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31% confirmed ORR (8 responses in 26 evaluable patients) across B7-H4 high tumors at intermediate doses

在中等剂量下，B7-H4高表达肿瘤的确认客观缓解率（ORR）为31%（26名可评估患者中有8例响应）。

44% confirmed ORR (7 responses in 16 evaluable patients) in the subset of patients with ≤4 prior lines of therapy

在接受≤4线先前治疗的患者子集中，44%确认的客观缓解率（16名可评估患者中有7例响应）。

CAMBRIDGE, Mass., June 02, 2025 (GLOBE NEWSWIRE) -- Mersana Therapeutics, Inc. (NASDAQ: MRSN), a clinical-stage biopharmaceutical company focused on the development of antibody-drug conjugates (ADCs) targeting cancers in areas of high unmet medical need, today announced additional interim Phase 1 clinical data for emiltatug ledadotin (Emi-Le; XMT-1660), the company’s B7-H4-directed Dolasynthen ADC.

剑桥，马萨诸塞州，2025年6月2日（环球新闻社）——Mersana Therapeutics, Inc.（纳斯达克股票代码：MRSN），一家专注于开发针对高未满足医疗需求领域癌症的抗体药物偶联物（ADC）的临床阶段生物制药公司，今天宣布了其B7-H4导向的Dolasynthen ADC药物emiltatug ledadotin（Emi-Le；XMT-1660）的更多一期临床中期数据。

These data are being presented in an oral session today at the American Society of Clinical Oncology (ASCO) 2025 Annual Meeting in Chicago, Illinois..

这些数据正在伊利诺伊州芝加哥举行的美国临床肿瘤学会 (ASCO) 2025 年年会上进行口头报告。

The presentation will focus on Emi-Le’s Phase 1 dose escalation and backfill cohorts as of a March 8, 2025 data cut-off in patients with triple-negative breast cancer (TNBC); hormone-receptor-positive, human epidermal growth factor receptor 2-negative breast cancer; ovarian cancer; endometrial cancer and adenoid cystic carcinoma type 1 (ACC-1)..

报告将聚焦于截至2025年3月8日数据截止时，Emi-Le的1期剂量递增和回填队列在三阴性乳腺癌（TNBC）、激素受体阳性且人表皮生长因子受体2阴性乳腺癌、卵巢癌、子宫内膜癌以及1型腺样囊性癌（ACC-1）患者中的表现。

“We are excited to share additional interim data in an oral presentation at ASCO,” said Martin Huber, M.D., President and Chief Executive Officer of Mersana Therapeutics. “The results from our dose escalation and backfill cohorts led us to focus our initial expansion work on patients with TNBC who have previously been treated with a topoisomerase-1 inhibitor ADC, a population with high unmet need that we believe Emi-Le may be uniquely suited to address within the B7-H4 ADC field.

“我们很高兴在ASCO会议上以口头报告的形式分享更多的中期数据，”Mersana Therapeutics公司总裁兼首席执行官马丁·胡伯医学博士表示。“我们的剂量递增和回填队列的结果使我们将初始扩展工作重点放在曾接受过拓扑异构酶-1抑制剂ADC治疗的三阴性乳腺癌（TNBC）患者身上。这一群体存在高度未满足的需求，我们认为Emi-Le可能在B7-H4 ADC领域中具有独特的优势来应对这一挑战。”

We also continue to be encouraged by the activity observed in other B7-H4-expressing tumor types, demonstrating Emi-Le’s broader development potential. On behalf of the Mersana team, we would like to express our gratitude to the patients and investigators who have participated in this clinical trial.”.

我们还继续受到其他表达B7-H4的肿瘤类型中观察到的活性的鼓舞，这显示了Emi-Le更广泛的发展潜力。代表Mersana团队，我们要对参与这项临床试验的患者和研究人员表示感谢。

Safety and tolerability as of the March 8, 2025 data cut-off were consistent with initial data previously reported in January 2025, and no new safety signals were observed. Additionally, the following clinical activity data are being presented from evaluable patients (those with measurable disease at baseline and at least one post-baseline scan):.

截至2025年3月8日的数据截止，安全性和耐受性与之前在2025年1月报告的初始数据一致，且未观察到新的安全性信号。此外，以下临床活性数据来自可评估患者（基线时有可测量疾病且至少进行过一次基线后扫描的患者）：。

31% confirmed objective response rate (ORR) (8/26) across all enrolled tumor types with B7-H4 high tumor expression (defined as a tumor proportion score of 70% or higher) receiving intermediate Emi-Le doses (38.1 milligrams per meter squared (mg/m

31% 的患者确认客观缓解率 (ORR) (8/26)，所有入组的肿瘤类型中 B7-H4 高表达（定义为肿瘤比例评分 70% 或更高）的患者接受中等 Emi-Le 剂量（38.1 毫克每平方米 (mg/m²)）。

2

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) to 67.4 mg/m

）至67.4毫克/米

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2

per cycle).

