Intravesical Immunotherapy of Spontaneous Canine Invasive Urothelial Carcinoma

PROJECT SUMMARY
Invasive bladder cancer is a lethal disease that often requires life-altering surgical removal of the
bladder to prevent or limit metastasis. Recent approvals of five checkpoint inhibitors for advanced or refractory
bladder cancers demonstrate its responsiveness to immunotherapy. However, less than half of advanced
bladder cancer patients benefit from checkpoint immunotherapy and antitumor responses are often transient.
Our previous preclinical studies in mice demonstrated that intravesical immunotherapy with interleukin-
12 (IL-12) formulated with the mucoadhesive biopolymer chitosan (CS), i.e., CS/IL-12, can eliminate nearly all
established orthotopic bladder tumors in a T cell-dependent manner. These studies also demonstrated that
intravesical CS/IL-12 can induce robust abscopal responses with the elimination of distant, untreated bladder
tumors in most mice. Although these data are promising, several limitations of implanted murine bladder tumor
models have hindered clinical translation. Thus, this application proposes to evaluate the safety and activity of
intravesical CS/canine IL-12 (caIL-12) immunotherapy in pet dogs with spontaneous invasive urothelial
carcinoma (UC) of the bladder. There are numerous similarities between canine and human bladder cancers
including mechanisms of tumorigenesis, rates and sites of metastasis, and distinguishable molecular subtypes.
Given these similarities, treatments found to be successful in dogs are more likely to be successful in people.
The objectives of this project are: 1) to demonstrate that intravesical CS/caIL-12 immunotherapy can
safely induce antitumor immunity against canine invasive UC; and 2) to determine if canine bladder cancer is a
useful model for the evaluation of this and other novel immunotherapies. The first objective will help prepare
intravesical CS/IL-12 for translation into human clinical trials, while the second objective will help bladder
cancer researchers overcome the limitations of rodent models and provide a more faithful representation of
human bladder cancer. To accomplish these objectives, 2 specific aims have been designed.
Aim 1 is focused on safety, as CS/caIL-12 has never been evaluated in dogs. After synthesizing and
validating recombinant caIL-12 in vitro, we will perform a dose-escalation study of intravesical CS/caIL-12 in
pet dogs with spontaneous invasive UC of the bladder. Aim 1 will establish a recommended dose (RD) based
on safety readouts that utilize a combination of clinical examinations and laboratory tests. Proposed
pharmacokinetic and immunophenotyping studies will investigate the possible systemic uptake and
dissemination of intravesical immunotherapy and the resulting immune impacts. Aim 2 will assess antitumor
and immunological responses to the RD of intravesical CS/caIL-12 in an expanded cohort of dogs with bladder
cancer. Correlative studies will determine if intravesical CS/caIL-12 influences T cell infiltration, the tumor-
immune microenvironment, neoantigen reactivity and/or T cell clonality. The influence of molecular subtype
and tumor mutational burden on antitumor and/or immune responsiveness will be assessed.