MagnICON system or tobacco mosaic virus- and potato virus X-based vectors,
revealed anti-proliferative effects, similarly to the current drug Herceptin.
The mouse/human chimeric anti-CD20 antibody C2B8 (rituximab) is the first
antibody-based drug approved by regulatory authorities for the treatment of patients
with recurrent B-cell lymphomas and is capable of depleting B cells in vivo (Reff
et al. 1994). Although only about 48% of patients treated with rituximab respond to
the therapy, with <10% showing a complete remission of the tumour (Davis et al.
2014), treatment with this drug associated with chemotherapy is a pillar for the
treatment of non-Hodgkin’s lymphomas (Plosker and Figgitt 2003).
In an effort to increase cost-effectiveness of rituximab, Biolex Therapeutics used
the proprietary protein expression (LEX System) in the aquatic plant Lemna minor to
produce a plant version of rituximab with fully human-like glycosylation pattern
with a single major N-linked glycan devoid of xylose or fucose (Cox et al. 2006).
This new product, named BLX-300, was shown to have the same target cell-binding
activity, improved antibody-dependent cellular cytotoxicity against B cells and
superior B-cell depletion, induction of apoptosis but attenuated complementdependent cytotoxicity in preclinical studies (Gasdaska et al. 2012).
A further approach to improve efficacy of therapy of B-cell malignancies is based
on the use of anti-CD20 antibodies to deliver cytokines to the tumour microenvironment. In particular, human interleukin 2 (IL-2)-based immunocytokines have
shown enhanced antitumour activity in several preclinical studies (List and Neri
2013).
The first successful example of a recombinant immunocytokine produced in agroinfiltrated N. benthamiana plants was reported in an unconventional yet effective
approach (Marusic et al. 2016). The immunocytokine was designed as a protein
fusion between an antibody scaffold derived from rituximab and the human IL-2.
In particular, a dimeric bivalent antibody format based on a scFv-Fc fused to IL-2
with highly homogeneous glycosylation devoid of the typical xylose/fucose Nglycosylation plant signature. In vitro studies showed that this antibody conjugate
has a CD20 binding activity comparable to that of rituximab and an efficient
elicitation of antibody-dependent cell-mediated cytotoxicity (ADCC). In addition,
hIL-2 in the context of 2B8-Fc-hIL-2 maintained the biological activity, as validated by 2B8-Fc-hIL-2 binding to the hIL-2 receptor and subsequent triggering of
T-cell proliferation. The final touch was the discovery that glycan engineering,
performed utilizing RNAi-silenced transgenic plants devoid of xylosyltransferase
and fucosyltransferase activity (Strasser et al. 2008), was the best way to achieve an
overall improvement of the biological functions (Marusic et al. 2018).
Among antibodies targeting B-cell malignancies, obinutuzumab is a third generation fully humanized from mouse monoclonal antibody that binds a CD20 epitope
partially overlapping that of rituximab (Klein et al. 2013). Obtained through a
proprietary GlycoMAb
® technology by GlycArt Biotechnology and developed
by Roche as a therapeutic of chronic lymphocytic leukaemia and other B-cell
non-Hodgkin’s lymphomas (Marcus et al. 2017), this glycoengineered mAb, when
produced in N. benthamiana plants, has been demonstrated substantially equivalent
to that derived from conventional Chinese hamster ovary (CHO) cells in binding to
CD20 and expanding the immune-mediated target cell death (Lee et al. 2018).
86
S. Massa et al.
revealed anti-proliferative effects, similarly to the current drug Herceptin.
The mouse/human chimeric anti-CD20 antibody C2B8 (rituximab) is the first
antibody-based drug approved by regulatory authorities for the treatment of patients
with recurrent B-cell lymphomas and is capable of depleting B cells in vivo (Reff
et al. 1994). Although only about 48% of patients treated with rituximab respond to
the therapy, with <10% showing a complete remission of the tumour (Davis et al.
2014), treatment with this drug associated with chemotherapy is a pillar for the
treatment of non-Hodgkin’s lymphomas (Plosker and Figgitt 2003).
In an effort to increase cost-effectiveness of rituximab, Biolex Therapeutics used
the proprietary protein expression (LEX System) in the aquatic plant Lemna minor to
produce a plant version of rituximab with fully human-like glycosylation pattern
with a single major N-linked glycan devoid of xylose or fucose (Cox et al. 2006).
This new product, named BLX-300, was shown to have the same target cell-binding
activity, improved antibody-dependent cellular cytotoxicity against B cells and
superior B-cell depletion, induction of apoptosis but attenuated complementdependent cytotoxicity in preclinical studies (Gasdaska et al. 2012).
A further approach to improve efficacy of therapy of B-cell malignancies is based
on the use of anti-CD20 antibodies to deliver cytokines to the tumour microenvironment. In particular, human interleukin 2 (IL-2)-based immunocytokines have
shown enhanced antitumour activity in several preclinical studies (List and Neri
2013).
The first successful example of a recombinant immunocytokine produced in agroinfiltrated N. benthamiana plants was reported in an unconventional yet effective
approach (Marusic et al. 2016). The immunocytokine was designed as a protein
fusion between an antibody scaffold derived from rituximab and the human IL-2.
In particular, a dimeric bivalent antibody format based on a scFv-Fc fused to IL-2
with highly homogeneous glycosylation devoid of the typical xylose/fucose Nglycosylation plant signature. In vitro studies showed that this antibody conjugate
has a CD20 binding activity comparable to that of rituximab and an efficient
elicitation of antibody-dependent cell-mediated cytotoxicity (ADCC). In addition,
hIL-2 in the context of 2B8-Fc-hIL-2 maintained the biological activity, as validated by 2B8-Fc-hIL-2 binding to the hIL-2 receptor and subsequent triggering of
T-cell proliferation. The final touch was the discovery that glycan engineering,
performed utilizing RNAi-silenced transgenic plants devoid of xylosyltransferase
and fucosyltransferase activity (Strasser et al. 2008), was the best way to achieve an
overall improvement of the biological functions (Marusic et al. 2018).
Among antibodies targeting B-cell malignancies, obinutuzumab is a third generation fully humanized from mouse monoclonal antibody that binds a CD20 epitope
partially overlapping that of rituximab (Klein et al. 2013). Obtained through a
proprietary GlycoMAb
® technology by GlycArt Biotechnology and developed
by Roche as a therapeutic of chronic lymphocytic leukaemia and other B-cell
non-Hodgkin’s lymphomas (Marcus et al. 2017), this glycoengineered mAb, when
produced in N. benthamiana plants, has been demonstrated substantially equivalent
to that derived from conventional Chinese hamster ovary (CHO) cells in binding to
CD20 and expanding the immune-mediated target cell death (Lee et al. 2018).
86
S. Massa et al.