18-19 - CAR-T CELL THERAPY - CAR-T cell therapy in oncology

Chimeric antigen receptor (CAR-T) cell therapy is a recent achievement in cancer therapy resulting in cures in several hard-to-treat blood cancers, including large B-cell lymphoma, acute lymphoblastic leukaemia and other relapsed/refractory haematologic cancer. First generation CAR-T cell therapy is a novel technology in which T cells derived from patient’s blood are engineered ex vivo to express artificial receptors targeted to cell surface tumour antigens, such as CD-19, CD20 and CD22, found predominantly in leukaemia and lymphoma. First generation CAR-T cell therapies have been approved by the US Food and Drug Administration (FDA). However, first generation CAR-T cells have yet to have consistent success against solid tumours.

While the potential of CAR-T therapies is extraordinary, the complexity and cost of their supply chains jeopardise scalability and long-term commercialisation. One of the primary reasons for this complexity is their personalisation. While ‘traditional’ therapeutics are produced in large batches for many people at once, CAR-Ts are typically manufactured in smaller – sometimes single dose – batches. Until recently, CAR-Ts were autologous therapies where the raw biological material for the therapy is derived from the person who will receive it. Today there is research using allogeneic CAR-T therapies, which are sourced from healthy donors that may overcome some of the complexities of autologous therapies while allowing for multiple modifications and CAR combinations.

Tracking the chain of identity, chain of custody and chain of condition is critical throughout the product journeys and managing the logistics orchestration is one of the biggest hurdles in autologous CAR-T therapies. Final doses of these therapies are typically cryopreserved and require special handling and active temperature monitoring to maintain -150 C (-238 F). In autologous therapies, the raw material collected from the patient is typically shipped ‘fresh’ from the collection site and must arrive at the manufacturing facility within 24 to 32 hours. The chain of identity starts with the initial cell collection and follows the single dose throughout the manufacturing process to final dosing of the patient. Temperature monitoring is required throughout the end-to-end process to avoid temperature excursions during transfers and handoffs between multiple parties – which must also be tracked and recorded as the chain of custody.

Within this complex supply chain, there are also manufacturing constraints to be managed. There is usually a limited number of manufacturing slots allocated to a specific therapy that requires multiple sites to coordinate patient schedules and book the apheresis process the day before an available manufacturing slot (to allow overnight shipment). The process involves multiple stakeholders including multiple departments at the apheresis and clinical sites, couriers, shipper providers, ancillary supply vendors and patient concierge services. Without a sufficiently flexible and redundant design, changing schedules at any point during collection, manufacturing, shipping and delivery can affect the entire workflow, potentially compromising patient and product safety. Conversely, allogeneic CAR-Ts are produced using healthy donor cells and can be ‘pre-manufactured’, eliminating the complexities of managing patient schedules to manufacturing slots. However, allogeneic therapies still present the special handling and storage challenges of working with cryopreserved doses.

In working with oncology CAR-T therapies, the stakes for an efficient cell and gene therapy (CGT) supply chain are especially high because recipients are often in the later stages of their illness. Many of these patients would not be able to withstand another cell collection so tracking includes GPS locations of the shipments along with live temperature monitoring.

First generation CAR-Ts have limitations in scalability due to their very time-consuming, complex, expensive and patient-specific ex vivo manufacturing process.

A major advance in development of second generation CAR-Ts is the genetic manipulation in situ (directly in the patient) with RNA or DNA encoding chimeric antigen receptors. Essentially, genetically reprogramming a patient’s immune system to manufacture his or her own cancer-targeting T cells. If successful, this will eliminate the complexity and expense required for individualised external manufacturing of cellular therapies and possibly, the lymphodepletion required to precondition the patient. In addition, it will eliminate the time delay prior to treatment including most of the logistical challenges highlighted in the previous section. The most common technologies being evaluated for in vivo transduction directly in the patient are lentiviral vectors and lipid nanoparticles.

The lentiviruses are non-integrating members of the retrovirus family that can transduce non-dividing cells and cannot cause insertional mutagenesis. Most importantly, lentiviral vectors can transduce dendritic cells that process and ‘present’ antigens to T cells that will initiate a T-cell response. It is hypothesised that by genetically engineering lentiviral vectors with cancer cell antigens and in turn, using these to transduce dendritic cells in situ, T cells can be activated to recognise and destroy tumours. Since dendritic cells will continue to display tumour antigens, this may provide a sustained T-cell response. It is also hypothesised that multiple tumour antigens can be coded within one vector, potentially broadening the T-cell attack on a tumour that may enhance efficacy. Results to date suggest that lentiviral vectors are both safe and effective.

