PROTACS Against Nef as a Functional Cure for HIV Infection

抽象的。现有的抗逆转录病毒药物不能清除HIV-1潜伏宿主，这突出表明迫切需要 新的治疗策略。HIV-1 Nef辅助因子是药物开发的一个有吸引力的靶点， 它在HIV-1生命周期和免疫系统逃逸中的关键作用。我们小组发现了一种新的小型 直接与Nef结合并阻断其许多功能的分子，包括增强病毒感染性， 在供体PBMC中复制。重要的是，我们的Nef抑制剂在潜伏性免疫缺陷中拯救细胞表面MHC-I表达。 感染的患者来源的CD 4 T细胞，能够被自体CTL识别和杀伤。因此，Nef抑制剂 代表了抗逆转录病毒疗法的一种创新方法，可能为根除病毒性逆转录病毒提供一条途径， 瞧。我们最有前途的一类抑制剂（羟基吡唑类）在体外与其Nef蛋白靶点紧密结合 KD值在nM至pM范围内。然而，Nef缺乏活性位点，这使得传统的 由于缺乏药物化学之间的相关性， Nef的体外结合亲和力和细胞系统中的抗逆转录病毒活性。 为了解决这个问题，我们建议使用我们现有的Nef结合化合物来开发蛋白水解酶。 靶向嵌合体（PROTAC）分子，用于靶向破坏HIV感染细胞中的Nef蛋白。在 通过这种方法，现有的羟基吡唑Nef结合化合物将偶联到泛素E3配体的配体上。 通过柔性接头连接。预期所得Nef PROTAC催化蛋白水解降解， Nef通过E3介导的多聚泛素化和蛋白酶体靶向。PROTAC方法的一个主要优点是 它只需要靶蛋白的选择性结合剂（在这种情况下为Nef），而不需要功能性抑制剂。我们 预期选择性PROTAC介导的降解将消除所有Nef功能，包括拯救细胞 表面MHC-I介导的HIV-1抗原呈递，导致通过CTL应答清除HIV+细胞， 这是潜在储层减少和功能性治愈战略的一部分。更一般地说，PROTAC方法 在制药行业引起了极大的兴奋，因为它提供了新的途径来抑制 以前被认为是不可用的蛋白质。虽然PROTAC具有比典型的小分子量更高的分子量， 分子药物，最近的临床前和I期临床研究已经证明了体内以及口服的活性 生物利用度对于该一期STTR项目，HIV-1 Nef PROTAC开发将结合联合收割机的药物 和药物化学专业知识的福克斯大通化学多样性中心，公司。（www.fc-cdci.com; FCCDC） 匹兹堡大学Smithgall实验室在HIV-1 Nef结构、功能和抑制剂方面的专业知识， 分析.我们的主要目标是合成和测试一系列具有不同Nef靶向部分的Nef PROTAC， 接头和E3泛素连接酶配体，以鉴定适合于体内概念验证研究的化合物。Suc- 第一阶段的顺利完成将为扩大药物开发计划奠定坚实的基础， 第二阶段，最终目标是临床转化。

Abstract. Existing antiretroviral drugs do not clear HIV-1 latent reservoirs, underscoring the urgent need for new therapeutic strategies. The HIV-1 Nef accessory factor is an attractive target for drug development because of its critical roles in the HIV-1 life cycle and immune system escape. Our group has discovered novel small molecules that bind directly to Nef and block many of its functions, including enhancement of viral infectivity and replication in donor PBMCs. Importantly, our Nef inhibitors rescue cell-surface MHC-I expression in latently in- fected, patient-derived CD4 T-cells, enabling recognition and killing by autologous CTLs. Thus, Nef inhibitors represent an innovative approach to antiretroviral therapy that may provide a path to eradication of viral reser- voirs. Our most promising class of inhibitors (hydroxypyrazoles) bind tightly to their Nef protein target in vitro with KD values in the nM to pM range. However, Nef lacks an active site, which has complicated traditional medicinal chemistry optimization of existing compounds for in vivo testing due to the lack of correlation between Nef binding affinity in vitro and antiretroviral activity in cell-based systems. To circumvent this issue, we propose to use our existing Nef-binding compounds to develop Proteolytic Targeting Chimera (PROTAC) molecules for the targeted destruction of the Nef protein in HIV-infected cells. In this approach, existing hydroxypyrazole Nef-binding compounds will be coupled to ligands for ubiquitin E3 lig- ases via a flexible linker. The resulting Nef PROTACs are anticipated to catalyze the proteolytic degradation of Nef via E3-mediated polyubiquitination and proteasomal targeting. A major advantage of the PROTAC approach is that it requires only a selective binder of the target protein (Nef in this case) and not a functional inhibitor. We anticipate that selective PROTAC-mediated degradation will eliminate all Nef functions, including rescue of cell surface MHC-I mediated HIV-1 antigen presentation, leading to clearance of HIV+ cells via the CTL response as part of a strategy for latent reservoir reduction and functional cure. More generally, the PROTAC approach has generated a great deal of excitement in the pharmaceutical industry, because it provides new avenues to inhibit proteins previously considered undruggable. While PROTACs have higher molecular weights that typical small molecule drugs, recent preclinical and Phase I clinical studies have demonstrated activity in vivo as well as oral bioavailability. For this Phase I STTR project, HIV-1 Nef PROTAC development will combine the pharmaceutical and medicinal chemistry expertise of the Fox Chase Chemical Diversity Center, Inc. (www.fc-cdci.com; FCCDC) with the expertise of the Smithgall Lab at the University of Pittsburgh in HIV-1 Nef structure, function and inhibitor analysis. Our broad goal is to synthesize and test a series of Nef PROTACs with different Nef-targeting moieties, linkers, and E3 ubiquitin ligase ligands to identify compounds suitable for in vivo proof-of-concept studies. Suc- cessful completion of Phase I will provide a strong foundation for an expanded drug development program in Phase II, with the ultimate goal of clinical translation.