Indatuximab ravtansine (BT062) combination treatment in multiple myeloma: pre-clinical studies
Schönfeld et al. Journal of Hematology & Oncology
Indatuximab ravtansine (BT062) combination treatment in multiple myeloma: pre-clinical studies
Kurt Schönfeld 1
Chantal Zuber 1
Jan Pinkas 0
Thomas Häder 1
Katrin Bernöster 1
Christoph Uherek 1
0 ImmunoGen Inc. , 830 Winter Street, Waltham 02451-1477, MA , USA
1 Biotest AG , Landsteinerstraße 5, 63303 Dreieich , Germany
Indatuximab ravtansine is a monoclonal antibody-linked cytotoxic agent that specifically targets CD138-expressing cells. Monotherapy has been shown to significantly inhibit multiple myeloma tumour growth in vivo and improve host survival. Here, we show that in most cell lines tested, indatuximab ravtansine acts additively or even synergistically with clinically approved therapies for treatment of multiple myeloma. In addition, in vivo mouse xenograft models confirmed the activity of indatuximab ravtansine in combination with lenalidamide and lenalidomide/dexamethasone. Indatuximab ravtansine may therefore be a suitable combination partner for multiple myeloma, and a clinical study is ongoing.
Multiple myeloma; Pre-clinical; Indatuximab ravtansine; Drug combination; Tumour regression
Multiple myeloma is a highly aggressive malignancy
characterised by the clonal proliferation of plasma cells
in the bone marrow and associated organ damage
resulting from the presence of monoclonal proteins
(M-proteins) in the blood or urine. The cell surface heparan
sulphate proteoglycan CD138 (syndecan-1) is a
transmembrane protein receptor for the extracellular matrix
(ECM) that mediates cell-cell adhesion via interactions
with heparan-binding molecules. In multiple myeloma,
CD138 has been shown to be a co-receptor for multiple
myeloma growth factors . CD138 is overexpressed on
malignant plasma cells and is used as a primary
diagnostic marker for multiple myeloma . Indatuximab
ravtansine (BT062) is an antibody-drug conjugate based
on a murine/human chimeric form of B-B4 (specific for
CD138), linked to the maytansinoid drug DM4 by
disulphide bonds and has previously been shown to
significantly inhibit multiple myeloma tumour growth in
vivo and to prolong host survival in xenograft mouse
models of human multiple myeloma . However,
treatment of multiple myeloma typically involves
combination therapy [4–6]. Since indatuximab ravtansine has a
1Biotest AG, Landsteinerstraße 5, 63303 Dreieich, Germany
Full list of author information is available at the end of the article
unique mode of action that is different to that of
standard of care therapies, it might be a suitable combination
partner with approved drugs for the treatment of
multiple myeloma. Therefore, the effects of indatuximab
ravtansine in combination with some clinically approved
therapies for multiple myeloma were investigated in
both in vitro and in vivo models (Additional file 1:
Methods). In vitro, anti-tumour-effect studies in RPMI
8226, MOLP-8 and U266 cell lines demonstrated significant
CD138 expression and sensitivity to indatuximab ravtansine
(Fig. 1a–c, Additional file 2: Figure S1; IC50 200 pM, RPMI
8226; 40 pM, MOLP-8; 20 pM, U266). Further in vitro
studies investigated the cytotoxic effects of potential drug
combinations. Additive or synergistic effects were observed
for indatuximab ravtansine in combination with
bortezomib, thalidomide, lenalidomide, melphalan or
dexamethasone in vitro in most cell lines (Fig. 1d).
Mouse xenograft models (MOLP-8 and MMXF L363)
were then used to investigate in vivo the anti-tumour
activity of combination therapy with indatuximab
ravtansine and clinically approved myeloma drugs. In MOLP-8
xenograft mouse models, indatuximab ravtansine
exhibited a dose-response effect on tumour regression and
this effect was enhanced when assessed in combination
with lenalidomide. Lenolidamide (and later in
combination with dexamethasone) was chosen for in vivo
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Fig. 1 Cytotoxic effects of indatuximab ravtansine. a Sensitivity of RPMI 8226, b MOLP-8 and c U266 cells to indatuximab ravtansine
(IR; 1 pM–100 nM) was determined by Alamar Blue proliferation assay and expressed as survival fractions. d Drug combinations of indatuximab
ravtansine with bortezomib, thalidomide, lenalidomide, melphalan and dexamethasone
studies based on the in vitro results and due to it being
an established, clinically approved treatment for multiple
myeloma. The greatest effects on MOLP-8 tumour
regression were observed with 21.2 mg/kg/day
indatuximab ravtansine and 100 mg/kg/day lenalidomide (Fig. 2a,
Additional file 3: Table S1).
