Project Summary Breast cancer is one of the most frequent cancers and leading causes of death for women in the U.S. with an estimated 287,850 new diagnoses of invasive breast cancer and 43,250 deaths in 2022. The vast majority (75%) of breast cancer is estrogen receptor-positive (ER+) breast cancer but unfortunately, about 50% of them become resistant and fail to respond to the current anti-estrogen therapies. There are currently no effective treatment approaches available for these therapeutic resistant breast cancer and patients often rely on highly toxic chemo- and radiation therapies, etc. Thus, the development of new and improved targeted treatment to overcome resistance and minimize side effects is urgently needed. Recent work has established tissue-specific ER coactivator MED1 as a key anti-estrogen treatment resistance gene in breast cancer. Importantly, MED1 is overexpressed in about 50% of all breast cancers and clinical evidence indicates that MED1 expression highly correlates with poor disease-free survival of breast cancer patients. RNA Nanotherapeutics and its research partners at the University of Cincinnati have developed an innovative patented RNA nanotechnology-based approach to target MED1 in breast cancer cells to overcome treatment resistance. These highly stable multifunctional RNA nanoparticles have been successfully tested in in vitro and in vivo preclinical models and exhibited highly desirable tumor-specific targeting and treatment efficacy with no apparent toxicity. In this Phase I STTR, RNA Nanotherapeutics, in collaboration with its research partners at the University of Cincinnati and an oligonucleotide therapeutics CMC/strategy consultant, will carry out the following specific aims: 1) test the efficacy of the pRNA-HER2apt-siMED1 nanoparticles in vivo in breast cancer patient-derived xenograft (PDX) models; and 2) assess the safety and toxicity of the pRNA-HER2apt- siMED1 nanoparticles in vivo. We expect successful completion of these proposed studies will provide the results and data needed for our Phase II efforts and further engagement with private-sector investors to carry out IND enabling studies for clinical trials. With the recent increased FDA approvals and broad use of RNA- based vaccines and medicines, we fully anticipate that our RNA nanotechnology-based product represents a highly promising next-generation therapy to benefit breast cancer patient care and beyond.

Project Narrative This proposal is relevant to public health because it aims to develop innovative multifunctional RNA nanoparticles to overcome human breast cancer treatment resistance. Our proposed project of developing next-generation better and safer new breast cancer therapy is therefore relevant to the mission of NIH/NCI to lead, conduct, and support cancer research across the nation to advance scientific knowledge and help all people live longer healthier lives.