerous indications. Similar to pharmaceutical products, challenges exist at nearly every stage of process development; however, the unique nature of a cellular therapy product can present exceptional challenges that are just beginning to emerge. The purpose of this review is to explore some of the most common challenges experienced during the early phases of development of CAR T cell products and to provide suggestions for navigating these challenges.

RECENT FINDINGS

Recent articles focused on CAR T cells are highlighted with special attention on aspects that relate to CAR T cell process development and clinical manufacturing. We examine the various stages of process development for CAR T cells and outline some of the obstacles that must be overcome in order to move from pre-clinical development into clinical manufacturing. As the field of CAR T cell therapy continues to grow, it is important to quickly move new CAR T cell products into and through early phase clinical trials and to ensure that the result of these trials can be adequately compared. Having laboratory and clinical investigators and GMP manufacturing facilities aligned on the numerous aspects of new product development will facilitate this process.

Bringing Safe and Standardized Cell Therapies to Industrialized Processing for Burns and Wounds

Cultured primary progenitor cell types are worthy therapeutic candidates for regenerative medicine. Clinical translation, industrial transposition, and commercial implementation of products based on such cell sources are mainly hindered by economic or technical barriers and stringent regulatory requirements. Applied research in allogenic cellular therapies in the Lausanne University Hospital focuses on cell source selection technique optimization. Use of fetal progenitor cell sources in Switzerland is regulated through Federal Transplantation Programs and associated Fetal Biobanks. Clinical applications of cultured primary progenitor dermal fibroblasts have been optimized since the 1990s as “Progenitor Biological Bandages” for pediatric burn patients and adults presenting chronic wounds. A single organ donation procured in 2009 enabled the establishment of a standardized cell source for clinical and industrial developments to date. Non-enzymatically isolated primary dermal progenitor fibroblasts (FE002-SK2 cell type) served for the establishment of a clinical-grade Parental Cell Bank, based on a patented method. Optimized bioprocessing methodology for the FE002-SK2 cell type has demonstrated that extensive and consistent progenitor cell banks can be established. In vitro mechanistic characterization and in vivo preclinical studies have confirmed potency, preliminary safety and efficacy of therapeutic progenitor cells. Most importantly, highly successful industrial transposition and up-scaling of biobanking enabled the establishment of tiered Master and Working Cell Banks using Good Manufacturing Practices. Successive and successful transfers of technology, know-how and materials to different countries around the world have been performed. Extensive developments based on the FE002-SK2 cell source have led to clinical trials for burns and wound dressing. Said trials were approved in Japan, Taiwan, USA and are continuing in Switzerland. The Swiss Fetal Transplantation Program and pioneer clinical experience in the Lausanne Burn Center over three decades constitute concrete indicators that primary progenitor dermal fibroblasts should be considered as therapeutic flagships in the domain of wound healing and for regenerative medicine in general. Indeed, one single organ donation potentially enables millions of patients to benefit from high-quality, safe and effective regenerative therapies. This work presents a technical and translational overview of the described progenitor cell technology harnessed in Switzerland as cellular therapies for treatment of burns and wounds around the globe.

Good Manufacturing Practice (GMP) Compliance for Phage Therapy Medicinal Products

Facing the emergence of difficult-to-treat bacterial infections, the perspective of using bacteriophages has re-gained interest in many countries. In terms of pharmaceutical classification in EU and United States, phages are considered as anti-infectious medicinal products and biological products, given the intended use and their live nature. During the production steps, the compliance with the Good Manufacturing Practice (GMP) represents the gold-standard to ensure the quality, safety and efficacy of medicinal products, either investigational or approved. In practice, the implementation of GMP rules for phage therapy medicinal products benefits from the long history of vaccine development. Accordingly, a well-structured strategy can be defined for each medicinal product, taking into account the specified indication (i.e., the target bacteria species, the infected site, the route of administration, the product composition). Based on the experience of different phage therapy medicinal products from the recent years, the most important requirements to achieve and claim GMP grade are reviewed here, including for genetically modified phages. Like all new medicinal products, the manufacturing of investigational phages incorporates significant challenges. However, the use of GMP-certified phages provides the best guarantee for the rigorous assessment of quality, safety and efficacy during the clinical development of phage medicinal products, thus appears as a key component for the successful development of phage therapy approaches.

Moving to CoPACaPAnA: Implementation of a continuous protein A capture process for antibody applications within an end-to-end single-use GMP manufacturing downstream process

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Combination of continuous protein A chromatography and end-to-end single-use downstream GMP process.

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Comparable and consistent product quality compared to conventional processes.

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Productivity is increased by 400–500%.

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Cost analysis and potential benefits from employing single-use process.

For the first time to our knowledge the implementation of a continuous protein A capture process for antibody applications (CoPACaPAnA) embedded in an end-to-end single-use 500 L GMP manufacturing downstream process of a multispecific monoclonal antibody (mAb) using a single-use SMB system was conducted. Throughout the last years, a change concerning the pipelines in pharmaceutical industry could be observed, moving to a more heterogeneous portfolio of antibodies, fusion proteins and nanobodies. Trying to adjust purification processes to these new modalities, a higher degree of flexibility and lower operational and capital expenditure is desired. The implementation of single-use equipment is a favored solution for increasing manufacturing agility and it has been demonstrated that continuous processing can be beneficial concerning processing cost and time. Reducing protein A resin resulted in 59% cost reduction for the protein A step, with additional cost reduction also for the intermediate and polishing step due to usage of disposable technology. The downstream process applied here consisted of three chromatography steps that were all conducted on a single-use SMB system, with the capture step being run in continuous mode while intermediate and polishing was conducted in batch mode. Further, two steps dedicated to virus inactivation/ removal and three filtration steps were performed, yielding around 100 g of drug substance going into clinical phase I testing. Therefore, in this study it has been demonstrated that employing a continuous capture within a GMP single-use downstream processing chain is feasible and worthy of consideration among the biotech industry for future application to modality-diverse pipelines.

Regulation of Regenerative Medicine Products

Cellular therapies have moved to the forefront based upon promising results from clinical trials using both chimeric antigen receptor T lymphocytes to treat leukemia and other cell types to restore structure and function to tissues that have been damaged by disease or physical injury. The pace at which these treatments have evolved has posed a regulatory challenge to agencies, such as the Food and Drug Administration (FDA). This chapter describes how a specific regulatory strategy was developed and how it has evolved in response to the demand for these new therapies.