Editor's Note: The 29th Annual Meeting of the Chinese Society of Clinical Oncology (CSCO) was held in Jinan, Shandong Province, from September 16 to 19, 2026. During the meeting, Professor Yongmei Yin of Jiangsu Province Hospital presented updated results from OptiTROP-Breast05, a multicenter Phase II study evaluating first-line sacituzumab tirumotecan (sacituzumab govitecan? No—sacituzumab tirumotecan, SKB264/MK-2870), China's first independently developed TROP2-directed antibody–drug conjugate (ADC), in advanced triple-negative breast cancer (TNBC). The objective response rate (ORR) reached 70.7%, and median overall survival (OS) was 32.8 months. At the opening ceremony on the first day of the CSCO Annual Meeting, the study received the “2026 Innovation Research Award,” reflecting strong recognition from Chinese experts. Oncology Frontier invited Professor Yongmei Yin, Lead Principal Investigator of OptiTROP-Breast05, to contribute this article exploring the far-reaching implications of China's innovative medicines. The full text follows.01. Updated OptiTROP-Breast05 Results: Median OS Reaches 32.8 Months in First-Line TNBC
TNBC is characterized by poor differentiation, aggressive behavior, and a high risk of recurrence and metastasis. Its five-year survival rate is substantially lower than that of the overall breast cancer population. Historically, chemotherapy has been the mainstay of treatment for advanced TNBC, while immunotherapy is suitable for fewer than 40% of patients. After first-line treatment, approximately 50% of patients lose the opportunity to receive second-line or subsequent therapy for various reasons. There is therefore an urgent clinical need for more effective first-line treatment options that can benefit a broader patient population. This is precisely the question that OptiTROP-Breast05 was designed to address.
Presented at this year’s CSCO Annual Meeting, OptiTROP-Breast05 is a multicenter, open-label Phase II clinical study evaluating sacituzumab tirumotecan, China’s first independently developed TROP2-directed ADC, as first-line treatment for TNBC. Preliminary results were previously presented orally at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting. The current report provides results from a longer follow-up period.
OptiTROP-Breast05 primarily enrolled patients with unresectable locally advanced or metastatic TNBC who had not received systemic treatment for advanced disease. Regardless of PD-L1 or TROP2 expression status, patients received sacituzumab tirumotecan monotherapy at 5 mg/kg every two weeks (Q2W). The primary endpoint was investigator-assessed ORR. Secondary endpoints included progression-free survival (PFS), duration of response (DOR), disease control rate (DCR), OS, and safety.
As of January 26, 2026, the study had enrolled 41 patients, including 32 with a PD-L1 combined positive score (CPS) below 10. Updated follow-up showed an ORR of 70.7%, a DCR of 92.7%, a median DOR (mDOR) of 12.1 months, a median PFS (mPFS) of 13.4 months, and a median OS (mOS) of 32.8 months in the overall population. Among patients with PD-L1 CPS below 10, mPFS was 13.1 months and mOS was also 32.8 months. The most common grade 3 or higher treatment-related adverse events were hematologic toxicities and oral mucositis, for which clinical management experience is relatively well established.
These findings offer greater hope for long-term survival in TNBC and provide a new precision treatment option for patients with PD-L1 CPS below 10, a population not adequately covered by immunotherapy. The study may therefore help reshape the clinical treatment landscape. We are honored that it received the “2026 Innovation Research Award” at this year’s CSCO Annual Meeting, representing strong recognition from Chinese experts of homegrown innovation in drug development.
02. OptiTROP-Breast03 Meets Its Primary Endpoint, Signaling a Potential New First-Line Treatment Landscape for TNBC
As evidence has accumulated, TROP2-directed ADCs have become standard treatment options for advanced TNBC, progressing from later-line treatment toward earlier settings. The 2026 CSCO Guidelines for Breast Cancer Diagnosis and Treatment identify sacituzumab tirumotecan as a Category I recommendation (1A) for patients with advanced TNBC whose disease has failed to respond to taxane treatment, and a Category II recommendation (2A) for patients whose disease remains taxane-sensitive. For immunotherapy combinations, SG plus a PD-1 inhibitor is a Category II recommendation (1B), regardless of taxane sensitivity. These recommendations demonstrate strong recognition among Chinese experts of the role of sacituzumab tirumotecan in TNBC and provide a foundation for further clinical research and broader application.
