Merck and Kelun-Biotech reported Phase 3 results at ASCO 2026 showing that the TROP2-directed sacituzumab tirumotecan (sac-TMT) added to Keytruda cut the risk of disease progression or death by 65% versus Keytruda alone in treatment-naïve, PD-L1–positive non-small cell lung cancer. The interim analysis left median progression-free survival (PFS) unreached in the combo arm versus 5.7 months for Keytruda alone, with a preliminary overall survival trend favoring the combination. The OptiTROP-Lung05 study in China is the first randomized Phase 3 win for an ADC–PD-1 immunotherapy combination in this frontline setting, escalating the contest for a new standard of care. The companies also noted the final PFS analysis is expected later this year as the primary completion target is marked for November. The updated efficacy positioning also comes as investors weigh competitive context from Harmoni-2’s PD-1×VEGF bispecific ivonescimab, which previously delivered a 49% PFS improvement versus Keytruda in the same patient subset. The head-to-head comparisons remain indirect, but the magnitude and follow-up duration of sac-TMT/Keytruda PFS effects add pressure to the bispecific frontier. With key overall survival data not yet mature, Merck and Kelun’s next catalysts will be the final PFS and OS readouts that typically shape regulatory and payer planning in frontline lung cancer.