Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare form of thrombotic microangiopathy (TMA) caused by an autoantibody-mediated deficiency of the von Willebrand factor (vWF) cleaving protease ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin-1 motifs, 13th Member) [1]. Without treatment, the disease is almost always fatal. In the last decades, the combination of therapeutic plasma exchange (TPE), corticosteroids, the chimeric anti-CD20 B-cell depleting monoclonal antibody rituximab and the anti-vWF nanobody caplacizumab, resulted in an improvement of survival rate, now exceeding 90% in the acute phase [2, 3]. However, relapses may occur during follow-up, exposing patients to death and treatment-related complications while increasing the burden of care. To circumvent these issues, a regular monitoring of ADAMTS13 activity during follow up, and the use of preemptive rituximab treatment in patients experiencing a severe ADAMTS13 deficiency (ADAMTS13 relapse) became a standard of care [3-5]. However, up to 15% of patients fail to improve ADAMTS13 activity following rituximab treatment; moreover, patients can develop adverse events, including immediate infusion intolerance or later serum sickness. In this context, alternative therapeutic options are needed, while evidence-based experience or direct comparisons of possible agents are scarce.

Obinutuzumab (Gazyvaro, Roche) is a type 2 humanized anti-CD20 monoclonal antibody, glyco-engineered to potently induce direct death of CD20-positive cells. Obinutuzumab proved to be efficient in various B-cell malignancies even following previous rituximab treatments, as well as in autoimmune diseases, where rituximab was contraindicated due to either resistance or intolerance. In iTTP, case reports and small series of patients suggested an efficacy for obinutuzumab in patients with intolerance or refractoriness to rituximab [6]. Here, we report from a large series of patients more definitive evidence that obinutuzumab is efficient and safe in preventing relapses in iTTP patients experiencing refractoriness or intolerance to rituximab.

Data on patients with a diagnosis of iTTP treated with obinutuzumab in the registry of the French Thrombotic Microangiopathies Reference Center (www.cnr-mat.fr) have been collected according to a predefined computerized dataset. Treatment of iTTP in the acute phase was based on current national and international guidelines [2-5]. Obinutuzumab was used as a compassionate off-label therapy; it was considered in patients with a persistent severe ADAMTS13 deficiency despite the use of rituximab, combined or not with other immunomodulators, or in patients with an ADAMTS13 relapse and intolerance to rituximab. Persistent severe ADAMTS13 deficiency was defined by an ADAMTS13 activity < 20% on at least two consecutive time points, on patients usually assessed for ADAMTS13 activity every month when ADAMTS13 activity is < 20%. All indications of obinutuzumab were extensively discussed through a national monthly advisory board, on which national experts of the French reference center for thrombotic microangiopathies (CNR-MAT) provide recourse advices for the most challenging patients. Obinutuzumab was administered as an intravenous infusion of 1000 mg; the first dose was administered in 2 days: 100 mg on the first day and 900 mg on the second day intravenously (the 1st and 2nd day was counted as one infusion in the description of treatment); subsequent doses were administered as single 1000 mg infusions, typically at Day-8, Day-15, Day-28 and eventually day-56. Premedication before obinutuzumab consisted in paracetamol, antihistamine and corticosteroid. To evaluate the efficacy of obinutuzumab, we determined both the clinical and ADAMTS13 relapse-free survival (RFS) as the time from first obinutuzumab administration to clinical relapse, or to ADAMTS13 relapse (ADAMTS13 activity < 20% in patients otherwise in clinical remission), respectively. Partial or complete ADAMTS13 response was defined by an improvement of ADAMTS13 activity ≥ 20% or ≥ 50%, respectively. ADAMTS13 activity and anti-ADAMTS13 antibodies were assessed before treatment and during follow-up, usually weekly for 1 month after the course of treatment with B-cell depleting agents, then monthly until ADAMTS13 activity normalization, and subsequently every 3 months [5]. The compassionate, off-label use of obinutuzumab including its expected benefits and disadvantages was extensively discussed with patients, and their informed consent was systematically obtained before treatment was initiated.

