Strategies to optimize chimeric antigen receptor T-cell therapy in hematologic malignancies: Experience from China

Chimeric Antigen Receptor (CAR) T-cell therapy has changed the course of treatment for numerous hematologic malignancies like leukemia, lymphoma, and multiple myeloma. China is at the forefront of CAR T-cell research with the maximum number of registered CAR T-cell clinical trials in the world.

The clinical triumphs notwithstanding, disease relapse, manufacturing complexities, and issues related to safety are some of the challenges remaining. The article discusses China’s experience with CAR T-cell therapy and suggests strategies to make its efficacy and safety in treating hematologic cancer stronger.

Over the past few decades, hematologic malignancy treatment has come a long way. Despite that, morbidity and mortality have still been very high. With knowledge of molecular genetics, our insight into how the immune system and cancer cells interact has heightened our awareness of T cells as the key to immunotherapy. Adoptive cell therapies, specifically with genetically modified CARs, have been constructed in order to specifically target cancer cells and elicit particular immune reactions.

CAR T-cell treatments have shown stunning effectiveness in malignancies such as acute lymphoblastic leukemia (ALL), large B-cell lymphoma (LBCL), and multiple myeloma (MM), revolutionizing cancer immunotherapy. Of note, China is now a CAR T-cell hotspot, with multiple clinical trials investigating diverse targets and approaches.

Despite promising outcomes, CAR T-cell therapy faces several challenges:

Disease Relapse: Some patients experience relapse due to antigen loss or the emergence of antigen-negative tumor variants.

Manufacturing Complexities: Producing CAR T cells involves intricate processes, including T-cell collection, genetic modification, expansion, and reinfusion, which can be time-consuming and costly.

Safety Concerns: Adverse events like cytokine release syndrome (CRS) and neurotoxicity pose significant risks, necessitating effective management strategies.

To overcome these challenges, Chinese researchers and clinicians have implemented several strategies:

Targeting Multiple Antigens: Developing CAR T cells that target multiple antigens can reduce the risk of relapse due to antigen loss.

Improving Manufacturing Processes: Streamlining production through automated systems and optimizing protocols can enhance efficiency and reduce costs.

Enhancing Safety Profiles: Implementing safety switches and developing strategies to manage adverse events can improve patient outcomes.

Overview of CAR T Cell therapy in China

China has surpassed the USA in the number of CAR T-cell clinical studies, particularly in hematologic malignancies. As of December 2022, there were 458 CAR T-cell trials from China registered on ClinicalTrials.gov, with 73% focused on hematologic malignancies. CD19 and B-cell maturation antigen (BCMA) are the most common targets in Chinese trials. Compared to the USA, China has a higher proportion of trials using multi-target CAR T cells.

Approved CAR T Cell therapies in China

Two CD19-targeted CAR T-cell therapies have been approved in China for large B-cell lymphoma:

Axicabtagene ciloleucel (Yescarta)

Relmacabtagene autoleucel (Carteyva)

Strategies to improve CAR T Cell therapy

Acute Lymphoblastic Leukemia

Allogeneic CAR T cells to overcome limitations of autologous therapy

Universal off-the-shelf CAR T cells

Targeting CD7 for T-cell ALL

Combining multiple targets (e.g. CD19/CD22) to prevent antigen escape

Optimizing CAR design with different co-stimulatory domains

Acute Myeloid Leukemia

Exploring targets like CD33, CD38, CLL1, and CD123

CLL1-targeted CAR T cells showed promise in pediatric AML

Lymphoma

CD19 remains the primary target, with 50-100% overall response rates

Multi-target approaches combining CD19 with CD22, CD20, etc.

Personalized multi-CAR T-cell regimens based on patient’s tumor antigen profile

Combining CAR T cells with other therapies like chemotherapy or radiation

Armored CAR T cells to overcome inhibitory tumor microenvironment

Multiple Myeloma

BCMA-targeted CAR T cells have shown great success

Dual-epitope binding CAR T cells (e.g. LCAR-B38M)

Combining BCMA with other targets like CD19 or CD38

Fourth-generation CAR T cells expressing additional cytokines

Challenges and future direction

Despite promising results, several challenges remain:

Relapse and resistance

Management of cytokine release syndrome (CRS) and neurotoxicity

Manufacturing complexities and high costs

Limited efficacy in solid tumors

Future research is focused on:

Optimizing CAR designs and manufacturing processes

Developing off-the-shelf allogeneic products

Combining CAR T cells with other therapies

Exploring new targets and multi-target approaches

Improving management of adverse events