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.