The anti-tumour activity of indatuximab ravtansine
was also investigated in combination with both
lenalidomide and dexamethasone in an aggressive xenograft
model using the plasma cell myeloma cell line MMXF
L363. In this xenograft model, indatuximab ravtansine
treatment alone (2 and 4 mg/kg), as well as the
combination of lenalidomide and dexamethasone resulted in
tumour growth delay (Fig. 2b). When assessed alone,
single-agent indatuximab ravtansine at a dose of 4 mg/
kg achieved similar anti-tumour activity as the
combination of lenalidomide and dexamethasone. Furthermore,
a stronger effect on tumour growth was observed when
indatuximab ravtansine 4 mg/kg was combined with
lenalidomide and dexamethasone (Fig. 2b). Treatment
with indatuximab ravtansine was well tolerated.
Single-agent indatuximab ravtansine has already been
shown to have clinical activity in patients with relapsed/
refractory multiple myeloma [7, 8]. These pre-clinical
data provide a basis for the development of indatuximab
ravtansine in combination with clinically approved
anti-myeloma drugs such as lenalidomide and
dexamethasone and in light of these results, a clinical
Fig. 2 Anti-tumour activity in MOLP-8 and MMXF L363 tumours. a Dose-response anti-tumour activity (median tumour volume) in female CB.17
SCID mice inoculated with MOLP-8 multiple myeloma xenografts with control PBS; or indatuximab ravtansine (IR; 5.3, 10.6 or 21.2 mg/kg body
weight); or lenalidomide (Len; 100 mg/kg/day); or combination of indatuximab ravtansine plus lenalidomide. Anti-tumour activity was evaluated
by comparison of maximum tumour volume inhibition compared to control. b Anti-tumour activity (median tumour volume) in female CB.17
SCID mice inoculated with plasma cell leukaemia model MMXF L363 multiple myeloma xenografts with control (PBS); or indatuximab ravtansine
(IR; 2 or 4 mg/kg/day); or lenalidomide (Len; 20 mg/kg/day) and dexamethasone (1.25 mg/kg/day); or combination of indatuximab ravtansine plus
lenalidomide and dexamethasone
phase I/IIa study has been initiated to evaluate the
safety and efficacy of indatuximab ravtansine in
combination with lenalidomide and dexamethasone in patients
with relapsed/refractory multiple myeloma. Promising
initial results from this study have been reported , and the
trial is currently ongoing.
Additional file 1: Methods. (DOCX 20 kb)
Additional file 2: Figure S1. CD138 expression. (PDF 134 kb)
Additional file 3: Table S1. Dose-response relationship of MOLP-8
tumours to indatuximab ravtansine alone, lenalidomide alone and
combination therapy. (DOCX 12 kb)
We thank Ian Morgan, Sarah Diffen and Katrina Mullin from 4C Consultants
International for editing and proofreading of the manuscript.
All authors contributed to study design, acquisition of data, analysis and
interpretation of data, manuscript drafting and approval.
Ethics approval and consent to participate
MOLP-8 xenograft mouse experiments were performed at ImmunoGen Inc.
(Waltham, USA). The study was conducted under Protocol PR-029.08 which
was approved by ImmunoGen’s Institutional Animal Care and Use Committee.
All procedures were carried out in accordance with the Guide for the Care and
Use of Laboratory Animals of the US National Institutes of Health. MMXF L363
xenograft experiments were carried out at Oncotest GmbH (Freiburg, Germany).
The animal experiments were approved by the Committee on the Ethics of
Animal Experiments of the regional council (permit number G-13/13) and
conducted according to the guidelines of the German Animal Welfare Act
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