Exploration of different immunotherapy modalities in osteosarcoma

Project Summary/Abstract
Osteosarcoma (OS) is the most common primary bone malignancy affecting long bones in children and the third
most frequent in adults in the United States. The survival rates over the last 20 years are unchanged. OS is also
the most common malignant bone tumor (80%) in dogs. Treatment options for OS are limited. Immunotherapy
is a promising new approach that has yet to be fully explored in OS. Chimeric antigen receptor (CAR) T cells are
designed to express recombinant receptors to target specific tumor cell surface antigens and promote T cell-
mediated cancer cell death. However, one of the biggest challenges in CAR T cell therapy is the
immunosuppressive tumor micro-environment (TME). Another immunotherapy strategy is the use of immune
checkpoint inhibitors, such as monoclonal antibodies (mAb) against PD-1. Anti-PD-1 mAbs have shown
significant efficiency in treating multiple tumors but cause adverse effects due to systemic delivery of the mAb.
To avoid systemic delivery, oncolytic viruses can be designed to produce immune checkpoint inhibitors directly
in TME to boost the immune system and enable T cells to kill tumor cells. Conditionally replicative adenoviruses
(CRAds) replicate only in tumor cells, lyse them, and stimulate anti-tumor immunity in TME and at distant sites
of disease, causing a bystander effect. However, the limited number of effector T cells against cancer antigens
limits the efficacy of this approach. Therefore, we propose a combination therapy to synergize these strategies
to combat tumor cells. We will combine CAR T cell therapy, oncolytic virus, and PD-1/PD-L1 inhibitor to target
osteosarcoma tumor cells. We have developed an armed oncolytic adenovirus to produce anti-PD-1 Ab in the
TME. We will create two more armed oncolytic viruses that will produce secreted single domain antibodies (sdAb)
to PD1 and PDL1. We will evaluate CRAd and CAR T cell (against B7-H3) induced tumor cells lysis. The
conditionally replicated oncolytic viruses will produce anti-PD1 and anti-PDL1 sdAb in TME, reducing the adverse
effects of systemic administration, and enhancing anti-tumor immunity. CAR T cells against B7-H3 will initiate
tumor cell killing in an activated TME. Ultimately, beyond the scope of this proposal, this approach will be tested
in spontaneous OS in canine patients, before translation to pediatric OS patients.

Grant Number: 1R15CA283777-01
NIH Institute/Center: NIH
Principal Investigator: Payal Agarwal