While acute stroke is a leading cause of human death and disability in the United States, unfortunately, clinical therapies for stroke are limited and unsatisfactory. The overwhelming failures of stroke treatments in clinical trials strongly indicate that, to battle this multifaceted brain disorder, novel strategies that target multiple cell types and afford different mechanisms of protection are needed to achieve positive therapeutic effects. One strategy, mechanical induction of mild hypothermia (defined as a 1-5oC decrease in body temperature), has shown remarkable neuroprotective effects against brain ischemia in both animal and human studies. At this time, however, available physical cooling techniques are ineffectual and usually impractical. A more recent focus has been to identify pharmacological compounds that can be used to induce hypothermia. In theory, pharmacologically induced hypothermia (PIH) can be initiated much earlier after the stroke event and in the absence of mechanical cooling. Even a small (1-2oC) decrease in body temperature during early hours after stroke prevents detrimental post-stroke hyperthermia, while mild hypothermia (2-5oC reduction) decreases the extent of ischemic injury. In our Phase I and Phase II investigations, we demonstrated that rapid and reproducible hypothermia is induced by several novel neurotensin receptor 1 (NTR1) agonists, resulting in significant neuroprotection against brain damage induced by ischemic stroke, hemorrhage stroke, or traumatic brain injury (TBI) in rodent models. The key breakthrough is that the NTR1 agonists do not induce shivering in the subject animals, the major problem associated with other agents that mechanically or pharmacologically induce hypothermia. The NTR1 compounds also act synergistically with tissue plasminogen activator (tPA), the only FDA-approved thrombolytic treatment at this time. During Phases I and II, we also demonstrated hypothermia induction by our leads in non-human primates, and completed a number of IND-enabling tasks with satisfactory outcomes. For this Phase IIb study, in Specific Aim 1, we will continue to study the hypothermic effect of our compounds in monkeys, with the overall opportunity of providing a clear bridge between rodent, non-human primates, and human clinical studies. In particular, we will demonstrate the stroke protection synergism between tPA and our NTR1 agonists, as was previously demonstrated in rodents.
In Specific Aim 2, required IND-enabling preclinical evaluations will be completed, while in Specific Aim 3, we will commission 28-day toxicity studies in two species (rat and dog), which also are necessary for IND preparation. Finally, in Specific Aim 4, we will prepare and submit the IND. When these four Specific Aims are completed satisfactorily, our lead will be ready to enter human clinical trials, which will serve as a major value influx point for seeking further funding to support the program.
Ischemic stroke is the third leading cause of human death and disability in the US. Our goal is to develop a clinically effective and feasible hypothermia therapy that could serve as an adjunct to, or replace, the only FDA approved therapy, tissue plasminogen activator (tPA). We have completed Phase I and II of this project. In Phase I, we synthesized and identified neurotensin receptor I derivatives for induction of hypothermia that served to dramatically decrease the size of an induced infarct. In Phase II, we demonstrated improvement of the therapeutic window of tPA with our lead, demonstrated the lack of negative behavioral and toxicity effects, and demonstrated that the hypothermic effect can be induced in non-human primates. In Phase IIb, other necessary preclinical studies will be completed and an IND will be written and submitted.
