Cell and Gene Therapy
Preclinical in vitro and in vivo proof-of-concept, pharmacology, and toxicology studies are conducted to establish feasibility and rationale for clinical use of the investigational CGT product, as well as characterize the product’s safety profile. These studies also provide the scientific basis to support the conclusion that it is reasonably safe to conduct the proposed clinical investigations. Due to the diverse biology and scientific issues associated with CGT products, it is important to conduct a careful benefit-risk analysis, performed in the context of the particular clinical condition under study. Preclinical data generated from studies conducted in appropriate animal species and animal models of disease contribute to defining reasonable risk for the investigational CGT product.
Preclinical studies are intended to define the pharmacologic and toxicologic effects predictive of the human response, not only prior to initiation of clinical trials, but also throughout drug development. The goals of these studies include the following: to define safe starting doses and escalation schemes for clinical trials, to identify target organs for toxicity and parameters to monitor in patients receiving these therapies, and to determine populations which may be at greater risk for toxicities of a given cellular or gene therapeutic.
Design of preclinical studies should take into consideration: 1) the population of cells to be administered or the class of vector used, 2) the animal species and physiologic state most relevant for the clinical indication and product class, and 3) the intended doses, route of administration, and treatment regimens.
The Preparation and Harvesting phase of cell and gene therapy includes the acclimatization of the test animals for extraction. Animal workstations are necessary for containment purposes during animal handling mainly for personnel and environment protection.
With the introduction of the VIVA® range, Esco applies decades of experience in clean air technologies to the animal research laboratory, protecting personnel and the laboratory environment from:
- Hazards related to the equipment, materials and practices used in performing routine animal husbandry;
- Hazards relating directly or indirectly to animal contact;
- Hazards related to the technique or materials or biohazardous substances that may be used during the course of animal research.
This phase also covers up the cell collection process, hence, it is extremely important to consider the following criteria before and/or after the cell/tissue of the species have been extracted:
- Cell types: The type(s) of cell to be used should be classified as autologous, allogeneic, or xenogeneic in origin. The tissue source and other relevant identifying information should be provided.
- Donor selection criteria: Any relevant characteristics of the donor(s) should be specified, including age and sex. Exclusion criteria should focus on the presence or likelihood of infection by HIV-1 and HIV-2, hepatitis B and C viruses, HTLV-1, and other infectious agents. Serological, diagnostic, and clinical history data to be obtained from donors should be specified.
- Tissue typing: If allogeneic donors are to be used, typing for polymorphisms such as blood type should be included when appropriate. The importance of matching for histocompatibility antigens (HLA class I and/or II, and perhaps minor antigens in some cases) between donor and recipient should be addressed, and typing procedures and acceptance criteria provided.
The transfer of genetic material can be accomplished in vivo through local or systemic inoculation or ex vivo where the target of interest is collected and modified outside of the organism before return to the host. Transfer of synthetic DNA can be accomplished by transduction or transfection. Such methods of transfer include either direct injection of DNA into the recipient cells, or utilising methods to induce membranes permeabilisation, receptor-mediated uptake or endocytosis. Transduction utilises recombinant virus as a vector for gene transfer.
While natural transfer of genetic material can be accomplished in several ways, degradation of plasmid DNA is susceptible because of biologic enzymes, hence the following synthetic delivery systems are used.
- Electroporation or electropermeabilization
Iontophoresis is a non-invasive method of propelling high concentrations of a charged substance, normally medication or bioactive agents, transdermally by repulsive electromotive force using a small electrical charge applied to an iontophoretic chamber containing a similarly charged active agent and its vehicle.
This is a significant increase in the electrical conductivity and permeability of the cell plasma membrane caused by an extremely applied electrical field. It is usually used as a way of introducing some substance into a cell, such as loading with a molecular probe, a drug that can change the cell’s function, or a piece of coding DNA.
This is a spherical vesicle with a membrane composed of phospholipid and cholesterol bilayer. Liposomes can be composed of naturally-derived phospholipids with mixed lipid chains or of pure surfactants. To deliver the molecules to sites of action, the lipid bilayer can fuse with other bilayers such as the cell membrane, thus delivering the liposome contents.
An injector is a pump-like device, which charges or discharges containers under pressure with suitable arrangements. Motive force is gained at the inlet from a suitable gas or liquid that is under pressure. Pneumatic injectors can deliver 10-15 L femtolitre of materials and specialized mechanical pumps are capable of 10-12 L picolitre delivery volumes.
Scaffolds used for tissue engineering and regeneration can be synthetic polymers, naturally derived proteins/polymers, and tissue derived scaffolds produced by decellularization. Synthetic scaffolds can be tailored and reproduced readily with controlled mechanical properties, porosity, and surface topography. However, this approach faces limitations such as uncertainties regarding the degradation rate and products as well as cell compatibility. Naturally derived proteins/polymers, such as collagen, fibrin, alginate, etc., possess intrinsic cell compatibility, but they are often weak in mechanical properties and difficult to manipulate.
