Novel use of PI3K inhibition to prevent recurrence of B-cell acute lymphoblastic leukemia

摘要 中枢神经系统（CNS）转移和复发发生在高达10%的急性淋巴细胞白血病患者中。 白血病（ALL），尽管使用细胞毒性化疗或颅脊髓照射进行CNS导向预防。与 没有统一有效的治疗选择，CNS复发带来了不到6个月的严峻预后。到现在为止， ALL侵袭CNS的分子机制尚不清楚， 发展我们的实验室最近发现了一种以前未知的机制，B-ALL细胞可以通过这种机制进入淋巴细胞。 CNS。这种侵入途径依赖于表面蛋白α 6整合素之间的关键分子相互作用 表达于ALL母细胞，其受体层粘连蛋白表达于连接血管的基底膜 颅骨和脊椎骨髓到中枢神经系统软脑膜。我们进一步证明了B-ALL 106 整联蛋白表达受PI 3 K信号传导调节，且PI 3 K β同种型抑制在小鼠模型体内 白血病阻断CNS转移。使用B-ALL的体外和体内小鼠模型，我们现在表明， 与泛-PI 3 K亚型抑制剂copanlisib一起具有额外的治疗效果，包括细胞周期阻滞， ALL母细胞的化学增敏作用。这些转化为减少中枢神经系统转移，减少全身性疾病 白血病小鼠中的负荷和延长的存活。基于这些数据，我们设计了一个新的窗口- 机会（WoO）临床试验，以表征人类ALL中对泛PI 3 K抑制的分子应答。我们 还设计了小鼠模型来研究PI 3 Ki对微小残留病持续性的影响 (MRD)化疗后，疾病复发的关键预后指标。在目前的研究方案中， 我们的目标是：1）对患者样本中的B-ALL细胞分子反应进行详细的相关分析， 以及2）确定copanlisib对pan-PI 3 K的抑制作用是否在我们的WoO试验中是有效的， 联合挽救性化疗可以降低我们的临床前B-ALL模型的MRD。治疗 PI 3 K抑制在ALL中的作用尚未确定;因此，从我们的WoO方案收集的数据和 本研究建议中描述的实验将为潜在的后续试验设计提供重要信息 copanlisib纳入现有ALL治疗方案的II期研究。如果成功，我们的工作将 代表了ALL CNS预防性治疗的新突破，解决了大量未满足的领域 患者的临床需要。

ABSTRACT Central nervous system (CNS) metastasis and relapse occurs in up to 10% of patients with acute lymphoblastic leukemia (ALL), despite CNS-directed prophylaxis with cytotoxic chemotherapy or craniospinal irradiation. With no uniformly effective treatment options, CNS relapse carries a grim prognosis of less than 6 months. Until now, the molecular mechanism of ALL invasion into the CNS has been poorly understood, preventing targeted drug development. Our lab recently discovered a previously unknown mechanism used by B-ALL cells to enter the CNS. This invasion pathway is dependent on key molecular interactions between 6 integrin, a surface protein expressed on ALL blasts, and its receptor laminin, expressed on the basement membrane of vessels connecting the calvarial and vertebral bone marrow to the CNS leptomeninges. We further demonstrated that B-ALL 6 integrin expression is regulated by PI3K signaling, and that PI3K isoform inhibition in vivo in mouse models of leukemia blocks CNS metastasis. Using in vitro and in vivo mouse models of B-ALL, we now show that treatment with the pan-PI3K isoform inhibitor copanlisib has additional therapeutic effects including cell cycle arrest and chemosensitization of ALL blasts. These translate to decreased CNS metastasis, reduced systemic disease burden and prolonged survival in leukemic mice. Based on these data, we have designed a novel window-of- opportunity (WoO) clinical trial to characterize molecular responses to pan-PI3K inhibition in ALL in humans. We have also designed mouse models to study the impact of PI3Ki on the persistence of minimal residual disease (MRD) following chemotherapy, a key prognostic indicator of disease relapse. In the current research proposal, we aim to: 1) Perform detailed correlative analyses of B-ALL cell molecular responses in patient samples pre- and post-copanlisib dosing in our WoO trial, and 2) Determine whether pan-PI3K inhibition by copanlisib combined with salvage chemotherapy can decrease MRD in our preclinical models of B-ALL. The therapeutic role of PI3K inhibition in ALL has not yet been established; therefore, data gathered from our WoO protocol and the experiments described within this research proposal will critically inform trial design of a potential follow-on phase II study of copanlisib incorporated into existing ALL treatment regimens. If successful, our work will represent a novel breakthrough in CNS prophylactic therapy for ALL, addressing an area of substantial unmet clinical need for patients.