Cell and Gene Therapy Frequently Asked Questions

Ensuring the safety and efficacy of gene and cell therapies is an essential yet daunting task during development. The medicines are highly individualized, and both the European Medicinal Agency (EMA) and the U.S. Food and Drug Administration Agency (FDA) have many regulations outlining the approval of these products. For these reasons, safety and risk minimization for patients begins during medicinal product design. For example, by implementing desired properties of viral vectors.

Novel gene and cell therapies are tested for safety during Proof of Concept (PoC) and non-clinical studies. At that level the bioprocess design is verified and attributes assessed for their impact on the product. Already in the early product and process development, Good Manufacturing Practices (GMP) and Good Laboratory Practices (GLP) deserve the utmost attention, as well as Good Distribution Practices apply. 

To ensure the safety of each product, facilities must carefully inspect their starting materials and manufacturing steps to determine their impact on the final product. Multiple active ingredients may generate unforeseen effects when processed together, so robust quality control is key to addressing safety and efficacy risks in the long term. Some examples of risks related to gene and cell therapy include:

• Vector insertional mutagenesis. Vector integration into a host cell genome may change activity of host genes, leading to gene mutation or increased activity of nearby genes. 
• Viral vector shedding. Excretion or release of virus gene therapy from the patient’s body.
• Biodistribution (BD). The distribution and the persistence of the vector/virus to target and nontarget tissues.
• Viral replication. When a virus infects a cell, it replicates (creation of new infectious virions) using the cell’s resources and releases itself into the body through it. As indicated by the US FDA in the guidance for industry 'Design and Analysis of Shedding Analysis for Various or Bacteria-based Gene Therapy and Oncolytic Products,' 'shedding' means release of virus or bacteria gene therapy or oncolytic products (VBGT) from the patient through one or all following ways: excreta (feces), secreta (e.g. urine, saliva) or through the skin (e.g. pustules, sores, wounds). It describes how a product is excreted or released from the patient's body.
• Clonal outgrowth. Delivery vectors that integrate with the genome run the risk of clonal outgrowth, leading to a large population of cells with the DNA mutation.
• Pediatric studies. CGT studies often begin with adult test subjects and slowly transition to younger age groups. Quality control for pediatric products requires long-term attention, which is not always applicable for genetic disorders. Besides, children account for 50% of rare disease patients.

Safety considerations are always at play, even after a CGT product obtains regulatory approval. That’s why follow-up studies, which can last up to 15 years for CGT products, are necessary for ensuring long-term safety and regulatory compliance.

2. How do you navigate the regulatory landscape and obtain necessary approvals from regulatory agencies such as the FDA and the EMA?

Legal compliance is a challenging endeavor in emerging fields of medicine like cell and gene therapy. Developers must consider both the United States Food and Drug Administration (FDA) and the European Union’s European Medicines Agency (EMA) requirements.

The FDA defines CGT medicines as biological products and regulates this market segment under the Center for Biologics Evaluation and Research (CBER). The EU has its own term, Advanced Therapy Medicinal Products (ATMP). Both agencies recognize that CGT is an emerging field with unique safety and efficacy requirements and have introduced new regulatory pathways to accelerate development and compliance.

One of the major pushes is for stronger communication between developers and regulators, which is important for emerging fields with little pre-existing knowledge. The agencies offer Initial Targeted Engagement for Regulatory Advice on CBER Products (INTERACT) meetings for this purpose, replacing the prior CBER pre- pre-Investigational New Drug (IND) meeting process for all products across the center.