Decellularization, on the other hand, removes cellular components from tissues/organs to generate extracellular matrix templates, a complex mixture of structural and functional proteins that can be used for tissue engineering applications. The removal of cellular content and antigens from the tissue-derived scaffolds reduces foreign body reaction, inflammation, and potential immune rejection. Effective decellularization methods include chemical, enzymatic, physical or combinational approaches. The working principle of these methods is that the cell membrane is disrupted, and the cellular contents are released and rinsed away.
Decellularization includes chemical methods such as the utilization of ionic detergents like sodium dodecyl sulfate (SDS), non-ionic detergents (Triton X-100), chelating agent (EDTA), zwitterionic-based detergent, acids and bases, hypotonic and hypertonic solutions, alcohols and acetone and enzymatic method such as trypsin treatment. Physical method like scraping, solution agitation, pressure gradient, and freezing.
Scaffolds are sterilized afterwards, preventing contamination and potential transmission of pathogens. Sterilization involves the use of sterility test isolators and acellular scaffolds including ethanol, peracetic acid, ethylene oxide, ultraviolet and gamma radiation. Aside from sterilization, scaffold stabilization is also used to delay degradation, neutralize antigens, and stabilize the overall structure of ECM.
Cryopreservation or lyopilization have also been both used in decellularization approaches for storage of scaffolds for easier handling. Cryopreservation is able to effectively preserve the acellular tissue scaffolds at sub-zero temperatures maintained by liquid nitrogen.
Different freeze drying applications such as preservation of biological samples, purification of proteins, and concentration of chemical products, are now done perfectly with SubliMate®.
The following criteria should also be considered during the phase III of regenerative therapy:
- Quality control procedures: In general, cell culture operations should be carefully managed in terms of quality of materials, manufacturing controls, and equipment validation and monitoring.
- Culture media: Acceptance criteria should be established for all media and components, including validation of serum additives and growth factors, as well as verification of freedom from adventitious agents. Medium components which have the potential to cause sensitization, for example certain animal sera, selected proteins, and blood group substances, should be avoided. For growth factors, measures of identity, purity, and potency should be established to assure the reproducibility of cell culture characteristics.
- Adventitious agents in cell cultures: Documentation should be provided that cells are handled, propagated, and subjected to laboratory procedures under conditions designed to minimize contamination with adventitious agents. During long term culturing, cells should be tested periodically for contamination. Testing should ensure that cells are free of bacteria, yeast, mold, mycoplasma, and adventitious viruses.
- Monitoring of cell identity and heterogeneity: Both manufacturing and testing procedures should be implemented which ensure the control of cell cultures with regard to identity and heterogeneity.
- Characterization of therapeutic entity: If the intended therapeutic effect is based on a particular molecular species synthesized by the cells, enough structural and biological information should be provided to show that an appropriate and biologically active form is present.
- Culture longevity: The essential characteristics of the cultured cell population (phenotypic markers such as cell surface antigens, functional properties, activity in bioassays, as appropriate) should be defined, and the stability of these characteristics established with respect to time in culture. This profile should be used to define the limits of the culture period.
CelCradle™ is a disposable bioreactor capable of high-density cell culture for protein expression, virus, and monoclonal antibody production. It is designed based on the concept of bellow-induced intermittent flow of media and air through porous matrices, where cells reside. This provides a low shear, high aeration, and foam-free culture environment.
Cell culturing practices and facilities should be designed to avoid contamination of one cell culture with another.
During cell culturing, extensive drift in the properties of a cell population, or overgrowth by a different cell type originally present in low numbers, may occur. To detect such changes, cell identity should be assessed quantitatively, for example, by monitoring cell surface antigens or biochemical markers. The method of identification chosen should also be able to detect contamination or replacement by other cells in use in the facility. Acceptable limits for culture composition should be defined. Quantitative assays of functional potency may sometimes provide a method for population phenotyping. The desired function should be monitored when the cells are subjected to manipulation, and the tests carried out periodically to assure that the desired trait is retained. Identity testing should in some cases include verification of donor-recipient matching and immunological phenotyping.
The major progress in microsystem technologies for creating small, integrated and reliable microtransducers devices in combination with biological sensing elements has revolutionized the field of biosensors during the last decade. Such micro-biosensor systems raised the expectation to get a comprehensive insight into dynamic cellular metabolic events and subsequently a complete understanding of the metabolism of human biology.
Quality Control of Regenerative Drug Products
- Risk and Sterility
- Effectiveness of Gown
- Isolator Technology for Gene/Cell Therapy
Two different critical factors govern the aseptic processing of aseptic drugs involving cell/gene therapy. The first of these is “risk evaluation/analysis”, the goal of which is risk quantification. The other is “risk mitigation” that considers the possibility of contamination during facility design, equipment selection, definition of process, and the operation of process itself. Risk mitigation can both indicate the level of need for process improvement and determine the priority that should be assigned to mitigation activities. Risk mitigation as it relates to aseptic processing generally means to properly control human intervention, but ultimately if risk mitigation is to be maximized, personnel must be completely removed from critical area of aseptic processing, or sterility test isolators should be utilized.
