Targeting Multiple Myeloma with Smac-mimetics and HDAC Inhibitors

描述(申请人提供)：尽管治疗取得了进步，但多发性骨髓瘤(MM)通常是无法治愈的，迫切需要新的和更有效的治疗方案。细胞凋亡抑制物(IAP)拮抗剂/Smac类似物，如LCL161或Birinopant，最初开发用于防止IAP抑制激活的caspase和细胞凋亡，已显示出临床前的潜力，用于抗癌，包括在MM中。最近的注意力集中在Sms下调核心E3泛素连接酶CIAP1/2的能力，从而抑制对MM细胞生存至关重要的规范和非规范的NF-κB途径，同时通过核小体激活外在的凋亡途径。组蛋白脱乙酰酶抑制物(HDACIs)调节多种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(与蛋白酶体抑制剂一起使用；PI)。最近，我们和其他人证明HDACI在调节NF-κB和外源性凋亡途径中发挥重要作用。在这里，我们基于多个互补的原理提出了一种新的机制驱动的策略，将SMS和HDACI结合在MM中，即：a)SMS和HDACI针对共同的信号级联，同时抑制规范和非典型的NF-κB途径，同时激活内在和外在的凋亡途径；b)由于频繁的遗传异常和骨髓微环境因素，MM细胞中的NF-κB被结构性地激活；c)NF-κB的抑制(例如，通过PI)显著增加MM中的HDACI活性。为了推进这一新概念，提出了三个目标。在特定的目标#1中，我们将定义MOAs，通过MOAs，Sms增强HDACi抗MM的活性，强调规范或非规范的NF-κB途径的破坏，以及通过核糖体参与外部途径的参与；建立对传统或新型药物耐药的MM细胞的治疗方案，特别是通过涉及激活外部凋亡途径的MOAs，通过绕过因Bcl2家族的异常表达而产生的获得性耐药性；确定该策略是否通过阻断非规范的NF-κB途径来规避微环境形式的耐药性。在具体目标#2中，我们将确定该方案是否选择性地杀死原代MM细胞，而保留正常细胞；测试该策略也针对MM干细胞样细胞的假设；确定某些具有涉及NF-κB或凋亡途径的遗传异常的原代MM细胞亚型是否对该方案特别敏感，如果是，哪些机制是可行的。在具体目标#3中，我们将在免疫功能低下或免疫功能正常的MM小鼠模型中测试该方案是否有效和耐受性，并确定体外鉴定的MOA在体内是否有效。如果成功，这些研究将为临床开发新的、可能更有效的复发/难治性MM的个体化治疗策略提供必要的基础。

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.