Astatine-211 Conditioning for Nonmyeloablative Hematopoietic Stem Cell Allografts

描述（由申请人提供）：异基因造血细胞移植（HCT）是恶性和非恶性血液系统疾病患者的重要治疗方式。然而，由于与所用预处理方案的毒性相关的并发症，这种治疗的应用仅限于相对年轻的患者。为了减少毒性，已经开发了非清髓性方案。虽然这些在主要组织相容性抗原复合物（MHC）相同的移植中已经相当成功，其中200 cGy的全身照射（TBI）足以用于植入，但在更复杂的MHC-单倍体相同的环境中，需要高得多的毒性TBI剂量以确保植入。我们建议研究一种全身靶向的放射形式，以取代TBI在MHC-相同和MHC-半相合的HCT，这将提供一种治疗方案，为患者没有MHC匹配的捐助者。具体而言，研究工作将确定当与泛造血抗CD 45单克隆抗体（MAb）缀合时，α发射放射性核素211 Astatine（211 At）是否可以取代TBI以调节接受者的同种异体HCT。我们将利用我们已建立的随机繁殖犬的临床前模型，该模型可预测人类的同种异体HCT。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。目前使用的用211 At标记单克隆抗体的最有效方法涉及两步过程，其中甲锡烷基苯甲酸酯被astatinated，然后与单克隆抗体缀合。待研究的方法将涉及将含有可与astatin反应的硼酸盐（2-）部分的分子与MAb偶联，然后进行astatin化。新标记方法的潜在优势包括更少的放射性材料处理，以及更高和更一致的标记产率。在具体目标2中，将在表达CD 45的细胞上和在小鼠模型中比较211 At标记的抗CD 45 MAb与用另一种α-发射放射性核素213 Bi（213 Bi）标记的MAb的功效和毒性。比较研究将允许使用先前使用213 Bi标记的单克隆抗体的研究中获得的信息，以帮助确定211 At研究的初始条件和数量。在具体目标3中，将在犬中进行211 At标记的MAb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。之后，将确定在涉及DLA相同同窝仔的HCT中获得稳定植入所需的211 At标记抗CD 45 MAb的量。最后，也是最重要的，研究将涉及确定在涉及DLA-半相合同窝出生的HCT中获得稳定植入所需的211 At标记的MAb的量。

DESCRIPTION (provided by applicant): 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 alpha-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 random bred 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 involving DLA- haploidentical littermates.