CHENGDU, China, February 4, 2026—Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. ("Kelun-Biotech" or the "Company", 6990.HK) announced that a new indication application for its TROP2-directed ADC sacituzumab tirumotecan (sac-TMT, also known as SKB264/MK-2870) (佳泰莱®) has been approved by the National Medical Products Administration (NMPA) of China for treatment of adult patients with unresectable or metastatic HR+/HER2- (IHC 0, IHC 1+ or IHC 2+/ISH-) breast cancer (BC) who have received prior endocrine therapy (ET) and at least one line of chemotherapy in advanced setting. This approval for HR+/HER2- BC after at least one prior line of chemotherapy marks the fourth indication for sac-TMT approved for marketing in China.
The approval is based on the positive results from the Phase III OptiTROP-Breast02 study which was selected as a Late-Breaking Abstract (LBA) and presented as an oral report at the 2025 European Society for Medical Oncology (ESMO) Congress.
The OptiTROP-Breast02 study evaluated the efficacy and safety of sac-TMT monotherapy compared to investigator's choice of chemotherapy in patients with unresectable or metastatic HR+/HER2- BC. Of the patients enrolled in this Phase III study, 95.7% had visceral metastases, 75.9% had liver metastases; 52.9% were HER2-zero (IHC 0), while 47.1% were HER2-low (IHC 1+ or IHC 2+/ISH-). All patients had received prior CDK4/6 inhibitor and taxane therapy; 56.6% had received ≥2 lines of prior chemotherapy in the advanced or metastatic setting.
Results showed that sac-TMT demonstrated a statistically significant and clinically meaningful increase in progression-free survival (PFS) as assessed by the Blinded Independent Central Review (BICR) compared to chemotherapy (8.3 vs. 4.1 months; hazard ratios (HR), 0.35; 95% CI: 0.26-0.48; p<0.0001). Consistent PFS benefits were observed across all pre-specified subgroups, including HER2-zero and HER2-low, number of chemotherapy lines received in the advanced or metastatic setting, presence of baseline visceral and liver metastases and previous CDK4/6 inhibitor use. According to BICR-assessed PFS results, the hazard ratios in the HER2-zero and HER2-low (IHC 1+ or IHC 2+/ISH-) subgroups were 0.39 (95% CI: 0.26-0.57) and 0.31 (95% CI: 0.20-0.48), respectively. A trend towards overall survival (OS) benefit and a significantly higher objective response rate (ORR) (41.5% vs. 24.1%) were also observed compared with chemotherapy. [1]
Currently, Phase III clinical studies of sac-TMT with or without pembrolizumab (KEYTRUDA®[2]) for the treatment of chemotherapy-naïve HR+/HER2- BC who have received prior ET have been initiated globally (NCT06312176) and in China (NCT07071337).
About HR+/HER2- Breast Cancer
Breast cancer is one of the most common malignant tumors that seriously threaten women's health worldwide. In 2022, there were about 2,297,000 new cases of breast cancer and 666,000 deaths worldwide. Among them, HR+/HER2- breast cancer is the most common subtype, accounting for about 70% of all breast cancer cases, and advanced HR+/HER2- breast cancer has a poor prognosis. This subtype is typically sensitive to hormonal therapy, and therefore, endocrine therapy combined with a CDK4/6 inhibitor constitutes the standard treatment. However, for patients with HR+/HER2- advanced breast cancer whose disease progresses on endocrine therapy, chemotherapy is widely used in clinical while it is associated with low response rate (ORR approximately 14%-22.9%) and limited survival benefit (mPFS approximately 4.0-4.9 months).
About Sac-TMT
Sac-TMT, a core product of the Company, is a novel human TROP2 ADC in which the Company has proprietary intellectual property rights, targeting advanced solid tumors such as non-small cell lung cancer (NSCLC), breast cancer (BC), gastric cancer (GC), gynecological tumors, among others. Sac-TMT is developed with a novel linker to conjugate the payload, a belotecan-derivative topoisomerase I inhibitor with a drug-to-antibody-ratio (DAR) of 7.4. Sac-TMT specifically recognizes TROP2 on the surface of tumor cells by recombinant anti-TROP2 humanized monoclonal antibodies, which is then endocytosed by tumor cells and releases the payload KL610023 intracellularly. KL610023, as a topoisomerase I inhibitor, induces DNA damage to tumor cells, which in turn leads to cell-cycle arrest and apoptosis. In addition, it also releases KL610023 in the tumor microenvironment. Given that KL610023 is membrane permeable, it can enable a bystander effect, or in other words kill adjacent tumor cells.
In May 2022, the Company licensed the exclusive rights to MSD (the tradename of Merck & Co., Inc, Rahway, NJ, USA) to develop, use, manufacture and commercialize sac-TMT in all territories outside of Greater China (which includes Mainland China, Hong Kong, Macao and Taiwan).
To date, four indications for sac-TMT have been approved and marketed in China for: EGFR mutant-positive locally advanced or metastatic non-squamous NSCLC following progression on EGFR-TKI therapy and platinum-based chemotherapy; unresectable locally advanced or metastatic TNBC who have received at least two prior systemic therapies (at least one of them for advanced or metastatic setting); EGFR mutant-positive locally advanced or metastatic non-squamous NSCLC who progressed after treatment with EGFR-TKI therapy; unresectable or metastatic HR+/HER2- (IHC 0, IHC 1+ or IHC 2+/ISH-) BC who have received prior ET and at least one line of chemotherapy in advanced setting. The first two indications listed above have been included in China's National Reimbursement Drug List (NRDL). This inclusion is expected to bring clinical benefits to a greater number of patients with BC and NSCLC. Additionally, sac-TMT has been granted six Breakthrough Therapy Designations (BTDs) by the NMPA.
Sac-TMT is the world's first TROP2 ADC drug approved for marketing in lung cancer. As of today, Kelun-Biotech has initiated 9 registrational clinical studies in China. MSD is evaluating16 ongoing Phase III global clinical studies of sac-TMT as a monotherapy or with pembrolizumab or other anti-cancer agents for several types of cancer. These studies are sponsored and led by MSD.
About Kelun-Biotech
Kelun-Biotech (6990.HK) is a holding subsidiary of Kelun Pharmaceutical, which focuses on the R&D, manufacturing, commercialization and global collaboration of innovative biological drugs and small molecule drugs. Kelun-Biotech focuses on major disease areas such as solid tumors, autoimmune, and metabolic diseases, and in establishing a globalized drug development and industrialization platform to address the unmet medical needs in China and the rest of world. Kelun-Biotech is committed to becoming a leading global enterprise in the field of innovative drugs. At present, Kelun-Biotech has more than 30 ongoing key innovative drug projects, of which 4 projects have been approved for marketing, more than 10 projects are in the clinical stage. Kelun-Biotech has established one of the world's leading proprietary ADC and novel DC platforms, OptiDC™, and has 2 ADC projects approved for marketing, and multiple ADC and novel DC assets in clinical or preclinical research stage. For more information, please visit https://en.kelun-biotech.com/.
Reference Sources：
[1] Fan Y, Li H, Wang H, et al. ESMO Congress 2025, LBA23.
[2] KEYTRUDA® (pembrolizumab) is a registered trademark of Merck Sharp & Dohme LLC (MSD), a subsidiary of Merck & Co., Inc., Rahway, NJ, USA.
