As higher vertebrates evolved from the sea into land dwellers and terrestrial antigen (Ag) exposure increased,
the adaptive immune system evolved from a centralized system to one dependent upon regional draining
lymph nodes (dLNs) that allow immune responses to multiple Ags while preserving central tolerance. Despite
the importance of LNs initiating immune responses for systemic immunity/tolerance, checkpoint blockade
immunotherapies (CBIs) are administered intravenously, often failing to reach the dLNs that are the sites of
dysfunctional T cell priming responsible for tolerance to tumor Ags (tAgs). When administered systemically,
these therapies act in an Ag-indiscriminate and system-wide fashion often breaching self-tolerance and leading
to severe immune related adverse events (irAEs).
We hypothesize that regional delivery of immunotherapies within the distinct lymphatic watersheds to dLNs will
(i) enhance systemic immunity or tolerance and (ii) substantially reduce irAEs when compared to systemic
delivery. Scientific justification for our hypothesis comes from our data in preclinical, orthotopic breast (4T1) and melanoma (B16F10) studies of cancer metastases. We show that lymphatic delivery of aCTLA-4 alone or
in combination with aPD-1 (i) improves anti-tumor responses, (ii) results in complete responses not seen with
systemic or i.v. administration, and/or (iii) ameliorates distant metastases in these otherwise non-immunogenic
models. Preclinical and clinical studies using microneedle array devices and near-infrared fluorescence
lymphatic imaging shows the technical ability to deliver drug specifically to regional lymph nodes. However,
there has been no preclinical demonstration that lymphatic delivery will alleviate irAEs, due to the lack of a
susceptible mouse model. Before further study of lymphatic delivery can be made or translated into cancer
patients, the benefit of reduced irAEs needs to be demonstrated. Because irAEs limit combinational aCTLA-4/aPD-1 therapy and the more toxic, agonist a4-1BB CBIs, lymphatic delivery could provide a substantial
breakthrough needed expand the use of CBIs to treat more cancer patients at earlier stages of disease.
In this NCI Clinical and Translational Exploratory/Developmental R21 (PAR-20-292) project, we propose to use
a well-characterized Foxp3-DTR mouse model of transient Treg depletion to provide a readout of irAEs from
i.v. and lymphatically delivered CBIs. Our specific aims are to (1) characterize immunological consequences
resulting from i.v. and lymphatic delivery of aCTLA-4/aPD-1 and a4-1BB in non-tumor bearing, C57BL/6 and
Balb/C strains of Foxp3-DTR mice and to (2) compare anti-tumor immunity and readouts of immunological
consequences from i.v. and lymphatic delivery of CBIs in 4T1 and B16F10 tumor bearing animals.
In practice, clinical observations of irAEs are associated as early indication of CBI response. If successful, we
will decouple irAEs from anti-tumor immunity and improve cancer treatments by changing the way we deliver
immune modifying therapeutics.