Pre-IND study of PMT-254, a pan-FLT3 inhibitor for the treatment of FLT3 driven cancers.

 描述（由申请方提供）：FLT 3激酶中的病理性激活突变代表了急性髓性白血病（AML）患者中最常见的遗传改变，发生在约三分之一的病例中。最近，我们进行了翻译研究，在用FLT 3抑制剂quizartinib（AC 220）治疗的AML患者复发时鉴定了FLT 3-ITD中的耐药激酶结构域突变，验证了FLT 3-ITD作为人AML的治疗靶点（N. Shah等人，Nature，2012，485，260-263）。为了促进快速鉴定可以更有效地治疗AML的潜在治疗剂，AML是一种没有新批准的有效治疗方法的癌症，我们创建了一种新的片段方法来发现激酶抑制剂，并建立了一系列体外和体内试验，以简化AML FLT 3抑制剂的开发。结果，鉴定了一种高效的FLT 3抑制剂临床候选物PMT-254。PMT-254是迄今为止开发的最有效的选择性FLT 3抑制剂，对FLT-ITD转化的Ba/F3细胞显示出0.009 nM的IC 50。此外，PMT-254实现了对奎扎替尼抗性F691 L、D835 V和D835 Y突变体的低纳摩尔抑制。值得注意的是，所有具有临床活性的研究性FLT 3抑制剂的效力都要低得多，并且没有实现类似的突变体活性特征。在人AML细胞系中，PMT-254在MV 4 -11和Molm-14 AML细胞系中均达到0.15 nM的IC 50。在含有内源性F691 L或D835 Y突变的Molm-14细胞中，PMT-254分别达到0.226 nM或2.2 nM IC 50值。PMT-254即使在10，000 nM的浓度下也不会损害亲本Ba/F3细胞的生长。针对96种激酶的激酶组进行筛选，发现PMT-254仅对FLT 3和FLT 3突变体具有选择性。显然，PMT-254不同于任何FLT 3抑制剂，如其超强力和超选择性所表现的，因此具有非凡的生物活性。 有可能改变FLT 3-ITD驱动的AML患者的治疗结果。在MV 4 -11异种移植物研究中，P0 1.0 mg/kg给药的PMT-254在短至4天内使肿瘤缩小至不可检测的水平（p <0.0001）。肿瘤体积达到1，200 mm 3的对照肿瘤以1.0和0.3 mg/kg PO给药，这在11天内将肿瘤负荷降低至不可检测的水平。允许来自初始治疗的不可检测的肿瘤反弹至1，200 mm 3的体积，此时开始用PMT-254治疗（PO 0.3mg/kg），这再次导致肿瘤体积减小至不可检测的水平。用PMT-254治疗的每只小鼠基本上治愈了肿瘤负荷，并且即使在连续40天接受每日口服剂量后也没有显示出毒性迹象。在本提案中，我们希望通过完成中试制剂、PK/PD和毒性研究来进一步开发我们的FLT 3抑制剂。这将获得必要的关键数据，以证明完成研究性新药（IND）包装的合理性。我们已经完成了初步的“概念验证”数据包，但缺乏临床前开发的具体方面，需要进行额外的IND前开发。随着这项提案的完成，我们将有一个数据包，将值得充分IND的发展。

 DESCRIPTION (provided by applicant): Pathological activating mutations in the FLT3 kinase represent the most common genetic alteration in patients with acute myeloid leukemia (AML), occurring in approximately one third of cases. Recently, we performed translational studies that identified drug-resistant kinase domain mutations in FLT3-ITD at the time of relapse in AML patients treated with the FLT3 inhibitor, quizartinib (AC220), validating FLT3-ITD as a therapeutic target in human AML (N. Shah et al, Nature, 2012, 485, 260-263). To facilitate the rapid identification of potential therapeutic agents that can treat AML more effectively, a cancer with no newly approved efficacious treatments, we have created a novel fragment approach to discover kinase inhibitors and established a series of in vitro and in vivo assays to streamline the development of FLT3 inhibitors for AML. As a result, a highly potent FLT3 inhibitor clinical candidate, PMT-254, was identified. PMT-254 is the most potent, selective FLT3 inhibitor developed to date, displaying an IC50 of 0.009 nM for FLT-ITD transformed Ba/F3 cells. Further, PMT-254 achieves low nanomolar inhibition of quizartinib-resistant F691L, D835V, and D835Y mutants. Notably, all clinically-active investigational FLT3 inhibitors are much less potent and do not achieve a similar mutant activity profile. In human AML cell lines, PMT-254 achieves an IC50 of 0.15 nM in both MV4-11 and Molm-14 AML lines. In Molm-14 cells harboring an endogenous F691L or D835Y mutation, PMT-254 achieves a 0.226 nM or 2.2 nM IC50 value, respectively. PMT-254 does not impair the growth of parental Ba/F3 cells, even at a concentration of 10,000 nM. Screened against a kinase panel of 96 kinases, PMT-254 was found exclusively selective for FLT3 and FLT3 mutants. Clearly, PMT-254 is unlike any FLT3 inhibitor as manifested by its ultra-potency and ultra-selectivity, and therefore has extraordinary potential to transform treatment outcomes for patients with FLT3-ITD-driven AML. In MV4-11 xenograft studies, PMT-254 dosed PO 1.0 mg/kg shrunk tumors to undetectable levels in as little as four days (p <0.0001). Control tumors that reached a tumor volume of 1,200 mm3 were dosed at PO 1.0 and 0.3 mg/kg, which reduced tumor burden to undetectable levels in 11 days. Undetectable tumors from original treatment were allowed to rebound to a volume of 1,200 mm3 at which point treatment with PMT-254 commenced (PO 0.3 mg/kg), which again caused reduction in tumor volume to undetectable levels. Every mouse treated with PMT-254 was essentially cured of tumor burden and displayed no signs of toxicity even after receiving daily oral doses for over 40 consecutive days. In this proposal, we wish to further develop our FLT3 inhibitor by completing pilot formulation, PK/PD, and toxicity studies. This will acquire pivotal data necessary to justify completing an investigative new drug (IND) package. We have completed a preliminary 'proof of concept' data package, but specific facets to preclinical development are lacking that warrant additional pre-IND development. With the completion of this proposal, we will have a data package that will merit full IND development.