Anti-NKG2C/IL-15/anti-CD33 killer engager directs primary and iPSC-derived NKG2C+ NK cells to target myeloid leukemia.

Natural killer (NK) cells mediate the cytolysis of transformed cells and are currently used as an adoptive cellular therapy to treat cancer. Infection with human cytomegalovirus has been shown to expand a subset of "adaptive" NK cells expressing the activation receptor NKG2C that have preferred functional attributes distinct from conventional NK cells. Because NKG2C delivers a strong activating signal to NK cells, we hypothesized that NKG2C could specifically trigger NK-cell-mediated antitumor responses. To elicit a tumor-directed response from NKG2C+ NK cells, we created an anti-NKG2C/IL-15/anti-CD33 killer engager called NKG2C-KE that directs NKG2C+ cells to target CD33+ cells and tumor-associated antigen expressed by acute myelogenous leukemia cells. The NKG2C-KE induced specific degranulation, interferon-γ production, and proliferation of NKG2C-expressing NK cells from patients who reactivated cytomegalovirus after allogeneic transplantation. The NKG2C-KE was also tested in a more homogeneous system using induced pluripotent stem cell (iPSC)-derived NK (iNK) cells that have been engineered to express NKG2C at high levels. The NKG2C-KE triggered iNK-cell-mediated cytotoxicity against CD33+ cells and primary AML blasts. The NKG2C-KE-specific interaction with adaptive NK and NKG2C+ iNK cells represents a new immunotherapeutic paradigm that uniquely engages highly active NK cells to induce cytotoxicity against AML through redirected targeting.

Tri-specific killer engager: unleashing multi-synergic power against cancer.

Cancer continues to be a global health concern, necessitating innovative solutions for treatment. Tri-specific killer engagers (TriKEs) have emerged as a promising class of immunotherapeutic agents, offering a multifaceted approach to cancer treatment. TriKEs simultaneously engage and activate natural killer (NK) cells while specifically targeting cancer cells, representing an outstanding advancement in immunotherapy. This review explores the generation and mechanisms of TriKEs, highlighting their advantages over other immunotherapies and discussing their potential impact on clinical trials and cancer treatment. TriKEs are composed of three distinct domains, primarily antibody-derived building blocks, linked together by short amino acid sequences. They incorporate critical elements, anti-cluster of differentiation 16 (CD16) and interleukin-15 (IL-15), which activate and enhance NK cell function, together with specific antibody to target each cancer. TriKEs exhibit remarkable potential in preclinical and early clinical studies across various cancer types, making them a versatile tool in cancer immunotherapy. Comparative analyses with other immunotherapies, such as chimeric antigen receptor-T (CAR-T) cell therapy, immune checkpoint inhibitors (ICIs), cytokine therapies, and monoclonal antibodies (mAbs), reveal the unique advantages of TriKEs. They offer a safer pathway for immunotherapy by targeting cancer cells without hyperactivating T cells, reducing off-target effects and complications. The future of TriKEs involves addressing challenges related to dosing, tumor-associated antigen (TAA) expression, and NK cell suppression. Researchers are exploring innovative dosing strategies, enhancing specificity through tumor-specific antigens (TSAs), and combining TriKEs with other therapies for increased efficacy.

Antibody variable region engineering for improving cancer immunotherapy.

The efficacy and specificity of conventional monoclonal antibody (mAb) drugs in the clinic require further improvement. Currently, the development and application of novel antibody formats for improving cancer immunotherapy have attracted much attention. Variable region-retaining antibody fragments, such as antigen-binding fragment (Fab), single-chain variable fragment (scFv), bispecific antibody, and bi/trispecific cell engagers, are engineered with humanization, multivalent antibody construction, affinity optimization and antibody masking for targeting tumor cells and killer cells to improve antibody-based therapy potency, efficacy and specificity. In this review, we summarize the application of antibody variable region engineering and discuss the future direction of antibody engineering for improving cancer therapies.

Trispecific killer engager 161519 enhances natural killer cell function and provides anti-tumor activity against CD19-positive cancers.

Objective: Natural killer (NK) cells have gained considerable attention due to their potential in treating "cold tumors," and are therefore considered as one of the new strategies for curing cancer, by using worldwide development of their new possibilities and interventions with NK cell-related therapeutic products. Methods: We constructed a trispecific killer engager (TriKE) consisting of anti-CD16, IL-15, and anti-CD19. This TriKE was designed to attract CD19+ tumor cells to CD16+ NK cells, whereas IL-15 sustained the proliferation, development, and survival of NK cells. Results: Treatment with 161519 TriKE in the presence of CD19+ targets upregulated expression of CD69, CD107a, TRAIL, IFN-γ, and TNF-α in NK cells, and significantly improved the proliferation and cytotoxicity of NK cells. NK cells "armed" with 161519 TriKE showed stronger cytolysis against CD19+ targets compared with that of "unarmed" NK cells. A preclinical model of B-cell lymphoma in human peripheral blood mononuclear cell-reconstituted xenograft mice showed significant inhibition of tumor growth and prolonged overall survival after treatment with 161519 TriKE, when compared with that in control mice or mice treated with 1619 BiKE. Combined use of IL-2 was a more effective treatment with 1619 BiKE, when compared with that using 161519 TriKE. Conclusions: The newly generated 161519 TriKE enhanced the proliferation, activation, cytokine secretion, and cytotoxicity of NK cells in the presence of CD19+ tumor cells. The 161519 TriKE aided inhibition of tumor growth and prolonged the overall survival of murine xenografts, and could be used to treat CD19-positive cancers.