每周期）。

44% confirmed ORR (7/16) in the subset of patients with ≤4 prior lines of therapy.

44%的患者（7/16）在≤4线先前治疗的子集中确认了ORR。

56% ORR (5/9, including one unconfirmed response as of the March 8, 2025 data cut-off that was subsequently confirmed) in ACC-1 regardless of dose and B7-H4 expression. Among all ACC-1 patients who were enrolled in the Phase 1 clinical trial, the median progression free survival (PFS) had not yet been reached as of the March 8, 2025 data cut-off.

无论剂量和B7-H4表达如何，在ACC-1中均观察到56%的客观缓解率（ORR）（9例中有5例，包括截至2025年3月8日数据截止时一个随后得到确认的未确认缓解）。在所有参与1期临床试验的ACC-1患者中，截至2025年3月8日数据截止时，尚未达到中位无进展生存期（PFS）。

ACC-1 is a rare and aggressive cancer that most frequently originates in the salivary glands. With no approved therapies, median PFS and median overall survival for patients with ACC-1 are reported to be 2-3 months and 2-3 years, respectively..

ACC-1是一种罕见且侵袭性强的癌症，最常起源于唾液腺。由于没有获批的治疗方法，ACC-1患者的中位无进展生存期和中位总生存期分别据报道为2-3个月和2-3年。

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“The clinical activity observed for emiltatug ledadotin across all enrolled tumor types is encouraging, and its safety and tolerability profile appears differentiated from many other ADCs,” said Antonio Giordano, MD, Ph.D., Assistant Professor of Medicine, Harvard Medical School, Dana-Farber Cancer Institute.

“Emiltatug ledadotin在所有入组肿瘤类型中观察到的临床活性令人鼓舞，其安全性和耐受性特征似乎与许多其他ADC有所不同，”哈佛医学院丹娜-法伯癌症研究所医学助理教授安东尼奥·乔治亚诺（Antonio Giordano）博士表示。

“The objective responses were particularly notable in patients with late-stage triple-negative breast cancer who were previously treated with topoisomerase-1 inhibitors and in patients with ACC-1, both of which are aggressive and difficult-to-treat cancers with high unmet need.”.

“特别是那些晚期三阴性乳腺癌患者，他们之前接受过拓扑异构酶-1抑制剂治疗，以及ACC-1患者，这两种癌症都是侵袭性强、难以治疗且存在高度未满足需求的癌症。”

The 2025 ASCO Annual Meeting data presentation can be accessed on the Publications section of the Mersana website at

2025年ASCO年会数据展示可以在Mersana官网的出版物栏目中访问。

www.mersana.com

www.mersana.com

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About Emi-Le

关于Emi-Le

Emi-Le is a B7-H4-directed Dolasynthen ADC with a precise, target-optimized drug-to-antibody ratio (DAR 6) and a proprietary auristatin payload with controlled bystander effect. This candidate is being investigated in Mersana’s ongoing Phase 1 clinical trial. The dose expansion portion of the Phase 1 clinical trial is enrolling patients with triple-negative breast cancer (TNBC) who have received one to four prior treatment lines, including at least one topoisomerase-1 inhibitor (topo-1) ADC..

Emi-Le 是一种针对 B7-H4 的 Dolasynthen 抗体药物偶联物 (ADC)，具有精确的、针对目标优化的药物抗体比 (DAR 6)，以及一种具有可控旁观者效应的专有 auristatin 有效载荷。该候选药物正在 Mersana 进行的 I 期临床试验中研究。I 期临床试验的剂量扩展部分正在招募接受过一至四线既往治疗（包括至少一种拓扑异构酶-1 抑制剂 (topo-1) ADC）的三阴性乳腺癌 (TNBC) 患者。

The U.S. Food and Drug Administration has granted two Fast Track designations to Emi-Le for the treatment of 1) adult patients with advanced or metastatic triple-negative breast cancer, and 2) advanced or metastatic HER2 low / HER2 negative breast cancer post-topo-1 ADC (including TNBC and certain HR+ breast cancers).

美国食品药品监督管理局（FDA）已授予Emi-Le两项快速通道资格，用于治疗：1) 晚期或转移性三阴性乳腺癌成年患者；2) 晚期或转移性HER2低表达/HER2阴性乳腺癌患者（包括TNBC和某些HR+乳腺癌），这些患者在接受过topo-1 ADC治疗后。

For more information about Mersana’s ongoing Phase 1 trial of Emi-Le, please visit clinicaltrials.gov (NCT05377996)..

