Slow-onset long-acting dopamine transport inhibitors for treating drug addiction

在2006年10月1日至2007年9月30日期间，该研究项目取得了适度进展。在此期间，我们证明了我们的主要概念验证缓慢起效的长效多巴胺转运蛋白（DAT）抑制剂- CTDP-30640 -增强了电脑刺激奖励，增强了大脑中奖励相关的丘脑核位点的细胞外多巴胺，刺激了运动活动，并显著减少了实验室大鼠的静脉内可卡因自我给药-所有这些都具有非常显著的缓慢起效的长效作用特征。在此期间，我们扩展了我们在这一领域的研究，包括我们使用计算机辅助分子药物设计和我们自己开发的药效团DAT模型重新设计和合成的另外三种化合物- CTDP-31345，CTDP-31346和CTDP-32476。 由于CTDP-31345和CTDP-31346的化学结构高度相似，因此决定仅通过全范围的临床前动物筛选范例运行这两种化合物中的一种- CTDP-31345。我们发现，CTDP-31345增强了脑电刺激奖励，增强了大脑中奖励相关的丘脑核位点的细胞外多巴胺，刺激了运动活动，并显著减少了实验室大鼠的静脉内可卡因自我给药-所有这些都具有非常明显的缓慢起效的长效作用特征。在一个不太有希望的注意，我们发现CTDP-31345在药物歧视动物行为范例中推广到可卡因，产生显著的运动敏化，并触发实验室大鼠的可卡因寻求行为复发，这些大鼠已经被脱毒并从先前的静脉注射可卡因习惯中行为消失。我们进一步发现，在这一系列广泛的临床前动物试验范例中，CTDP-32476显示出与CTDP-30640和CTDP-31345基本相同的特征。此外，我们发现我们的先导化合物CTDP-30640的作用与可卡因的作用完全相加，这表明了共同的作用机制。然而，令我们惊讶的是，CTDP-31345和可卡因的作用虽然仍然显著相加，但不完全相加。这表明CTDP-31345可能在某种程度上起部分激动剂的作用，甚至在某种程度上起“竞争性”激动剂的作用。总之，这些数据表明，新的后续缓慢起效的长效DAT抑制剂CTDP-31345和CTDP-32476在与药物成瘾相关的多种动物模型中模拟可卡因的作用，但具有明显的缓慢起效和明显的作用持续时间。并且，反式氨基四氢萘化合物CTDP-31345可能比茚满胺化合物CTDP-30640更像美沙酮。我们的化合物显示出慢得多的起效和长得多的作用持续时间（例如，单次注射后96小时）比作为潜在抗成瘾药物疗法开发的其他DAT抑制剂（例如，GBR-12909），从而证明了我们的药效团模型、我们的分子药物设计程序和我们的前药药物开发策略的有效性。然而，这种显著缓慢起效和长效的DAT抑制剂作为抗成瘾、抗渴望和抗复发药物的潜在效用仍有待确定。显然，必须考虑到这样的化合物产生戏剧性的运动激活，戏剧性的行为敏化，并明确触发复发的药物寻求行为。至于潜在的作用机制，我们在报告期内进行了一系列广泛的研究，在同一组与药物成瘾有关的多种动物模型中比较了海洛因和美沙酮的作用。我们发现美沙酮作为海洛因的竞争性功能拮抗剂。因此，尽管CTDP-31345在机制上似乎比CTDP-30640更像美沙酮，但美沙酮作为阿片类药物成瘾的治疗与缓效长效DAT抑制剂作为精神兴奋剂成瘾的治疗之间的类比可能存在机制缺陷。需要进一步的研究来解决这个问题。在纯分子药物设计水平上，在报告期间，我们还成功地设计和合成了新的缓慢起效的长效哌甲酯类似物，其对多巴胺转运蛋白的选择性增加。

During the period 01 Oct 06 to 30 Sept 07, modest progress was made on this research project. During this period, we showed that our lead proof-of-concept slow-onset long-acting dopamine transporter (DAT) inhibitor - CTDP-30640 - enhances electrical brain-stimulation reward, enhances extracellular dopamine in the reward-related nucleus accumbens locus in the brain, stimulates locomotor activity, and significantly reduces intravenous cocaine self-administration in laboratory rats - all with a very pronounced slow-onset long-acting profile of action. During this sdame period, we extended our research in this area to include three additional compounds that we designed and synthesized de novo using computer-assisted molecular drug design and a pharmacophore DAT model that we ourselves developed - CTDP-31345, CTDP-31346, and CTDP-32476. Because of the high degree of similarity between the chemical structures of CTDP-31345 and CTDP-31346, a decision was made to run only one of those two compounds through a full range of preclinical animal screening paradigms - CTDP-31345. We found that CTDP-31345 enhances electrical brain-stimulation reward, enhances extracellular dopamine in the reward-related nucleus accumbens locus in the brain, stimulates locomotor activity, and significantly reduces intravenous cocaine self-administration in laboratory rats - all with a very pronounced slow-onset long-acting profile of action. On a less promising note, we found that CTDP-31345 generalizes to cocaine in the drug-discrimination animal behavioral paradigm, produces dramatic locomotor sensitization, and triggers relapse to cocaine-seeking behavior in laboratory rats who has been pharmacologically detoxified and behaviorally extinguished from their prior intravenous cocaine-taking habits. We further found that CTDP-32476 displays essentially the same profile as CTDP-30640 and CTDP-31345 in this extensive battery of preclinical animal test paradigms. Further, we found that the effects of our lead compound CTDP-30640 are fully additive with those of cocaine, suggesting a common mechanism of action. However, to our surprise, the effects of CTDP-31345 and cocaine, while still significantly additive, are less than fully additive. This suggests that CTDP-31345 may function to some degree as a partial agonist or even to some degree as a "competitive" agonist. Taken together, these data show that the new follow-on slow-onset long-lasting DAT inhibitors CTDP-31345 and CTDP-32476 mimic cocaine's actions in multiple animal models relating to drug addiction, but with pronounced slow onsets and pronounced durations of action. And, the trans-aminotetralin compound CTDP-31345 may be more methadone-like than the indanamine compound CTDP-30640. Our compounds show much slower onsets and much longer durations of action (e.g., 96 hours following a single injection) than other DAT inhibitors developed as potential anti-addiction pharmacotherapies (e.g., GBR-12909), thus demonstrating the validity of our pharmacophore model, our molecular drug design procedures, and our pro-drug medication development strategy. However, the potential utility of such dramatically slow-onset and long-acting DAT inhibitors as anti-addiction, anti-craving, and anti-relapse medications remains to be determined. The fact that such compounds produce dramatic locomotor activation, dramatic behavioral sensitization, and clear triggering of relapse to drug-seeking behavior must obviously be taken into account. And, with respect to underlying mechanism of action, we carried out an extensive series of studies during the reporting period in which we compared heroin's actions to methadone's actions in the same battery of multiple animal models relating to drug addiction. We found that methadone acts as a competitive functional antagonist of heroin. Thus, the analogy frquently drawn between methadone as a treatment for opiate addiction and slow-onset long-lasting DAT inhibitors as treatments for psychostimulant addiction may be mechanistically flawed, although CTDP-31345 appears more methadone-like mechanistically than does CTDP-30640. Further research is needed to resolve this issue. On a purely molecular drug design level, during the reporting period we also successfully designed and synthesized new slow-onset long-duration methylphenidate analogs with increased selectivity for the dopamine transporter.