The competition among three TROP2 antibody-drug conjugates is entering a new stage as Kelun-Biotech’s Merck & Co.-partnered sacituzumab tirumotecan (sac-TMT) has become the second therapy in the class to win a marketing approval.

Chinese regulators have approved sac-TMT to treat patients with advanced triple-negative breast cancer (TNBC) who have received at least two prior systemic therapies, including at least one in the advanced setting, Kelun said Wednesday.

Sac-TMT’s nod matches the first-in-class blessing that Gilead Sciences’ Trodelvy secured from China’s National Medical Products Administration in June 2022. Trodelvy has not been placed on China’s national reimbursement drug list since then. Chinese authorities are scheduled to release the new roster Thursday following a round of price negotiations in October.

Sac-TMT, also known as SKB264 or MK-2870, represents the first asset in Kelun’s multitarget, multibillion-dollar ADC collaboration with Merck. In May 2022, the New Jersey pharma obtained ex-China rights to the drug by paying $47 million upfront and committing up to $1.36 billion in potential milestones.

The approval is based on results from the phase 3 OptiTROP-Breast01 trial conducted in China. Among TNBC patients who have received at least two prior therapies, sac-TMT significantly reduced the risk of death by 47% compared with a physician’s choice of chemotherapy. At an interim analysis performed at a median follow-up of 10.4 months, patients in the chemo arm lived a median 9.4 months, while the median overall survival was not reached with sac-TMT.

Sac-TMT also significantly reduced the risk of progression or death by 69% versus chemo. The median progression-free survival time was 5.7 months versus 2.3 months, respectively.