Mcl-1 inhibition for induction of hematopoietic chimerism without nonselective myeloablative treatments in nonhuman primates

项目摘要/摘要 造血干细胞移植(HSCT)有可能应用于各种医疗环境 超越当前的护理标准(SOC)，如自身免疫性疾病的治疗、基因修饰或诱导 移植耐受性。然而，其更广泛的临床应用目前受到清髓性和 成功植入HSC所需的遗传毒性调节。这种条件反射通常包括非 选择性清髓治疗，如全身照射(TBI)、环磷酰胺或氟达拉滨 与严重的全身副作用有关，包括全血细胞减少、感染、不孕不育，以及 很少见，死亡。 为了开发一种更安全的调节方案，而不会产生这种清髓和遗传毒性后果，一种 选择性地耗尽宿主造血干细胞(HSCs)并打开物理空间的治疗方式 在骨髓(BM)中，需要确定利基。基于对小鼠的研究，我们假设选择性 抑制抗凋亡B细胞淋巴瘤2(Bcl2)可有效诱导HSCs凋亡，从而促进 不需要非选择性清髓治疗的造血干细胞移植。事实上，一种选择性的Bcl-2抑制剂， VENTOTOCLAX通过耗尽非小鼠骨髓细胞壁龛中的HSCs而显著促进造血嵌合体。 人类灵长类(NHP)。虽然这是在没有严重的全血细胞减少的情况下实现的，但仍然需要一些脑损伤。 诱导嵌合体的发生是因为单用万乃克莱限制了HSC的耗竭。自Mcl-1以来，另一种抗细胞凋亡药物 蛋白质，最近被报道对HSCs的生存更关键，我们进一步假设抑制 Mcl-1单独或与Bcl2联合使用将更有效地耗尽宿主HSCs，从而产生足够的 在骨髓壁龛的空间，并允许最佳的同种异体造血干细胞植入而无需任何清髓治疗。这个 初步研究的结果是令人鼓舞的，其中成功地诱导了造血嵌合体 通过联合小剂量Mcl-1抑制剂和万乃克拉克斯实现无脑损伤。R21的主要目标是 项目是测试Mcl-1抑制或与Bcl2联合抑制是否可以持续和安全地诱导 MHC不相合NHP HSCT中无TBI的造血嵌合体。由这种方法引起的嵌合体将 然后进行诱导同种异体肾移植耐受试验。由于只有有限的信息可在 不同的抗凋亡蛋白在灵长类动物中的作用，我们还将描述内在的凋亡途径 在这项研究中，HSCs在NHP中的数量。

PROJECT SUMMARY / ABSTRACT Hematopoietic stem cell transplantation (HSCT) is potentially applicable to various medical settings beyond current standard of care (SOC), such as therapy for autoimmune disease, gene modification or induction of transplant tolerance. However, its wider clinical application is currently hampered by the myeloablative and genotoxic conditioning required for successful HSC engraftment. Such conditioning generally includes non- selective myeloablative treatments, such as total body irradiation (TBI), cyclophosphamide, or fludarabine that are associated with serious systemic side-effects including pancytopenia, infections, infertility, and, not infrequently, death. To develop a safer conditioning regimen without such myeloablative and genotoxic consequences, a therapeutic modality that selectively depletes host hematopoietic stem cells (HSCs) and opens a physical space in bone marrow (BM) niches needs to be identified. Based on murine studies, we hypothesized that selective inhibition of antiapoptotic B cell lymphoma 2 (Bcl-2) may effectively induce apoptosis of HSCs, thereby promoting HSC engraftment without need for non-selective myeloablative treatments. Indeed, a selective Bcl-2 inhibitor, Venetoclax, appeared significantly promotes hematopoietic chimerism by depleting HSCs in BM niches in non- human primates (NHPs). Although this was achieved without severe pancytopenia, some TBI was still required to induce chimerism as depletion of HSCs was limited with Venetoclax alone. Since Mcl-1, another anti-apoptotic protein, has recently been reported to be more critical for survival of HSCs, we further hypothesize that inhibition of Mcl-1 alone or in combination with Bcl-2 will more effectively deplete host HSCs, thereby creating sufficient space in BM niches and allowing optimal allogeneic HSC engraftment without any myeloablative treatment. The results of preliminary study have been encouraging, where successful induction of hematopoietic chimerism was achieved without TBI by combining low dose Mcl-1 inhibitor and Venetoclax. The main objective of this R21 project is to test whether Mcl-1 inhibition alone or with Bcl-2 co-inhibition can consistently and safely induce hematopoietic chimerism without TBI in MHC mismatched NHP HSCT. Chimerism induced by this approach will then be tested for induction of renal allograft tolerance. Since there is only limited information available on the role of different anti-apoptotic Bcl-2 proteins in primates, we will also characterize the intrinsic apoptotic pathways of HSCs in NHPs in this study.