Macrophage Based Gene Therapy for Hereditary Pulmonary Alveolar Proteinosis

描述（由申请人提供）：遗传性肺泡蛋白沉积症（hPAP）是一种表面活性剂积累增加导致呼吸衰竭的疾病，目前尚无药物治疗方法。它是由分别编码GM-CSF受体(GM-R) α和β亚基的CSF2RA或CSF2RB突变破坏GM-CSF向肺泡巨噬细胞（AMs）的信号通路引起的。长期目标是开发基因疗法来恢复AM中的GM-CSF信号，从而恢复GM-CSF依赖性AM对表面活性剂清除、肺泡内稳态、肺功能和宿主防御至关重要的功能。目的是评估一种新的治疗方法，肺巨噬细胞移植（PMT）。初步数据显示，GM-R缺陷（GM-RKO）小鼠发生与人类hPAP相同的hPAP肺部疾病，包括肺GM-CSF水平升高，这为具有功能性GM-R的AMs提供了选择性生存优势。该研究的中心假设是，安全性增强的、慢病毒载体介导的GM-R在造血干细胞/前体细胞（HSPCs）中的表达、向巨噬细胞的扩增和基因校正细胞的自体PMT（不含骨髓消融）作为hPAP治疗将是有效和安全的。初步数据显示，单次PMT治疗可以纠正GM-RKO小鼠的hPAP至少一年（评估的最长时间）而没有相关的不良事件，并且在申请人的实验室中，人类HSPCs可以很容易地通过成熟的方法转导并扩增成表达功能性GM-Rs的巨噬细胞。其基本原理是，预期结果将为未来临床试验的设计提供信息，并提供临床前安全性和有效性数据以及GMP

DESCRIPTION (provided by applicant): Hereditary pulmonary alveolar proteinosis (hPAP) is a disorder of increased surfactant accumulation resulting in respiratory failure for which no pharmacologic therapy exists. It is caused by disruption of GM-CSF signaling to alveolar macrophages (AMs) by mutations in CSF2RA or CSF2RB, which encode GM-CSF receptor (GM-R) α and β subunits, respectively. The long-term goal is to develop gene therapy to restore GM-CSF signaling in AMs and, thereby, GM-CSF-dependent AM functions critical to surfactant clearance, alveolar homeostasis, lung function and host defense. The objective here is to evaluate a novel therapeutic approach, pulmonary macrophage transplantation (PMT). Preliminary data show that GM-R deficient (GM-RKO) mice develop hPAP lung disease that is identical to hPAP in humans including an increased level of pulmonary GM-CSF, which confers a selective survival advantage to AMs with functional GM-Rs. The central hypothesis is that safety-enhanced, lentiviral vector-mediated GM-R expression in hematopoietic stem/precursor cells (HSPCs), expansion into macrophages, and autologous PMT of gene-corrected cells without myeloablation will be effective and safe as therapy of hPAP. Preliminary data show that a single PMT treatment can correct hPAP in GM-RKO mice for at least one year (the longest time evaluated) without associated adverse events, and that human HSPCs can be readily transduced using well-established methods in the applicants' laboratory and expanded into macrophages expressing functional GM-Rs. The rationale is that anticipated results will inform the design of future a clinical trial and provide the preclinical safety and efficacy data, and GMP manufacturing procedures and validation data required to obtain regulatory approval to test this approach in humans. The hypothesis will be tested in four specific aims: 1) determine the efficiency and kinetics of gene transfer/PMT therapy of hPAP in GM-RKO mice; 2) optimize the expansion of human HSPC-derived, gene- corrected macrophages with maximum PMT engraftment potential; 3) determine the safety of gene transfer/PMT in preclinical studies related to gene transfer, macrophage expansion from HSPCs, PMT, and pharmacologic depletion of transduced cells in GM-RKO mice; 4) develop and validate protocols for the manufacture of HSPC-derived, gene-corrected macrophages, and write a clinical protocol and investigational new drug application for gene transfer/PMT therapy of hPAP. The approach is innovative because it departs markedly from the current inefficient, highly invasive method of physically removing surfactant by whole lung lavage and in- stead uses a novel approach to restore AM function. The proposed research is significant because it is expected to establish the feasibility of a specific therapy for children with hPAP and a new type of therapy (PMT) that may be useful for other diseases, and evaluate multiple safety improvements to reduce the risks of gene therapy. Results will inform a fundamental mechanism by which GM-CSF regulates AM population size, pro- vide an estimate of AM lifespan, and lay the foundation for the development of macrophage-based therapy.