Other regulatory considerations to make include:

• Cell sourcing. The FDA and EMA have different expectations regarding cell banks and where manufacturers can source their cells. Expectations are very similar in the EU and US. For autologous and allogeneic cells (from healthy donors) leveraged for cell therapies or as ex vivo modified gene therapies, a manufacturer should provide information about the source of cells, the collection procedure, and compliance with donor eligibility requirements (21 CFR 1271). For autologous cells, DE is recommended, but not required (FDA). More Info about MCB, WCB can be found in ICH Q5D and in the US FDA transcripts.
• Quality control criteria. CGT manufacturing is notoriously complex, so the criteria for safety and efficacy aren’t always clear. Both the FDA and EMA recommend combining multiple testing methodologies together. This is especially applicable for potency assays. For example, validation of potency assays, n=3 different types of assays are recommended.
• A potency assay. The potency assay is a metric of how effectively a product can generate a biological response. Choosing this assay is another consideration for measuring efficacy, though regulatory agencies accept surrogate assays that correlate with functional assays during early studies.
• Changes to the manufacturing process. Changes to the manufacturing process over time may introduce variability within each batch of the final product. The EMA cites comparisons between the product batches using calculated standard deviations. In the 'Reflection paper on statistical methodology for the comparative assessment of quality attributes in drug development' EMA suggests discussing the operating characteristics of approaches used to determine reference range, e.g. the range between min-max data points, x-sigma intervals or tolerance intervals. The risk of a false positive should be acceptable low. For smaller amounts of samples, there is uncertainty in the estimates of SD due to the large multiplier.
• Non-clinical studies. Before moving on to clinical studies, EU regulators require the Genetically Modified Organism (GMO) application, a prerequisite for in vivo gene therapy prior to Clinical Trials Application (CTA).

Cell and gene therapy operates in a unique regulatory environment. Current standards do not accommodate the new challenges of CGT, so both the EMA and FDA essentially encourage manufacturers to evaluate risks in each step of the manufacturing process on a case-by-case basis.

3. How do you optimize and scale up the manufacturing process for gene and cell therapies, including the selection of appropriate cell lines and vectors?

The medical industry is searching for ways to scale up cell and gene therapy manufacturing. As the field emerges, unique challenges present themselves:

• Finding partnerships. Outsourcing will be a key solution in addressing supply chain problems related to CGT manufacturing. Companies must find reliable suppliers for raw materials and enable clear communication to synchronize operations and create realistic milestones and timelines. Because CGT is a personalized medicine (each patient receives a tailored batch), any miscommunication can have serious consequences.
• Packaging and transportation. CGT medical products must be shipped with temperature constraints. Cryogenic conditions are often necessary, and packaging must withstand the temperatures involved. Regulatory requirements also ensure that containers withstand pressure differences during flights.
• Timing. Controlled freezing and thawing are essential parts of transporting CGT products and materials, but slow freezing can also negatively impact the quality of certain cell lines, RNA, and plasmid DNA.
• Tracking shipments. CGT medicines are highly personalized, and sending the wrong shipment to a patient can result in significant toxic effects. The industry is experimenting with end-to-end monitoring of each batch via RFID tags.
• Quantity of cells. Different dosages should be assessed during the non-clinical tox study and Phase 2 CTs.

Generating specialized cells starts with pluripotent stem cells (PSCs), which evolve to become tissue-specific and usable in CGT. To scale up manufacturing, the industry is looking to study PSC biology more closely and generate more specialized cells from fewer PSCs. Generally, there are different types of cells used for CGTs.

4. How do you design clinical trials that effectively demonstrate the safety and efficacy of gene and cell therapies in target patient populations?

The clinical trials for cell and gene therapies are significantly different from those of other medical fields. Clinical studies aim to identify safety concerns within medical products. But while many drugs are chemical in nature and have a direct impact on the patient, CGTs are released into host cells. For example, gene therapies with a viral vector serve as the carrier are released into the nucleus of the host cell.

There are additional risks to human test subjects during CGT clinical trials, such as the side effects of genome insertions. 

