Myeloid checkpoint blockade improves killing of T-acute lymphoblastic leukemia cells by an IgA2 variant of daratumumab

Abstract

Antibody-based immunotherapy is increasingly employed to treat acute lymphoblastic leukemia (ALL) patients. Many T-ALL cells express CD38 on their surface, which can be targeted by the CD38 antibody daratumumab (DARA), approved for the treatment of multiple myeloma. Tumor cell killing by myeloid cells is relevant for the efficacy of many therapeutic antibodies and can be more efficacious with human IgA than with IgG antibodies. This is demonstrated here by investigating antibody-dependent cellular phagocytosis (ADCP) by macrophages and antibody-dependent cell-mediated cytotoxicity (ADCC) by polymorphonuclear (PMN) cells using DARA (human IgG1) and an IgA2 isotype switch variant (DARA-IgA2) against T-ALL cell lines and primary patient-derived tumor cells. ADCP and ADCC are negatively regulated by interactions between CD47 on tumor cells and signal regulatory protein alpha (SIRPα) on effector cells. In order to investigate the impact of this myeloid checkpoint on T-ALL cell killing, CD47 and glutaminyl-peptide cyclotransferase like (QPCTL) knock-out T-ALL cells were employed. QPTCL is an enzymatic posttranslational modifier of CD47 activity, which can be targeted by small molecule inhibitors. Additionally, we used an IgG2σ variant of the CD47 blocking antibody magrolimab, which is in advanced clinical development. Moreover, treatment of T-ALL cells with all-trans retinoic acid (ATRA) increased CD38 expression leading to further enhanced ADCP and ADCC, particularly when DARA-IgA2 was applied. These studies demonstrate that myeloid checkpoint blockade in combination with IgA2 variants of CD38 antibodies deserves further evaluation for T-ALL immunotherapy.

Characterization of human Fc alpha receptor transgenic mice: comparison of CD89 expression and antibody-dependent tumor killing between mouse strains

“…In this study we thoroughly characterized a hCD89 transgenic mouse model regulated by the endogenous human promoter. Our results, along with previous studies, indicate that CD89 expression and function in this model highly resemble the human situation [ 12 , 46 ]. We and others observed that CD89 expression is highest in neutrophils, intermediate on other myeloid cells such as eosinophils and DC subsets and inducible on monocytes and Kupffer cells, among others.…”

Deciphering the role of QPCTL in glioma progression and cancer immunotherapy

“…Since QPCTL expression is closely related to cytokine and chemokine function and modulation of QPCTL synergized with anti-PD-L1 expands CD8 + T cells and limits tumor growth, targeting QPTCL constitutes an effective approach for myeloid cell-targeted cancer immunotherapy; it prevents monocyte migration across inflammatory conditions ( 22 ). Knocking out QPCTL suppressed tumor growth via disrupting monocyte homeostasis, and knocking out QPCTL together with blocking immune checkpoint CD47 has been verified to improve the killing of T-acute lymphoblastic leukemia cells ( 29 , 36 ). In a recent study, it was found that CD47 deficiency or pyroglutamylation inhibition increases myeloid cell-mediated T-ALL killing; QPCTL deficiency reduced 78% of the binding between CD47 and SIRPα ( 36 ).…”

“…Knocking out QPCTL suppressed tumor growth via disrupting monocyte homeostasis, and knocking out QPCTL together with blocking immune checkpoint CD47 has been verified to improve the killing of T-acute lymphoblastic leukemia cells ( 29 , 36 ). In a recent study, it was found that CD47 deficiency or pyroglutamylation inhibition increases myeloid cell-mediated T-ALL killing; QPCTL deficiency reduced 78% of the binding between CD47 and SIRPα ( 36 ). The regulation function of QPCTL of monocyte infiltration under inflammatory conditions had been demonstrated a long time ago ( 37 ).…”

Dual checkpoint blockade of CD47 and LILRB1 enhances CD20 antibody-dependent phagocytosis of lymphoma cells by macrophages

“…Antibodies were purified by affinity chromatography using CaptureSelect ™ IgG-CH1 affinity matrix (Thermo Fisher Scientific) as described earlier (47) and dialyzed against PBS (Thermo Fisher Scientific). The IgA2 isotype variants of rituximab (RTX-IgA2) and the anti-epidermal growth factor receptor (EGFR) antibody cetuximab have been described previously and were expressed in CHO-S cells (Thermo Fisher Scientific) by transient transfection following published procedures (48)(49)(50).…”