MmpL3 as a target for novel anti-TB agents

 描述(申请人提供)：结核病(TB)，由结核分枝杆菌(Mtb)引起，仍然是世界范围内的一个主要公共卫生问题，也是艾滋病毒携带者，包括正在接受抗逆转录病毒治疗的人中最常见的疾病。结核病也是艾滋病毒携带者的主要死因，占与艾滋病毒/艾滋病相关的死亡人数的四分之一。迫切需要开发耐受性好、对多重和广泛耐药(MDR/XDR)结核分枝杆菌有效并适合结核病/艾滋病毒联合治疗的更短、更简单的药物方案。人们重新对基于全细胞的筛选来鉴定新的抗结核化合物感兴趣，这导致了一些有希望的抑制剂的鉴定。有趣的是，据报道，包括结核病候选药物SQ109在内的几个化合物通过抑制霉菌酸转运蛋白MmpL3而杀死结核分枝杆菌。分枝杆菌酸是一种在细胞质中合成的丰富的长链(C60-C90)脂肪酸，存在于所有分枝杆菌外膜的内外小叶中；通过阻止分枝杆菌酸输出到周质空间，MmpL3的抑制作用阻止了结核分枝杆菌外膜的形成。多个化学支架通过对MmpL3的明显抑制来阻止结核分枝杆菌的生长，这一事实可能反映了这种转运蛋白的不同寻常的脆弱性和“可药性”。或者，我们的初步结果使我们质疑其中一些化合物抑制MmpL3的直接机制。因此，尽管人们对MmpL3作为一种新的治疗靶点越来越感兴趣，而且由于开发这种大的膜蛋白的转运分析相关的技术挑战，MmpL3尚未被证实为任何Mtb抑制剂的直接靶点。迫切需要新的治疗方法来治疗MDR/XDR-Mtb感染，以及了解小分子抑制剂的作用模式以推动其优化过程的重要性，使得验证MmpL3作为新的药物靶点和开发该转运体的抑制试验成为当务之急。该建议是通过确定MMPL3的易损性来确定其治疗潜力(即， 需要在多大程度上抑制靶的活性才能阻止细菌生长)在体外和在 体内(目标1)，开发筛选、验证和优化该转运蛋白的抑制剂所需的完整的基于细胞的和无细胞的分析(目标2)，并提供小分子抑制剂对其可药性的概念证明(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).