From January 2020 (date of the first patients with iTTP treated with obinutuzumab in France) until June 2024, 60 iTTP patients were treated with obinutuzumab in France and recruited in the CNR-MAT registry (44 female, 16 male). Baseline characteristics, previous therapeutic lines, details of obinutuzumab administration and outcome after obinutuzumab therapy are reported in Table 1. One pediatric patient (3 years old) and two adolescents (16 and 17 years old) with proven iTTP were included in the analysis. Significant comorbidities were reported in 42 patients (Table S1). Patients received a median of three previous treatments (IQR, 2–5), which included rituximab in all cases (Table S2). Obinutuzumab was administered for refractoriness to rituximab (N = 32), intolerance (N = 25), or both refractoriness and intolerance to rituximab (N = 3). Intolerance to rituximab included serum sickness (25 cases) and allergic reaction to rituximab (3 cases). Obinutuzumab was administered pre-emptively in 49 patients and in the acute phase of the disease in 11.

Patients received a median of 3 (IQR, 1–4) obinutuzumab infusions. Nine patients received obinutuzumab in combination with another immunosuppressive therapy. Following obinutuzumab treatment, 51 (85%) patients improved ADAMTS13 activity ≥ 20%, including 43 patients (72% among all) who normalized ADAMTS13 activity (activity ≥ 50%). The nine others (15%) were unresponsive to obinutuzumab as they maintained a persistently undetectable ADAMTS13 activity (activity < 20%) for a median time of 11 weeks (IQR, 9–30) following obinutuzumab initiation, which included at least 2 consecutive measurements 1 month apart showing an undetectable ADAMTS13 activity. The median time to ADAMTS13 activity ≥ 20% and ≥ 50% was 36 days (IQR, 17–80 days) and 76 days (IQR, 33–234 days), respectively (Table 1). By comparing responsive and unresponsive patients, no significant risk factors for refractoriness were identified among age, sex, ethnicity, number of previous treatment lines, time from diagnosis to obinutuzumab, and number of obinutuzumab infusions. However, patients formerly unresponsive to rituximab improved ADAMTS13 activity post-obinutuzumab less frequently than patients intolerant to rituximab (27/35 [77%] vs. 27/28 [96%], respectively, p < 0.05; OR = 0.13; 95% CI 0.003–1.07); among patients refractory to obinutuzumab, most were also formerly unresponsive to rituximab (N = 8; 89% of patients unresponsive to obinutuzumab) (Table S3, Figure S1). Of note, a patient previously refractory to daratumumab responded to obinutuzumab therapy.

B-cell depletion following obinutuzumab treatment was available in 34 cases; in all, a total B-cell depletion (peripheral CD19⁺ B-cell lymphocytes < 1%) was observed within 2 months following obinutuzumab initiation.

After an initial response to obinutuzumab, 3 patients experienced an ADAMTS13 relapse (N = 2) or a clinical relapse (N = 1) (Table 1). By considering the whole population, median combined RFS was not reached after a median follow up of 11 months (IQR, 4–19 months) (Table 1, Figure S2). Two-year and five-year combined RFS was 86% and 61%, respectively. After excluding three patients who were both refractory and intolerant to previous rituximab treatment, the comparison of patients refractory to rituximab to those intolerant to rituximab found similar combined RFS (p = 0.72, HR = 3.22, 95% CI 0.81–13) (Figure S3). For both groups, median combined RFS was not reached; 1-year and 2-year combined RFS was 96% and 84% in patients intolerant to rituximab, respectively, and 68% at both time points for patients refractory to rituximab (Figure S3).

Two patients died during follow-up, one intracranial hemorrhage during a clinical relapse of iTTP in a pediatric patient and one cardiac arrest due to a history of severe valvular heart disease. None of these events were considered adverse events related to obinutuzumab.

Treatment-related adverse events occurred in 11 patients (Table S4). The most prevalent toxicity was infusion-related reaction, described in 6 patients. No severe treatment-related adverse events were described.

From this large series of patients, we provide more definitive evidence that obinutuzumab allows achieving high response rates in iTTP patients unresponsive or intolerant to rituximab and other immunosuppressants. Even in heavily pre-treated patients, we observed a response rate of 85% on ADAMTS13 activity, with acceptable adverse events.

