Combining daratumumab with CD47 blockade prolongs survival in preclinical models of pediatric T-ALL

Abstract

Acute lymphoblastic leukemia (ALL) is the most common malignant disease affecting children. Although therapy strategies improved, T-cell acute lymphoblastic leukemia (T-ALL) relapse is associated with chemoresistance and a poor prognosis. One strategy to overcome this obstacle is the application of monoclonal antibodies. Here, we show that leukemic cells from T-ALL patients express surface CD38 and CD47, both attractive targets for antibody therapy. We therefore investigated the commercially available CD38 antibody daratumumab (Dara) in combination with a proprietary modified CD47 antibody (Hu5F9-IgG2σ) in vitro and in vivo. Compared to single treatments, this combination significantly increased in vitro antibody-dependent cellular phagocytosis (ADCP) in T-ALL cell lines as well as in random de novo and in relapsed/refractory T-ALL patient derived xenograft (PDX) samples. Similarly, enhanced ADCP was observed when combining Dara with pharmacological inhibition of CD47 interactions using a glutaminyl cyclase inhibitor. Phase II-like preclinical in vivo trials using T-ALL PDX samples in experimental minimal residual disease like (MRD-like) and overt leukemia models revealed a high anti-leukemic efficacy of CD47 blockade alone. However, T-ALL xenograft mice subjected to chemotherapy first (post-chemo MRD) and subsequently co-treated with Dara and Hu5F9-IgG2σ displayed significantly reduced bone marrow infiltration as compared to single treatments. In relapsed and highly refractory T-ALL PDX combined treatment with Dara and Hu5F9-IgG2σ was required to substantially prolong survival as compared to single treatments. These findings suggest that combining CD47 blockade with Dara is a promising therapy for T-ALL, especially for relapsed/refractory disease harbouring a dismal prognosis in patients.

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

“…Tumor cell killing by myeloid cells can be improved by disrupting CD47/SIRPα interactions, for example with CD47 blocking antibodies ( 11 , 26 ). Pharmacological inhibition of glutaminyl cyclases that catalyze the formation of pyro-glutamate on CD47 in tumor cells, has been identified as another potential strategy ( 12 , 15 – 17 ). As a more direct approach to investigate the impact of both strategies on myeloid cell-mediated T-ALL killing, ADCP and ADCC experiments were performed with MOLT-13 cells, in which the CD47 or QPCTL genes were knocked-out by CRISPR/Cas technology.…”

“…MOLT-13 control cells were transfected with Cas9 only (without gRNA). Primary T-ALL cells were from patients included in the ALL-BFM study 2000/2009 and described elsewhere ( 12 ).…”

“…Myeloid cell-mediated ADCC or ADCP can be increased by blocking myeloid checkpoint molecules – such as the CD47/signal regulatory protein alpha (SIRPα) axis ( 11 ). For example, daratumumab in combination with CD47 blockade was effective in T-ALL cell depletion in vivo in xenograft NSG mouse models ( 12 ), which was most likely caused by myeloid effector cells since these severely immunocompromised mice do not have T or NK cells and lack a functional complement system. The CD47 blocking antibody hu5F9-G4 (magrolimab) combined with the CD20 antibody rituximab showed promising clinical activity in advanced lymphoma patients ( 13 ).…”

Molecular Determinants Underlying the Anti-Cancer Efficacy of CD38 Monoclonal Antibodies in Hematological Malignancies

“…It was also able to reduce the capacity of AML transendothelial migration by 50% [ 83 ]. In a more recent study, combining daratumumab with a CD47-blocking antibody substantially prolonged survival as compared to single treatments, and it was hypothesized that the CD47 blockade was able to overcome the immunosuppressive effects on ADCP mediated by dysregulated CD38 expression in T-ALL [ 84 ].…”

A Bright Horizon: Immunotherapy for Pediatric T-Cell Malignancies

“…As an unconjugated monoclonal antibody, it is unlikely to be efficacious as a sole treatment; however, it may be more promising in conjunction with other therapies. In a preclinical xenograft T-ALL model, Müller and colleagues recently demonstrated that co-targeting of CD47 and CD38 with anti-CD47 monoclonal antibodies plus daratumumab in combination significantly enhanced in vitro phagocytosis and prolonged survival as compared with single agent treatment [ 65 ].…”