Astatine-211 Conditioning for Nonmyeloablative Hematopoietic Stem Cell Allografts

描述(申请人提供)：异基因造血细胞移植(HCT)是治疗恶性和非恶性血液病患者的一种重要方法。然而，由于与所使用的条件调节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。虽然这些方法在主要组织相容性抗原复合体(MHC)相合的移植中相当成功，在200cGy体照射(TBI)就足以植入的情况下，在更复杂的MHC半相合环境中，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相合和MHC半相合的HCT中的TBI，这将为没有MHC相合供者的患者提供一种治疗选择。具体地说，研究工作将确定，当α发射放射性核素211他汀类(211 At)与全造血抗CD45单抗(MAb)结合时，是否可以取代TBI，用于异基因HCT的条件受者。我们将利用我们建立的随机繁殖的狗的临床前模型，该模型已经预测了人类的同种异体血细胞移植。在具体目标1中，我们将评估和优化一种用~(211)At标记单抗的新方法。目前使用的~(211)At标记单抗最有效的方法包括两步过程，即将苯甲酸锡酯标记，然后与单抗结合。所要研究的方法将包括将含有反式反应性硼酸盐(2-)部分的分子偶联到MAb上，然后进行反式反应。新标记方法的潜在优势包括处理更少的放射性物质，以及更高和更一致的标记产率。在特定目的2中，将~(211)At标记的抗CD45单抗与另一种a-放射性核素~(213)铋(~(213)Bi)标记的单抗在CD45表达细胞和小鼠模型上进行疗效和毒性比较。比较研究将允许使用在先前对~(213)Bi标记的单抗进行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，将在狗身上进行211At标记的单抗的评估，以找到狗白细胞抗原(DLA)相合和DLA单倍体相合的HCT的有效剂量。最初，将进行剂量发现研究，以确定对骨髓抑制有效的最小剂量。随后，将确定获得稳定植入DLA相合窝胎的HCT中所需的211At标记的抗CD45单抗的数量。最后，也是最重要的一项研究，将涉及确定在涉及DLA-单倍体相合的小鼠的HCT中获得稳定植入所需的211At标记单抗的数量。

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.