One of the main reasons of obinutuzumab initiation in our study was serum sickness following rituximab. In this context, obinutuzumab represents an attractive alternative strategy for B-cell depletion for these patients. Although serum sickness following obinutuzumab has been described, it seems rare; in this regard, no serum sickness was documented in our cohort following obinutuzumab administration.

Obinutuzumab was also effective in patients with previous refractoriness to rituximab, with impressive response rates of 77%. The exact mechanism by which obinutuzumab circumvents rituximab refractoriness is not completely understood. In autoimmune diseases studies emphasize the superior B-cell depleting capacity of obinutuzumab as a background for efficiency.

The limitations of our study include the retrospective data collection; although the general diagnostic and treatment guidelines of TTP are well standardized in France, time points for the first ADAMTS13 measurement after initiating a new preemptive therapy remained variable between centers.

The optimal management of iTTP patients unresponsive or intolerant to rituximab is still in debate, while multiple immunosuppressive strategies are available. Cyclosporine A and lymphoablation with cyclophosphamide were reported as valuable options, but their tolerability might limit their use. Data are limited for plasma cell-directed therapies with bortezomib and daratumumab, which use might probably be devoted to patients who are unresponsive to intensive B-cell depletion. Consequently, and based on our results, obinutuzumab could represent the first option for patients with iTTP who experience intolerance or refractoriness to rituximab. Efforts from international, prospective trials should more definitely demonstrate the role of obinutuzumab as a valuable salvage immunosuppressive therapy in iTTP.

免疫介导的血栓性血小板减少性紫癜（iTTP）是一种罕见的血栓性微血管病（TMA），由自身抗体介导的血管性血友病因子（vWF）裂解蛋白酶ADAMTS13缺乏症（一种具有血小板反应蛋白-1基序的整合素和金属蛋白酶，第13成员）引起[1]。如果不进行治疗，这种疾病几乎总是致命的。在过去的几十年里，治疗性血浆置换 （TPE）、皮质类固醇、嵌合抗 CD20 B 细胞耗竭单克隆抗体利妥昔单抗和抗 vWF 纳米抗体卡普拉珠单抗的组合导致存活率提高，现在急性期超过 90% [2， 3]。然而，在随访期间可能会复发，使患者面临死亡和治疗相关并发症，同时增加护理负担。为了规避这些问题，在随访期间定期监测ADAMTS13活动度，以及对重度ADAMTS13虚（ADAMTS13复发）患者使用抢先利妥昔单抗治疗成为标准治疗[3-5]。然而，高达 15% 的患者在利妥昔单抗治疗后未能改善ADAMTS13活性;此外，患者可能会出现不良事件，包括立即输注不耐受或以后的血清病。在这种情况下，需要替代治疗选择，而缺乏循证经验或对可能药物的直接比较。

Obinutuzumab （Gazyvaro， Roche） 是一种 2 型人源化抗 CD20 单克隆抗体，经过糖工程改造可有效诱导 CD20 阳性细胞直接死亡。即使在先前的利妥昔单抗治疗后，Obinutuzumab 也被证明对各种 B 细胞恶性肿瘤有效，以及由于耐药或不耐受而禁忌使用利妥昔单抗的自身免疫性疾病。在 iTTP 中，病例报告和小型患者系列研究表明，obinutuzumab 对利妥昔单抗不耐受或难治性患者有效 [6]。在这里，我们从大量患者那里报告了更明确的证据，表明 obinutuzumab 在预防对利妥昔单抗难治或不耐受的 iTTP 患者复发方面是有效和安全的。

