Current state of U.S. Food and Drug Administration regulation for cellular and gene therapy products: potential cures on the horizon

Cellular & Gene Therapies (CGTs) are complex products, which have been key foci of the International Society for Cell & Gene Therapy (ISCT). For this ISCT North American Legal & Regulatory Affairs Committee review publication, CGTs include but are not limited to somatic cell-based therapies, pluripotent cell-derived cell-based therapies, gene- or non-gene-modified or gene edited versions of these cell-based therapies, in vivo gene therapies, organ/tissue engineered products, and relevant combination products. These products are regulated by the Food and Drug Administration (FDA) in the United States. This publication reviews selected laws, regulations, guidance, definitions, processes, types of meetings and submissions, and other key factors that the FDA follows and implements to regulate and support development of these types of products. These factors may be considered in order to help current and potential product developers/sponsors/applicants navigate through FDA regulatory pathways. We also review expedited programs including types of Designations available at the FDA, and their specific eligibility criteria. We include FDA and other stakeholder resources to consider regarding CGT regulation, to help prepare for CGT development and subsequent FDA approval.     

Longitudinal two-dimensional gas chromatography mass spectrometry as a non-destructive at-line monitoring tool during cell manufacturing identifies volatile features correlative to cell product quality

Background aimsCell therapies have emerged as a potentially transformative therapeutic modality in many chronic and incurable diseases. However, inherent donor and patient variabilities, complex manufacturing processes, lack of well-defined critical quality attributes and unavailability of in-line or at-line process or product analytical technologies result in significant variance in cell product quality and clinical trial outcomes. New approaches for overcoming these challenges are needed to realize the potential of cell therapies.MethodsHere the authors developed an untargeted two-dimensional gas chromatography mass spectrometry (GC×GC-MS)-based method for non-destructive longitudinal at-line monitoring of cells during manufacturing to discover correlative volatile biomarkers of cell proliferation and end product potency.ResultsSpecifically, using mesenchymal stromal cell cultures as a model, the authors demonstrated that GC×GC-MS of the culture medium headspace can effectively discriminate between media types and tissue sources. Headspace GC×GC-MS identified specific volatile compounds that showed a strong correlation with cell expansion and product functionality quantified by indoleamine-2,3-dioxygenase and T-cell proliferation/suppression assays. Additionally, the authors discovered increases in specific volatile metabolites when cells were treated with inflammatory stimulation.ConclusionsThis work establishes GC×GC-MS as an at-line process analytical technology for cell manufacturing that could improve culture robustness and may be used to non-destructively monitor culture state and correlate with end product function.     

Chimeric antigen receptor–T cell therapy manufacturing: modelling the effect of offshore production on aggregate cost of goods

Cell and gene therapies have demonstrated excellent clinical results across a range of indications with chimeric antigen receptor (CAR)–T cell therapies among the first to reach market. Although these therapies are currently manufactured using patient-derived cells, therapies using healthy donor cells are in development, potentially offering avenues toward process improvement and patient access. An allogeneic model could significantly reduce aggregate cost of goods (COGs), potentially improving market penetration of these life-saving treatments. Furthermore, the shift toward offshore production may help reduce manufacturing costs. In this article, we examine production costs of an allogeneic CAR-T cell process and the potential differential manufacturing costs between regions. Two offshore locations are compared with regions within the United States. The critical findings of this article identify the COGs challenges facing manufacturing of allogeneic CAR-T immunotherapies, how these may evolve as production is sent offshore and the wider implication this trend could have.     

Stem-like memory T cells are generated during hollow fiber perfusion-based expansion and enriched after cryopreservation in an automated modular cell therapy manufacturing process

Background aimsModular automation is a flexible and reliable option to build the foundation of a new or evolving process or to introduce automation to a process that is already established. Herein the authors demonstrate that modular automation provides both high-quality and high-yield T-cell products.MethodsCells from three individual donors collected on an automated continuous flow centrifugation system were successfully expanded in a functionally closed, automated, perfusion-based hollow fiber bioreactor. These cells were then prepared for cryopreservation in an automated closed-system device that maintains temperature and aliquots a mixed cell product and cryoprotectant into product bags. Cell product bags were thawed and expanded in flasks. Samples taken throughout this manufacturing process were analyzed for cell phenotype, exhaustion markers and functionality. The proportion of CD4+ and CD8+ T cells was maintained through each step, from pre-expansion and post-expansion to immediately after thaw and 24 h after thaw.ResultsInterestingly, phenotypic markers such as CD45RO, CD45RA and CCR7 evolved throughout the process and stem-like memory T cells emerged as the predominant phenotype in the clinically relevant 24-h post-thaw sample.ConclusionsModular automation supported the generation of stem-like memory T cells that were not terminally exhausted and were able to produce effector cytokines upon restimulation.     

