BIFUNCTIONAL OPIOID PEPTIDE ANALGESICS

描述(由申请人提供)：临床上迫切需要开发具有新的生物活性特征的阿片类镇痛剂，这种镇痛剂没有目前可用的阿片剂的有限副作用。研究表明，阿片激动剂产生镇痛耐受和身体依赖的倾向可以通过联合使用d阿片拮抗剂、大麻素(CB1)拮抗剂、P物质(NK1)拮抗剂或阿片受体样(ORL1)拮抗剂来减少。基于这一证据，我们建议开发具有系统活性的双功能化合物，将阿片类激动剂/d阿片类拮抗剂-、激动剂/CB1拮抗剂-、激动剂/NK1拮抗剂-或激动剂/ORL1拮抗剂组合作为止痛剂，预期产生很少或根本没有耐受性和身体依赖性，并具有较低的成瘾倾向。具有这些特征的具有系统活性并能够穿过血脑屏障(BBB)的双功能配体迄今尚未有报道。双功能配体的设计将基于不同的拮抗剂药效团(肽和非肽)直接或通过短接头连接到有效和高选择性阿片激动剂多肽[DMT1]DALDA(H-DMT-D-Arg-Phe-Lys-NH2；DMT=2‘，6’-二甲基酪氨酸)的不同位置，而不干扰这两个组分的激动剂/拮抗剂特性。这将通过仔细考虑这两个组分的已知结构-活性关系(SAR)以及配体对接到受体结合位点的分子模型来完成。[DMT1]DALDA具有较高的镇痛力、口服生物利用度、较高的稳定性、较长的消除半衰期和较长的作用时间，因此被选为激动剂。有证据表明，所建议的[DMT1]DALDA-拮抗剂结合物将能够渗透到中枢神经系统，因为[DMT1]DALDA组分将赋予整个双功能结构跨越血脑屏障的能力。已经证明，两种已经制备的阿片激动剂/d拮抗剂在皮下给药(S.C.)时会产生强大的中枢介导的抗伤害性作用。双功能配体将通过固相合成或固相与溶液相结合的多肽合成技术来制备。这些化合物的体外生物学特性将通过进行受体结合试验、分离组织试验和[35S]GTP？S结合试验，使用含有单一表达的阿片、d阿片、CB1、NK1或ORL1受体的HEK细胞来确定。它们的止痛效力将在急性疼痛模型(甩尾和热板)和作为神经病理性疼痛模型的慢性缩窄性损伤模型中确定。此外，还将检查化合物产生止痛耐受性、身体依赖性、成瘾(位置条件反射范式)、便秘和呼吸抑制的倾向。

DESCRIPTION (provided by applicant): There is an urgent clinical need for the development of opioid analgesics with novel biological activity profiles that lack the limiting side effects of the currently available opiates. It has been shown that the propensity of ¿ opioid agonists to produce analgesic tolerance and physical dependence can be reduced by co-administration of a d opioid antagonist, a cannabinoid (CB1) antagonist, a substance P (NK1) antagonist or an opioid receptor like (ORL1) antagonist. On the basis of this evidence we propose to develop systemically active, bifunctional compounds with a mixed ¿ opioid agonist/d opioid antagonist-, ¿ agonist/CB1 antagonist-, ¿ agonist/NK1 antagonist- or ¿ agoist/ORL1 antagonist profile as analgesics expected to produce little or no tolerance and physical, dependence, and with low addiction liability. Bifunctional ligands with these profiles that are systemically active and able to cross the blood-brain barrier (BBB) have not been reported to date. The design of the bifunctional ligands will be based on attachment of the various antagonist pharmacophores (peptides and non-peptides) to various sites of the potent and highly selective ¿ opioid agonist peptide [Dmt1]DALDA (H-Dmt-D-Arg-Phe-Lys-NH2; Dmt = 2'6'- dimethyltyrosine) either directly or via a short linker in a way that does not interfere with the agonist/antagonist properties of the two components. This will be done by careful consideration of known structure-activity relationships (SAR) of the two components in conjunction with molecular modeling of ligand docking to the receptor binding sites. [Dmt1]DALDA was chosen as the ¿ agonist component because of its high analgesic potency, oral bioavailability, high stability, long elimination half-life and long duration of action. There is evidence to indicate that the proposed [Dmt1]DALDA-antagonist conjugates will be able to penetrate into the central nervous system because the [Dmt1]DALDA component will confer blood-brain barrier crossing ability upon the entire bifunctional construct. This has been shown to be the case with two already prepared ¿ opioid agonist/d antagonists of this type which produced potent centrally mediated antinociception when given subcutaneously (s.c.). The bifunctional ligands will be prepared by solid-phase synthesis or by a combination of solid-phase- and solution peptide synthesis techniques. The in vitro biological profiles of the compounds will be determined by performing receptor binding assays, isolated tissue assays and [35S]GTP?S binding assays using HEK cells containing singly expressed ¿ opioid, d opioid, CB1, NK1, or ORL1 receptors. Their analgesic potencies will be determined in acute pain models (tail-flick and hot plate) and in the chronic constriction injury model as a model of neuropathic pain. Furthermore, the propensities of the compounds to produce analgesic tolerance, physical dependence, addiction (place conditioning paradigm), constipation and respiratory depression will be examined.