Astatine-211 Conditioning for Nonmyeloablative Hematopoietic Stem Cell Allografts

异基因造血细胞移植（HCT）是一种重要的治疗方式， 恶性和非恶性血液病。然而，这种治疗方法的应用 由于与预处理方案毒性相关的并发症， 采用为了减少毒性，已经开发了非清髓性方案。虽然这些已经相当 在主要组织相容性抗原复合体（MHC）相同的移植中成功，其中200 cGy的总剂量 在更复杂的MHC-半相合的情况下，全身照射（TBI）对于植入是足够的， 需要更高的毒性TBI剂量以确保植入。我们建议系统地研究 靶向形式的辐射，以替代MHC-相同和MHC-半倍体相同HCT中的TBI， 为没有MHC匹配供体的患者提供治疗选择。具体而言，研究工作将 确定当与泛造血抗-CD 44抗体缀合时，α-发射放射性核素211 Astatine（211 At） CD 45单克隆抗体（MAb）可替代TBI为受者提供同种异体HCT的条件。我们将利用 我们建立的随机繁殖犬的临床前模型， 人类 在具体目标1中，我们将评估和优化用211 At标记单克隆抗体的新方法。最 目前使用的用211 At标记单克隆抗体的有效方法包括两步过程， 将甲锡烷基苯甲酸酯进行酯化，然后与单克隆抗体偶联。 涉及将含有与astatin反应的硼酸盐（2-）部分的分子缀合至MAb，然后 震惊新标记方法的潜在优点包括减少放射性物质的处理， 以及更高和更一致的标记产率。在具体目标2中，研究了211 At-211的功效和毒性。 将标记的抗CD 45单克隆抗体与用另一种α-发射放射性核素标记的单克隆抗体进行比较， 213铋（213 Bi）对表达CD 45的细胞和小鼠模型的作用。比较研究将允许使用 在先前使用213 Bi标记的MAb的研究中获得的信息，以帮助确定初始条件， 211 At研究的数量。在具体目标3中，将在犬中进行211 At标记的MAb的评价 以找到犬白细胞抗原（DLA）-相同和DLA-半倍体-相同HCT的有效剂量。最初， 将进行剂量探索研究，以确定对骨髓抑制有效的最小剂量。 随后，测定在HCT中获得稳定植入所需的211 At标记的抗CD 45单抗的量 将确定涉及DLA相同的同窝仔。最后，也是最重要的，研究将涉及 确定在涉及DLA的HCT中获得稳定植入所需的211 At标记的MAb的量， 同窝单倍型

Allogeneic hematopoietic cell transplantation (HCT) is an important treatment modality for patients with both malignant and nonmalignant hematologic disorders. However, the application of this treatment has been limited to relatively young patients by complications related to the toxicity of the conditioning regimens used. To decrease toxicities, nonmyeloablative regimens have been developed. While these have been quite successful in major histocompatibility antigen complex (MHC)-identical transplants, where 200 cGy total body irradiation (TBI)is adequate for engraftment, in the more complex MHC-haploidentical setting much higher and toxic TBI doses are required to ensure engraftment. We propose to investigate a systemically targeted form of radiation to replace TBI in both MHC-identical and MHC-haploidentical HCT which would provide a treatment option for patients without MHC-matched donors. Specifically, the research efforts will determine if the a-emitting radionuclide 211 Astatine (211At), when conjugated to a panhematopoietic anti- CD45 monoclonal antibody (MAb), can replace TBI to condition recipients for allogeneic HCT. We will utilize our well-established preclinical model of randombred dogs which has been predictive of allogeneic HCT in humans. In specific aim 1, we will evaluate and optimize a new method for labeling MAbs with 211At. The most effective method for labeling MAbs with 211At used currently involves a two-step process where a stannylbenzoate ester is astatinated, then conjugated with the MAb.The method to be investigated will involve conjugation of a molecule containing an astatine-reactive borate(2-) moiety to the MAb, followed by astatination. Potential advantages of the new labeling method include less handling of radioactive materials, as well as higher and more consistent labeling yields. In specific aim 2, the efficacy and toxicity of 211At- labeled anti-CD45 MAbs will be compared with MAbs labeled with another a-emitting radionuclide, 213Bismuth (213Bi) on CD45-expressing cells and in a mouse model. The comparative studies will allow use of information obtained in prior studies with 213Bi-labeled MAbs to help determine initial conditions and quantities for the 211At studies. In specific aim 3, evaluations of 211At-labeled MAbs will be conducted in dogs to find effective doses for both dog leukocyte antigen (DLA)-identical and DLA-haploidentical HCT.Initially, dose-finding studies will be conducted to determine the minimal dose that is effective for myelosuppression. Following that, quantity of 211At-labeled anti-CD45 MAb required to obtain stable engraftment in HCT involving DLA-identical littermates will be determined. The final, and most important, studies will involve determining the quantity of 211At-labeled MAb required to obtain stable engraftment in HCT involvingDLA- haploidentical littermates.