Management of externally manufactured cell therapy products: the Mayo Clinic approach

BackgroundThe rise of investigative and commercially available cell therapy products adds a new dynamic to academic medical centers; that is, the management of patient-specific cell products. The scope of cell therapy has rapidly expanded beyond in-house collection and infusion of cell products such as bone marrow and peripheral blood transplant. The complexities and volumes of cell therapies are likely to continue to become more demanding. As patient-specific “living drugs,” cell therapy products typically require material collection, product provenance, transportation and maintenance of critical quality attributes, including temperature and expiration dates. These requirements are complicated by variations in product-specific attributes, reporting requirements and interactions with industry not required of typical pharmaceuticals.MethodsTo manage these requirements, the authors set out to establish a framework within the Immune, Progenitor and Cell Therapeutics Lab, the Current Good Manufacturing Practice facility responsible for cell manufacturing at Mayo Clinic Rochester housed within the Division of Transfusion Medicine. The authors created a work unit (biopharmaceutical unit) dedicated to addressing the specialized procedures required to properly handle these living drugs from collection to delivery and housing the necessary processes to more easily integrate externally manufactured cell therapies into clinical practice.ResultsThe result is a clear set of expectations defined for each step of the process, with logical documentation of critical steps that are concise and easy to follow.ConclusionsThe authors believe this system is scalable for addressing the promised growth of cell therapy products well into the future. Here the authors describe this system and provide a framework that could be used by other centers to manage these important new therapies.     

Misfolding of the cystic fibrosis transmembrane conductance regulator and disease

Understanding the structural basis for defects in protein function that underlie protein-based genetic diseases is the fundamental requirement for development of therapies. This situation is epitomized by the cystic fibrosis transmembrane conductance regulator (CFTR)-the gene product known to be defective in CF patients-that appears particularly susceptible to misfolding when its biogenesis is hampered by mutations at critical loci. While the primary CF-related defect in CFTR has been localized to deletion of nucleotide binding fold (NBD1) residue Phe508, an increasing number of mutations (now ca. 1,500) are being associated with CF disease of varying severity. Hundreds of these mutations occur in the CFTR transmembrane domain, the site of the protein's chloride channel. This report summarizes our current knowledge on how mutation-dependent misfolding of the CFTR protein is recognized on the cellular level; how specific types of mutations can contribute to the misfolding process; and describes experimental approaches to detecting and elucidating the structural consequences of CF-phenotypic mutations.     

Molecular profiling indicates orthotopic xenograft of glioma cell lines simulate a subclass of human glioblastoma

Cell line models have been widely used to investigate glioblastoma multiforme (GBM) pathobiology and in the development of targeted therapies. However, GBM tumours are molecularly heterogeneous and how cell lines can best model that diversity is unknown. In this report, we investigated gene expression profiles of three preclinical growth models of glioma cell lines, in vitro and in vivo as subcutaneous and intracerebral xenografts to examine which cell line model most resembles the clinical samples. Whole genome DNA microarrays were used to profile gene expression in a collection of 25 high-grade glioblastomas, and comparisons were made to profiles of cell lines under three different growth models. Hierarchical clustering revealed three molecular subtypes of the glioblastoma patient samples. Supervised learning algorithm, trained on glioma subtypes predicted the intracerebral cell line model with one glioma subtype (r = 0.68; 95% bootstrap CI -0.41, 0.46). Survival analysis of enriched gene sets (P < 0.05) revealed 19 biological categories (146 genes) belonging to neuronal, signal transduction, apoptosis- and glutamate-mediated neurotransmitter activation signals that are associated with poor prognosis in this glioma subclass. We validated the expression profiles of these gene categories in an independent cohort of patients from 'The Cancer Genome Atlas' project (r = 0.62, 95% bootstrap CI: -0.42, 0.43). We then used these data to select and inhibit a novel target (glutamate receptor) and showed that LY341595, a glutamate receptor specific antagonist, could prolong survival in intracerebral tumour-implanted mice in combination with irradiation, providing an in vivo cell line system of preclinical studies.     