Liposomes are composed of a lipid bilayer that form a hollow sphere encompassing an aqueous internal phase. As such, most drugs can be encapsulated within liposomes in either the aqueous compartment for water-soluble/hydrophilic drugs or within the lipid bilayer for fat-soluble/lipophilic drugs.

Lipid nanoparticles (LNPs) are liposome-like structures especially useful in encapsulating nucleic acids (RNA and DNA). LNPs used to deliver genes are primarily synthesised using cationic, or positively charged, lipids that associate with anionic, or negatively charged, nucleic acids. As such, LNPs are commonly used as a nonviral gene delivery system. Chemical modifications of LNP using PEGylated lipids may enhance stability, time in the circulation to find their target tissue, less immunogenicity and even tissue-specific targeting.

First-generation CAR-T cell therapies have limitations related to clinical efficiencies, safety and efficacy that include:

Required medical procedures related to leukapheresis and lymphodepletion that can be co-dependent upon limited, available manufacturing slots
Time required to produce individualised therapy, necessitating patients wait for weeks before treatment
Significant and even life-threatening side effects related to overstimulation of the immune system
Lack of sustained efficacy directed to a broad range of tumour types.

In first-generation technology, once a therapy is delivered into a patient’s tissue, it’s impossible to regulate levels of cell expansion or gene expression.

Common safety signals seen with first generation CAR-T technology are fever, malaise, fatigue, myalgia, nausea and anorexia. More serious safety signals observed are tachycardia/hypotension, capillary leak, cardiac dysfunction, renal impairment, hepatic failure and disseminated intravascular coagulation, as well as neurologic side effects such as speech problems, tremors, delirium and seizures. Finally, life-threatening side effects are related to cytokine release syndrome, commonly called cytokine storm. Known long-term side effects post-anti-CD19 CAR-T cell therapy include decreased blood B-cell counts and hypogammaglobulinaemia resulting in increased infection risk. Many of the more serious side effects are related to how the body reacts against the profoundly simulated immune state.

Another major advance in development of second-generation CAR-T technology is the control over T-cell expansion and CAR-T expression in the patient. This may allow the patient’s immune response to be both accelerated for greater efficacy or braked when required to better control toxicities. There are many expansion/expressing switches being developed in second-generation CAR-T technology, such as tetracycline-regulated systems, rapamycin-regulated systems, RU486-regulated systems, hypoxia-regulated systems and small molecule splicing modulators. It may also be possible to eliminate the preconditioning lymphodepletion step using a highly regulated, second-generation system.

Currently, six CAR-T cell therapies have been approved by the FDA and many others are in clinical development. To date, all are approved for the treatment of blood cancers, including lymphomas, leukaemias, and, most recently, multiple myeloma. Utility in solid tumours has yet to be consistently demonstrated. Despite the excitement using these therapies in lymphomas and leukaemias, they lead to long-term survival benefits in less than 50% of patients treated. In addition to these clinical limitations, there are also significant cost, manufacturing and logistical limitations associated with first generation CAR-T cell technology.

However, it is well recognised that the full potential of CAR-T cell therapy has yet to be fully exploited. Second-generation CAR-T cell technology is being developed that may address the limitations of first generation technology that will enable:

Facilitate manufacturing by creation of CAR-T cells in situ. This may also address many of the logistical complexities
Control of some of the serious toxicities by enabling up- or down-regulation of expression
Broader applicability to a range of solid tumours.
One thing is clear in this new frontier of medicine: cell and gene therapies are bringing new options to patients – and the future of medicine looks bright.

To obtain the list of references for this article, please email editor@pmlive.com.

CAR-T cell therapy in oncology

The future of cancer treatments is here with cell and gene therapies bringing new options to patients

Managing the complexities of current generation CAR-T therapies

Next generation CAR-T cell therapy

Scalability

1. Lentiviral vectors:

2. Lipid nanoparticles (LNP):

Clinical complexities

Clinical safety

Clinical efficacy

Summary