Summary
A new targeted therapy produced a 94% response rate in ROS1-positive lung cancer, with strong results even against brain metastases.
ROS1-positive lung cancer is a rare form of non-small cell lung cancer caused by a specific gene rearrangement that fuels tumor growth. Because it’s driven by this one identifiable change, it can be targeted directly with drugs built to block it. New results presented at WCLC 2026 show one of these drugs working unusually well.
In a trial called ARROS-1, researchers tested a new targeted therapy, zidesamtinib, in patients newly diagnosed with advanced ROS1-positive lung cancer who had not yet received any ROS1-targeted treatment. The results: 94% of patients saw their tumors respond, and 15% had no detectable cancer remaining afterward.
The most striking part of the results involved the brain. ROS1-positive lung cancer often spreads there, and brain metastases are usually harder to treat than tumors elsewhere in the body. Among the 10 patients in the trial whose cancer had already reached the brain, every one saw those tumors shrink, and 70% saw them disappear completely. A year after starting treatment, 90% of patients had not seen their cancer get worse, and most of the responses researchers saw were still holding at that point.
Side effects were relatively manageable. The most common were swelling in the arms or legs, a rise in a muscle-related lab value called CPK, and constipation. Few patients needed to lower their dose or stop treatment altogether because of side effects.
This drug is not yet approved, and these results come from a single trial rather than a large-scale confirmatory study. But for a rare, often under-researched subtype of lung cancer, especially one prone to spreading to the brain, results this strong are a meaningful development to watch.
