Triple negative breast cancer (TNBC) is an orphan disease that attacks 46,000 US women every year. TNBC cells lack human estrogen receptor, progesterone receptor, and epidermal growth factor receptor 2 (Her2), the targets of existing medicines. TNBC recurs after standard-of-care chemotherapy and radiation, killing its victims within 4 years. New promising therapies such as poly(ADP-ribose) polymerase (PARP) inhibitors only benefit a small subset of patients with BRCA1/2 mutations. Thus, TNBC shows a critical need for molecularly-targeted therapy. Most TNBC cells and associated stroma show high microRNA 21 (miR-21), which decreases tumor suppressor proteins that keep cell growth in check. A molecularly-targeted therapeutic to block miR-21 in TNBC is our objective. Premise: We have designed a strong miR-21 blocking agent using aminomethyl bridged nucleic acid (BNA), with strong basepairing, Tm >80C, low toxicity, and serum stability, conjugated to a peptide ligand for endocytosis by the insulin-like growth factor 1 receptor (IGF1R). 42% of TNBC tumors show constitutive IGF1R signaling. The peptide ligand for IGF1R provides a unique strategy for delivering miR-21 blocker specifically into the TNBC cells. Our agent basepairs with miR-21 in the RNA- induced silencing complex (RISC), freeing target mRNAs from miR-21 attack. Our miR-21 BNA elevated tumor suppressor proteins, suppressed immune checkpoint gene expression, increased apoptosis, slowed proliferation and migration in multiple TNBC lines. BNA-peptide in sterile saline can be administered by infusion. Our strategy optimizes cancer cell-specific delivery to block proliferation and immune checkpoints, covered by a pending PCT patent application, licensed by Bound Therapeutics LLC. Hypothesis: Our unique design for short microRNA blockers conjugated to a receptor ligand will direct TNBC cell uptake and slow the growth of TNBC orthotopic xenografts with minimal toxicity.
Aim 1 : Measure the effects of the lead miR-21 blocker on proliferation, apoptosis, invasion, and cellular expression of miR-21 target mRNAs and checkpoint proteins in 5 molecular subtypes of TNBC cells. Measure tumor response and immune activation by the lead miR-21 blocker in TNBC 4T1-luciferase orthotopic xenografts in immunocompetent syngeneic mice. Predicted results: Significant inhibition of tumor growth and immune checkpoints, and elevation of T-cell response.
Aim 2 : Measure toxicity of the lead miR-21 blocker in human hepatocytes by transcriptome analysis. Measure toxicity of the lead miR-21 blocker in mice by liver and kidney serum markers and weight. Measure on-target and off-target transcriptome effects, pharmacokinetics, and biodistribution of the lead miR-21 blocker in the mouse model. Predicted results: Minimal toxicity to human hepatocytes and murine host cells. Impact: We seek proof-of-concept to derisk the commercialization of a BNA-peptide TNBC therapeutic, enabling a full preclinical study of potency, T-cell response, toxicology, and pharmacokinetics, prior to IND and a Phase I single agent safety trial. We expect that miRNA blockade will significantly increase TNBC patient survival.
We propose to slow the growth of triple negative breast cancer cells with minimal side effects. We discovered a new principle in the genetic code of triple negative breast cancer cells that enables us to design novel, safer medicines. We will identify the version of our triple negative breast cancer medicine that works best in human triple negative breast cancer cells in culture, then test our medicine in living laboratory mice, leading to future trials in human triple negative breast cancer patients.
