Auditory Neuroprotection by Small Molecule Agonists of the TrkB Receptor

描述（由申请人提供）：神经营养因子的外源性应用拯救螺旋神经节（SG）神经元免于因耳蜗毛细胞损失而导致的变性。由于SG神经元的存活是耳蜗植入物工作的基础，因此这些令人鼓舞的结果激发了人们对以预防为导向的研究的极大兴趣，该研究旨在将外源性神经营养因子应用于人类耳蜗，以促进严重感音神经性听力损失患者耳蜗中残留SG神经元的存活。然而，在第一系列论文发表12年后，这些研究都没有进入临床试验阶段。阻碍临床转化的主要障碍之一是如何以所需剂量实现长期、反复和安全地递送到耳蜗中。我们最近发现了一些高效的小分子脑源性神经营养因子的模拟物。这些化合物很容易穿过血脑屏障进入耳蜗。它们在极低浓度下激活TrkB受体。最有效的化合物之一，7，8-二羟基黄酮（7，8-DHF），在低于100 nM时有效激活TrkB受体。该化合物还在许多体内模型中表现出有效的神经保护作用。与该项目最相关的是，我们已经获得了初步数据，表明通过腹腔注射全身应用7，8-DHF显著地保护了小鼠SG神经元免于变性，而没有任何明显的副作用。这些数据是从连接蛋白26（Cx 26）突变引起的人类耳聋的小鼠模型中获得的，连接蛋白26突变是人类语言前非综合征性耳聋的最常见原因。这些结果提出了克服药物递送的主要障碍的希望，以将听觉神经保护作用转化为有益于患者的作用。该资助旨在支持在体外试验和体内动物模型中测试7，8-DHF的功效，并对该化合物进行临床前试验以确定其毒性和药代动力学。通过完成项目中提出的具体目标，我们将能够在资助期结束时收集向美国食品药品监督管理局（FDA）提交研究性新药（IND）申请所需的关键临床前数据。 该资助旨在支持在体外试验和体内动物模型中测试7，8-DHF的功效，并对该化合物进行临床前试验以确定其毒性和药代动力学。我们的具体目标是：具体目标1：我们将进行体外试验的7，8-DHF，以确定其在促进SG神经元在确定的培养基中培养的存活的功效。我们还将测试7，8-DHF和去极化是否对体外SG神经元的存活具有协同作用。具体目标2：在条件性Cx 26缺失小鼠模型中测试7，8-DHF在体内保护SG神经元免受变性的功效。具体目标3：在耳毒性药物所致的豚鼠模型中，测试7，8-DHF在体内保护SG神经元免于变性的功效。具体目标4：在这一特定目标中，我们将对化合物7，8-DHF进行FDA要求的临床前试验，以获得药物的器官靶向、毒性、全身副作用和药代动力学信息。通过完成这些具体目标，我们将能够在资助期结束时收集向美国食品药品监督管理局（FDA）提交研究性新药（IND）申请所需的关键临床前数据。

DESCRIPTION (provided by applicant): Exogenous application of neurotrophins rescues spiral ganglion (SG) neurons from degeneration resulted from the loss of cochlear hair cells. Since the survival of SG neurons is the basis for cochlear implants to work, these encouraging results have stimulated enormous interest in translation-oriented research aiming at applying exogenous neurotrophin(s) to the human cochlea to promote the survival of residual SG neurons in the cochlea of severe sensorineural hearing loss patients. However, none of these studies have advanced to the phase of clinical trials twelve years after the first series of papers were published. One of the major hurdles hindering the clinical translation is how to achieve long-term, recurring and safe deliveries at desired dosage into the cochlea. We have recently identified a number of high-potency small mimetic molecules of brain derived neurotrophic factor. These compounds readily crossed the blood brain barrier and into the cochlea. They activated TrkB receptors at extremely low concentrations. One of the most potent compounds, 7,8- dihydroxyflavone (7,8-DHF), effectively activated the TrkB receptor at less than 100 nM. The compound also demonstrated effective neuroprotective effects in a number of in vivo models. Most relevant to this project, we have obtained preliminary data showing that systemic application of 7,8-DHF by intraperitoneal injections dramatically protected SG neurons from degeneration without any obvious side effects in mice. The data were acquired from a mouse model of human deafness caused by connexin26 (Cx26) mutations, which is the most common cause of prelingual non-syndromic deafness in humans. These results raise the hope of overcoming the major hurdle of drug delivery for the translation of the auditory neuroprotective effect to benefit patients. This grant seeks support to test the efficacy of 7,8-DHF in both in vitro assay and in vivo animal models, and to conduct preclinical trials for the compound to determine its toxicity and pharmacokinetics. By finishing the specific aims proposed in the project, we will be able to collect crucial preclinical data required for filing an investigational new drug (IND) application with the food and drug administration (FDA) at the end of the funding period. This grant seeks support to test the efficacy of 7,8-DHF in both in vitro assay and in vivo animal models, and to conduct preclinical trials for the compound to determine its toxicity and pharmacokinetics. Our specific aims are: Specific aim 1: We will perform in vitro tests of 7,8-DHF to determine its efficacy in promoting the survival of SG neurons cultured in defined media. We will also test whether 7,8-DHF and depolarization have synergistic effects on the survival of SG neurons in vitro. Specific aim 2: Test the efficacy of 7,8-DHF in vivo for protecting SG neurons against degeneration in conditional Cx26 null mouse models. Specific aim 3: Test the efficacy of 7,8-DHF in vivo for protecting SG neurons against degeneration in a guinea pig model deafened by ototoxic drugs. Specific aim 4: In this specific aim we will perform FDA required preclinical trials for the compound, 7,8-DHF, to obtain organ targeting, toxicity, systemic side effects and pharmacokinetic information for the drug. By finishing these specific aims, we will be able to collect crucial preclinical data required for filing an investigational new drug (IND) application with the food and drug administration (FDA) at the end of the funding period.