Targeted Delivery of Tumor Antigen esaRNA to the Spleen for Cancer Immunotherapy

Project Summary This application is in response to Notice of Special Interest (NOSI) NOT-AI-24-007 (RNA Delivery Technologies to Allow Speciflc Tissue Target Homing) to support the development of non-viral technologies to deliver RNA-based therapeutics to disease-relevant cells and tissues in vivo. We propose an innovative strategy that combines enhanced self-amplifying RNA (esaRNA) and spleen-targeting delivery nanomaterials to confer a therapeutic anti- tumoral immune response. We have developed esaRNAs, which include an engineered flrst ORF (that normally only encodes the alpha viral nonstructural proteins) that incorporates a constitutively active STING protein that is expressed early but at low level in transfected cells in concert with the normal self-amplifying RNA replication complex, leading to superior innate immune signaling without signiflcantly sacriflcing expression of the desired encoded antigen. Tiba’s proprietary RNA encapsulation compounds are based on molecularly deflned, biodegradable dendritic structures with ionizable amine moieties and terminal lipid extensions. This platform generates highly compact and monodisperse nanoparticles with superior consistency in particle diameter and stability than competing systems. The spleen is the largest secondary lymphoid organ and is a primary site of action where antigens are presented to the immune system to initiate the deployment of effector lymphocytes into circulation. Delivery to antigen presenting cells that are populous in the spleen has been previously established to improve the immunogenicity of RNA-encoded antigens and can lead to improved tumor clearance. This proposal will test the proposed platform in (i) a human papillomavirus (HPV)-based tumor model and (ii) a melanoma model as a proving ground. The model antigens of interest (HPV16 E7 and Trp2) are selected for the ease of preclinical testing in small animals and because of their clinical relevance in humans. The purpose of Aim 1 is to study Tiba’s existing panel of spleen-specific formulation candidates in terms of potency in desirable APC subsets and undesirable inflammatory effects. The goal of Aim 2 is to validate the biological efficacy of the lead RNABL spleen delivery formula in terms of adaptive cellular immune response against a model HPV tumor antigen and protection in prophylactic and therapeutic modalities. Finally, Aim 3 will follow a similar experimental design as Aim 2 using the B16 melanoma cell model. The conclusion of this project will set the stage for a Phase II SBIR application to advance the platform through late preclinical development with the goal of establishing a pre- IND package against a lead tumor-associated antigen target.