Motixafortide for Hematopoietic Stem and Progenitor Cell Mobilization and Collection in Sickle Cell Disease

Background and Significance: Gene therapy for sickle cell disease (SCD) using ex vivo modified autologous hematopoietic stem cells (HSCs) is advancing rapidly, with two cellular products approved in 2023 by the US Food and Drug Administration (FDA) and several others in ongoing clinical trials. All ex vivo modified autologous HSC-based products require peripheral blood (PB) mobilization and collection of patient HSCs, however several complications inherent to SCD may impair HSC collection. These include a stressed and damaged bone marrow niche, myelosuppression by the most commonly used disease modifying agent hydroxyurea (HU), and inability to mobilize with granulocyte colony stimulating factor (G-CSF). Mobilization of HSCs to the PB using the CXCR4 antagonist plerixafor followed by apheresis collection is the current strategy for harvesting HSCs. However, most patients require at least two mobilization cycles to collect the large numbers of HSCs required to manufacture an adequate cellular product. Each collection cycle, consisting of multi-day apheresis, must be separated by at least 2-4 weeks, which complicates manufacturing, increases cost, delays therapy, and increases the probability of adverse events. Moreover, failure to obtain adequate numbers of HSCs can prohibit gene therapy for some patients. Motixafortide, a novel CXCR4 inhibitor peptide with high affinity CXCR4 receptor occupancy and extended pharmacodynamic effects, was recently FDA approved for mobilizing HSCs in individuals with multiple myeloma. Compared to plerixafor, motixafortide results in higher and more sustained levels of mobilized PB CD34+ cells with minimal adverse effects (Abraham et al. Clin Cancer Res.2017). Similar to plerixafor and in contrast to GCSF, motixafortide causes minimal neutrophil activation that can be dangerous in SCD. Therefore, motixafortide may represent an improved strategy to isolate patient HSCs for gene therapy applications by reducing the required number of mobilization cycles and increasing the proportion of patients for whom adequate numbers of HSCs can be obtained without the additional risk of severe events associated with GCSF. Study Design and Methods: This is a phase 1 multicenter study (NCT06442761) to investigate the safety and tolerability of a single dose (Part A) or two daily doses (Part B) of motixafortide for HSC mobilization followed by apheresis collection in 12 adult participants with SCD. Participants with severe SCD of any genotype who are >/=18 years of age and willing to undergo mobilization and collection will be eligible. Participants must have adequate organ function, negative infectious disease testing, and be able to hold HU for at least 30 days. Participants with a history of recent acute SCD-related complications requiring medical care, use of an alternative investigational agent, history of an allogeneic bone marrow transplant, or inability to receive red blood cell transfusion will be excluded. If a participant is taking HU, it will be held for 30 days prior to mobilization, and blood transfusions will be recommended to limit the risk of sickle-related complications while HU is on hold. Participants will undergo red cell exchange transfusion to reduce the fraction of sickle hemoglobin near 30% within one week before mobilization. Arm A (N=6) will evaluate single dose motixafortide mobilization (1.25mg/kg) followed by a single apheresis collection. Arm B (N=6) will evaluate daily motixafortide administration (1.25mg/kg) for two days with two consecutive apheresis collections. During mobilization and apheresis, the kinetics of peripheral CD34+ cell mobilization will be analyzed by flow cytometry from blood collected at scheduled timepoints. A portion of mobilized mononuclear cells will be cryopreserved as a back-up product for possible future use by the participant. The statistical design is a modified 3+3 design with a safety review of dose-limiting toxicities after enrolling 3 participants at a time. Due to the small sample size, data related to all objectives will be analyzed and reported descriptively. Conclusion: HSC mobilization with motixafortide may represent a safe and effective strategy to improve HSC mobilization and collection in individuals with SCD. Information gained by this study may contribute to the medical care, treatment, and advancement of transformative therapy for individuals with SCD.

背景与意义：使用体外修饰的自体造血干细胞（HSCs）对镰状细胞病（SCD）进行基因治疗进展迅速，2023年美国食品药品监督管理局（FDA）批准了两种细胞产品，还有其他几种正在进行临床试验。所有基于体外修饰的自体HSC的产品都需要动员外周血（PB）并采集患者的HSCs，然而SCD固有的一些并发症可能会影响HSC的采集。这些包括应激和受损的骨髓微环境、最常用的疾病修饰剂羟基脲（HU）引起的骨髓抑制以及无法用粒细胞集落刺激因子（G - CSF）进行动员。使用CXCR4拮抗剂普乐沙福将HSCs动员到外周血，然后进行单采术采集，是目前采集HSCs的策略。然而，大多数患者需要至少两个动员周期才能采集到制造足够细胞产品所需的大量HSCs。每个采集周期包括多天的单采术，必须间隔至少2 - 4周，这使得生产过程复杂化，增加了成本，延误了治疗，并增加了不良事件发生的概率。此外，无法获得足够数量的HSCs可能会使一些患者无法进行基因治疗。 莫替沙福肽是一种新型的CXCR4抑制肽，对CXCR4受体具有高亲和力且药效作用持久，最近被FDA批准用于动员多发性骨髓瘤患者的HSCs。与普乐沙福相比，莫替沙福肽能使动员到外周血的CD34 +细胞数量更多且更持久，不良反应极小（Abraham等人，《临床癌症研究》，2017年）。与普乐沙福类似，且与GCSF不同的是，莫替沙福肽引起的中性粒细胞活化极小，而中性粒细胞活化在SCD中可能是危险的。因此，莫替沙福肽可能是一种改进的策略，通过减少所需的动员周期数量，并增加能够获得足够数量HSCs且无GCSF相关严重事件额外风险的患者比例，从而为基因治疗应用分离患者的HSCs。 研究设计与方法：这是一项1期多中心研究（NCT06442761），旨在研究单剂量（A部分）或每日两剂量（B部分）的莫替沙福肽用于动员HSCs，然后对12名成年SCD患者进行单采术采集的安全性和耐受性。任何基因型的重度SCD患者，年龄≥18岁且愿意接受动员和采集的，将符合条件。患者必须有足够的器官功能，传染病检测呈阴性，并且能够停用HU至少30天。有近期需要医疗护理的急性SCD相关并发症病史、使用替代研究药物、有同种异体骨髓移植病史或无法接受红细胞输注的患者将被排除。如果患者正在服用HU，在动员前需停用30天，并且建议输血以限制HU停用期间镰状相关并发症的风险。患者将在动员前一周内进行红细胞交换输血，以使镰状血红蛋白的比例降低至接近30%。A组（N = 6）将评估单剂量莫替沙福肽动员（1.25mg/kg），然后进行单次单采术采集。B组（N = 6）将评估每日给予莫替沙福肽（1.25mg/kg），连续两天，然后进行两次连续的单采术采集。在动员和单采术期间，将通过流式细胞术分析在预定时间点采集的血液中外周CD34 +细胞动员的动力学。一部分动员的单核细胞将被冷冻保存，作为参与者未来可能使用的备用产品。统计设计是一种改良的3 + 3设计，每次招募3名参与者后对剂量限制性毒性进行安全审查。由于样本量较小，与所有目标相关的数据将进行描述性分析和报告。 结论：使用莫替沙福肽动员HSCs可能是一种安全有效的策略，可改善SCD患者的HSC动员和采集。本研究获得的信息可能有助于SCD患者的医疗护理、治疗以及变革性疗法的进步。