52 THE SCIENTIST | the-scientist.com
BIO BUSINESSW
hen the first anticancer thera-
pies based on engineered T cells
hit the market a few years ago,
they offered the possibility of what would
have once been perceived as a medical mir-
acle: a one-shot cure for certain blood can-
cers. Chimeric antigen receptor (CAR) T
cell therapies, as they are known, involve
harnessing the patient’s own immune cells,
genetically modifying them with cancer-
specific receptors for maximum potency
against cancerous cells, then reinjecting
them into the patient. But for all that cancer-
fighting ability, CAR T cells come at a cost:
potentially severe side effects, massive price
tags, and slow manufacture.
Now a new cell therapy for cancer is
edging into the spotlight. Natural killer
(NK) cells have potential as a cellular anti-
cancer therapy that could be significantly
safer, cheaper, and faster, researchers s ay.
While T cells are part of the adaptive
immune system—they are primed to rec-
ognize a specific threat by the immune
proteins (antigens) on a foreign cell sur-
face—NK cells are part of the innate
immune response, meaning that they
respond to anything that appears to be
non-self. This broad action makes them
suitable for use not only as engineered
cell therapies, but as unmodified cells
administered on their own.
Both the unmodified and the engineered
forms of NK cell treatment are showing
promise in early clinical trials in patients
with cancer. And so far, they haven’t shown
any of the significant toxicities—such as
graft-versus-host disease, in which the
transplanted cells attack the host as for-
eign, or cytokine release syndrome, in which
immune cells pour out dangerous amounts
of inflammatory signaling molecules—that
plague CAR T cell therapies.
“ Yo u have these cells that have an
innate capability to recognize tumor cells,and they don’t cause graft-versus-host
disease, so you could potentially manu-
facture multiple doses of these cells...
to treat multiple patients,” says Katy Rez-
vani, an immunotherapist at the Univer-
sity of Texas MD Anderson Cancer Center.
This combination of efficacy, safety, and
relative ease of supply is “the holy grail of
cell therapy.”
It is still early days for NK immuno-
therapies, which now face many of the
same challenges that have limited CAR T
cell therapies’ broader application, par-
ticularly in targeting harder-to-treat can-cers such as solid tumors. NK cells also
have their own disadvantages compared
to their adaptive immune cousins: they
don’t last as long in the body, for example,
and they don’t proliferate as easily.
But the excitement surrounding exper-
imental NK-based cancer treatments is
nevertheless translating into serious com-
mercial interest. Biotechnology company
Nkarta last year raised $114 million to take
its NK cell therapy into clinical trials, and
Celgene has paid a total of $83 million
since 2017 in a partnership with Dragon-
fly Therapeutics for its NK cell programs.NK cell therapies offer a potentially cheaper and safer route to cancer treatment
than their T cell–based predecessors.BY BIANCA NOGRADYNatural Killers Catch Up with CAR T
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