A novel anti-CD19 monoclonal antibody (GBR 401) with high killing activity against B cell malignancies

Abstract

BackgroundCD19 is a B cell lineage specific surface receptor whose broad expression, from pro-B cells to early plasma cells, makes it an attractive target for the immunotherapy of B cell malignancies. In this study we present the generation of a novel humanized anti-CD19 monoclonal antibody (mAb), GBR 401, and investigate its therapeutic potential on human B cell malignancies.MethodsGBR 401 was partially defucosylated in order to enhance its cytotoxic function. We analyzed the in vitro depleting effects of GBR 401 against B cell lines and primary malignant B cells from patients in the presence or in absence of purified NK cells isolated from healthy donors. In vivo, the antibody dependent cellular cytotoxicity (ADCC) efficacy of GBR 401 was assessed in a B cell depletion model consisting of SCID mice injected with healthy human donor PBMC, and a malignant B cell depletion model where SCID mice are xenografted with both primary human B-CLL tumors and heterologous human NK cells. Furthermore, the anti-tumor activity of GBR 401 was also evaluated in a xenochimeric mouse model of human Burkitt lymphoma using mice xenografted intravenously with Raji cells. Pharmacological inhibition tests were used to characterize the mechanism of the cell death induced by GBR 401.ResultsGBR 401 exerts a potent in vitro and in vivo cytotoxic activity against primary samples from patients representing various B-cell malignancies. GBR 401 elicits a markedly higher level of ADCC on primary malignant B cells when compared to fucosylated similar mAb and to Rituximab, the current anti-CD20 mAb standard immunotherapeutic treatment for B cell malignancies, showing killing at 500 times lower concentrations. Of interest, GBR 401 also exhibits a potent direct killing effect in different malignant B cell lines that involves homotypic aggregation mediated by actin relocalization.ConclusionThese results contribute to consolidate clinical interest in developing GBR 401 for treatment of hematopoietic B cell malignancies, particularly for patients refractory to anti-CD20 mAb therapies.

The “less-is-more” in therapeutic antibodies: Afucosylated anti-cancer antibodies with enhanced antibody-dependent cellular cytotoxicity

“… 70 Chimeric IgG1     GBR 401CD19Reduced (∼50%)CHO cells with reduced fucosylationEnhanced B-cell depletion over rituximab in xenografted SCID mouseBreton et al. 107 Humanized IgG1     Inebilizumab/MEDI-551CD19afucosylatedFUT8 −/− CHO cells (Potelligent® Technology)Enhanced B-cell depletion in huCD19/CD20 transgenic mouse over rituximabHerbst et al. 105 Humanized IgG1   A direct comparison between MEDI-551 and the fucosylated anti-CD19 in CD19 + Raji and Daudi cells lymphoma xenograft SCID mouse model only showed minor or insignificant improvement in tumor inhibition respectivelyWard et al.…”

“…Several groups have developed anti-CD19 antibodies that are afucosylated. 103-107 These afucosylated antibodies generally showed enhanced B-cell depletion in murine and non-human primate models compared with the fucosylated counterparts. However, anti-CD19 monoclonal antibody MEDI-551 only showed a minor or insignificant improvement in tumor inhibition in CD19 + Raji and Daudi cell lymphoma xenograft SCID mouse models 104 .…”

Second-generation inhibitors of Bruton tyrosine kinase

“…Novel agents targeting biomarker molecules in lymphocytes are revolutionizing treatment of lymphoid malignancies [25–33]. Since BTK is a critical effector molecule for B cell development and plays a major role in lymphomagenesis, BTK inhibitors have been investigated as potential treatments [11, 34–37].…”

Bruton tyrosine kinase inhibitor ONO/GS-4059: from bench to bedside

“…Novel targeted agents have led to revolutions of lymphoma treatment [22–31]. Since BTK plays a critical role in B cell development and lymphomagenesis, BTK inhibitors have been in active clinical development [32–36].…”