Astatine-211 Conditioning for Nonmyeloablative Hematopoietic Stem Cell Allografts

描述（由申请人提供）：同种异体造血细胞移植（HCT）是恶性和非恶性血液疾病患者的重要治疗方式。然而，由于所使用的调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，已经开发了非清髓方案。虽然这些方法在主要组织相容性抗原复合体（MHC）相同的移植中相当成功，其中200 cGy的全身照射（TBI）足以植入，但在更复杂的MHC-单倍体相同的情况下，需要更高的毒性TBI剂量来确保植入。我们建议研究一种系统靶向的放射形式，以取代mhc -相同和mhc -单倍体相同的HCT中的TBI，这将为没有mhc匹配供体的患者提供一种治疗选择。具体来说，研究工作将确定α -发射放射性核素211砹（2111at），当与一种全造血抗CD45单克隆抗体（MAb）结合时，是否可以取代TBI，使受体接受同种异体HCT。我们将利用我们完善的临床前模型，随机饲养的狗已经预测了人类异体HCT。在具体目标1中，我们将评估和优化一种用211At标记单克隆抗体的新方法。目前使用2111at标记单克隆抗体最有效的方法是两步过程，先将苯甲酸丁酯沉淀，然后与单克隆抗体偶联。所研究的方法将涉及将含有砹反应性硼酸盐（2-）片段的分子偶联到单抗上，然后进行砹化。新标记方法的潜在优点包括较少处理放射性物质，以及更高和更一致的标记收率。在特定目的2中，将比较211At标记的抗cd45单克隆抗体与另一种发射a的放射性核素213Bismuth （213Bi）标记的单克隆抗体对cd45表达细胞和小鼠模型的疗效和毒性。比较研究将允许使用在213bi标记的单克隆抗体先前研究中获得的信息，以帮助确定211At研究的初始条件和数量。在具体目标3中，将在狗身上对2111at标记的单克隆抗体进行评估，以找到狗白细胞抗原（DLA）相同和DLA单倍体相同HCT的有效剂量。最初，将进行剂量研究，以确定对骨髓抑制有效的最小剂量。随后，将确定2111at标记的抗cd45单抗的数量，以在涉及dla相同的幼崽的HCT中获得稳定的植入。最后，也是最重要的，研究将包括确定2111at标记的单抗的数量，以获得涉及DLA-单倍相同窝代的HCT的稳定植入。

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.