On May 18, 2026, global pharmaceutical giant Merck (MSD) and China's Kelun-Biotech jointly announced that their collaboratively developed TROP2-targeting antibody-drug conjugate (ADC), sacituzumab tirumotecan (sac-TMT, brand name: Jatai®), met its primary endpoints in a global Phase III clinical trial (TroFuse-005) for advanced or recurrent endometrial cancer. This is the world’s first ADC therapy to simultaneously demonstrate statistically significant improvements in both overall survival (OS) and progression-free survival (PFS) in endometrial cancer patients who have progressed after platinum-based chemotherapy and immunotherapy, breaking the long-standing treatment gap for this difficult-to-treat patient population.

Milestone Breakthrough: First OS/PFS Dual-Positive Phase III Data
According to pre-specified interim analysis results, sac-TMT demonstrated statistically significant and clinically meaningful improvements in both primary endpoints of OS and PFS, significantly superior to the physician's choice chemotherapy (doxorubicin or paclitaxel). The study also successfully met the key secondary endpoint of objective response rate (ORR). This randomized, open-label, multicenter global Phase III trial enrolled 776 patients with endometrial cancer and carcinosarcoma who had previously received platinum-based chemotherapy and anti-PD-1/L1 immunotherapy (either in combination or sequential use). It is worth emphasizing that this is the first and only Phase III clinical trial globally to achieve dual-positive OS and PFS results in this specific patient population, marking a historic milestone. "Despite recent treatment advances, patients who progress after platinum and immunotherapy still urgently need new therapeutic options," said Dr. Domenica Lorusso, principal investigator of the study from Humanitas University. "These findings show for the first time that a TROP2 ADC may be an effective treatment option." In terms of safety, sac-TMT demonstrated a consistent profile with all previous studies, with no new safety signals identified. Both companies stated that complete study data will be presented at upcoming major medical conferences, and they will immediately engage with global regulatory authorities to expedite approval for this indication.
17 Global Phase III Studies Fully Underway, 4 Indications Approved in China
Merck and Kelun-Biotech entered into a strategic collaboration in 2022 to jointly develop multiple innovative ADC drugs, including sac-TMT. Since the collaboration, both parties have rapidly advanced the clinical development and commercialization of sac-TMT in China, securing 4 indication approvals to date:
November 2024: First approval for third-line triple-negative breast cancer (TNBC), becoming the first domestically developed TROP2 ADC approved for marketing in China
March 2025: Approved for EGFR mutation-positive non-small cell lung cancer (NSCLC)
Subsequently received approvals for two additional NSCLC indications and one HER+/HER2 breast cancer indication
Currently, the global clinical development program for sac-TMT includes 17 ongoing Phase III studies covering multiple solid tumor types including endometrial cancer, bladder cancer, breast cancer, cervical cancer, gastric cancer, NSCLC, and ovarian cancer, making it the TROP2 ADC with the broadest indication portfolio globally. Among these, 10 Phase III studies are focused on female cancers alone. Beyond the endometrial cancer data announced today, both companies will present multiple Phase III trial results for sac-TMT in lung and breast cancers at the upcoming American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago later this month, which is expected to further expand its indication landscape. On the regulatory front, Merck has obtained a National Priority Review Voucher (CNPV) from the US FDA, which will significantly shorten the FDA review timeline for sac-TMT's marketing application and accelerate its global approval process.
Merck's Critical Strategy to Address Keytruda Patent Expiry
The success of sac-TMT holds critical strategic significance for Merck, which faces the impending patent expiration of Keytruda (pembrolizumab). As Merck's "cash cow" product, Keytruda contributed nearly half of the company's sales (approximately $8.15 billion) in the first quarter of 2026, but its core patent protection expires at the end of 2028. To address this significant challenge, Merck is aggressively building its next-generation oncology pipeline, with ADCs as one of its core strategic focus areas. However, in the TROP2 ADC space, Merck remains in a catch-up position. Gilead's Trodelvy (sacituzumab govitecan) was first to market in 2020, becoming the first approved TROP2 ADC globally; AstraZeneca and Daiichi Sankyo's Datroway (datopotamab deruxtecan) was also approved in 2025. The breakthrough progress of sac-TMT in the endometrial cancer indication is expected to help Merck establish a differentiated competitive advantage in this intense market. Citigroup analyst Geoffrey Meacham stated in a client report: "Merck is building its next-generation oncology pipeline and broader R&D portfolio through ongoing business development and active clinical catalysts to offset the impact of Keytruda's patent expiry. In our view, the impact of this headwind is gradually diminishing."
Industry Outlook: TROP2 ADC Competition Heats Up
With the success of sac-TMT in the endometrial cancer Phase III trial and the upcoming blockbuster data to be presented at the ASCO Annual Meeting, the Merck-Kelun ADC collaboration is poised for a new wave of breakthroughs. If subsequent clinical development proceeds smoothly, sac-TMT has the potential to become a blockbuster ADC drug covering multiple solid tumor indications, offering more treatment options for cancer patients worldwide. At the same time, the success of this trial once again validates the significant value of the TROP2 target in oncology treatment and the tremendous potential of ADC technology in overcoming difficult-to-treat cancers. Looking ahead, as more innovative ADC drugs receive marketing approval, the oncology treatment landscape is expected to undergo further transformation.