Dual-Targeted Nanobody-Based Bispecific Antibody for Acute Myeloid Leukemia: Harnessing CD3E and LILRB4

VHH-P316 is an innovative bispecific humanized nanobody fusion construct currently in the Biological Testing stage, specifically designed to target the CD3 epsilon subunit of the T-cell receptor complex (CD3E) and leukocyte immunoglobulin like receptor B4 (LILRB4). By engaging these two pivotal immune cell surface markers, VHH-P316 aims to harness and redirect T-cell cytotoxicity against leukemic cells. The first-in-class molecular architecture of VHH-P316 enables selective and potent targeting of malignant cells in acute myeloid leukemia, presenting a promising therapeutic strategy with the potential to address critical gaps in current AML treatments.

Licensing Opportunity

VHH-P316 is available for out-licensing and partnership opportunities. We welcome collaboration with industry partners seeking to advance novel immunotherapeutics for acute myeloid leukemia leveraging dual-targeted nanobody technology.

Development Phase

Modality

VHH-P316 is a bispecific antibody fusion composed of two polypeptide chains. The first chain integrates a humanized single-domain nanobody targeting LILRB4, connected by a flexible G4S linker to a humanized VH fragment directed at CD3E, followed by an IgG1 Fc domain engineered with knob mutations. The second chain consists of a VHH domain fused to an IgG1 Fc domain containing hole mutations. Expressed in ExpiCHO-S cells using knobs-into-holes technology, this construct leverages the inherent advantages of nanobodies, such as small molecular size, remarkable stability, and efficient tissue penetration. Such attributes confer enhanced ability to engage tumor sites and penetrate dense leukemic environments typical of acute myeloid leukemia, potentially overcoming conventional antibody limitations in solid and hematological malignancies.

Target

CD3E and LILRB4 are the core targets of VHH-P316. CD3E is a critical component of the T-cell receptor complex, fundamentally involved in T-cell activation and signal transduction, predominantly expressed on T-lymphocytes. LILRB4, an inhibitory immune checkpoint receptor, is notably expressed on myeloid cells, including monocytic leukemia cells. CD3E is essential for triggering T-cell–mediated cytotoxicity, while LILRB4 is implicated in immune evasion and resistance mechanisms in AML. Recent studies highlight LILRB4 as a negative regulator in the leukemia microenvironment, making it a strategic target for immunotherapy. By simultaneously engaging CD3E and LILRB4, VHH-P316 addresses the unique immunosuppressive context of AML, creating a differentiated approach aimed at improving patient outcomes and providing a valuable asset for AML drug development.

Mechanism of Action

VHH-P316 functions as a bispecific antibody engaging both CD3E and LILRB4. By binding to CD3E on T cells and LILRB4 on leukemia cells, this construct effectively redirects T-cell cytotoxic activity specifically toward malignant cells expressing LILRB4. The interaction with CD3E triggers T-cell activation and proliferation, while engagement with LILRB4 overrides inhibitory signals in the tumor microenvironment, leading to targeted leukemia cell lysis. The nanobody-based platform offers additional versatility for engineering next-generation therapeutics, including potential development as an antibody-drug conjugate or alternative bispecific formats. This dual-targeting mechanism offers precise modulation of immune responses with minimized off-target effects, presenting a highly strategic approach for AML immunotherapy.

Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is an aggressive hematological malignancy characterized by the rapid proliferation of immature myeloid cells in the bone marrow and peripheral blood. Affecting both adults and children globally, AML presents significant clinical challenges due to its heterogeneity and high relapse rates. Standard therapies include intensive chemotherapy, targeted therapies, and hematopoietic stem cell transplantation. Despite these approaches, many patients relapse or develop resistance, highlighting a substantial unmet medical need for novel treatments. Immunotherapeutic strategies are increasingly explored, yet the complexity of AML’s microenvironment limits the efficacy of many conventional agents. VHH-P316, with its bispecific nanobody construct targeting both CD3E and LILRB4, is designed to overcome immunosuppressive barriers and precisely direct T-cell cytotoxicity against leukemic cells. This innovative modality holds promising potential to achieve improved clinical outcomes for patients with AML, representing a significant advancement in AML therapeutic development.