Pneumocystis jirovecii Targeted Antiopportunistic Agents

描述（由申请人提供）：尽管有高效抗逆转录病毒治疗（HAART或ART），但机会性感染（OI）仍然是HIV感染者相当高的发病率和死亡率的主要原因，如CDC在MMWR（2009年4月10日）中所述。这对于由耶氏肺孢子虫引起的主要OI肺炎（PCP）尤为重要。甲氧苄氨嘧啶/磺胺甲恶唑（TMP/SMX），即二氢叶酸还原酶（DHFR）抑制剂（TMP）和二氢蝶酸合酶（DHPS）抑制剂（SMX）的组合，是PCP的一线药物。由于对磺胺类药物和TMP的不良反应和耐药性沿着二线药物的失败率和不良反应，这种选择失败，迫切需要替代药物。我们的小组已经从人类病原体耶氏肺孢子虫（Pneumocystis jirovecii，pjDHFR）中分离出难以捉摸的DHFR，并对其进行了表征，并表明其与其替代品卡氏肺孢子虫（Pneumocystis carinii，pcDHFR）（发生在啮齿动物中）在治疗药物的抑制活性方面是不同的。此外，我们已经鉴定了两个系列的化合物（1、3、5和6），其对pjDHFR的选择性是对hDHFR的19-99倍，具有pjDHFR的皮摩尔和纳摩尔Ki和IC 50值。据我们所知，我们是唯一能够获得pjDHFR和对pjDHFR具有高选择性（19-99倍）和效力（皮摩尔和纳摩尔）（与hDHFR相比）的化合物的小组。最近，我们还克隆并表达了临床相关的，TMP抗性的pjDHFR双突变体，并发现我们的化合物在TMP的500倍抗性面前保留了对双突变体pjDHFR的纳摩尔抑制，并且也将在我们的评估中使用这些。这是在评价用于耶氏肺孢子虫感染的药物中的一个范式改变事件，到目前为止，该事件已经使用替代品卡氏肺孢子虫用于DHFR以及体内模型。具体目标是：1）合成系列I-XII中提出的化合物; 2）评估化合物作为hDHFR和野生型和耐药突变体pjDHFR的抑制剂; 3）评估目标2中选定的类似物在人胚肺成纤维细胞中的毒性; 4）评估目标2和3中选定的类似物（5）的血清结合、代谢稳定性和药代动力学，并在耶氏疟原虫感染的小鼠模型中开发和评估。Cody博士将对1、3和5以及系列I-XII中选定的具有pjDHFR和hDHFR的化合物进行X射线晶体结构测定，以提供对类似物的选择性和效力的分子理解。这项研究将确定有效和选择性抑制pjDHFR的结构要求，并将有助于未来的药物设计和药效团的产生。此外，它将首次提供基于来自人类病原体（P. jirovecii）而不是替代物（P. carinii）的DHFR的Jirovecii动物模型中的化合物评价。该研究应确定单独使用或联合使用的潜在化合物，用于对五氯苯酚和耐药性五氯苯酚进行临床评价。

DESCRIPTION (provided by applicant): Despite the availability of highly active antiretroviral therapy (HAART or ART), opportunistic infections (OIs) remain the leading cause of considerable morbidity and mortality in HIV infected persons as stated by the CDC in MMWR, April 10, 2009. This is particularly important with the leading OI, pneumonia (PCP), caused by Pneumocystis jirovecii. Trimethoprim/sulfamethoxazole (TMP/SMX), the combination of a dihydrofolate reductase (DHFR) inhibitor (TMP) and a dihydropteroate synthase (DHPS) inhibitor (SMX) for PCP is the first- line agent. The failure of this option due to adverse reactios and resistance to the sulfa drug as well as TMP along with the failure rate and adverse reactions of second-line agents necessitates the urgent need for alternate agents. Our group has isolated and characterized the elusive DHFR from the human pathogen Pneumocystis jirovecii (pjDHFR) and shown it to be distinct and different from its surrogate Pneumocystis carinii (pcDHFR) (occurs in rodents), with respect to inhibitory activities of therapeutic agents. n addition, we have identified two series of compounds (1, 3, 5 and 6) with selectivity for pjDHFR over hDHFR of 19-99-fold with picomolar and nanomolar Ki and IC50 values for pjDHFR. To our knowledge, we are the only group with access to pjDHFR and compounds that have both high selectivity (19-99-fold) and potency (picomolar and nanomolar) against pjDHFR (compared to hDHFR). Recently we have also cloned and expressed clinically relevant, TMP-resistant double mutants of pjDHFR and found that our compounds retain nanomolar inhibition against the double mutant pjDHFR in the face of TMP's 500-fold resistance, and will also use these in our evaluations. This is a paradigm changing event in the evaluation of drugs for P. jirovecii infection that up until now has utilized the surrogate P. carinii for DHFR as well as in vivo models. The Specific Aims are to: 1) synthesize proposed compounds in Series I-XII; 2) evaluate the compounds as inhibitors of hDHFR and wild type and resistant mutant pjDHFR; 3) evaluate selected analogs from Aim 2 in human embryonic lung fibroblasts for toxicity; 4) evaluate selected analogs (5) from Aims 2 and 3 for serum binding, metabolic stability and pharmacokinetics and develop and evaluate in a mouse model of P. jirovecii infection. X-ray crystal structure determination of 1, 3 and 5 and selected compounds from Series I-XII with pjDHFR and hDHFR will be done by Dr. Cody to afford a molecular understanding of the selectivity and potency of the analogs. This study will determine the structural requirements for potent and selective inhibition of pjDHFR and will assist in future drug design and pharmacophore generation. In addition it will provide, for the first time, the evaluation of compounds in a P. jirovecii animal model based on DHFR from the human pathogen (P. jirovecii) rather than a surrogate (P. carinii). The study should identify potential compounds for clinical evaluation against PCP and resistant PCP to be used alone or in combination.