法国血栓形成微血管病参考中心 （www.cnr-mat.fr） 登记处诊断为 iTTP 接受 obinutuzumab 治疗的患者数据已根据预定义的计算机化数据集收集。急性期 iTTP 的治疗基于当前的国家和国际指南 [2-5]。Obinutuzumab 被用作一种富有同情心的标签外治疗;对于尽管使用利妥昔单抗，与其他免疫调节剂联合或不联合使用，但仍持续存在严重ADAMTS13缺乏症的患者，或ADAMTS13复发和对利妥昔单抗不耐受的患者，可以考虑使用利妥昔单抗。持续严重ADAMTS13缺乏症定义为至少连续两个时间点的ADAMTS13活动 < 20%，当患者活动为 < 20% 时，通常每月评估一次ADAMTS13活动ADAMTS13。obinutuzumab 的所有适应症都通过国家月度咨询委员会进行了广泛讨论，该委员会法国血栓性微血管病参考中心 （CNR-MAT） 的国家专家为最具挑战性的患者提供补救建议。Obinutuzumab 以 1000 mg 的静脉输注给药;第一剂在 2 天内给药：第一天 100 毫克，第二天 900 毫克静脉注射（第 1 天和第 2 天在治疗描述中算作一次输注）;随后的剂量作为单次 1000 mg 输注给药，通常在第 8 天、第 15 天、第 28 天和最终的第 56 天给药。obinutuzumab 前的术前用药包括对乙酰氨基酚、抗组胺药和皮质类固醇。 为了评价 obinutuzumab 的疗效，我们确定了临床和ADAMTS13无复发生存期 （RFS） 分别是从第一次 obinutuzumab 给药到临床复发或ADAMTS13复发的时间 （ADAMTS13活性 < 20% 在临床缓解的患者中）。部分或完全ADAMTS13反应定义为ADAMTS13活性分别提高 ≥ 20% 或 ≥ 50%。治疗前和随访期间评估ADAMTS13活性和抗 ADAMTS13 抗体，通常在 B 细胞耗竭剂治疗后 1 个月内每周一次，然后每月一次，直到 ADAMTS13 活性恢复正常，随后每 3 个月一次 [5]。与患者广泛讨论了 obinutuzumab 的富有同情心的超适应症使用，包括其预期的益处和缺点，并在治疗开始前系统地获得了他们的知情同意。

从 2020 年 1 月（法国首例接受 obinutuzumab 治疗的 iTTP 患者之日）到 2024 年 6 月，60 名 iTTP 患者在法国接受了 obinutuzumab 治疗，并在 CNR-MAT 登记处招募（44 名女性，16 名男性）。基线特征、既往治疗线、obinutuzumab 给药的详细信息和 obinutuzumab 治疗后的结果见表 1。分析包括一名确诊 iTTP 的儿科患者 （3 岁） 和两名青少年 （16 岁和 17 岁）。42 例患者报告了严重的合并症 （表 S1）。患者接受 3 种既往治疗的中位数 （IQR， 2-5），其中所有病例包括利妥昔单抗（表 S2）。Obinutuzumab 用于对利妥昔单抗难治 （N = 32） 、不耐受 （N = 25） 或对利妥昔单抗难治性和不耐受 （N = 3）。对利妥昔单抗不耐受包括血清病 （25 例） 和对利妥昔单抗的过敏反应 （3 例）。49 例患者先发制人地给予 Obinutuzumab，11 例患者处于疾病急性期。

患者接受 3 次 （IQR， 1-4） obinutuzumab 输注的中位值。9 例患者接受了 obinutuzumab 联合另一种免疫抑制治疗。在 obinutuzumab 治疗后，51 例 （85%） 患者的ADAMTS13活动改善≥ 20%，包括 43 例患者 （其中 72%） ADAMTS13活动正常 （活动≥ 50%）。其他 9 人 （15%） 对 obinutuzumab 无反应，因为他们在 obinutuzumab 开始后 11 周的中位时间 （IQR， 9-30） 保持持续检测不到的 ADAMTS13 活性（活性 < 20%），其中包括至少 2 次间隔 1 个月的连续测量显示检测不到的 ADAMTS13 活性。ADAMTS13活动≥ 20% 和 ≥ 50% 的中位时间分别为 36 天（IQR，17-80 天）和 76 天（IQR，33-234 天）（表 1）。通过比较反应和无反应的患者，在年龄、性别、种族、既往治疗线数量、从诊断到 obinutuzumab 的时间以及 obinutuzumab 输注次数中未发现难治性的显着危险因素。然而，以前对利妥昔单抗无反应的患者在 obinutuzumab 后改善ADAMTS13活性的频率低于对利妥昔单抗不耐受的患者（分别为 27/35 [77%] 对 27/28 [96%]，p < 0.05;OR = 0.13;95% CI 0.003–1.07）;在 obinutuzumab 难治的患者中，大多数以前也对利妥昔单抗无反应 （N = 8;89% 的患者对 obinutuzumab 无反应） （表 S3，图 S1）。值得注意的是，一名先前对 daratumumab 无效的患者对 obinutuzumab 治疗有反应。

