On May 21, 2025 Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. (the "Company") reported that a new indication application (the "Application") for the Company’s trophoblast cell-surface antigen 2 (TROP2)-directed antibody-drug conjugate (ADC) sacituzumab tirumotecan (sac-TMT, also known as SKB264/MK-2870) was accepted by the Center for Drug Evaluation (CDE) of the National Medical Products Administration (NMPA) of China for the treatment of adult patients with unresectable locally advanced, metastatic hormone-receptor positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-) breast cancer (BC) who have received prior endocrine therapy and other systemic treatments in the advanced or metastatic setting (Press release, Kelun, MAY 21, 2025, View Source [SID1234653277]). This acceptance is based on the positive results from the registrational phase 3 OptiTROP-Breast02 study, and the Application is the fourth indication application for sac-TMT that has been accepted by the NMPA.
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OptiTROP-Breast02 is a randomized, open-label, multi-center, Phase 3 clinical study that evaluates the efficacy and safety results of sac-TMT monotherapy 5mg/kg every other week (Q2W) versus chemotherapy treatment of physician’s choice for the treatment of patients with unresectable locally advanced or metastatic HR+/HER2- (Immunohistochemistry [IHC] 0, IHC 1+ or IHC 2+/ In Situ Hybridization [ISH]-) BC. Primary efficacy endpoint of this Phase 3 clinical study was reached according to a pre-specified interim analysis, where sac-TMT monotherapy demonstrated a statistically significant and clinically meaningful improvement in the primary endpoint of progression-free survival (PFS) as assessed by the blinded independent review committee (BIRC) compared with chemotherapy treatment of physician’s choice and the risk of disease progression or death was significantly reduced. Sac-TMT also demonstrated the beneficial trend for overall survival (OS).
On May 16, 2024, the CDE’s official website announced that the Application would be reviewed via the priority review and approval process. This marks the fourth sac-TMT indication to go through the CDE’s priority review and approval process, with three previous sat-TMT indications approved following priority review.
Dr. Michael Ge, CEO of Kelun-Biotech said, "We are very pleased that the NDA application for the fourth indication of our core product, sac-TMT, has been accepted by the CDE of NMPA, which is another breakthrough for the breast cancer treatment field. This not only verifies the clinical value and innovative nature of sac-TMT, but also highlights the ‘patient-centered’ mission of Kelun-Biotech. We look forward to the OS results of sac-TMT with longer follow-up. In the future, we will continue to explore sac-TMT as an oncology therapeutic agent, aiming to address new indications with unmet clinical needs, so as to benefit more oncology patients globally."
About HR+/HER2- BC
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 [1]. 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 [2]. Patients with this subtype of breast cancer are often hormone-sensitive, so the preferred treatment option is endocrine therapy combined with CDK4/6 inhibitors. Rescue chemotherapy is preferred for patients with advanced HR+/HER2- breast cancer with visceral metastases who require rapid disease remission, who are previously resistant to endocrine therapy, or who do not have optimal endocrine therapy options. There is currently no standard treatment option for second- and third-line HR+/HER2-advanced breast cancer patients who have failed first-line chemotherapy. In summary, there is an unmet clinical need for patients with unresectable locally advanced or metastatic HR+/HER2- breast cancer who have received prior endocrine therapy and have received other systemic therapies in the advanced or metastatic stages.
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), 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 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 (includes Mainland China, Hong Kong, Macao, and Taiwan).
To date, two indications for sac-TMT have been approved and marketed in China for the treatment of adult patients with unresectable locally advanced or metastatic triple negative breast cancer (TNBC) who have received at least two prior systemic therapies (at least one of them for advanced or metastatic setting) and epidermal growth factor receptor (EGFR) mutation-positive locally advanced or metastatic non-squamous NSCLC following progression on EGFR-tyrosine kinase inhibitor (TKI) therapy and platinum-based chemotherapy. Sac-TMT became the first domestically developed and fully approved for marketing ADC in China with global intellectual property rights . It is also the world’s first TROP2 ADC to be approved for marketing in a lung cancer indication. In addition, the new indication application for sac-TMT for the treatment of adult patients with EGFR-mutant locally advanced or metastatic NSCLC who progressed after treatment with EGFR-TKI therapy was accepted by the NMPA, and was included in the priority review and approval process. As of today, the Company has initiated 8 registrational clinical studies in China. MSD has initiated 14 ongoing Phase 3 global clinical studies of sac-TMT as a monotherapy or with pembrolizumab or other agents for several types of cancer. These studies are sponsored and led by MSD.