It continues to be widely assumed by some scientists and engineers that aseptic conditions can be adequately maintained if the personnel conducting aseptic processing wear aseptic gowns properly and exhibit sound aseptic technique in conducting their work. However, it is clear from published research data that personnel emit very high levels of microbiological contamination into the environment. This is true even when state-of-the-art gowns are chosen and worn properly. According to Ljungqvist et al., personnel wearing previously unused sterilized gowns emit 1500–3000 cfu/h of microbiological contamination even when conducting limited operations
The microbiological contamination released by personnel can increase to ≥10,000 cfu/h during complex operations that require the execution of many physical tasks.
The total number of aerobic bacteria existing on human skin is normally >1.2 million per square meter. The number of microorganisms existing on a healthy human’s hands and arms are in the range 0.9–3 million per square meter. Microorganisms are emitted by gowned personnel by a pumping effect of the technician’s gown during operation. Hence, advanced aseptic processing technologies include Blow-Fill Seal and Restricted Access Barrier System on top of isolators (Compounding Aseptic Containment Isolator and Compounding Aseptic Isolator) are used to reduce the possibility of product contamination caused by personnel.
The closed RABS is an intermediate solution between isolators and open RABS. A closed operation RAB provides a higher level of contamination control because the RABs barrier doors remain closed from the point of the last bio-decontamination, through initial set-up through processing. These systems typically use transfer systems that are similar to isolator type transfer systems that are closed and dock with the RABs.
Isolator systems do not allow direct interventions by personnel into the enclosure’s aseptic processing area. To ensure that contamination is not introduced into the isolator, it is critical to have means to bring materials into and out of the isolator in a way that presents the transfer of contamination into the isolator. The sterility assurance provided by an isolator is a product of physical separation of personnel, elimination of risk of introduction of airborne contamination, and systems that prevent the introduction of non-sterile materials into the isolator. Safe, contamination free transfer of materials into and out of the isolator can be assured by the use of devices known as decontamination pass boxes and circular-shaped rapid transfer ports (RTP); also decontamination interfaces for attaching devices to isolators have been developed.
Large volumes of air are required to properly satisfy the international standards for clean room air. Air handling systems such as isolators and the built and design of the cleanroom is critical as these will edict the permitted processes during the sterile compounding.
ISO 5/Grade A environments are required for the critical area of aseptic processing. The critical area in aseptic processing is defined as the part of a facility where product and sterilized components are brought together and filled and/or assembled. It is necessary to install and operate this ISO 5/Grade A critical zone environment within an ISO 7/Grade B environment and, of course, to provide proper gowning and support facilities to ensure safe, contamination-free personnel and component entry. Alternatively, in some modern facilities, the entire aseptic processing room can be designed to ISO 5/Grade A requirements; however, such a facility is both expensive to build and also to operate.
The facility and the utility requirements are the fundamental support of the process flow and production effectiveness. In facility design, it is important to consider the regulatory nature of the industry and seeking some in-depth knowledge of the requirements, hence, serving the most basic foundation for a safe, effective, and pure drugs while maintain the cost.
Cleanrooms are extremely critical on the manufacturing of biologics, hence the used of Cross Contamination Facility Integrated Barrier (CCFIB) can maximize the performance given by a cleanroom to ensure the purity of any drug product. This equipment will minimize the exposure of chemical or biological contaminants, such as micro-organisms or adventitious agents, thus providing utmost protection to the product, operator and the environment.
The CradlePro-Iso is an integrated system that combines the Esco Versati™ Centrifuge, Esco CO2 incubator, and CelCradle™ benchtop bioreactor system inside the Esco HPI G3. The CelCradle™ system provides cells with an environment of low shear stress, zero foaming, and of high rates of aeration and nutrition, while the CO2 incubator controls the cells surrounding conditions.
The CradlePro-Iso was designed to fully enclose the cell processing system inside an isolator to ensure the safety of the operator, without compromising the quality of the product.
RABS and isolators can be used in the manufacture of biologics, including vaccines, gene therapies, and protein-based drugs. Often, biologic products are preservative-free, contain growth media, and are easily susceptible to contamination. Another area that demands the use of RABS and isolators is the manufacture of sterile drug products with toxic, cytotoxic, and highly potent molecules, which require stringent barriers to protect personnel who are handling these materials. In general, RABS and isolators are being used for smaller-volume and high-value pharmaceuticals. The benefit/cost balance has to be considered when discussing the use of barriers: RABS and isolators come with a high price tag and are associated with additional expenses related to the operation of a cleanroom, such as energy costs, operating costs, testing costs, and gown costs.
Additional cGMP requirements are also included for the commercial production and delivery of large molecules. These requirements are but not limited to: cleanliness, validation and commissioning, process-material personnel and air flows, cold storage, dry storage, emergency procedures, safety, security, pest control, environmental monitoring, preventive maintenance and