34 例 obinutuzumab 治疗后 B 细胞耗竭;总而言之，在 obinutuzumab 开始后 2 个月内观察到总 B 细胞耗竭 （外周 CD19⁺ B 细胞淋巴细胞 < 1%）。

在对 obinutuzumab 产生初始反应后，3 例患者出现ADAMTS13复发 （N = 2） 或临床复发 （N = 1） （表 1）。通过考虑整个人群，中位随访 11 个月后未达到中位联合 RFS （IQR，4-19 个月）（表 1，图 S2）。两年和五年综合 RFS 分别为 86% 和 61%。在排除 3 名对既往利妥昔单抗治疗难治且不耐受的患者后，对利妥昔单抗难治患者与利妥昔单抗不耐受的患者进行比较，发现相似的联合 RFS （p = 0.72，HR = 3.22,95% CI 0.81-13）（图 S3）。对于两组，均未达到中位合并 RFS;对利妥昔单抗不耐受的患者，1 年和 2 年联合 RFS 分别为 96% 和 84%，对于利妥昔单抗难治性患者，在两个时间点分别为 68%（图 S3）。

2 例患者在随访期间死亡，1 例儿科患者 iTTP 临床复发期间颅内出血，1 例因严重瓣膜性心脏病病史而心脏骤停。这些事件均不被视为与 obinutuzumab 相关的不良事件。

11 例患者发生治疗相关不良事件 （表 S4）。最普遍的毒性是输液相关反应，在 6 例患者中描述。未描述严重的治疗相关不良事件。

从这一大系列患者中，我们提供了更明确的证据表明，obinutuzumab 可以在对利妥昔单抗和其他免疫抑制剂无反应或不耐受的 iTTP 患者中实现高反应率。即使在既往接受过大量治疗的患者中，我们观察到ADAMTS13活性的反应率为 85%，不良事件可接受。

在我们的研究中，开始 obinutuzumab 的主要原因之一是利妥昔单抗后的血清病。在这种情况下，obinutuzumab 代表了这些患者 B 细胞耗竭的一种有吸引力的替代策略。尽管已经描述了 obinutuzumab 后的血清病，但似乎很少见;在这方面，在 obinutuzumab 给药后，我们的队列中没有血清病的记录。

Obinutuzumab 对既往利妥昔单抗难治的患者也有效，反应率高达 77%。obinutuzumab 规避利妥昔单抗难治性的确切机制尚不完全清楚。在自身免疫性疾病中，研究强调 obinutuzumab 卓越的 B 细胞耗竭能力作为效率的背景。

我们研究的局限性包括回顾性数据收集;尽管 TTP 的一般诊断和治疗指南在法国已经很好地标准化，但在开始新的抢先治疗后首次ADAMTS13测量的时间点在中心之间仍然不同。

对利妥昔单抗无反应或不耐受的 iTTP 患者的最佳管理仍在争论中，同时有多种免疫抑制策略可供选择。据报道，环孢素 A 和环磷酰胺淋巴消融术是有价值的选择，但它们的耐受性可能会限制它们的使用。硼替佐米和 daratumumab 的浆细胞定向治疗的数据有限，其使用可能专门用于对强化 B 细胞耗竭无反应的患者。因此，根据我们的结果，obinutuzumab 可能代表对利妥昔单抗不耐受或难治的 iTTP 患者的首选。国际前瞻性试验的努力应该更明确地证明 obinutuzumab 作为 iTTP 中有价值的挽救性免疫抑制疗法的作用。