Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
Rocket Pharmaceuticals Ltd, New York City, NY, USA.
J Gene Med. 2018 Oct;20(10-11):e3050. doi: 10.1002/jgm.3050. Epub 2018 Oct 1.
Gene therapy approaches for the treatment of Fanconi anemia (FA) hold promise for patients without a suitably matched donor for an allogeneic bone marrow transplant. However, significant limitations include the collection of sufficient stem cell numbers from patients, the fragility of these cells during ex vivo manipulation, and clinically meaningful engraftment following transplantation. With these challenges in mind, we were interested in determining (i) whether gene-corrected cells at progressively lower numbers can successfully engraft in FA; (ii) whether low-dose conditioning facilitates this engraftment; and (iii) whether these cells can be selected for post-transplant.
Utilizing a well characterized mouse model of FA, we infused donor bone marrow from healthy heterozygote littermates that are unaffected carriers of the FANCA mutation to mimic a gene-corrected product, after administering low-dose conditioning. Once baseline engraftment was observed, we administered a second, very-low selective dose to determine whether gene-corrected cells could be selected for in vivo.
We demonstrate that upfront low-dose conditioning greatly increases successful engraftment of hematopoietic corrected cells in a pre-clinical animal model of FA. Additionally, without conditioning, cells can still engraft and demonstrate a selective advantage in vivo over time following transplantation, and these corrected cells can be directly selected for in vivo after engraftment.
Minimal conditioning prior to bone marrow transplant in Fanconi anemia promotes the multi-lineage engraftment of 10-fold fewer cells compared to nonconditioned controls. These data provide important insights into the potential of minimally toxic conditioning protocols for FA gene therapy applications.
对于没有合适匹配供体进行异基因骨髓移植的范可尼贫血（FA）患者，基因治疗方法具有很大的应用前景。然而，该方法存在一些局限性，包括从患者中采集足够数量的干细胞、这些细胞在体外操作过程中的脆弱性以及移植后具有临床意义的植入。考虑到这些挑战，我们感兴趣的是确定（i）在数量逐渐减少的情况下，基因修正细胞是否可以成功植入 FA；（ii）低剂量预处理是否有利于这种植入；以及（iii）这些细胞是否可以在移植后进行选择。
我们利用经过充分表征的 FA 小鼠模型，输注来自健康杂合子同窝仔鼠的供体骨髓，这些仔鼠是 FANCA 突变的无影响携带者，以模拟基因修正产物，在给予低剂量预处理后。一旦观察到基线植入，我们给予第二次非常低的选择性剂量，以确定基因修正细胞是否可以在体内进行选择。
我们证明，在 FA 的临床前动物模型中， upfront 低剂量预处理极大地增加了造血校正细胞的成功植入。此外，即使没有预处理，细胞仍然可以植入，并且在移植后随着时间的推移在体内具有选择性优势，并且这些修正细胞可以在植入后直接在体内进行选择。
与非预处理对照相比，在骨髓移植前进行最小剂量预处理可促进多达 10 倍数量的细胞多谱系植入。这些数据为 FA 基因治疗应用中最小毒预处理方案的潜力提供了重要的见解。