Recently, the Phase III OptiTROP-Breast03 study also announced positive results for first-line sacituzumab tirumotecan in patients with TNBC who are not suitable for immunotherapy, with detailed data expected to be released soon. The study included patients with PD-L1 CPS below 10, as well as those whose disease recurred after prior PD-1/PD-L1 inhibitor treatment in the early-stage setting. It specifically focused on patients with advanced TNBC who are not suitable for immunotherapy and demonstrated a significant improvement in PFS, with a favorable trend in OS.
Looking across first-line treatment options for advanced PD-L1-negative TNBC, three TROP2-directed ADCs are under investigation: sacituzumab tirumotecan, sacituzumab govitecan (SG), and datopotamab deruxtecan (Dato-DXd).
In ASCENT-03, SG monotherapy achieved an ORR of 48% and an mPFS of 9.7 months. In TROPION-Breast02, Dato-DXd achieved an ORR of 63% and an mPFS of 10.8 months (HR 0.57; 95% CI, 0.44–0.73; P < 0.0001). In the Phase II OptiTROP-Breast05 study, sacituzumab tirumotecan achieved an ORR of 71.9% among patients with PD-L1 CPS below 10—the highest response rate reported for a TROP2-directed ADC in this setting to date—along with an mPFS of 13.1 months. It is therefore the first TROP2-directed ADC in this setting to demonstrate a PFS exceeding one year. These results make the positive findings from the Phase III OptiTROP-Breast03 study particularly noteworthy.
More importantly, both OptiTROP-Breast05 and OptiTROP-Breast03 involve Chinese patient populations, making their findings especially relevant to patients with advanced TNBC in China. We look forward to OptiTROP-Breast03 helping support approval of sacituzumab tirumotecan for first-line TNBC and potentially establishing a new treatment standard. This would give Chinese patients with TNBC access to the first first-line TROP2-directed ADC approved on the basis of data from a Chinese patient population, offering a treatment option more closely aligned with their needs.
03. Chinese Innovation Opens New Horizons and Helps Bring Chinese Standards to the World
The encouraging clinical evidence for sacituzumab tirumotecan is rooted in its innovative mechanism of action. Its antibody component is a high-affinity humanized monoclonal antibody targeting TROP2. Its cytotoxic payload, T030, is a novel topoisomerase I inhibitor incorporating a methylsulfonyl structure to enhance stability. A high drug-to-antibody ratio (DAR) of up to 7.4 supports potent tumor-killing activity. The antibody and payload are irreversibly conjugated through an optimized, cleavable CL2A linker, improving stability in circulation and reducing the risk of premature payload release.
These structural optimizations enable sacituzumab tirumotecan to exert antitumor activity through three complementary mechanisms: targeted internalization and payload release; a bystander effect that kills neighboring cells with low TROP2 expression; and pH-dependent hydrolysis of the linker in the tumor microenvironment. Together, these mechanisms aim to achieve high response rates while maintaining a manageable safety profile.
In China, sacituzumab tirumotecan has now received approval for four indications across lung and breast cancer, while six new drug applications (NDAs) have been accepted and included in priority review. Internationally, Kelun-Biotech has granted Merck exclusive global development and commercialization rights to sacituzumab tirumotecan outside Greater China. Fifteen global clinical trials in the TroFuse development program have been initiated, covering breast cancer, gastric cancer, cervical cancer, gynecologic cancers, bladder cancer, cholangiocarcinoma, and other tumor types. Seven of these trials have entered Phase III. The growing global influence of innovative anticancer medicines developed in China is becoming a reality.
As an investigator deeply involved in the clinical development of sacituzumab tirumotecan, I am pleased to have witnessed the OptiTROP-Breast studies present their findings on international platforms such as ESMO and ASCO, alongside the global expansion of the TroFuse program. These achievements reflect the continued improvement of China’s research capabilities, innovation capacity, and clinical trial data quality.
The CSCO Breast Cancer Expert Committee will continue to provide a reliable platform and the necessary support for clinical research on innovative medicines developed in China through the “2030 Innovation-Driven Breast Cancer Collaborative Group.” As the number of multinational clinical trials led by Chinese investigators continues to grow, the influence of Chinese clinical guidelines will gradually expand, helping shape new global standards. Together with China’s innovative medicines, these efforts will advance cancer care worldwide.
Looking ahead, I hope collaboration among industry, academia, research institutions, and healthcare providers will deepen further. By keeping patients’ needs at the center, we must continue to advance innovative medicines and improve access, ensuring that China’s innovation progresses steadily through precision and standardized clinical practice and benefits more patients with cancer, both in China and around the world.
Professor Yongmei Yin
