BMS-986397, a First-in-Class Molecular Glue Degrader of Casein Kinase 1α (CK1α) for the Treatment of Acute Myeloid Leukemia (AML) and High-Risk Myelodysplastic Syndrome (HR-MDS) Harboring Functional TP53

BMS-986397, a First-in-Class Molecular Glue Degrader of Casein Kinase 1α (CK1α) for the Treatment of Acute Myeloid Leukemia (AML) and High-Risk Myelodysplastic Syndrome (HR-MDS) Harboring Functional TP53

Introduction: The Casein Kinase 1α (CK1α) gene resides on chromosome 5q and has haploid status in del5q MDS (Myelodysplastic Syndrome). Lenalidomide is a weak, but significant degrader of CK1α, and has clinical efficacy in del5q MDS relative to non-del5q MDS. Therefore, development of a strong degrader of CK1α that may have activity in myeloid malignancies irrespective of 5q status is warranted. We identified BMS-986397 as a potent, specific, oral CELMoD molecular glue degrader of CK1α. Here, we present preclinical evidence of p53-dependent efficacy of BMS-986397 in AML (Acute Myeloid Leukemia) and HR-MDS (High-Risk Myelodysplastic Syndrome). Methods: To assess the anti-proliferative activity and molecular mechanism of BMS-986397, AML parental and genetically engineered cell lines with CRISPR/Cas9-mediated knockout of Cereblon (CRBN) or TP53 or overexpressing a non-degradable CK1α mutant were evaluated by proliferative assays, flow cytometry, and immunoblotting. As BMS-986397 is pharmacology active in different species, informative in vivo studies in rodent models and in ex vivo models using primary samples from healthy volunteers and AML patients were conducted to assess pharmacokinetics (PK), pharmacodynamics (PD), and antitumor activity. Additionally, single- and repeat-dose toxicity studies in rats, monkeys and primary human samples were executed to determine the CK1α on-target toxicity and the toxicologic profile of BMS-986397. All preclinical data described above were leveraged and integrated into a PK/PD model to establish key safety, efficacy, and PD relationships informing the starting dose/schedules for the FIH (Firs-in-Human) clinical study. Results: BMS-986397 exhibits a strong antiproliferative effect in TP53 WT (Wild-Type) AML cancer cell lines through potent and selective degradation of CK1α regardless of FAB subtype or any common oncogenic-driver mutations, with the exception of TP53. Degradation of CK1α leads to p53 stabilization and the consequent induction of p53 transcriptional targets including p21, PUMA, and BAX, thereby inducing cell cycle arrest and acute apoptosis of AML cells. This anti-AML activity is dependent on upon CRBN, CK1α, and p53. The growth inhibitory effect of BMS-986397 is also observed in hematopoietic progenitors and leukemic cells from multiple AML patient samples harboring functional p53, while sparing normal T-lymphocytes. Normal hematopoietic progenitors are less responsive to BMS-986397 treatment in a time and dose-dependent fashion. Pharmacodynamic (PD) studies indicate that sustained CK1α degradation for a minimum of 48 hours is required to stabilize p53 and, therefore, achieve antileukemic efficacy compromising AML blasts viability. A faster recovery of normal marrow progenitors and stem cells is observed compared to AML blasts, further supporting a reasonable therapeutic index for the treatment of AML and HR-MDS. Similarly, in vivo pharmacology studies in cell line-derived AML xenograft models determined a dose- and schedule-dependent PK/PD relationship, a significant CK1α degradation and consequent activation of downstream pathways led to marked tumor burden reduction and prolonged mice survival. Integrative modeling of PK/PD, efficacy, and toxicity data established key safety, efficacy, and target engagement relationships which suggested that short and intense schedules followed by prolonged off-treatment period instead of more frequent intermittent schedules may maximize cytotoxicity on AML blasts while allowing for extended recovery period of hematopoietic progenitors. Conclusions: BMS-986397 is a novel CELMoD agent with a first in class mechanism targeting CK1α degradation exhibiting strong anti-leukemic activity as a single agent in models of TP53 WT AML and HR-MDS. These data support the clinical investigation of BMS-986397 in patients with R/R AML and HR-MDS patients (NCT04951778).

