Daratumumab displays in vitro and in vivo anti-tumor activity in models of B-cell non-Hodgkin lymphoma and improves responses to standard chemo-immunotherapy regimens.

CD38 is expressed in several types of non-Hodgkin lymphoma (NHL) and constitutes a promising target for antibody-based therapy. Daratumumab (Darzalex) is a first-in-class anti-CD38 antibody approved for the treatment of relapsed/refractory (R/R) multiple myeloma (MM). It has also demonstrated clinical activity in Waldenström macroglobulinaemia and amyloidosis. Here, we have evaluated the activity and mechanism of action of daratumumab in preclinical in vitro and in vivo models of mantle cell lymphoma (MCL), follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL), as monotherapy or in combination with standard chemo-immunotherapy. In vitro, daratumumab engages Fc-mediated cytotoxicity by antibody-dependent cell cytotoxicity and antibody-dependent cell phagocytosis in all lymphoma subtypes. In the presence of human serum, complement-dependent cell cytotoxicity was marginally engaged. We demonstrated by Selective Plane Illumination Microscopy that daratumumab fully penetrated a three-dimensional (3D) lymphoma organoid and decreased organoid volume. In vivo, daratumumab completely prevents tumor outgrowth in models of MCL and FL, and shows comparable activity to rituximab in a disseminated in vivo model of blastic MCL. Moreover, daratumumab improves overall survival (OS) in a mouse model of transformed CD20dim FL, where rituximab showed limited activity. Daratumumab potentiates the antitumor activity of CHOP and R-CHOP in MCL and FL xenografts. Furthermore, in a patient-derived DLBCL xenograft model, daratumumab anti-tumor activity was comparable to R-CHOP and the addition of daratumumab to either CHOP or R-CHOP led to full tumor regression. In summary, daratumumab constitutes a novel therapeutic opportunity in certain scenarios and these results warrant further clinical development.

Selective BTK inhibition improves bendamustine therapy response and normalizes immune effector functions in chronic lymphocytic leukemia.

The Bruton's tyrosine kinase (BTK) inhibitor ibrutinib has been shown to be highly effective in patients with chronic lymphocytic leukemia (CLL) and is approved for CLL treatment. Unfortunately, resistance and intolerance to ibrutinib has been observed in several studies, opening the door for more specific BTK inhibitors. CC-292 (spebrutinib) is a BTK inhibitor with increased specificity for BTK and less inhibition of other kinases. Our in vitro studies showed that CC-292 potently inhibited B-cell receptor signaling, activation, proliferation and chemotaxis of CLL cells. In in vivo studies using the adoptive transfer TCL1 mouse model of CLL, CC-292 reduced tumor load and normalized tumor-associated expansion of T cells and monocytes, while not affecting T cell function. Importantly, the combination of CC-292 and bendamustine impaired CLL cell proliferation in vivo and enhanced the control of CLL progression. Our results demonstrate that CC-292 is a specific BTK inhibitor with promising performance in combination with bendamustine in CLL. Further clinical trials are warranted to investigate the therapeutic efficacy of this combination regimen.

Cytoplasmic cyclin D1 controls the migration and invasiveness of mantle lymphoma cells.

Mantle cell lymphoma (MCL) is a hematologic neoplasm characterised by the t(11;14)(q13;q32) translocation leading to aberrant cyclin D1 expression. The cell functions of cyclin D1 depend on its partners and/or subcellular distribution, resulting in different oncogenic properties. We observed the accumulation of cyclin D1 in the cytoplasm of a subset of MCL cell lines and primary cells. In primary cells, this cytoplasmic distribution was correlated with a more frequent blastoid phenotype. We performed immunoprecipitation assays and mass spectrometry on enriched cytosolic fractions from two cell lines. The cyclin D1 interactome was found to include several factors involved in adhesion, migration and invasion. We found that the accumulation of cyclin D1 in the cytoplasm was associated with higher levels of migration and invasiveness. We also showed that MCL cells with high cytoplasmic levels of cyclin D1 engrafted more rapidly into the bone marrow, spleen, and brain in immunodeficient mice. Both migration and invasion processes, both in vivo and in vitro, were counteracted by the exportin 1 inhibitor KPT-330, which retains cyclin D1 in the nucleus. Our data reveal a role of cytoplasmic cyclin D1 in the control of MCL cell migration and invasion, and as a true operator of MCL pathogenesis.

