Novel Biomimetic Platform Revolutionizes CAR T Cell Therapy for Relapsed Leukemia

Chimeric antigen receptor T (CAR T) cell therapy represents a significant advancement in treating leukemia. However, a major hurdle remains: over 50% of patients relapse because leukemia cells can evade treatment by reducing or losing expression of the targeted antigen, rendering CAR T cells ineffective. Addressing this limitation has historically involved complex and time-consuming genetic engineering of CAR structures.

"A key limitation is that over 50% of patients relapse because leukemia cells can reduce or lose expression of the targeted antigen, making CAR T cells ineffective."

Now, researchers from the Institute of Process Engineering (IPE) of the Chinese Academy of Sciences have introduced a groundbreaking biomimetic platform designed to bolster CAR T cell therapy for relapsed and refractory leukemia. Crucially, this innovative strategy achieves enhanced efficacy without necessitating genetic modification of CAR T cells. Reported in Cell on March 9th, this platform has undergone rigorous validation in vivo in multiple relapsed and refractory leukemia mouse models and in vitro using patient-derived samples.

Unlocking a Universal Target: CD71

Through a collaborative effort with Zhujiang Hospital and the Institute of Hematology & Blood Diseases Hospital, extensive analysis of clinical samples revealed a critical insight: CD71, a protein involved in iron transport, is highly expressed on leukemia cells across various types and stages. Remarkably, CD71 is also found on autologous CAR T cells, presenting a unique opportunity for therapeutic intervention.

Introducing FACE: A Molecular Bridge for Enhanced Engagement

Leveraging this discovery, the researchers engineered a biomimetic ferritin aggregation cell engager, or FACE. This was achieved by meticulously controlling solvent and assembly conditions to induce the ordered self-assembly of ferritin, the natural ligand of CD71.

FACE functions as a molecular "bridge" that significantly reinforces the crucial interface between CAR T cells and leukemia cells. During the CAR T cell preparation phase, FACE binds to CD71 on the surface of the CAR T cells. Following infusion into the patient, the FACE molecules on the CAR T cells then attach to CD71 expressed on the leukemia cells, thereby strengthening their interaction. This enhanced engagement leads to improved CAR T cell recognition and more effective elimination of leukemia cells.

Dramatic Preclinical Success

The impact of FACE-CAR T cells was profound in leukemia patient-derived xenograft (PDX) models:

• In models with normal antigen expression, FACE-CAR T cells achieved a similar therapeutic effect to conventional CAR T cells using only one-fifth of the cell dose, while also reducing the risk of cytokine release syndrome.
• Even under challenging conditions where leukemia antigen levels dropped below 10% of normal—a scenario where conventional CAR T cells were largely ineffective—FACE-CAR T cells effectively eliminated leukemia cells, achieving 100% survival in PDX models.

FACED: Expanding the Therapeutic Arsenal with Targeted Drug Delivery

Building on this success, the researchers further developed a drug-loaded version of FACE, termed FACED, by utilizing ferritin's inherent cage-like structure. FACED-CAR T cells demonstrated their ability to effectively treat PDX models with an initial leukemia burden of up to 40% and low antigen expression. Crucially, FACED-CAR T cells also proved capable of eliminating antigen-negative leukemia cells, a notorious population often responsible for patient relapse.

Expert Acclaim and Translational Promise

Prof. WEI Wei from IPE, a corresponding author on the study, highlighted the practical advantages of the FACE platform:

"The FACE platform uses an endogenous protein and FDA-approved polymer derivatives, can be prepared simply and scalably, and integrates seamlessly into existing CAR T cell manufacturing workflows as a culture supplement without genetic engineering of CARs."

Prof. MA Guanghui from IPE further emphasized the platform's broad potential, noting that "systematic evaluation across diverse patient-derived leukemia samples and clinically relevant PDX models demonstrated its broad applicability across disease subtypes and treatment-resistant settings." The team also established an efficacy database and an AI-assisted predictive framework to guide future applications.

Peer reviewers at Cell lauded the findings as "highly relevant to the CAR T field" and a "promising translational approach" for improving responsiveness against hematologic malignancies. They particularly emphasized that the strategy's lack of additional genetic engineering could significantly facilitate broad clinical implementation and potentially counteract the inherent heterogeneity of leukemia antigens.

This study introduces a robust biomimetic platform poised to enhance CAR T cell performance through improved cell engagement and targeted drug delivery. Supported by compelling preclinical validation, this strategy offers a practical and scalable approach to significantly improve outcomes in patients battling relapsed and refractory leukemia.