A groundbreaking gene therapy is offering renewed hope for patients battling aggressive T-cell acute lymphoblastic leukemia (T-ALL), a rare and fast-moving blood cancer. Scientists at University College London (UCL) and Great Ormond Street Hospital (GOSH) have developed BE-CAR7, a treatment that uses precisely edited immune cells to target and destroy cancerous cells, even in cases where standard therapies have failed. This approach represents a significant advancement in cancer treatment, particularly for those with limited options.
The innovation lies in “base editing,” a sophisticated form of CRISPR technology that allows researchers to develop highly accurate changes to individual DNA letters within living cells. Unlike traditional CRISPR methods that cut DNA, base editing minimizes the risk of unintended genetic damage. This precision is crucial when engineering immune cells to fight cancer, as it prevents the modified cells from attacking healthy tissue or each other. The development of BE-CAR7 marks the first time base-edited therapy has been used in a patient globally, a milestone reached in 2022.
Alyssa Tapley, now 16, from Leicester, was the first patient to receive this experimental treatment. Diagnosed with T-cell leukemia in May 2021 after months of illness, Alyssa had exhausted conventional treatment options, including chemotherapy and a bone marrow transplant. Her case, once considered palliative, became a beacon of hope when the research team offered her a place in the clinical trial. Today, Alyssa is thriving, fully engaged in school and activities, and pursuing her dream of becoming a research scientist.
Since Alyssa’s pioneering treatment, BE-CAR7 has been administered to eight more children and two adults at GOSH and King’s College Hospital (KCH). Early results from the clinical trial, published in the New England Journal of Medicine and presented at the 67th American Society of Hematology Annual Meeting, demonstrate remarkable efficacy. According to the study, 82% of patients achieved very deep remission after receiving BE-CAR7, allowing them to proceed to a stem cell transplant without detectable disease. 64% of patients remain leukemia-free, with the earliest treated individuals disease-free and off therapy for up to three years.
The Challenge of T-Cell Leukemia and the Promise of CAR T-Cell Therapy
CAR T-cell immunotherapy has emerged as a powerful tool in the fight against several blood cancers. The process involves modifying a patient’s own T-cells – a type of immune cell – to express a chimeric antigen receptor (CAR). This CAR acts like a guided missile, enabling the T-cells to recognize and destroy cancer cells displaying specific markers on their surface. However, developing CAR T-cell therapies for T-cell leukemias presents a unique challenge: how to eliminate cancerous T-cells without causing the engineered cells to attack healthy T-cells.
“Developing CAR T-cell therapies for leukemias that originate in T-cells has been especially difficult,” explains Professor Waseem Qasim, professor of cell and gene therapy at UCL and honorary consultant immunologist at GOSH. “The challenge is that the treatment must wipe out cancerous T-cells without triggering the engineered cells to attack one another.” The BE-CAR7 therapy overcomes this hurdle through its innovative use of base editing.
Creating “Universal” CAR T-Cells with Base Editing
BE-CAR7 utilizes a next-generation genome editing method that doesn’t cut DNA, reducing the risk of chromosomal damage. Researchers used CRISPR-based tools to alter single DNA letters, effectively reprogramming the T-cells. This allowed them to create “universal” CAR T-cells – cells derived from healthy donors that can be stored and used for multiple patients. The process involves several key steps:
- Removing existing receptors to ensure the donor cells won’t be rejected by the recipient’s immune system.
- Removing the CD7 marker, which identifies cells as T-cells. This prevents the engineered T-cells from attacking each other – a “friendly-fire” scenario.
- Removing CD52, another marker that would otherwise be targeted by immunosuppressant antibodies, allowing the engineered cells to thrive.
- Adding a Chimeric Antigen Receptor (CAR) that specifically recognizes CD7 on leukemic T-cells, directing the engineered cells to attack and destroy the cancer.
The engineered cells are manufactured in a specialized clean room facility at GOSH using custom RNA, mRNA, and a lentiviral vector within an automated system. This meticulous process ensures the quality and consistency of the CAR T-cells.
From Cancer Clearance to Immune Rebuilding
Once infused into a patient, the base-edited CAR T-cells rapidly locate and destroy T-cells throughout the body, including the cancerous ones. If leukemia is cleared within the first month, patients then undergo a bone marrow transplant to restore a functioning immune system. This transplant provides the patient with healthy blood-forming cells, rebuilding their immune defenses over the following months. While side effects such as low blood counts, cytokine release syndrome, and rashes are expected and generally manageable, the greatest risks are associated with viral infections during the period when the immune system is rebuilding.
Dr. Rob Chiesa, a study investigator and bone marrow transplant consultant at GOSH, emphasizes the significance of this therapy for patients who don’t respond to standard treatments. “Although most children with T-cell leukemia will respond well to standard treatments, around 20% may not,” he said. “It’s these patients who desperately need better options, and this research provides hope for a better prognosis for everyone diagnosed with this rare but aggressive form of blood cancer.”
Looking Ahead: Expanding Access and Continued Research
The clinical trial is sponsored by GOSH and supported by the Medical Research Council, Wellcome, and the National Institute for Health and Care Research (NIHR). GOSH Charity has committed over £2 million to support treatment for an additional 10 T-ALL patients, expanding access to this potentially life-saving therapy and contributing to the fundraising campaign for a new Children’s Cancer Centre. Professor Qasim notes the importance of learning from every experience, acknowledging that outcomes haven’t been positive for all children treated. “We’ve shown that universal or ‘off the shelf’ base-edited CAR T-cells can seek and destroy very resistant cases of CD7+ leukemia,” he said.
Alyssa Tapley’s story serves as a powerful testament to the potential of this innovative therapy. “I chose to take part in the research as I felt that, even if it didn’t function for me, it could aid others,” she shared. “Years later, we recognize it worked and I’m doing really well. I’ve done all those things that you’re supposed to do when you’re a teenager.” Alyssa now aspires to develop into a research scientist, hoping to contribute to the next breakthrough in cancer treatment.
Researchers are continuing to monitor patients and gather data to further refine the BE-CAR7 therapy and explore its potential for treating other types of cancer. The next steps involve expanding the clinical trial to include more patients and investigating ways to improve the long-term durability of the response. Patients eligible for NHS care who are interested in participating in the trial should discuss it with their healthcare team.
Disclaimer: The information provided in this article is for general knowledge and informational purposes only, and does not constitute medical advice. This proves essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.
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