Current state of Health Canada regulation for cellular and gene therapy products: potential cures on the horizon

We provide an overview of the regulatory framework, pathways and underlying regulatory authority for cell, gene and tissue-engineered therapies in Canada. Canada's regulatory approach uses three sets of regulations, namely, the Cells, Tissues and Organs Regulations, the Food and Drug Regulations and the Medical Devices Regulations. We provide an overview of each these sets of regulations as they apply to clinical investigation to post-market product lifecycle stages. Information is provided on the current sources of relevant Health Canada guidance documents. We highlight several regional success stories including Prochymal, a cell therapy product that achieved Canadian regulatory approval using the conditional marketing approval system. We also examine the perceived gaps in the Canadian regulations and how those gaps are being addressed by interactions between the government, stakeholders and international bodies. We conclude that the risk-benefit approach used by Health Canada for regulatory approval processes is sufficiently flexible to enable to development of novel cell and gene therapy products in Canada, yet stringent enough to protect patient safety.     

Manufacturing mesenchymal stromal cells for clinical applications: A survey of Good Manufacturing Practices at U.S. academic centers

Background aimsMesenchymal stromal cells (MSC) have gained prominence in the field of regenerative medicine due to their excellent safety profile in human patients and recently demonstrated efficacy in late-stage clinical studies. A prerequisite to achieving successful MSC-based therapies is the development of large-scale manufacturing processes that preserve the biological potency of the founder cell population. Because no standardized manufacturing process exists for MSCs, understanding differences in these processes among U.S. academic facilities would allow for better comparison of results obtained in the clinical setting.MethodsWe collected information through a questionnaire sent to U.S. academic centers that produce MSCs under Good Manufacturing Practice conditions.ResultsThe survey provided information on the number and geographic location of academic facilities in the United States and major trends in their manufacturing practices. For example, most facilities employed MSCs enriched from bone marrow by plastic adherence and expanded in media supplemented with pooled human platelet lysate. Sterility testing and product identification via cell surface phenotype analysis were commonly reported practices, whereas initial and working cell plating densities, culture duration, product formulation and the intended use of the MSC product were highly variable among facilities. The survey also revealed that although most facilities assessed product potency, the methods used were limited in scope compared with the broad array of intended clinical applications of the product.ConclusionsSurvey responses reported herein offer insight into the current best practices used to manufacture MSC-based products in the United States and how these practices may affect product quality and potency. The responses also provide a foundation to establish standardized manufacturing platforms.     

Monoclonal antibodies: Longitudinal prescribing information analysis of hypersensitivity reactions

Monoclonal antibodies (mAbs) are known to cause hypersensitivity reactions (HSRs). The reactions pose a significant challenge to investigators, regulators, and health providers. Because HSRs cannot be predicted through the pharmacological basis of a therapy, clinical data are often relied upon to detect the reactions. Unfortunately, clinical studies are often unable to adequately characterize HSRs especially in therapies for orphan diseases. HSRs can go undetected until post-marketing safety surveillance when a large number of patients have been exposed to the therapy. The presented data demonstrates how hypersensitivity reaction warnings have changed over time in the prescribing information (PI), i.e., the drug package insert, through August 1, 2011 for 28 US-marketed mAbs. Tracking all PI revisions for each mAb over time revealed that hypersensitivity warning statements were expanded to include more severe manifestations. Over the course of a mAb therapy’s life cycle, the hypersensitivity warning is twice more likely to be upgraded than downgraded in priority. Approximately 85% of hypersensitivity-associated fatality warnings were added in PI revisions as a result of post-marketing experience. Over 60% (20/33) of revisions to hypersensitivity warnings occurred within 3–4 y of product approval. While HSRs are generally recognized and described in the initial PI of mAbs, fatal HSRs are most commonly observed in post-marketing surveillance. Results of this study suggest that initial product labeling information may not describe rare but clinically significant occurrences of severe or fatal HSRs, but subsequent label revisions include rare events observed during post-marketed product use.     

RNA Interference-Based Therapy for Spinocerebellar Ataxia Type 7 Retinal Degeneration

Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant neurodegenerative disease characterized by loss of motor coordination and retinal degeneration with no current therapies in the clinic. The causative mutation is an expanded CAG repeat in the ataxin-7 gene whose mutant protein product causes cerebellar and brainstem degeneration and retinal cone-rod dystrophy. Here, we reduced the expression of both mutant and wildtype ataxin-7 in the SCA7 mouse retina by RNA interference and evaluated retinal function 23 weeks post injection. We observed a preservation of normal retinal function and no adverse toxicity with ≥50% reduction of mutant and wildtype ataxin-7 alleles. These studies address an important safety concern regarding non-allele specific silencing of ataxin-7 for SCA7 retinal therapy.     

