Targeted Cancer Immunotherapy by Nanoparticle T Cell Engagers

Acute myeloid leukemia (AML) is the most common type of leukemia. Emerging immunotherapies such as chimeric antigen receptor T (CAR-T) cells and T cell engagers (TCEs), have the potential to enhance T cell recognition and response against cancers, but come with serious limitations such as short half-life, complex production, high cost, and inability to customize for another antigen. To overcome these limitations, we previously developed a nanoparticle-based T cell engagers (nanoTCEs) technology that has a longer half-life (60h vs 2h for TCEs), is convenient to make, easily customizable, and robustly activates T cells for cancer killing. In this study, we hypothesized that nanoTCEs targeting CD33/CD3 would effectively activate T cell response in an AML disease model.Liposomes were produced via the thin-film hydration method with cholesterol, DPPC, and DSPE-PEG200 at a molar ratio of 30:65:5 respectively (Figure 1A). CD33/CD3 nanoTCEs were created by conjugating anti-CD3 and anti-CD33 monoclonal antibodies (mAbs) on liposome surface with streptavidin-biotin chemistry. Liposome binding to human T cells and AML cell lines was performed with fluorescently labeled nanoTCEs for 2 hours. The activation of T cell subsets and killing of AML cell lines was analyzed by flow cytometry after 4 days in a 3D culture model. For in vivo efficacy, immunodeficient NCG mice were inoculated with AML cell line and received Isotype/CD3 or CD33/CD3 nanoTCEs injections (0.5 mg/mouse) weekly and monitored for tumor progression and survival.AML cell lines (K052, MOLM-14. NOMO-1, and THP-1) exhibited high expression of CD33 compared to controls. CD33/CD3 nanoTCEs bound to human T cells and AML cell lines with higher specificity than isotype controls. In addition, the CD33/CD3 nanoTCEs induced increased activation of both CD4+ and CD8+ T cells (Figure 1B, 1C) and achieved greater AML killing compared to the untreated and Isotype/CD3 groups (Figure 1D). Lastly, our in vivo results showed that weekly CD33/CD3 nanoTCE injections extended survival and decreased tumor progression of AML bearing mice compared to Isotype/CD3 nanoTCEs treated mice. By day 66 of the in vivo study, none of the Isotype/CD3 cohort was alive, while 100% of the CD33/CD3 cohort remained living (Figure 2).This study shows that nanoTCEs are a promising novel platform for immunotherapy in AML. CD33/CD3 nanoTCEs demonstrated specific engagement of T cells to AML cells, which induced T cell activation and AML cell killing both in vitro and in vivo. It not only circumvented the limitations of traditional T cell engagers, but also presented numerous advantages such as short production time, low cost, and superior pharmacokinetic profile. Moreover, this technology is highly customizable and can be tailored to target multiple cancer antigens simultaneously. The current findings provide a strong preclinical basis for future first-in-human clinical trials of CD33/CD3 nanoTCEs as a novel AML immunotherapy.