Translational Studies to facilitate Rational Therapeutic Combinations of Letrozole for the Treatment of Glioblastoma

胶质母细胞瘤(GBM)是最致命的脑肿瘤之一，其患者的预后仍然很差。我们的 最近的发现提供了强有力的证据表明，来曲唑(LTZ)，一种芳香化酶抑制剂，用于 乳腺癌的治疗，有可能成为治疗GBM的突破性治疗方法。我们的 数据包括：1)LTZ处理患者来源的GBM细胞显著降低细胞活力和球体生长； 2)LTZ可增强TMZ中GBM化疗的主要药物替莫唑胺(TMZ)的活性。 3)免疫活性大鼠的药代动力学/药效学(PK/PD)研究 原位移植C6大鼠胶质瘤显示LTZ很容易通过血脑屏障(BBB)， 显著缩小肿瘤体积并延长生存期(对照组为10天，LTZ组为60天)； 组织(N&GT；90例)的免疫组织化学分析表明，芳香化酶的表达是 与低级别胶质瘤相比，GBM中的GT；5X显著更高。此外，在正在进行的0/1期临床试验中， 哪些复发的GBM患者在手术切除前接受了LTZ(2.5-12.5 mg，N=14例)，分析 对切除的肿瘤的研究表明，LTZ在人类中很容易穿过血脑屏障。RNAseq分析显示 驱动细胞增殖标记物的癌基因显著下调和肿瘤抑制上调 标记(降低的DNA损伤修复能力)以LTZ剂量依赖的方式。我们的长期目标是 将LTZ重新用作抗GBM药物。鉴于GBM的表型/基因复杂性，联合治疗 将是临床上的必需品。为了支持这一目标，我们的目标是进行全面的PK/PD研究 LTZ及其联合用药在免疫缺陷(裸鼠)患者来源的异种异种移植中的作用 老鼠。通常，这样的研究是利用无症状/SCID小鼠进行的。然而，消除半衰期 小鼠的LTZ很短(~2.5小时)，而大鼠的LTZ PK更接近于人类，需要使用 裸鼠裸鼠。因此，我们建议进行一项基于里程碑的量化研究，使用初级和 复发的患者来源的基底膜。我们将严格测试LTZ的联合用药，强烈建议 通过我们的RNAseq和其他数据，合理地推进II期临床试验的2-3个组合。 具体目标：1：LTZ基于协同效应对抗GBM线的等级-顺序组合伙伴 体外实验2：测定联合用药±LTZ的体内血脑屏障通透性。3：建立PDOX裸鼠模型 体内PK/PD研究模型，4：应用PDOX模型评价LTZ±联合制剂的PK/PD。 R61期的里程碑包括协同抑制细胞活力(组合指数，CI&lt；1)和血脑屏障 渗透性(血浆到大脑的分割)(目标1和2)。同时，一个裸鼠裸鼠模型将被 在目标3中建立/验证。在R33阶段(目标4)使用这些模型，剂量-反应关系将 将2-3个LTZ组合推进到II期临床试验。一个由多学科协作者组成的团队 将参与这一重要的下一步，将LTZ重新用于GBM治疗，这是一种紧急的未得到满足的医疗需求。

The prognosis for patients with glioblastoma (GBM), one of the most lethal brain tumors, remains dismal. Our recent discoveries provide robust evidence suggesting that letrozole (LTZ), an aromatase inhibitor used in the treatment of breast cancer, has the potential to be a breakthrough therapeutic for the treatment of GBM. Our data include: 1) LTZ treatment of patient-derived GBM cells markedly reduced cell viability and spheroid growth; 2) LTZ potentiated the activity of temozolomide (TMZ), the primary agent used in chemotherapy of GBM in TMZ- resistant cells; 3) Pharmacokinetics/Pharmacodynamics (PK/PD) studies in immunocompetent rats orthotopically implanted with C6 rat glioma revealed that LTZ readily crosses the blood-brain barrier (BBB), markedly reduces tumor volume and extends survival (10 vs. > 60 days in control vs. LTZ); and 4) immunohistochemical analysis of tissues (N > 90 patients) demonstrated that the aromatase expression is strikingly higher (> 5X) in GBM relative to low-grade gliomas. Moreover, in an ongoing phase 0/1 clinical trial in which recurrent GBM patients received LTZ (2.5 -12.5 mg, N = 14 subjects) prior to surgical resection, analyses of the excised tumor revealed that LTZ readily traverses the BBB in humans. RNAseq analysis showed significant downregulation of oncogenes driving cell proliferation markers and upregulation of tumor suppression markers (reduced DNA damage repair capacity) in a LTZ dose-dependent manner. Our long-term goal is to repurpose LTZ as an anti-GBM drug. Given the phenotypic/genotypic complexity of GBM, combination therapy will be a clinical necessity. To support this goal, our objective here is to conduct comprehensive PK/PD studies of LTZ and combination agents in patient-derived orthotopic xenograft (PDOX) immunodeficient (athymic nude) rats. Typically, such studies are performed utilizing athymic/SCID mice. However, the elimination half-life of LTZ in mice is short (~ 2.5 hours), whereas LTZ PK in rats are closer to that in humans requiring the use of athymic nude rats. Thus, we propose to conduct a quantitative milestone-based study employing primary and recurrent patient-derived GBM. We will rigorously test combination agents for LTZ, strongly suggested collectively by our RNAseq and other data and rationally advance 2-3 combinations for phase II clinical trials. Specific Aims: 1: Rank-order combination partners for LTZ based on synergistic effects against GBM lines in vitro 2: Determine in vivo BBB permeability of combination agents ± LTZ. 3: Establish PDOX athymic nude rat models for in vivo PK/PD studies, 4: Evaluate PK/PD of LTZ ± combination agent employing the PDOX models. The R61 phase milestones include synergistic inhibition of cell viability (Combination Index, CI< 1) and BBB permeability (plasma to brain partitioning) (Aims 1 and 2). Concurrently, an athymic nude rat models will be established/validated in Aim 3. Using these models in the R33 phase (Aim 4), dose-response relationship will be derived to advance 2-3 LTZ combinations to phase II clinical trials. A multidisciplinary team of collaborators will participate in this important next step to repurpose LTZ for GBM treatment, an urgent unmet medical need.