Biomedical Engineering Reference
In-Depth Information
been tested against a wide variety of tumor models in mice showing tumor inhibi-
tion or regression.
166,186,187
In combinations of CD40 agonists and TLR ligands,
highly potent anti-tumor responses were stimulated in vivo.
188,189
But, systemic
overexposure to CpG with dangerous side effects such as lymphoid follicle
destruction and the suppression of adaptive T-cell immunity via indoleamine
2,3-dioxygenase (IDO) induction in the spleen and have been reported.
190-192
As a result of the dangers of systemic immunostimulatory therapy, intratu-
moral or peritumoral treatments have been studied to reduce the level of side
effects.
115
Local immunotherapy has been proposed for the treatment of unre-
sectable tumors or for post-surgical therapy to prevent local recurrence.
193,194
Anti-CD40
175
, CpG,
195
target antibody-cytokine (IL-2) fusion proteins,
196
or
other immunostimulants
167,197,198
that successfully inhibited the growth of distal
untreated tumors when used as local therapies applied at a single tumor site.
115
Recently in a phase I clinical trial, the intratumoral injection of CpG against
B-cell lymphoma in humans exhibited anti-lymphoma clinical responses at
distant, untreated tumor sites in some patients.
199
But despite such therapeutic
benefits, it has been established in pre-clinical and clinical studies that local
injection of soluble agonists
200,201
or controlled release of drugs from a local
injection site
202,203
does not prevent such agonists from entering the systemic
circulation and dispersing to distal organs through drainage through lymphatics
to the thoracic duct or via direct entry into the bloodstream from leaky tumor
vessels. Subcutaneous or intratumoral administrations of cytokines IL-2
204
or
IL-12/GM-CSF
205
in mice showed rapid clearance within minutes after injec-
tion. In human patients, intratumoral/subcutaneous injection showed high cir-
culating levels of IL-12
206
or IL-2
201
within 30 min or 3 h (respectively). Thus,
the undesired widespread exposure and off-target inflammatory symptoms may
still limit the maximum tolerated dose in local immunotherapy.
115
A biomaterial-based delivery strategy for immunostimulatory factors that
could retain injected therapeutics at a local tumor site, limit the tissue drain-
age, and maintain their potent therapeutic efficacy in activating an anti-tumor
immune response will be ideal for immunotherapy. With this as a goal, the
group of Kwong
115
coupled anti-CD40 and CpG to the surface of PEGylated
unilamellar liposomes, for simultaneous co-delivery. Attaching both molecules
to liposomal carriers for a more confined biodistribution after intratumoral
injection would enhance local retention while maintaining bioactivity. The stud-
ied carried out to achieve their goal are presented and their protocols may be
applied to other immunotherapeutic ensembles and NPs.
7.4.3.1 Protocol for the Synthesis of Liposome-anchored
Anti-CD40 and CpG
115
The liposomes that are synthesized using this protocol are specifically designed
for the anti-CD40 and CpG. The process may also be used for other biomol-
ecules with respective optimization of the various parameters.
