Dual epitope anti-LILRB4 synthetic T-cell receptor and antigen receptor (STAR)-T-cell therapy for relapsed/refractory acute myeloid leukemia | Meng Lv et al. | ResearchPod

Transcript: Dual epitope anti-LILRB4 synthetic T-cell receptor and antigen receptor (STAR)-T-cell therapy for relapsed/refractory acute myeloid leukemia

Sam: A phase I trial of a dual-epitope STAR-T cell therapy against LILRB4 reported a 50 percent objective response rate in heavily pretreated AML, with no grade 3 or higher neurotoxicity. The work was led by Xiangyu Zhao and published in Signal Transduction and Targeted Therapy.

Alex: Fifty percent in that population is notable, but I'd want the denominator before I react to it. And why a synthetic T-cell receptor rather than a conventional CAR?

Sam: The denominator is six evaluable patients, so three responders. I'll come back to what that can support. On the architecture, the problem in AML is antigen density. Conventional CARs need a fairly high density of target to trigger signaling. STAR-T cells instead fuse targeting nanobodies to the native TCR alpha and beta constant regions, so they use the native TCR signaling cascade, which is inherently more sensitive to sparse antigen than synthetic CAR domains.

Alex: So the receptor lowers the activation threshold. Where does the dual-epitope part come in?

Sam: Two nanobodies bind different contact points on LILRB4. That raises avidity, so the T cell stays engaged even when expression on the blasts is low. It also hedges against antigen escape, because losing one epitope doesn't remove the other.

Alex: Binding strength is one thing. What spares normal hematopoiesis?

Sam: Target selection. LILRB4 is highly expressed on monocytic AML blasts but largely absent from normal hematopoietic stem cells. That should limit the on-target, off-tumor toxicity that would otherwise drive myelosuppression. Together with the absence of severe neurotoxicity, that makes the safety profile look favorable on its face.

Alex: "On its face" is doing some work, though. These are people with advanced AML. You'd expect a lot of adverse events regardless of the product.

Sam: Yes. The patients were heavily pretreated and already profoundly neutropenic. There were deaths, but the study did not classify them as dose-limiting toxicities, because they were linked to infections in that neutropenic setting rather than to the cells. That's the authors' attribution, and with six patients it's hard to test independently. Persistent cytopenia and infection risk are the reason they argue future trials need stricter screening for fungal and bacterial colonization before infusion.

Alex: Then let's go to the non-responders. Why did half the patients not respond?

Sam: This is where the single-cell RNA sequencing comes in, and I'd call it the most informative part of the paper. In non-responders, the myeloid compartment looked immunosuppressive. Monocytic myeloid-derived suppressor cells were present, and the data pointed to suppression of T-cell function through pathways including LGALS9 and MIF. Their myeloid cells also showed higher reactive oxygen species activity, which correlated with inhibitory capacity.

Dual epitope anti-LILRB4 synthetic T-cell receptor and antigen receptor (STAR)-T-cell therapy for relapsed/refractory acute myeloid leukemia

Meng Lv, Hongli Zheng, Xuying Pei, Lei Lei, Wenbo Chen, Yutong Bao, Yiyang Ding, Zhengli Xu, Lijuan Hu, Zhe Wan, Xueqiang Zhao, Zhixiao Zhou, Xin Lin, Xiaojun Huang, Jiasheng Wang, Xiangyu Zhao

Jun 1, 2026·5:00·doi·Original Paper

STAR-T-cell therapyLILRB4Acute myeloid leukemia (AML)Dual epitope targetingClinical trialAcute Myeloid Leukemia (AML)

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Summary

Research Question

Acute myeloid leukemia (AML) remains difficult to treat due to the lack of highly specific tumor antigens and a suppressive bone marrow microenvironment. This study investigates whether targeting LILRB4—a receptor highly expressed on monocytic AML blasts but largely absent on normal hematopoietic stem cells—using a novel synthetic T-cell receptor and antigen receptor (STAR-T) platform can provide a safe and effective therapeutic option for relapsed/refractory (R/R) AML.