引言：酪蛋白激酶1α（CK1α）基因位于5号染色体长臂（5q），在5q缺失的骨髓增生异常综合征（MDS）中为单倍体状态。来那度胺是一种较弱但显著的CK1α降解剂，相对于无5q缺失的MDS，其在5q缺失的MDS中具有临床疗效。因此，有必要开发一种强效的CK1α降解剂，使其在髓系恶性肿瘤中无论5q状态如何都可能具有活性。我们发现BMS - 986397是一种强效、特异的口服CELMoD分子胶CK1α降解剂。在此，我们展示了BMS - 986397在急性髓系白血病（AML）和高危骨髓增生异常综合征（HR - MDS）中依赖p53发挥疗效的临床前证据。 方法：为了评估BMS - 986397的抗增殖活性和分子机制，我们使用增殖试验、流式细胞术和免疫印迹法对AML亲本细胞系以及通过CRISPR/Cas9介导的Cereblon（CRBN）或TP53基因敲除或过表达不可降解的CK1α突变体的基因工程细胞系进行了评估。由于BMS - 986397在不同物种中具有药理活性，我们在啮齿动物模型以及使用来自健康志愿者和AML患者的原代样本的体外模型中进行了有价值的体内研究，以评估药代动力学（PK）、药效动力学（PD）和抗肿瘤活性。此外，我们在大鼠、猴子和原代人类样本中进行了单次和多次给药毒性研究，以确定BMS - 986397对CK1α的靶向毒性和毒理学特征。上述所有临床前数据都被利用并整合到一个PK/PD模型中，以建立关键的安全性、疗效和PD关系，为首次人体（FIH）临床研究的起始剂量/给药方案提供依据。 结果：BMS - 986397通过对CK1α的强效和选择性降解，在TP53野生型（WT）AML癌细胞系中表现出强烈的抗增殖作用，无论FAB亚型或任何常见的致癌驱动突变如何（TP53突变除外）。CK1α的降解导致p53稳定，进而诱导p53转录靶点，包括p21、PUMA和BAX，从而诱导AML细胞的细胞周期停滞和急性凋亡。这种抗AML活性依赖于CRBN、CK1α和p53。在来自多个具有功能性p53的AML患者样本的造血祖细胞和白血病细胞中也观察到BMS - 986397的生长抑制作用，而对正常T淋巴细胞无影响。正常造血祖细胞对BMS - 986397治疗的反应呈时间和剂量依赖性降低。药效动力学（PD）研究表明，至少持续48小时的CK1α降解是稳定p53并因此实现抗白血病疗效、降低AML原始细胞活力所必需的。与AML原始细胞相比，观察到正常骨髓祖细胞和干细胞恢复更快，这进一步支持了其在治疗AML和HR - MDS中具有合理的治疗指数。同样，在细胞系衍生的AML异种移植模型中的体内药理学研究确定了剂量和给药方案依赖性的PK/PD关系，显著的CK1α降解以及随后下游通路的激活导致肿瘤负荷显著降低和小鼠生存期延长。PK/PD、疗效和毒性数据的综合建模建立了关键的安全性、疗效和靶点结合关系，这表明短期高强度给药方案后接较长的停药期，而非更频繁的间歇给药方案，可能在使AML原始细胞的细胞毒性最大化的同时，允许造血祖细胞有更长的恢复时间。 结论：BMS - 986397是一种新型的CELMoD药物，具有针对CK1α降解的首创机制，在TP53野生型AML和HR - MDS模型中作为单一药物表现出强大的抗白血病活性。这些数据支持对复发/难治性AML患者和HR - MDS患者进行BMS - 986397的临床研究（NCT04951778）。