CHENGDU, China, May 21, 2026 /PRNewswire/ -- Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. ("Kelun-Biotech" or the "Company", 6990.HK) announced today that the Independent Data Monitoring Committee (IDMC) concluded that the Phase III clinical study (OptiTROP-Breast03) of the Company's trophoblast cell-surface antigen 2 (TROP2)-directed antibody drug conjugate (ADC) sacituzumab tirumotecan (sac-TMT, also known as SKB264/MK-2870)(佳泰莱^®) versus investigator's choice of chemotherapy as first‑line treatment for unresectable locally recurrent or metastatic triple‑negative breast cancer (TNBC) has met its primary endpoint of progression‑free survival (PFS) at a prespecified interim analysis, demonstrating a statistically significant and clinically meaningful improvement. Overall survival (OS) data are immature, a positive trend is currently observed.

OptiTROP-Breast03 is a randomized, open‑label, multicenter Phase III clinical study designed to evaluate the efficacy and safety of sac‑TMT versus investigator's choice of chemotherapy in patients with unresectable recurrent or metastatic TNBC who have not received prior systemic therapy for advanced disease. The enrolled population includes patients with programmed death ligand 1 (PD-L1)‑negative expression, as well as those with PD‑L1‑positive expression who have relapsed after prior anti-PD-(L)1 inhibitor in early stage disease. Two independent primary endpoints of the study are PFS and OS. At this pre-specified interim analysis, sac-TMT monotherapy demonstrated a statistically significant and clinically meaningful improvement in PFS. OS data are immature, a positive trend is currently observed. Follow-up will continue per protocol and further evaluation will be conducted in subsequent prespecified analyses. The safety profile of sac-TMT was consistent with that observed in previously reported studies, and no new safety signals were observed. Based on the results from the interim analysis, the Company plans to communicate with the Center for Drug Evaluation (CDE) of the National Medical Products Administration of China regarding the subsequent regulatory pathway for sac‑TMT in this indication.

This is the first registrational Phase III clinical study of sac-TMT to achieve positive results in the first-line treatment of TNBC. Previously, sac-TMT has been approved for the treatment of unresectable locally advanced or metastatic TNBC in patients who have received at least two prior systemic therapies (including at least one for advanced or metastatic disease) based on the results of OptiTROP-Breast01 study. The achievement of the primary endpoint of PFS in the Phase III OptiTROP-Breast03 study builds on the ongoing development of sac-TMT and supports further evaluation of its potential in the first-line setting in TNBC and across treatment settings, aligned with the Company's broader clinical development strategy to address patient needs.

Currently, the global Phase III TroFuse-011 study (NCT06841354) of sac-TMT monotherapy or in combination with pembrolizumab as first-line treatment for PD-L1 Combined Positive Score (CPS)＜10 TNBC is ongoing.

About sac-TMT(佳泰莱^®)

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 and genitourinary tumors, among others. Sac-TMT is developed with a unique, bifunctional linker that maximizes payload delivery to tumor cells both through its irreversible connection with the anti-TROP2 monoclonal antibody sacituzumab and its pH-sensitive cleavage from a belotecan-derivative topoisomerase I inhibitor payload in the lysosome, 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: 1) 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); 2) epidermal growth factor receptor (EGFR) mutant-positive locally advanced or metastatic non-squamous NSCLC following progression on EGFR–tyrosine kinase inhibitor (EGFR-TKI) therapy and platinum-based chemotherapy; 3) EGFR mutant-positive locally advanced or metastatic non-squamous NSCLC who progressed after treatment with EGFR-TKI therapy; 4) unresectable or metastatic hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) (Immunohistochemistry (IHC) 0, IHC 1+ or IHC 2+/In Situ Hybridization (ISH)-) BC who have received prior endocrine therapy and at least one line of chemotherapy in advanced setting. The first two indications above have been included in China's National Reimbursement Drug List (NRDL). This inclusion is expected to bring clinically meaningful 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. A new indication application for sac-TMT in combination with pembrolizumab (KEYTRUDA^®) as first‑line treatment for locally advanced or metastatic NSCLC who have PD-L1 TPS≥1% and are EGFR-negative and ALK-negative has been accepted for review by the NMPA, and has entered the priority review and approval process. As of today, Kelun-Biotech has initiated 9 registrational clinical studies in China. MSD has initiated 17 ongoing global Phase III clinical studies of sac-TMT as a monotherapy or in combination 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 with 8 indications have been approved for marketing, 1 project is in the NDA stage and 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 with 5 indications 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/.