Approach

The researchers developed a dual-epitope STAR-T cell therapy (DE STAR-T) by fusing two high-affinity nanobodies targeting distinct LILRB4 epitopes to the constant regions of the T-cell receptor. They compared the efficacy of these DE STAR-T cells against single-epitope STAR-T cells and conventional CAR-T cells in vitro and in vivo. Following preclinical validation, they conducted a first-in-human phase I clinical trial (NCT05548088) in nine patients with LILRB4-positive R/R AML, using single-cell RNA sequencing to analyze mechanisms of response and treatment failure.

Main Findings

Preclinical results showed that DE STAR-T cells exhibited superior cytotoxicity, cytokine production, and tumor control compared to monovalent STAR-T or dual-epitope CAR-T cells, particularly against tumor cells with low LILRB4 expression. In the clinical trial, the therapy demonstrated an overall response rate (ORR) of 50% in the efficacy-evaluable set. While no severe cytokine release syndrome (CRS) or neurotoxicity (ICANS) was observed, all patients experienced grade 3 or higher adverse events, primarily pancytopenia and severe infections, which led to three deaths. Single-cell analysis suggested that monocyte-mediated suppression of autologous T-cell function is a primary driver of treatment failure in nonresponders.

Why It Matters

This study provides proof-of-concept for LILRB4 as a viable target for AML immunotherapy. By utilizing the STAR-T platform, which mimics native TCR signaling, the researchers achieved potent antitumor effects even against low-antigen-expressing leukemia cells. While the safety profile—specifically the high rate of severe infections—necessitates caution and improved supportive care, the clinical responses observed in heavily pretreated patients suggest that this approach could be a transformative strategy for monocytic AML.

Key Terms and Definitions

LILRB4 — An immunosuppressive receptor highly expressed on monocytic AML blasts that facilitates immune evasion and tumor infiltration.
STAR-T cells — Synthetic T-cell receptor and antigen receptor T-cells that integrate structural features of native TCRs and conventional CARs to improve signaling fidelity and antigen sensitivity.
Dual Epitope Targeting — A strategy using two distinct nanobodies to bind different parts of the same target antigen, designed to enhance binding breadth and reduce the risk of antigen escape.
M-MDSCs — Monocytic myeloid-derived suppressor cells that contribute to an immunosuppressive bone marrow microenvironment and were found to inhibit T-cell function in nonresponding patients.
Relapsed/Refractory (R/R) AML — A form of acute myeloid leukemia that has either failed to respond to initial treatment or has returned after a period of remission, representing a high-risk patient population with limited options.

Abstract

Acute myeloid leukemia (AML) is a rapidly progressive malignancy with poor prognosis. To date, chimeric antigen receptor (CAR) T-cell therapy in AML has been limited by the lack of antigens with high specificity for AML cells. Here, we developed a synthetic T-cell receptor and antigen receptor-T (STAR-T) cell therapy targeting LILRB4, an immunosuppressive receptor highly expressed on monocytic AML blasts but not on hematopoietic stem cells. Two nanobodies with the highest affinity for LILRB4 were identified through phage display library screening and used to construct nanobody-based dual epitope anti-LILRB4 STAR-T cells, which exhibit more potent tumor inhibition in vitro and in vivo than single epitope anti-LILRB4 STAR-T cells or dual epitope anti-LILRB4 CAR-T cells do. We subsequently conducted the first human clinical trial (NCT05548088) involving 9 patients with LILRB4-positive relapsed and refractory (R/R) AML. Six patients completed the safety and efficacy evaluation (median follow-up, 10.7 months). No immune effector cell-associated neurotoxicity (ICANS) or grade ≥3 cytokine release syndrome (CRS) was observed. Three patients died due to laboratory-confirmed infections. The best overall response rate (ORR) was 50.0% (3/6) in the efficacy assessable set and 33.3% in the full analysis set. The number of LILRB4-positive STAR-T cells significantly increased, and the number of LILRB4-positive target cells decreased. Single-cell RNA sequencing revealed that monocyte-mediated suppression of autologous T-cell function may be a primary mechanism underlying the failure of STAR-T therapy in nonresponders. In conclusion, this first-in-human trial demonstrates the therapeutic potential of targeting LILRB4 with STAR-T-cell therapy in AML and warrants further investigation.

Dual epitope anti-LILRB4 synthetic T-cell receptor and antigen receptor (STAR)-T-cell therapy for relapsed/refractory acute myeloid leukemia: Research Paper Podcast