Page 191 - Haematologica April 2020

Daratumumab in B-NHL
Introduction
B-cell non-Hodgkin’s lymphoma (B-NHL) constitutes 4- 5% of all hematologic neoplasia with increasing incidence in western countries.1 DLBCL and FL represent the most fre- quent aggressive and indolent NHL, accounting for approx- imately 35% and 20% of all lymphomas, respectively.2,3 Moreover, roughly one third of FL patients develop a histo- logic transformation (tFL) to DLBCL leading to a dismal prognosis.4 Both entities are currently treated with chemo- immunotherapy including a rituximab backbone.5,6 FL responses are usually high, although recurrence occurs in the majority of the cases.7 In DLBCL, currently classified into germinal center type (GCB) or activated B-cell type (ABC),8 treatment is not guided by subtype, and responses to chemo-immunotherapy are normally higher in the GCB subtype. Nevertheless, a portion of DLBCL (20%) do not respond to this regimen.9 Several second-generation anti- CD20 antibodies, such as the Food and Drug Administration-approved obinutuzumab have been clini- cally tested to overcome these limitations.10,11 However, an alternative evolving therapeutic approach is to target a dif- ferent antigen. In this regard, both FL and DLBCL originate in the germinal center (GC) and consequently express high levels of CD38, making this molecule an attractive thera- peutic target.12
MCL is a rare NHL (6% of all NHL) with an aggressive evolution and clinically challenging.13,14 Its frontline therapy, although heterogeneous, typically consists of rituximab- based chemo-immunotherapy followed by autologous- stem cell transplantation and/or rituximab maintenance. Even with intensive therapy, MCL patients ultimately relapse.15 Novel targeted therapies currently approved for R/R MCL include14 the mTOR inhibitor temsirolimus, the immunomodulatory agent lenalidomide, the proteasome inhibitor bortezomib,16 also approved in front-line, and the BTK inhibitor ibrutinib that achieves the highest response rates.17 However, MCL patients failing ibrutinib treatment have very limited therapeutic options.18 In this situation, where virtually all MCL cases express some level of CD38, this antigen represents a potential alternative target to be explored. Moreover, CD38 is associated with nodal disease and poorer survival19,20 and high CD38 expression correlates with poor in vivo response to bortezomib.21 Thus, targeting CD38 could hold promise as a strategy for MCL, also in bortezomib resistant tumors.
CD38 is present at high levels in bone marrow (BM) pre- cursor cells and it is downregulated in resting normal B cells. The molecule is re-expressed at high density once naïve B lymphocytes are activated, and peaks when B cells enter the GC. Terminally differentiated plasma cells and their pathological counterparts express the highest surface densi- ty among human cells, while it is completely absent in memory B cells.22 CD38 behaves simultaneously as an enzyme and as a receptor. The extracellular domain of CD38 contains an enzymatic site that can generate cyclic ADP ribose (cADPR) and ADPR from nicotine adenine din- ucleotide (NAD+). This control of adenosine synthesis by CD38 may be important in the context of the characteristic immunosuppressive tumor microenvironment.
Daratumumab (Darzalex) is a first-in-class, human IgG1κ monoclonal antibody (mAB) that targets the CD38 epitope. It was approved by the Food and Drug Administration in 2015 as a monotherapy for patients with MM, who have received at least three prior therapies.23 Currently, daratu-
mumab has been approved in combination with dexam- ethasone plus either lenalidomide or bortezomib, or poma- lidomide for the treatment of relapsed MM patients.24 Daratumumab has a broad-spectrum killing activity in MM engaging complement-dependent cytotoxicity (CDC), anti- body-dependent cellular cytotoxicity (ADCC),25 antibody- dependent cellular phagocytosis (ADCP),26 and apoptosis.27 Moreover, daratumumab modulates the enzymatic activity of CD3828 and induces an immunomodulatory role in MM by depleting CD38+ immune suppressive cells29 contributing to its antitumor activity. In chronic lymphocytic leukemia (CLL), we have demonstrated that daratumumab induces cytotoxic activity in vitro via ADCC and ADCP in primary CLL cells and cell lines. In vivo, daratumumab significantly prolongs OS of animals in systemic CLL murine models. Daratumumab also affects tumor-microenvironment inter- actions by blocking CLL homing and dissemination to sec- ondary lymphoid organs in vitro and in vivo.30
In the present study, we aimed to investigate in vitro and in vivo activity of daratumumab on MCL, FL and DLBCL cells as monotherapy and in combination with standard therapies.
Methods
Therapeutic drugs
Daratumumab (Darzalex, anti-CD38mAb, IgG1) and the iso- type control mAb (CNTO 3930, IgG1) were provided by Janssen. Rituximab (Mabthera, anti-CD20 mAb, IgG1) and the chemother- apy regimen CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) were obtained from the department of pharmacy of the Hospital Clínic of Barcelona.
Subcutaneous pre-emptive mouse models
SCID mice (Janvier Laboratories) were subcutaneously (sc) injected with 10x106 RL-luc cells in the FL model or 10x106 REC-1 cells in the MCL model, respectively, following a protocol approved by the Animal Testing Ethic committee of the University of Barcelona and Generalitat de Catalunya (Protocol # 9971). Mice were randomly assigned into cohorts of six mice per group and received one intraperitoneal (ip) injection of 10 mg/kg of daratu- mumab or isotype control every other week, starting the day of cell inoculation.
Patient-derived DLBCL xenograft model
ST1361 is a DLBCL patient-derived xenograft model developed using a DLBCL tumor originated in a metastatic site from a
58-year-old chemotherapy-naïve Hispanic male. ST1361 was GCB subtype transformed from an Epstein-Barr virus negative FL tumor.
The DLBCL tumor was homogeneously chopped into frag- ments of similar size and injected sc into SCID mice. Treatment was initiated when mean tumor volume was approximately 150-250 mm3. Daratumumab 20 mg/kg was administered weekly for three weeks alone or in combination with CHOP (20 mg/kg cyclophosphamide, 1.25 mg/kg doxorubicin, 0.2 mg/kg vincristine [intravenously on Day 0], and 0.15 mg/kg prednisone [Days 0-4]; once a day (QD) for five days) or R-CHOP (10 mg/kg rituximab [intraperitoneally on Day 0]+ CHOP as before).
Statistical analysis
Unpaired and paired t-tests were used to assess statistical differ- ences between two groups using GraphPad Prism software 4.0. For Kaplan-Meier survival curves, SPSS19 software was used.
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