MmpL3 as a target for novel anti-TB agents

 描述（由申请人提供）：由结核分枝杆菌（Mtb）引起的结核病（TB）仍然是全球主要的公共卫生问题，也是艾滋病毒感染者（包括正在接受抗逆转录病毒治疗的人）最常见的疾病。结核病也是艾滋病毒感染者死亡的主要原因，占艾滋病毒/艾滋病相关死亡的四分之一。迫切需要开发更短和更简单的药物方案，这些方案耐受性良好，对多重和广泛耐药（MDR/XDR）Mtb有效，并适用于联合TB/HIV治疗。对基于全细胞的筛选以鉴定新型抗TB化合物的兴趣的回归导致了许多有前途的抑制剂的鉴定。有趣的是，已经报道了包括TB候选药物SQ 109在内的其中几种药物通过其对分枝菌酸转运蛋白MmpL 3的抑制活性杀死Mtb。分枝菌酸是在细胞质中合成的丰富的长链（C60-C90）脂肪酸，其填充所有分枝杆菌的外膜的内小叶和外小叶;通过防止分枝菌酸输出到周质空间，MmpL 3的抑制防止Mtb的外膜的形成。多种化学支架通过明显抑制MmpL 3来阻断Mtb的生长的事实可能反映了这种转运蛋白的不寻常的脆弱性和“药物性”。或者，我们的初步结果使我们质疑这些化合物中的一些抑制MmpL 3的直接机制。因此，尽管对MmpL 3作为新的治疗靶标的兴趣越来越大，并且由于与开发这种大的膜蛋白的转运测定相关的技术挑战，MmpL 3尚未被验证为任何Mtb抑制剂的直接靶标。对治疗MDR/XDR-Mtb感染的新型治疗方法的迫切需求以及理解小分子抑制剂的作用模式以驱动其优化过程的重要性使得MmpL 3作为新型药物靶标的验证以及该转运蛋白的抑制测定的开发成为高度优先事项。该提案旨在通过确定MmpL 3的脆弱性（即， 阻断细菌生长需要多大程度的靶活性抑制）。 体内（目标1），开发筛选、验证和优化该转运蛋白抑制剂所需的全细胞和无细胞测定法（目标2），并提供小分子抑制剂的可药用性的概念验证（目标3）。

 DESCRIPTION (provided by applicant): Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a major public health problem worldwide and the most common presenting illness among people living with HIV, including those who are taking antiretroviral treatment. TB is also the leading cause of death among people living with HIV, accounting for one in four HIV/AIDS-associated deaths. The development of shorter and simpler drug regimens that are well tolerated, effective against multiple and extensively drug-resistant (MDR/XDR) Mtb and appropriate for joint TB/HIV treatment is urgently needed. The return of interest in whole cell-based screens to identify novel anti-TB compound has led to the identification of a number of promising inhibitors. Intriguingly, several of them including the TB drug candidate SQ109 have been reported to kill Mtb through their inhibitory activity on the mycolic acid transporter, MmpL3. Mycolic acids are abundant long chain (C60-C90) fatty acids synthesized in the cytoplasm that populate both the inner and the outer leaflets of the outer membrane of all mycobacteria; by preventing mycolic acids from being exported to the periplasmic space, the inhibition of MmpL3 prevents the formation of the outer membrane of Mtb. The fact that multiple chemical scaffolds block the growth of Mtb through the apparent inhibition of MmpL3 may reflect the unusual vulnerability and "druggability" of this transporter. Alternatively, our preliminary results have led us to question the direct mechanism of inhibition of MmpL3 by some of these compounds. Thus, in spite of the growing interest in MmpL3 as a novel therapeutic target and owing to the technical challenges associated with the development of transport assays for this large membrane protein, MmpL3 has not yet been validated as the direct target of any Mtb inhibitor. The critical need for novel therapeutic approaches to treat MDR/XDR-Mtb infections and the importance of understanding the mode of action of small molecule inhibitors to drive their optimization process make the validation of MmpL3 as a novel drug target and the development of inhibition assays for this transporter a high priority. This proposal is to establish the therapeutic potential of MmpL3 by determining its vulnerability (i.e., how much inhibition of the target's activity is required to block bacterial growth) in vitro and in vivo (Aim 1), to develop the whole cell-based and cell-free assays required for the screening, validation and optimization of inhibitors of this transporter (Aim 2) and to provide proof-of-concept of its druggability by small molecule inhibitors (Aim 3).