有关Mersana正在进行的Emi-Le一期试验的更多信息，请访问clinicaltrials.gov（NCT05377996）。

About Mersana Therapeutics

关于Mersana Therapeutics

Mersana Therapeutics is a clinical-stage biopharmaceutical company focused on the development of novel antibody-drug conjugates (ADCs) and driven by the knowledge that patients are waiting for new treatment options. The company has developed proprietary cytotoxic (Dolasynthen) and immunostimulatory (Immunosynthen) ADC platforms that have generated a pipeline of wholly-owned and partnered product candidates with the potential to treat a range of cancers.

Mersana Therapeutics是一家临床阶段的生物制药公司，专注于开发新型抗体药物偶联物（ADC），并深知患者正在等待新的治疗选择。该公司已开发出专有的细胞毒性（Dolasynthen）和免疫刺激性（Immunosynthen）ADC平台，这些平台生成了一系列全资拥有和合作的产品候选药物，有望治疗多种癌症。

Its pipeline includes Emi-Le (emiltatug ledadotin; XMT-1660), a Dolasynthen ADC targeting B7-H4, and XMT-2056, an Immunosynthen ADC targeting a novel epitope of human epidermal growth factor receptor 2 (HER2). Mersana routinely posts information that may be useful to investors on the “Investors & Media” section of its website at .

其研发管线包括Emi-Le（emiltatug ledadotin；XMT-1660），一种靶向B7-H4的Dolasynthen抗体药物偶联物（ADC），以及XMT-2056，一种靶向人类表皮生长因子受体2（HER2）新表位的Immunosynthen抗体药物偶联物（ADC）。Mersana经常在其网站的“投资者与媒体”部分发布可能对投资者有用的信息。

www.mersana.com

www.mersana.com

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Forward-Looking Statements

前瞻性声明

This press release contains “forward-looking” statements and information within the meaning of the Private Securities Litigation Reform Act of 1995. These statements may be identified by words such as “aims,” “anticipates,” “believes,” “could,” “estimates,” “expects,” “forecasts,” “goal,” “intends,” “may,” “plans,” “possible,” “potential,” “seeks,” “will” and variations of these words or similar expressions, although not all forward-looking statements contain these words.

本新闻稿包含根据1995年《私人证券诉讼改革法》定义的“前瞻性”声明和信息。这些声明可能通过诸如“旨在”、“预期”、“相信”、“可能”、“估计”、“预计”、“预测”、“目标”、“打算”、“或许”、“计划”、“可能”、“潜在”、“寻求”、“将”等词语或类似表达方式来识别，尽管并非所有前瞻性声明都包含这些词语。

Forward-looking statements in this press release include, but are not limited to, statements concerning the potential clinical benefits of and opportunity for Emi-Le and the development and potential of Mersana’s product candidates, platforms, technology and pipeline of ADC candidates. Mersana may not actually achieve the plans, intentions or expectations disclosed in these forward-looking statements, and you should not place undue reliance on these forward-looking statements.

本新闻稿中的前瞻性陈述包括但不限于关于Emi-Le的潜在临床益处和机会，以及Mersana的产品候选药物、平台、技术和ADC候选药物管线的开发与潜力的陈述。Mersana可能无法实际实现这些前瞻性陈述中披露的计划、意图或预期，您不应过度依赖这些前瞻性陈述。

Actual results or events could differ materially from the plans, intentions and expectations disclosed in these forward-looking statements as a result of various factors, including, among other things, uncertainties inherent in research and development, in the advancement, progression and completion of clinical trials and in the clinical development of Mersana’s product candidates, including Emi-Le; the risk that Mersana may face delays in patient enrollment in its Phase 1 clinical trial of Emi-Le; the risk that outcomes of preclinical studies may not be predictive of clinical trial results; the risk that initial or interim results from a clinical trial may not be predictive of the final results of the trial or the results of future trials; the risk that clinical trial data may not support regulatory applications or approvals; th.

实际结果或事件可能与这些前瞻性声明中披露的计划、意图和预期有重大差异，原因包括各种因素，尤其是研发、临床试验的推进、进展和完成以及Mersana产品候选物（包括Emi-Le）的临床开发中固有的不确定性；Mersana可能在其Emi-Le的I期临床试验中面临患者招募延迟的风险；临床前研究结果可能无法预测临床试验结果的风险；临床试验的初步或中期结果可能无法预测该试验最终结果或未来试验结果的风险；临床试验数据可能无法支持监管申请或批准的风险。

Contact:

联系人：

Jason Fredette

杰森·弗雷德特

617-498-0020

617-498-0020

jason.fredette@mersana.com

jason.fredette@mersana.com

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Sources: Ferrarotto et al., Clin Can Res. 2020; de Sousa Clin Can Res. 2023; Hanna et al., Cancer Res Commun. 2023; Ferrarotto et al., Abs 903P, ESMO 2023

来源：Ferrarotto 等，《Clin Can Res》2020；de Sousa《Clin Can Res》2023；Hanna 等，《Cancer Res Commun》2023；Ferrarotto 等，摘要 903P，《ESMO 2023》