Radikal Therapeutics (RTX) is developing a first-in-class cytoprotective small molecule (R-801) for the prevention of spinal cord injury (SCI) based upon the chemical fusion of 2 discrete chemical domains that: 1) target redox stress via a nitroxide spin-trap moiety, and 2) trigger the endogenous ischemic-preconditioning response via mitochondrial-selective K+-ATP channel activation. We have confirmed a powerful effect of R- 801 in rodent models of trauma, including hemorrhagic shock and ischemia reperfusion injury of the heart, lung, limb, and kidney. In a pilot study of spinal cord trauma (SCT), resuscitation of mice with R-801 produced an accelerating and non-plateauing improvement in motor function (20% total recovery over the first 10 days). R-801 has shown no evidence of toxicity in rodents and large animals. At present, R-801 is the first and only safe, effective, and selective mito-K+-ATP channel opener in development, as no other firm or academic center has succeeded to date in inventing a safe, effective, and selective mito-K+-ATP channel opener. We now propose to verify the pre-clinical feasibility of R-801 in a classic model of SCT and to deepen the understanding of its mechanism of action. Phase 1 SBIR Specific Aim: Establish the PD profile of R-801 in an experimental murine model of SCI. In order to test the hypothesis that R-801 effectively resuscitates SCT, RTX will carry out a pathologic and functional analysis in a prospective, randomized, single-blinded, placebo-controlled investigation in mice. In collaboration with Professor Philip Popovich (Ohio University), adult female CD1 mice will be subjected to SCT using a standardized model of contusion injury. Sham injury (laminectomy without SCT) and vehicle control groups will be compared to a group receiving R-801. The initial 2 doses of R-801 (80 mg/kg/dose), given 1 and 3 h after SCT, will be administered intraperitoneally (IP) in order to obtain a rapid tissue penetration of high levels of the drug int spinal cord tissue. Thereafter, R-801 will be provided in the drinking water (as a 0.2% solution) in order to optimize steady-state drug exposure. In Series A, mice (n=10 per group) will be sacrificed 48 h after SCT for histologic and immunohistochemical analysis of the spinal cord for evidence of of poly(ADP-ribose) polymerase activation and ONOO- formation. In Series B, open field locomotor function will be analyzed in adult female SCI mice (n=10 per group) for a period of 2 months post SCT. Mice will be acclimated to the open field ~1 week prior to SCT. Indices of functional recovery will be measured using the Open field-testing (Basso Mouse Scale;BMS) locomotor rating scale. BMS scores will then be obtained pre-injury and again at weekly intervals. Terminal plasma concentrations of R-801 will be obtained, in order to construct a PD profile relating the efficacy in each dose group to functional, morphologic, and immunohistochemical endpoints. Verification that R-801 resuscitation ameliorates morphologic and functional outcomes will provide a logical foundation for commercial development of parenteral R-801 as an emergent therapy for acute SCI.
Spinal cord injury is managed conservatively today, as there are no specific medical or surgical interventions that change the ultimate neurological outcome. We are developing a novel drug that targets the basic mechanisms of disease pathogenesis of this condition and is intended as a therapeutic agent in the acute management of spinal cord injury. We will test this agent in a clinically-relevant small animal model of spinal cord injury.