Inducible Regulatory T Cells for the Prevention and Treatment of Acute GVHD

描述（由申请人提供）：急性移植物抗宿主病（aGVHD）是异体造血干细胞移植（HSCT）术后发病和死亡的主要原因。T调节性细胞（Tregs）是CD4+ T细胞的一个子集，它们共同表达高水平的IL-2Ra链（CD25）和转录因子FoxP3。在小鼠胸腺中产生的天然treg （nTreg, CD4+CD25brFoxP3+）的过继转移已经被证明可以预防aGVHD和自身免疫，但需要高比例的nTreg：供体T细胞。外周血源性nTregs的低频率和低增殖潜力阻碍了其临床应用。在外周，非Treg CD4+ t细胞群体可以被诱导获得Treg表型和功能-这些细胞被称为可诱导Treg （iTregs）。我们的研究小组首次证明，在IL-2、雷帕霉素和TGFss存在的情况下，人类iTregs可以可靠地激活，从而在异种GVHD小鼠模型中获得Foxp3稳定表达和有效抑制aGVHD的群体。此外，我们最近开发了一种使用GMP试剂进行细胞纯化、活化和扩增的生产程序。重要的是，我们已经完成了规模研究，并证明我们可以在培养开始后的2周内，从PB黄皮中可重复培养bbx109个iTregs细胞和从全单采PB产品中可重复培养~240x109个细胞。在这样的扩增率下，我们期望实现iTreg：供体T细胞比例达到5:1，显著超过预防aGVHD的目标最小比例1:1，正如临床前小鼠模型所显示的那样。然而，活动性疾病患者可能需要更高比例或多剂量的iTreg。我们的最终目标是生产用于aGVHD预防和治疗的临床级“现成”第三方iTreg产品

DESCRIPTION (provided by applicant): Acute graft-versus-host disease (aGVHD) is a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). T regulatory (Tregs) cells are a subset of CD4+ T cells that co-express high levels of the IL-2Ra chain (CD25) and the transcription factor, FoxP3. Adoptive transfer of natural Tregs (nTregs, CD4+CD25brFoxP3+) that arise in the thymus have already been shown to prevent aGVHD and autoimmunity in mice but high ratios of nTreg:donor T cells are required. Clinical application of nTregs has been hampered by low frequency and low proliferative potential of nTregs derived from peripheral blood (PB). In the periphery, a population of non-Treg CD4+ T-cells can be induced to acquire a Treg phenotype and function - these cells are referred to as inducible Tregs (iTregs). Our group was the first to show that human iTregs could be reliably activated in the presence of IL-2, rapamycin and TGFss, leading to a population with stable Foxp3 expression and potent suppressive of aGVHD in a xenogeneic GVHD murine model. Furthermore, we have recently developed a manufacturing procedure using GMP reagents for cell purification, activation and expansion. Importantly, we have already completed scale-up studies and have demonstrated that we can reproducibly culture >109 iTregs from a PB buffy coat and ~240x109 cells from a full apheresis PB product within 2 weeks of culture initiation. With these expansion rates, we expect to achieve an iTreg:donor T cell ratio up to 5:1, remarkably in excess of the targeted minimum of 1:1 ratio for aGVHD prevention, as shown in preclinical murine models. However, it is possible that higher ratios or multiple doses of iTreg may be required in patients with active disease. With the ultimate goal of manufacturing a clinical grade 'off the shelf' 3rd party iTreg product for aGVHD prophylaxis and treatment, we will embark on a series of 'first-in-human' clinical trials to methodically evaluate the safety and potential efficacy of iTregs. Here, we will establish the safety and kinetics of HLA matched, partially matched, and unmatched iTregs for aGVHD prevention. We will perform a series of phase I trials with an extension phase to determine the MTD, safety profile and potential efficacy of fresh and subsequently cryopreserved iTregs. We will first establish the safety of fresh HLA matched iTregs in recipients of HLA matched sibling donor HSCT, followed by a follow-up study using fresh (and later cryopreserved) HLA mismatched iTregs obtained from a haploidentical relative for use in recipients of HLA-matched, unrelated donor HSCT. The successful completion of these first two clinical trials and the subsequent testing of cryopreserved iTregs, will justify the penultimate trial testing banked 'off-the-shelf' iTregs from an HLA mismatched donor. In parallel to the clinical trials, we will optimize the culture conditions for iTreg expanson required to permit multi-dose infusions and establishment of an "off-the-shelf" product. At the completion of these studies, we will have developed a bank of iTregs for immediate 'off-the-shelf' use for the prevention and treatment of aGVHD.