Targeting Multiple Myeloma with Smac-mimetics and HDAC Inhibitors

描述（由申请人提供）：尽管治疗进展，多发性骨髓瘤（MM）通常是无法治愈的，迫切需要新的和更有效的治疗方案。凋亡抑制剂（IAP）拮抗剂/ smac - mimitics (SMs)，如LCL161或biinopant，最初是为了防止IAP抑制活化的半胱氨酸酶和细胞凋亡而开发的，已经显示出作为抗癌药物的临床前潜力，包括在MM中。最近的关注集中在SMs下调核心E3泛素连接酶cIAP1/2的能力，从而抑制典型和非典型NF-κB通路，这对MM细胞存活至关重要。同时通过核溶体激活外源性凋亡途径。组蛋白去乙酰化酶抑制剂（HDACIs）调节许多非组蛋白底物的基因表达和乙酰化。值得注意的是，HDACI panobinostat （PB）最近被批准用于MM（与蛋白酶体抑制剂；pi）。最近，我们和其他人已经证明HDACIs在调节NF-κB和外源性凋亡途径中发挥重要作用。在此，我们提出了一种新的机制驱动策略，基于多个互补的原理，即：a) SMs和HDACIs靶向常见的信号级联，同时抑制典型和非典型NF-κB通路，同时激活内源性和外源性凋亡通路；b) NF-κB在MM细胞中因频繁的遗传畸变和骨髓微环境因素而构成性激活；c) NF-κB抑制（例如，通过pi）显着增加MM中HDACI的活性。事实上，初步证据表明，在各种MM细胞类型中，SMs和HDACIs之间存在高度协同作用。为了推进这一新概念，提出了三个目标。在Specific Aim #1中，我们将定义SMs增强HDACI抗mm活性的MOAs，强调典型或非典型NF-κ b途径的破坏，以及通过核酶体参与外部途径；通过激活外源性凋亡通路的moa，绕过Bcl-2家族异常表达引起的获得性耐药，建立方案对MM细胞耐受常规或新型药物的疗效；确定该策略是否通过阻断非典型NF-κB通路来规避微环境形式的耐药。在特异性目标#2中，我们将确定该方案是否选择性地杀死原代MM细胞，同时保留正常细胞；验证该策略也针对MM干细胞样细胞的假设；确定某些涉及NF-κB或凋亡途径的遗传畸变的原代MM细胞亚型是否对该方案特别敏感，如果是，哪些机制是有效的。在Specific Aim #3中，我们将测试该方案在免疫功能低下或免疫功能正常的MM小鼠模型中是否有效和耐受，并确定体外鉴定的moa在体内是否有效。如果成功，这些研究将为复发/难治性MM的新的和潜在的更有效的个体化治疗策略的临床开发提供必要的基础。

DESCRIPTION (provided by applicant): Despite therapeutic advances, multiple myeloma (MM) is generally incurable, and new and more effective treatment options are urgently needed. Inhibitor of apoptosis (IAP) antagonists/Smac-mimetics (SMs) such as LCL161 or birinopant, initially developed to prevent IAPs from inhibiting activated caspases and apoptosis, have shown pre-clinical potential as anti-cancer agents, including in MM. Recent attention has focused on the ability of SMs to down-regulate the core E3 ubiquitin ligases cIAP1/2, thereby inhibiting both the canonical and non-canonical NF-κB pathways, critical for MM cell survival, while activating the extrinsic apoptotic pathway through the ripoptosome. Histone deacetylase inhibitors (HDACIs) modulate gene expression and acetylation of numerous non-histone substrates. Notably, the HDACI panobinostat (PB) has very recently been approved (with proteasome inhibitors; PIs) in MM. Recently, we and others have demonstrated that HDACIs play important roles in regulation of the NF-κB and extrinsic apoptotic pathways. Here, we propose a novel mechanism-driven strategy combining SMs with HDACIs in MM based on multiple complementary rationales i.e., a) SMs and HDACIs target common signaling cascades, and in combination simultaneously inhibit both the canonical and non-canonical NF-κB pathways while activating the intrinsic and extrinsic apoptotic pathways; b) NF-κB is constitutively activated in MM cells due to frequent genetic aberrations and bone marrow microenvironmental factors; c) NF-κB inhibition (e.g., by PIs) significantly increases HDACI activity in MM. Indeed, preliminary evidence suggests highly synergistic interactions between SMs and HDACIs in various MM cell types. To advance this novel concept, three Aims are proposed. In Specific Aim #1, we will define MOAs by which SMs potentiate HDACI anti-MM activity, highlighting disruption of the canonical or non- canonical NF-κB pathways, and engagement of the extrinsic pathway via the ripoptosome; establish regimen efficacy in MM cells resistant to conventional or novel agents, particularly by bypassing acquired resistance due to aberrant Bcl-2 family expression through MOAs involving activation of the extrinsic apoptotic pathway; determine whether this strategy circumvents microenvironmental forms of drug-resistance by interrupting the non-canonical NF-κB pathway. In Specific Aim #2, we will determine whether the regimen selectively kills primary MM cells while sparing normal cells; test the hypothesis that this strategy also targets MM stem cell- like cells; determine whether certain primary MM cell subtypes with genetic aberrations involving NF-κB or apoptotic pathways are particularly sensitive to this regimen, and if so, which mechanisms are operative. In Specific Aim #3, we will test whether the regimen is effective and tolerated in immunocompromised or immunocompetent MM mouse models, and determine if MOAs identified in vitro are operative in vivo. If successful, these studies will provide the necessary foundation for clinical development of a new and potentially more effective individualized treatment strategy for relapsed/refractory MM.