The history of cell and gene therapy is not one without its peaks and pitfalls. This novel type of therapy promised to treat and cure almost any disease by inserting a corrective gene into the cells, with an important caveat: the molecular pathogenesis of the disease had to be properly understood.
This year marks the eighteenth anniversary of Jesse Gelsinger’s death, the first directly attributed to gene therapy treatment. Gelsinger had ornithine transcarbamylase (OTC) deficiency, a metabolic disorder that prevents the body from breaking down and eliminating the build-up of ammonia. The gene delivery vehicle — a recombinant adenoviral vector — provoked an immune reaction, causing brain damage and organ failure. Gelsinger died a few days later in the autumn of 1999. His death rocked the gene therapy community and resulted in increased regulatory control in gene therapy trials.
Since the 90s, the field of cell and gene therapy has progressed by leaps and bounds with the refinement of chimeric antigen receptor (CAR) T-cell therapy. The aim of CAR T-cell therapy is to harness the body’s immune T-cells, which normally target and kill infected cells, and genetically modify them to recognise and target tumour antigens. We can achieve this by endowing the T-cell with a CAR, which is a synthetic protein that combines the antigen-binding domain of an antibody with the T-cell signalling machinery. In a nutshell, the patient’s immune cells are harvested, genetically modified to express a a CAR in a purpose-built clean-room, and then expanded to billions of cells before cryopreservation and subsequent re-infusion into the patient at the bedside.
Over the last five years, CAR T-cell therapy has made waves in the scientific and medical community. Clinical trials in the US and worldwide have shown great promise, particularly in the treatment of B-cell malignancies in patients who have become refractory to both first-line treatment and salvage therapy, causing remissions in a number of patients. To date, over 1500 patients have been enrolled and treated in CAR T-cell trials worldwide.
The UCL CAR Immunotherapy Programme was launched under the direction of Dr Martin Pule, senior lecturer in haematology at UCL. This started with a Bloodwise-funded study, called COBALT, targeting CD19 in diffuse large B-cell lymphoma.
At the initial development stage, we designed and created a whole range of candidate CARs in order to provide and deliver the best possible therapeutic living drug. Each candidate had different binding domains from antibodies targeting CD19 and different T-cell activation domains. Our CAR candidates were engineered from donated peripheral blood with target-positive tumour cells expressing CD19 and target-negative tumour cells lacking CD19. During the preclinical in vitro development that followed, we aimed to determine the efficacy of the candidates based on their ability to firstly recognise and specifically kill tumour cells, and secondly to proliferate and expand after antigen recognition. By co-culturing genetically modified T-cells expressing the various CAR candidates with target-positive (CD19-positive) tumour cells and CD19-negative tumour cells, we were able to determine the tumour-specific lysis of target cells, essentially demonstrating the modified cells’ ability to kill tumour cells.
Next, we sought to demonstrate that these CAR T-cells could proliferate on recognition of tumour cells, thereafter expanding and killing them to drive their numbers down. By culturing these CAR T-cells with cells derived from B-cell lymphomas over seven days, we achieved a 25-fold expansion of CAR T-cells. This shows their potential to expand inside the body and combat disease, essentially acting as a living drug.
After four months of in vitro testing, we whittled down the candidates to two CARs: MP28 and MP30. The next step after in vitro assays and before clinical trials is in vivo animal modelling; it is the current standard for modelling toxicity, off-target effects, pharmacokinetics and efficacy in the next best surrogate for the human body. Modelling of the final candidate CARs established their ability to recognise tumours (CD19-positive lymphoma in this case) and kill them, leaving the animals disease-free.
After careful assessment and consensus on a final CAR candidate, the fruits of research are taken out of the labs and into the manufacturing pipeline. Production of the lentiviral vector encoding our CAR candidate was outsourced to our colleagues at King’s College London Rayne Cell Therapy Suite, and cell manufacture to UCL Gene Therapies Labs based at the UCL Great Ormond Street Institute of Child Health.
CAR development in clinical trials is typically a multifaceted approach that involves research scientists specialising in a diverse range of disciplines. Trial design, methodology, patient recruitment, logistics, follow-up, protocol, ethics and regulation are all undertaken by a large team of clinicians, trial coordinators, statisticians and everyone in between. The pilot COBALT trial has helped lay the groundwork for future trials and bring departments together to deliver a common goal.
The translation from bench to bedside can take many years notwithstanding the decades of basic research that underpins applied science. It is not surprising, therefore, that the COBALT clinical trial took over three years to move from preclinical workup and the research pipeline to product manufacture. Since its inception, the UCL CAR Immunotherapy Programme has spawned four individual Phase I clinical trials, of which three target CD19 to treat paediatric acute lymphoblastic leukaemia (ALL) and adult diffuse large B-cell lymphoma (DLBCL) amongst other post-transplantation CD19-positive malignancies. The fourth trial targets disialoganglioside (GD2) for the treatment of paediatric neuroblastoma. Six additional trials are earmarked to open within the next two years. These trials will apply CAR T-cell therapy to the treatment of adult ALL (ALLCAR19), glioma (gCARV3), primary central nervous system lymphoma (CNSLCAR19), T-cell lymphoma (TCAR), B-cell cancers and multiple myeloma. These studies are made possible by generous funding from the National Institute for Health Research, the Wellcome Trust, Cancer Research UK, and the UCL Business biopharmaceutical spin-out Autolus.
By Gordon Weng-Kit Cheung Research Scientist,
Research Department of Haematology
UCL Cancer Institute