Chinese pharmaceutical company Sichuan Kelun-Biotech Biopharmaceutical Co Ltd (HK:6990) announced on Friday that China's National Medical Products Administration (NMPA) has approved a new indication application for its TROP2-directed ADC sacituzumab tirumotecan (sac-TMT, also known as SKB264/MK-2870) for the treatment of adult patients with unresectable or metastatic HR+/HER2- (IHC 0, IHC 1+ or IHC 2+/ISH-) breast cancer who have received prior endocrine therapy (ET) and at least one line of chemotherapy in advanced setting.

The approval for HR+/HER2- breast cancer after at least one prior line of chemotherapy marks the fourth indication for sac-TMT approved for marketing in China.

The decision was based on positive results from the Phase III OptiTROP-Breast02 study, which evaluated the efficacy and safety of sac-TMT monotherapy compared to investigator's choice of chemotherapy in patients with unresectable or metastatic HR+/HER2- breast cancer. 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 at least 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). 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. 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.