The Phase 3 OptiTROP-Lung05 trial, conducted in China and led by Kelun-Biotech, demonstrated a 65% reduction in the risk of tumor progression when sacituzumab tirumotecan (sac-TMT, also known as SKB264/MK-2870) was combined with Merck’s KEYTRUDA (pembrolizumab), compared with KEYTRUDA alone in previously untreated patients with PD-L1-positive advanced non-small cell lung cancer (NSCLC). Kelun-Biotech announced the top-line results on Nov. 24, 2025, stating that the study met its primary endpoint of progression-free survival (PFS) with a statistically significant and clinically meaningful benefit.

According to Kelun’s press release, the combination therapy showed a positive trend in overall survival (OS), although the data remain preliminary and require longer follow-up for confirmation.

Multiple reports, including those from STAT and BioPharma Dive, noted the early survival benefit favoring sac-TMT but emphasized that the OS data are not yet mature. The topline announcements did not include detailed OS hazard ratios or median survival figures.

The trial enrolled patients with PD-L1 expression of 1% or higher and compared the sac-TMT plus KEYTRUDA regimen to KEYTRUDA monotherapy. Kelun’s newsroom highlighted that in a separate sac-TMT lung cancer study involving chemotherapy, median PFS was 8.3 months versus 4.1 months, with a hazard ratio of 0.35, underscoring the drug’s broader efficacy in lung cancer. Subgroup analyses reported by Kelun showed hazard ratios of 0.39 for HER2-zero and 0.31 for HER2-low patients, although these findings were not specific to the OptiTROP-Lung05 trial. An objective response rate (ORR) of 41.5% versus 24.1% was also cited in a separate lung cancer dataset posted by Kelun.

The OptiTROP-Lung05 trial is the first Phase 3 study to demonstrate the successful combination of an antibody-drug conjugate (ADC) targeting TROP2 with a PD-1 immune checkpoint inhibitor in the first-line treatment of advanced NSCLC, according to Kelun. The company described sac-TMT as a TROP2-directed ADC and views the data as supporting a potential new first-line treatment option for a subset of NSCLC patients. Merck, which partnered with Kelun-Biotech on the drug’s development, reiterated these findings in its ASCO 2026 materials, where the study was presented in the metastatic lung cancer oral abstract session.

Safety data from the trial were consistent with prior testing of sac-TMT, though detailed adverse event information was not included in the publicly available reports. Merck’s ASCO 2026 release noted ongoing global Phase 3 studies evaluating sac-TMT both in combination with pembrolizumab and as monotherapy. Kelun confirmed plans to engage with Chinese regulatory authorities to discuss potential approval filings based on the OptiTROP-Lung05 results.

The development of sac-TMT remains in late-stage clinical testing, with the OptiTROP-Lung05 findings serving as an important proof of concept for the Merck-Kelun collaboration in advancing ADC and immune checkpoint inhibitor combinations earlier in lung cancer treatment. The companies continue to explore the drug’s potential across multiple studies worldwide.