Identification and characterization of the avian erythroblastosis virus erbB gene product as a membrane glycoprotein

Avian erythroblastosis virus causes erythroid leukemia and sarcomas in chickens. The viral oncogene responsible for these diseases, erb, is divided into two regions known as erbA and erbB, and recent evidence suggests that it is the erbB gene that is responsible for the transforming activity. From rats bearing avian erythroblastosis virus-induced sarcomas, we have obtained antisera which are specific for the erb gene products. Using such antisera, we have been able to characterize the erbB gene product as a 68,000 molecular weight protein. Pulse-chase and cell-free in vitro translation experiments show that the initial product is a 62,500 dalton protein which is initially modified to a 66,000 dalton protein, and then further modified to a 68,000 dalton form. These modifications could be shown to be associated with glycosylation and phosphorylation. Cell fractionation experiments revealed that the 66,000 and 68,000 dalton proteins were located in cell membrane fractions, and immunofluorescence results showed the erbB gene product to be expressed on the cell surface.     

Characterization of the expression of the petunia glycine-rich protein-1 gene product

We have examined the expression of the petunia (Petunia hybrida) glycine-rich protein-1 (ptGRP1) gene product using an antibody raised against a synthetic peptide comprising amino acids 22 through 36 of the mature ptGRP1 protein. This antibody recognizes a single protein of 23 kilodaltons. Cell fractionation studies showed that, as predicted (CM Condit, RB Meagher [1986] Nature 323: 178-181), ptGRP1 is most likely localized in the cell wall. In addition, it was found that (extractable) ptGRP1 is present in much higher abundance in unexpanded than in fully expanded tissue, with highest levels of accumulation in the bud. This same developmentally regulated pattern of protein expression was found in all varieties of petunia tested. In addition, tissue blots of petunia stem sections showed that ptGRP1 is localized to within the vascular tissue (to at least the phloem or cambium) and to either the epidermal cells or to a layer of collenchyma cells directly below the epidermis. Localization of ptGRP1 antigen in these cell types is shown to occur at different times in the overall development of the plant and at different quantitative levels.     

A Multiparametric Computational Algorithm for Comprehensive Assessment of Genetic Mutations in Mucopolysaccharidosis Type IIIA (Sanfilippo Syndrome)

Mucopolysaccharidosis type IIIA (MPS-IIIA, Sanfilippo syndrome) is a Lysosomal Storage Disease caused by cellular deficiency of N-sulfoglucosamine sulfohydrolase (SGSH). Given the large heterogeneity of genetic mutations responsible for the disease, a comprehensive understanding of the mechanisms by which these mutations affect enzyme function is needed to guide effective therapies. We developed a multiparametric computational algorithm to assess how patient genetic mutations in SGSH affect overall enzyme biogenesis, stability, and function. 107 patient mutations for the SGSH gene were obtained from the Human Gene Mutation Database representing all of the clinical mutations documented for Sanfilippo syndrome. We assessed each mutation individually using ten distinct parameters to give a comprehensive predictive score of the stability and misfolding capacity of the SGSH enzyme resulting from each of these mutations. The predictive score generated by our multiparametric algorithm yielded a standardized quantitative assessment of the severity of a given SGSH genetic mutation toward overall enzyme activity. Application of our algorithm has identified SGSH mutations in which enzymatic malfunction of the gene product is specifically due to impairments in protein folding. These scores provide an assessment of the degree to which a particular mutation could be treated using approaches such as chaperone therapies. Our multiparametric protein biogenesis algorithm advances a key understanding in the overall biochemical mechanism underlying Sanfilippo syndrome. Importantly, the design of our multiparametric algorithm can be tailored to many other diseases of genetic heterogeneity for which protein misfolding phenotypes may constitute a major component of disease manifestation.     

Critical testing and parameters for consideration when manufacturing and evaluating tumor–associated antigen-specific T cells

The past year has seen remarkable translation of cellular and gene therapies, with U.S. Food and Drug Administration (FDA) approval of three chimeric antigen receptor (CAR) T-cell products, multiple gene therapy products, and the initiation of countless other pivotal clinical trials. What makes these new drugs most remarkable is their path to commercialization: they have unique requirements compared with traditional pharmaceutical drugs and require different potency assays, critical quality attributes and parameters, pharmacological and toxicological data, and in vivo efficacy testing. What's more, each biologic requires its own unique set of tests and parameters. Here we describe the unique tests associated with ex vivo–expanded tumor-associated antigen T cells (TAA-T). These tests include functional assays to determine potency, specificity, and identity; tests for pathogenic contaminants, such as bacteria and fungus as well as other contaminants such as Mycoplasma and endotoxin; tests for product characterization, tests to evaluate T-cell persistence and product efficacy; and finally, recommendations for critical quality attributes and parameters associated with the expansion of TAA-Ts.