Shares of Amgen surged 4.4% to $410.35, capping a five-session streak that has added roughly $34 per share since September 15. The catalyst: a one-two punch of clinical and regulatory wins for the company's targeted lung cancer therapy, tarlatamab — developments that could meaningfully expand the drug's commercial ceiling in a disease that kills most patients within a year of diagnosis.
A First-Line Survival Win Opens a Far Bigger Patient Pool. On September 8, Amgen announced that its Phase 3 trial met its primary endpoint, showing a statistically significant improvement in overall survival when tarlatamab was combined with AstraZeneca's durvalumab versus durvalumab alone.
The study randomized 563 patients with extensive-stage small cell lung cancer whose tumors had not yet worsened after initial treatment. That distinction matters: AstraZeneca estimates roughly 195,000 people worldwide will be treated for this cancer in 2026 , and until now the drug was only approved for patients who had already failed chemotherapy — a much smaller group. Tarlatamab sales already hit $258 million in Q1 2026, up 219% year-over-year , and a first-line label expansion could push the drug toward consensus peak sales estimates of $2.8 billion by 2035.
Shorter Hospital Stays Remove a Real-World Adoption Barrier. On September 14, the FDA approved a label update slashing required monitoring time for the first two doses from 22–24 hours to just 6–8 hours. That is not a trivial paperwork change. An estimated 80–85% of U.S. cancer patients receive treatment in community oncology practices , many of which lack overnight observation capacity. Cutting the stay by roughly two-thirds makes tarlatamab practical for clinics that previously could not administer it, widening the prescribing funnel without spending a dime on sales reps.
The Fine Print: No Hard Numbers Yet. Amgen did not disclose specific hazard ratios, median survival figures, or percentage-point improvements — only that the trial was stopped early for benefit. The study started in mid-2024 with a primary completion date of July 2027, meaning efficacy was declared at roughly one-third of the planned timeline — and stopping early for benefit tends to overstate effect size. Until full data are presented at an upcoming medical congress, the magnitude of the survival gain remains an open question, leaving room for the stock to give back gains if the numbers underwhelm.
Bottom line: These developments position tarlatamab as potentially the most important oncology franchise Amgen has built in a decade — but investors are currently buying the headline, not the data.