The Human CD38 Monoclonal Antibody Daratumumab Shows Antitumor Activity and Hampers Leukemia-Microenvironment Interactions in Chronic Lymphocytic Leukemia.

Purpose: To establish a proof-of-concept for the efficacy of the anti-CD38 antibody daratumumab in the poor prognosis CD38+ chronic lymphocytic leukemia (CLL) subtype.Experimental Design: The mechanism of action of daratumumab was assessed in CLL primary cells and cell lines using peripheral blood mononuclear cells to analyze antibody-dependent cell cytotoxicity (ADCC), murine and human macrophages to study antibody-dependent cell phagocytosis (ADCP), or human serum to analyze complement-dependent cytotoxicity (CDC). The effect of daratumumab on CLL cell migration and adhesion to extracellular matrix was characterized. Daratumumab activity was validated in two in vivo models.Results: Daratumumab demonstrated efficient lysis of patient-derived CLL cells and cell lines by ADCC in vitro and ADCP both in vitro and in vivo whereas exhibited negligible CDC in these cells. To demonstrate the therapeutic effect of daratumumab in CLL, we generated a disseminated CLL mouse model with the CD38+ MEC2 cell line and CLL patient-derived xenografts (CLL-PDX). Daratumumab significantly prolonged overall survival of MEC2 mice, completely eliminated cells from the infiltrated organs, and significantly reduced disease burden in the spleen of CLL-PDX. The effect of daratumumab on patient-derived CLL cell dissemination was demonstrated in vitro by its effect on CXCL12-induced migration and in vivo by interfering with CLL cell homing to spleen in NSG mice. Daratumumab also reduced adhesion of CLL cells to VCAM-1, accompanied by downregulation of the matrix metalloproteinase MMP9.Conclusions: These unique and substantial effects of daratumumab on CLL viability and dissemination support the investigation of its use in a clinical setting of CLL. Clin Cancer Res; 23(6); 1493-505. ©2016 AACR.

Disruption of follicular dendritic cells-follicular lymphoma cross-talk by the pan-PI3K inhibitor BKM120 (Buparlisib).

PURPOSE: To uncover the signaling pathways underlying follicular lymphoma-follicular dendritic cells (FL-FDC) cross-talk and its validation as new targets for therapy. EXPERIMENTAL DESIGN: FL primary cells and cell lines were cocultured in the presence or absence of FDC. After 24 and 48 hours, RNA was isolated from FL cells and subjected to gene expression profiling (GEP) and data meta-analysis using DAVID and GSEA softwares. Blockade of PI3K pathway by the pan-PI3K inhibitor BKM120 (buparlisib; Novartis Pharmaceutical Corporation) and the effect of PI3K inhibition on FL-FDC cross-talk were analyzed by means of ELISA, RT-PCR, human umbilical vein endothelial cell tube formation, adhesion and migration assays, Western blot, and in vivo studies in mouse FL xenografts. RESULTS: GEP of FL-FDC cocultures yields a marked modulation of FL transcriptome by FDC. Pathway assignment by DAVID and GSEA software uncovered an overrepresentation of genes related to angiogenesis, cell adhesion, migration, and serum-response factors. We demonstrate that the addition of the pan-PI3K inhibitor BKM120 to the cocultures was able to downregulate the expression and secretion of proangiogenic factors derived from FL-FDC cocultures, reducing in vitro and in vivo angiogenesis. Moreover, BKM120 efficiently counteracts FDC-mediated cell adhesion and impedes signaling and migration induced by the chemokine CXCL12. BKM120 inhibits both constitutive PI3K/AKT pathway and FDC- or CXCL12-induced PI3K/AKT pathway, hampers FDC survival signaling, and reduces cell proliferation of FL cells in vitro and in mouse xenografts. CONCLUSIONS: These data support the use of BKM120 in FL therapy to counteract microenvironment-related survival signaling in FL cells.