At ASCO, Merck Makes Case for a ‘Cornerstone’ Cancer Drug

Why It Matters

The therapy could fill the revenue gap left by Keytruda’s patent loss and reshape Merck’s oncology pipeline, while also influencing the broader ADC market.

Key Takeaways

• Sac‑TMT reduced progression risk by 65% vs Keytruda alone
• Merck launched 17 Phase 3 ADC trials across multiple tumor types
• Shares rose over 5% after positive ASCO data release
• Keytruda patent expiry drives Merck to seek new oncology blockbusters
• Competing TROP2 ADCs face mixed results, raising market uncertainty

Pulse Analysis

Merck’s oncology pipeline faces a looming revenue cliff as its flagship immune‑checkpoint inhibitor Keytruda approaches patent expiration in the United States and Europe. The company has signaled that a new generation of antibody‑drug conjugates (ADCs) will be essential to sustain growth, and it has turned to a Chinese‑origin molecule discovered by Kelun‑Biotech. Sacituzumab tirumotecan, known as sac‑TMT, joins a wave of ADCs that aim to deliver cytotoxic payloads directly to cancer cells, potentially replacing conventional chemotherapy in a variety of indications.

Data presented at the American Society of Clinical Oncology conference showed that sac‑TMT combined with Keytruda cut the risk of disease progression or death by 65 % compared with Keytruda alone in a Chinese Phase 3 lung‑cancer study, with median progression‑free survival not yet reached. The benefit appeared consistent across squamous and non‑squamous subgroups and across a wide range of PD‑L1 expression levels. Analysts also noted a cleaner safety profile than expected, a factor that could differentiate sac‑TMT from rival TROP2‑targeting ADCs such as AstraZeneca’s Datroway and Gilead’s Trodelvy.

The positive readout sent Merck’s stock up more than 5 % and reinforced investor confidence that the drug could become a “cornerstone” ADC for the company. However, uncertainties remain: the Chinese trial used a Keytruda‑only control rather than the standard chemo‑plus‑Keytruda regimen, and global studies must replicate the efficacy signal. Competition in the TROP2 space is intensifying, and emerging PD‑1/VEGF combinations could further compress the market. If sac‑TMT delivers durable survival gains in upcoming multinational trials, it may secure a critical revenue stream for Merck as Keytruda’s exclusivity wanes.