Anit-PR1 Immune Therapy for Myeloid Leukemia

我们的长期目标是开发针对异常表达的蛋白水解酶的免疫疗法。 原始细胞和白血病干细胞。PR1肽(VLQELNVTV)是一种来源于白血病的多肽- 相关抗原蛋白3(P3)和中性粒细胞弹性蛋白酶(NE)，表达于人类白细胞抗原A2~PR1-2。 特异性细胞毒T淋巴细胞(PR1-CTL)。在上一次资助期间，我们发现PR1是交叉的。 由树突状细胞(DC)和B细胞提出，我们显示了需要蛋白酶体的机制 切割抗原提呈细胞摄取的外源性P3和NE。我们完成了第2阶段优先级 多肽疫苗试验显示58%的人有免疫反应，16%的人有临床反应，但 仅限于白血病负担较低的患者。我们制定了一种策略，通过收养转移捐献者- 衍生的PR1-CTL用于干细胞移植受者治疗高白血病负担。作为一种替代策略， 我们鉴定了一种T细胞受体(TCR)样单抗(8F4)，该抗体具有构象特异性 与人类白细胞抗原A2分子结合的PR1表位。8F4诱导小鼠补体依赖性细胞毒作用 AML和LSC并抑制AML祖细胞的生长，但不抑制正常的骨髓祖细胞，这 支持进一步研究8F4作为一种潜在的治疗AML的单抗。我们的预赛 数据显示，8F4阻止了AML的植入，减少或消除了已建立的原发人类AML 体内异种移植。8F4还显著减少或消除了小鼠模型中的白血病干细胞(LSCs)。 我们生产了人源化的8F4(Hu8F4)，并显示它显著降低了(&gt；95%)已建立的人类 急性髓系白血病异种移植。因此，8F4是第一个TCR样单抗，可以抑制AML和LSC的生长，并消除 活体内的AML。在这笔赠款的前几年，我们使用了PRI多肽疫苗来诱导患者的免疫 对于AML、CML和MDS，以及最近我们启动了两个针对PRI的过继细胞治疗试验 急性髓系白血病和慢性粒细胞白血病分别为CTL和CML。在这个提案中，我们将8F4单抗描述为一种新的 白血病的治疗方法。我们的中心假设是针对表面的免疫治疗 PR1/HLA-A2分子可选择性清除白血病和白血病干细胞，但不正常 造血细胞。研究这种新型抗体的治疗潜力，以改善预后 对于髓系恶性肿瘤患者，我们将追求以下特定目标1)表征其活性 HU-8F4抗人AML，2)进行HU-8F4临床前治疗验证和安全性研究，以及 3)在复发AML患者中使用Hu8F4进行首例人类1期临床试验。 相关性(请参阅说明)： 这些研究的成功完成将为探索提供生物学、临床前和临床基础 一种高度新颖的TCR样抗体(8F4)治疗白血病的潜力。8F4消除 白血病和白血病干细胞在不排除正常小鼠模型中的原发人类白血病 血细胞或正常的造血干细胞。因此，8F4作为高度特定于AML的 具有低潜在毒性的试剂。我们将在急性髓细胞白血病中使用这种抗体进行首次人类临床试验。

Our long-term goal Is to develop Immune therapies that target aberrantly expressed proteases In blasts and leukemia stem cells. PR1 peptide (VLQELNVTV) is a peptide derived from the leukemia- associated antigens proteinase 3 (P3) and neutrophil elastase (NE), which is presented on HLA-A2 to PR1- speclfic cytotoxic T lymphocytes (PR1-CTL). During the last grant period, we showed that PR1 is cross- presented by dendritic cells (DCs) and B cells, and we showed the mechanism required proteasome cleavage exogenous P3 and NE taken up by antigen-presenting cells. We completed a phase 2 PRI peptide vaccine trial that showed immune responses in 58% and clinical responses in 16%, but responses were limited to patients with low leukemia burden. We developed a strategy to adoptively transfer donor- derived PR1-CTL to stem cell transplant recipients to treat high leukemia burden. As an alternate strategy, we identified a T cell receptor (TCR)-like monoclonal antibody (8F4) with specificity for a conformational epitope of PR1 bound to the HLA-A2 molecule. 8F4 induces complement-dependent cytotoxicity (CDC) of AML and LSC and inhibits AML progenitor cell growth but not normal bone marrow progenitors, which supports further study of 8F4 as a potential therapeutic monoclonal antibody (mAb) for AML. Our preliminary data show that 8F4 prevents AML engraftment and reduced or eliminated established primary human AML xenografts in vivo. 8F4 also significantly reduced or eliminated leukemia stem cells (LSCs) in mouse models. We produced a humanized 8F4 (Hu8F4) and showed it significantly reduced (>95%) established human AML xenografts. Thus, 8F4 is the first TCR-like mAb that inhibits growth of AML and LSC and eliminates AML in vivo. In prior years of this grant, we have used a PRI peptide vaccine to induce immunity in patients with AML, CML, and MDS and more recently we initiated two adoptive cell therapy trials with PRI-specific CTL in AML and CML, respectively. In this proposal, we will characterize the 8F4 mAb as a novel therapeutic modality for leukemia. Our central hypothesis is that immune therapy targeting surface PR1/HLA-A2 molecules can selectively eliminate leulfemia and leuliemia stem cells, but not normal hematopoietic cells. To investigate the therapeutic potential of this novel antibody to improve the outcome of patients with myeloid malignancies, we will pursue the following Specific Aims 1) characterize the activity of HU-8F4 against human AML, 2) perform pre-clinical treatment validation and safety studies of Hu-8F4, and 3) conduct a first-in-human phase 1 clinical trial with Hu8F4 in patients with relapsed AML. RELEVANCE (See instructions): Successful completion of these studies will provide the biological, pre-clinical and clinical bases for exploring the therapeutic potential of a highly novel TCR-like antibody (8F4) to treat leukemia. 8F4 eliminates leukemia and leukemia stem cells in mouse models of primary human leukemia without eliminating normal blood cells or normal hematopoietic stem cells. Therefore, 8F4 shows promise as a highly AML-specific agent with low potential for toxicity. We will conduct a first-in-human clinical trial with this antibody in AML.