CGT’s unpredictable interactions with the human body have called for a new approach to clinical trials:

• Finding trial participants. CGT clinical trials suffer from a limited pool of potential test subjects, as many of them target rare diseases. And the few that do sign up must agree to long-term follow-ups for up to 15 years afterward. Some companies are contacting patient advocacy groups to help locate patients for testing, even those in separate geographic locations.
• Ensuring safety. The risks associated with CGT treatments are currently not fully understood, and some adverse effects may take a long time to manifest in a clinical setting. Additional study will be necessary to determine side effects and how a patient’s medical history and genetic background impact the treatment.
• Lack of data. Rare diseases having few treatments available on the market, clinical trials must turn to disease or patient registries to measure the efficacy of their treatments. Finding comparators in currently available data will be a priority for CGT.

5. How to ensure long-term product stability, including the preservation and storage of cell-based therapies and the durability of genetic modifications?

The cell and gene therapy sector will call for cold storage to preserve and transport its medicines and products. The demand for cryogenic facilities, liquid nitrogen, and other storage mediums with temperatures below -80 degrees Fahrenheit rose during COVID-19 to store heat-sensitive CGT products.

It’s worth noting that slow freezing and thawing can also negatively impact the quality of CGT-related products, such as certain cell lines and RNA, so controlled freezing and thawing will be necessary for transport.

The containers carrying cell and gene therapy products must also withstand pressure differences brought on by international flights.

6. How to monitor and manage the risk of adverse events and side effects associated with gene and cell therapies?

Like any emerging field of medicine, cell and gene therapy suffers from limited knowledge. The risk profile for CGT products is relatively unknown. Gene expression is often unpredictable, and clinical trials must measure physiological change carefully in their test subjects.

Developers must establish standards while working closely with regulatory agencies to provide a foundation for CGT. And because the potential toxicity effects of CGT are significant, companies must conduct a careful risk vs. reward assessment when administering treatments.

However, the adverse effects of CGT products are not easy to measure, even in a clinical setting. They may take time to manifest and are heavily reliant on the patient’s medical history and genetic profile. Managing risks in these clinical trials will require long-term observation of at least 3 or 4 weeks.

Shipping and delivery will also require attention. Cell and gene therapies are tailored toward individual patients, so transportation must ensure the correct treatment reaches the correct patient.

7. How to develop appropriate dosing and administration strategies for gene and cell therapies, taking into account factors such as the duration of therapeutic effect and potential for off-target effects?

Determining optimal dosage strategies for cell and gene therapies will be a significant talking point for researchers in the industry. What dosage induces a therapeutic response in the patient without leading to toxicity? How do you prevent issues like liver or kidney damage when administering CGT treatments?

In gene therapy, dosage is a vital topic since re-dosing isn’t always an option and the body’s response to the treatment may be limited. However, new advancements are looking to optimize the adeno-associated virus (AAV), the delivery vector for gene therapy, through directed evolution. The result is a lower necessary dose and a lower chance of toxicity.

In cell therapy, the dosage of cells required for a patient depends on the target organ or tissue. Some applications require over 1 billion specialized cells per dose for cell replacement therapy, while other areas like brain or central nervous system regeneration might require fewer. Cell therapy is currently searching for ways to optimize stem cell engineering to yield more specialized cells from the same stem cell bank.

8. How to foster partnerships and collaborations with academic, industry, and patient organizations to support the development and commercialization of gene and cell therapies?

How to manage the cost-effectiveness and affordability of gene and cell therapies, including the development of reimbursement and pricing strategies?

In addition to developmental challenges, cell and gene therapies are currently set back by high dosage costs and affordability concerns for patients. Zolgensma, one gene therapy drug for treating spinal muscular atrophy, notably costs $2.1 million per dose.

However, a single dose with long-term effects may still be preferable to constant treatments spanning a lifetime. CGT must mainly grapple with making upfront costs more accessible, which may involve:

• Working with governmental agencies like health technology assessment bodies to determine cost-effective measures for ensuring affordability.
• Designing new payment plans, such as staggered payments.
• Turning to performance-based pricing. Instead of using a base price, patients pay based on how well the treatment has performed.

While this latter option is attractive for being patient-focused, it’s also not always easy to determine treatment performance, especially in the long term.