Evaluation of lead FANA oligos targeting FOXP3, with and without anti-PD-1 mAb, as an approach for cancer immunotherapy

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PROJECT SUMMARY/ABSTRACT Lung cancer accounts for >25% of cancer-related deaths in both men and women, making it the largest source of cancer-related mortality. Despite advancements in surgical intervention, radiation, chemotherapy, and immunotherapy, the 5-year survival rate for all types of lung cancer is 19%. The advent of immune checkpoint inhibitor therapy is associated with remarkable efficacy is some patients with lung cancers, but >75% of patients do not achieve meaningful clinical responses. Currently, T-regulatory (Treg) T cells are regarded as one of the major obstacles to the successful clinical application of tumor immunotherapy. Tregs contribute to the early establishment and progression of tumors, dampen effector cell responses by various mechanisms, and promote and support pro-tumoral myeloid-derived suppressor cell development and function. Tregs are thereby key to the immunosuppressive state of the tumor microenvironment that prevents effective anti-tumor immune responses. Pre-clinical studies show targeting of Tregs, by their depletion or functional modulation, can have significant therapeutic benefit, alone or in combination with other immunomodulatory approaches. We and others have described the significant accumulation of intratumoral Treg in lung cancer patients, and their increased intratumoral numbers correlate with poor prognosis in many types of cancers. Tregs are defined by their expression of the transcription factor FOXP3, which controls Treg development, stability, and function. FOXP3 is the key element of multiple Treg-associated molecular complexes that regulate the Treg-specific gene network and mechanisms of Treg-mediated immune regulation. FOXP3 is located intracellularly, and previous efforts to target Tregs using their CD25 surface marker have unintentionally co-targeted CD25+ activated T effector cells, causing a lack of robust anti-tumoral efficiency in pre-clinical and clinical studies, along with severe adverse effects and toxicity. On the other hand, Foxp3-specific depletion of Treg using tumor bearing DEREG transgenic mice, in combination with anti-tumor vaccine therapy, resulted in robust antitumor immunity and an absence of overt autoimmunity. Thus, there is an urgent and unmet need for therapies that can selectively target Treg cells, allowing the body to mount its normal defenses against the cancer, without negative influences on the rest of the immune system. We have developed third generation FANA antisense oligonucleotides (FANA ASOs) that selectively inhibit Tregs by knockdown of FOXP3 expression. This next generation of ASO differs from their predecessors by chemical modifications that allow their efficient (gymnotic) self-delivery, even to resting cells, and make them resistant to degradation by endogenous nucleases. In preliminary studies, anti-Foxp3 FANA ASOs reduced Foxp3 expression and suppressive functions of murine Tregs, and in 50% of syngeneic mice bearing lung tumors, daily injection of FANA ASOs showed complete destruction of the tumors as compared to scrambled controls and without overt toxicity. We now propose validation of newly developed human FOXP3 FANAs, alone or in conjunction with anti-PD-1 monoclonal antibody therapy. Aim 1 will assess their ability to knockdown FOXP3 and promote anti-tumor immunity in humanized mice in vivo. Aim 2 will evaluate their activity against actual human lung cancer associated Treg cells.