Kelun-Biotech Reports Positive Phase 3 Results for sac-TMT in First-Line Triple-Negative Breast Cancer

Could TROP2 ADCs reshape first-line treatment for metastatic TNBC?

Sichuan Kelun-Biotech announced that its Phase 3 OptiTROP-Breast03 study evaluating sacituzumab tirumotecan (sac-TMT) met the primary endpoint of progression-free survival (PFS) in patients with unresectable locally recurrent or metastatic triple-negative breast cancer (TNBC). According to the company, the TROP2-directed antibody-drug conjugate (ADC) demonstrated a statistically significant and clinically meaningful improvement in PFS compared with investigator’s choice chemotherapy in the first-line setting.¹

The randomized, open-label multicenter trial enrolled patients with PD-L1-negative TNBC as well as patients with PD-L1-positive disease who relapsed after prior anti-PD-(L)1 treatment in early-stage disease. Overall survival data remain immature, although the company reported a positive trend at the interim analysis.¹

The results mark the first positive registrational Phase 3 study for sac-TMT in first-line TNBC and may further intensify competition within the rapidly expanding ADC landscape in breast cancer.

Why is the result clinically significant for patients with TNBC?

Triple-negative breast cancer remains one of the most aggressive breast cancer subtypes and is associated with limited targeted treatment options, particularly in patients who relapse after immunotherapy exposure.² Standard chemotherapy has historically produced modest outcomes in metastatic disease, driving interest in ADCs that combine tumor-targeting antibodies with potent cytotoxic payloads.

Sac-TMT targets trophoblast cell-surface antigen 2 (TROP2), a protein commonly overexpressed in multiple solid tumors, including TNBC.¹ The drug uses a topoisomerase I inhibitor payload linked through a proprietary bifunctional linker designed to improve intracellular drug delivery and enhance bystander tumor cell killing.¹

The positive PFS outcome is clinically notable because it suggests TROP2-directed ADCs may continue moving earlier in the treatment paradigm, potentially expanding beyond heavily pretreated metastatic settings into frontline therapy. The findings also reinforce broader industry confidence in ADCs as a major therapeutic class in oncology.

How does sac-TMT fit into the broader ADC market?

ADCs have become one of the most competitive areas in oncology drug development as pharmaceutical companies pursue more targeted approaches for difficult-to-treat cancers. Several TROP2-targeted therapies are already reshaping treatment strategies in breast and lung cancer markets.³

Sac-TMT was previously approved in China for metastatic TNBC after at least two prior systemic therapies based on results from the OptiTROP-Breast01 study.¹ The therapy has also received approvals in multiple lung cancer indications and hormone receptor-positive/HER2-negative breast cancer in China.¹

Kelun-Biotech licensed rights to develop and commercialize sac-TMT outside Greater China to MSD, known as Merck & Co., Inc. in the US and Canada, in 2022.¹ The collaboration reflects growing global interest in ADC platforms capable of addressing both breast cancer and broader solid tumor markets.

The companies are also continuing global development through the ongoing Phase 3 TroFuse-011 study evaluating sac-TMT alone or in combination with pembrolizumab in first-line TNBC patients with low PD-L1 expression.¹

What could the regulatory pathway look like next?

Kelun-Biotech stated it plans to communicate with China’s Center for Drug Evaluation regarding the regulatory pathway for the TNBC indication following the interim analysis.¹ Continued follow-up for overall survival and additional analyses are expected as the study progresses.

If future data confirm durable clinical benefit and manageable safety, sac-TMT could strengthen its position within the increasingly crowded ADC market and potentially influence treatment sequencing strategies for metastatic TNBC patients globally.

References

1. Kelun-Biotech Announces Phase III Trial of Sacituzumab Tirumotecan (sac-TMT) versus Chemotherapy as First-line Treatment for Advanced TNBC Met Primary Endpoint of PFS. (2026 May 21). PR Newswire. https://prnmedia.prnewswire.com/news-releases/kelun-biotech-announces-phase-iii-trial-of-sacituzumab-tirumotecan-sac-tmt-versus-chemotherapy-as-firstline-treatment-for-advanced-tnbc-met-primary-endpoint-of-pfs-302779075.html
2. Bianchini G., Balko J. M., Mayer I. A., Sanders M. E., Gianni L. (2016 May 17). Triple-negative breast cancer: challenges and opportunities of a heterogeneous disease. Nat Rev Clin Oncol. https://pubmed.ncbi.nlm.nih.gov/27184417/
3. Cortes J, Cescon DW, Rugo HS, et al. (2022 Aug 26). Sacituzumab Govitecan in Hormone Receptor-Positive/HER2-Negative Advanced Breast Cancer. J Clin Oncol. https://ascopubs.org/doi/10.1200/JCO.22.01002
4. Goldenberg DM, Sharkey RM. (2019 Aug). Antibody-drug conjugates targeting TROP-2 and incorporating SN-38: a case study of anti-TROP-2 sacituzumab govitecan. MAbs. https://pubmed.ncbi.nlm.nih.gov/31208270/