Animal testing of RNA aptamers as ALS drug candidate

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Project Summary The goal of this research is to make a class of RNA aptamers that act as AMPA receptor inhibitors, and test the efficacy and safety of these aptamers in a mouse model. These RNA aptamers could become a new, potential drug candidate for treatment of amyotrophic lateral sclerosis (ALS). ALS is a neurodegenerative disorder characterized by the progressive loss of motor neurons in the brain, brainstem and spinal cord. Currently none of ALS drugs effectively alters the disease course. Developing better inhibitors to control the excessive AMPA receptor activity is a promising strategy for the discovery of new and more effective ALS drugs. This is because Ca2+ influx through abnormally expressed, Ca2+- permeable AMPA receptors in motor neurons leads to selective cell death. Riluzole, one of the two FDA- approved ALS drugs, actually has anti-glutamatergic properties. Using an in vitro evolution approach, we have identified a group of 14 potent RNA aptamers targeting AMPA receptors. These aptamers are more potent, highly selective and water soluble, as compared with conventional small-molecule inhibitors. These properties should enable us to use aptamers at the lowest dose possible to achieve therapeutic efficacy by more tightly and selectively blocking AMPA receptor activities in vivo with minimal or even no dose-dependent side effects. The hypothesis to be tested is that a combination of using aptamers as better AMPA receptor antagonists and testing them in the AR2 mouse model will allow us to assess the therapeutic efficacy and safety of our aptamers. The AR2 mouse is a unique animal model where an abnormally Ca2+-permeable AMPA receptor subunit is expressed in motor neurons, causing eventual cell death. Thus, the AR2 mouse model is ideal to test our AMPA receptor aptamers in blocking abnormal AMPA receptor activity. In Aim 1, we propose to make a large quantity for each of the 14 chemically modified aptamers. These aptamers will be pure, stable and biologically functional assayed by whole-cell recording. In Aim 2, we will test each of these 14 aptamers, both individually and in combination, in first in AR2 mice. Aptamers will be administrated through intracerebroventricular injection to bypass the blood- brain barrier. Aptamer-treated and -untreated mice will be compared for changes in TDP-43 immunohistochemistry, behaviors, loss of motor neurons and body weight, and survival rate to assess the efficacy and the safety of the aptamers. The outcome of this research is to identify a set of aptamers that are efficacious, safe, and well tolerated. If successful, this research should lay ground work for clinical testing of some of these aptamers as a potential new ALS therapy.