Localized immunotherapy using alum-binding therapeutics

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Project Summary/Abstract Combination treatments aiming to stimulate synergistic immune pathways employing cytokines or immunomodulatory antibodies are generally more effective than monotherapies in preclinical models of cancer immunotherapy. However when given systemically, these combination treatments suffer from high toxicity from on-target off-tumor stimulation as well as low local concentrations at the tumor site due to poor tumor penetrance and high clearance rates. Local intratumoral therapy is a viable approach to bypass some of the challenges associated with systemic delivery, but requires optimization to promote retention of the therapeutic agent at the injection site and minimize leakage into the circulation. We have recently developed an approach to enhance vaccine efficacy by engineering the binding of immunogens to the commonly used adjuvant aluminum hydroxide (alum) via a site-specific phosphoserine (pSer) peptide tag. The pSer moieties undergo a ligand-exchange reaction with free hydroxyl groups on the surface of alum leading to stable anchoring of proteins on alum particles. We propose here to apply this alum-anchoring platform in the context of cancer to retain potent immune agonists within the tumor site, promoting a robust systemic immune response with minimal toxicity. Our preliminary results show that this simple approach can be used to load stimulatory cytokines onto alum for retention at the tumor site up to a month, stimulating a strong anti-tumor response from a single shot treatment. We plan to develop and optimize this translational strategy through the following specific aims: (1) use in-cell phosphorylation to produce phosphoserine-tagged cytokines and other candidate immune agonists for optimal alum binding, (2) determine optimal treatment regimens for these intratumoral alum-bound therapeutic agents in vivo in multiple tumor models, (3) define the mechanism of action through which this therapy elicits a response, (4) evaluate the systemic immune response and assess strategies to enhance abscopal effects by promoting the transfer of immunostimulatory payloads to motile lymphocytes for trafficking to distal untreated tumors. These studies will establish a robust technology platform capable of safely delivering treatments currently viewed as too toxic, by addressing key limitations in existing localized therapeutic strategies