What did GSK report at the 2026 World Conference on Lung Cancer in Seoul about Jideytro (zidesamtinib), its ROS1 inhibitor, in the phase 1/2 ARROS 1 trial for adults with advanced ROS1 positive non small cell lung cancer who had not previously received a ROS1 tyrosine kinase inhi

GSK reported that Jideytro (zidesamtinib) produced a 94% objective response rate in the evaluable, ROS1-TKI–naïve ARROS-1 cohort, with durable systemic and intracranial activity and comparatively few treatment-related dose changes. These are promising single-arm phase 1/2 results, but they are not a randomized head-to-head comparison with established frontline ROS1 inhibitors. 7

• Efficacy: Among 94 efficacy-evaluable patients with advanced/metastatic ROS1-positive NSCLC, 88 responded (94%; 95% CI, 87–98) and 14 (15%) had complete responses after median follow-up of 15.2 months. At 12 months, 90% were progression-free; median PFS and duration of response had not yet been reached. 7

• Brain metastases: All 10 patients with measurable baseline brain metastases had an intracranial response, seven (70%) had complete clearance of detectable brain tumors, and 78% retained intracranial response at 12 months. No CNS progression was reported among patients without baseline brain metastases. 7

• Safety/tolerability: The most common treatment-related adverse events were peripheral edema, weight gain, elevated creatine phosphokinase, dysgeusia, and elevated AST; most were low grade. Treatment-related adverse events caused dose reductions in 11% and discontinuation in 1% of patients. 7

• Context versus current first-line options: The 94% response rate is numerically higher than the approximately 68–79% response rates reported historically for frontline drugs such as crizotinib and entrectinib. However, cross-trial comparisons are inherently uncertain because ARROS-1 was a non-randomized, single-arm study with a relatively small efficacy population; it does not establish superiority. 2

• Study population: ARROS-1 is a global, single-arm phase 1/2 study. The frontline cohort allowed up to one prior chemotherapy and/or immunotherapy line: 27% had prior chemotherapy, including 17% who had also received immunotherapy; 17% had CNS metastases at baseline. The 94-patient efficacy analysis was selected from 183 patients receiving their first ROS1-targeted therapy, with measurable disease and sufficient follow-up. 7

• Disease scale: GSK describes ROS1 alterations as occurring in about 2% of NSCLC—consistent with the commonly cited roughly 1–2% range—and estimates about 50,000 new cases worldwide annually. 7

• Regulatory status: On July 22, 2026, FDA approved Jideytro for adults with locally advanced or metastatic ROS1-positive NSCLC previously treated with at least one ROS1 TKI. In the 117-patient previously treated efficacy population, confirmed ORR was 44%; it was 49% after one prior ROS1 TKI and 38% after two or more. FDA states that the product received orphan-drug designation. 1

• Designation caveat: I found authoritative confirmation of orphan-drug designation, but insufficient evidence in the FDA announcement to confirm a breakthrough-therapy designation. 1

• Next step: GSK said it plans to submit a supplemental FDA application in 2026 seeking a first-line indication; Jideytro is not currently approved anywhere as first-line therapy. 7

• Market reaction: GSK shares rose on the announcement day—one market report put the intraday gain at about 3.4%—but the move followed two positive GSK lung-cancer data releases, not Jideytro alone. Evidence is insufficient to attribute a broader healthcare-sector rise specifically to these ARROS-1 data. 5