Jideytro Delivered a 94% Response Rate in ROS1-TKI–Naïve NSCLC in ARROS-1

GSK presented updated first-line ARROS-1 results for Jideytro (zidesamtinib) at the 2026 World Conference on Lung Cancer in Seoul. In the efficacy-evaluable group of patients with advanced or metastatic ROS1-positive non-small cell lung cancer (NSCLC) who had not previously received a ROS1 tyrosine kinase inhibitor (TKI), 88 of 94 patients responded to treatment. The early efficacy and brain-metastasis results are notable, but the study’s single-arm design means it does not prove that Jideytro is better than other frontline ROS1 inhibitors. 723

What ARROS-1 found in ROS1-TKI–naïve patients

The analysis included 94 patients with measurable disease and sufficient follow-up from the global phase 1/2 ARROS-1 study. After a median follow-up of 15.2 months:

• Objective response rate (ORR): 94% (88 of 94 patients; 95% CI, 87%–98%)
• Complete response rate: 15% (14 of 94)
• Progression-free survival (PFS) at 12 months: 90%
• Patients still responding at 12 months: 86%
• Median duration of response and median PFS: not yet reached at the data cutoff 7

An objective response means a complete or partial reduction in tumor burden measured under the study’s response criteria. A 94% ORR is therefore an encouraging signal, while the unreached median PFS and duration of response mean longer follow-up is needed to define how long benefit lasts for the overall cohort.

Intracranial activity was a key result

Brain metastases are an important challenge in advanced ROS1-positive NSCLC. Among 10 response-evaluable patients with measurable baseline brain metastases, all 10 had an intracranial response to zidesamtinib. Seven patients, or 70%, achieved complete clearance of detectable brain tumors. At 12 months, 78% maintained an intracranial response. GSK also reported no central nervous system progression events among patients who did not have brain metastases at baseline. 7

These data suggest meaningful CNS activity, but the measurable-brain-metastasis subgroup was very small. The 100% intracranial response figure should be interpreted with its wide confidence interval and limited sample size in mind. 37

Safety profile and treatment changes

The most commonly reported treatment-related adverse events were peripheral edema, weight gain, increased creatine phosphokinase, dysgeusia and increased aspartate aminotransferase. GSK characterized most treatment-related events as low grade. 7

Across the reported safety population, treatment-related adverse events led to dose reductions in 11% of patients and discontinuation in 1%. 715

Low discontinuation and dose-reduction rates can be clinically relevant for a targeted therapy intended for continued use, although a full assessment of tolerability depends on longer follow-up and detailed peer-reviewed safety reporting.

How does the 94% response rate compare with existing therapies?

The reported 94% ORR is numerically above historical response rates often cited for established first-line ROS1-targeted medicines, including crizotinib and entrectinib. But comparisons across separate trials are not reliable measures of relative efficacy: patient populations, baseline brain-metastasis status, follow-up time, imaging review and study methods may differ.

ARROS-1 was a non-randomized, single-arm phase 1/2 study with no placebo or active-drug comparator. It therefore supports further regulatory and clinical evaluation but does not establish that Jideytro is superior to any existing frontline ROS1 inhibitor. 23

Who was studied?

ARROS-1 is a global, single-arm phase 1/2 trial in advanced or metastatic ROS1-positive NSCLC. The TKI-naïve cohort permitted up to one prior line of chemotherapy and/or immunotherapy. In the analysis described by GSK, 27% of patients had received prior chemotherapy, including 17% who had received both chemotherapy and immunotherapy; 17% had CNS metastases at baseline. 7

ROS1-positive disease is uncommon: GSK describes ROS1 alterations as occurring in about 2% of NSCLC. That rarity makes rigorous molecular testing important when selecting targeted treatment options. 7

Current FDA status and the path to first-line use

The FDA approved Jideytro on July 22, 2026, for adults with locally advanced or metastatic ROS1-positive NSCLC who had received at least one prior ROS1 TKI. In the 117-patient previously treated efficacy population supporting that approval, the confirmed ORR was 44%; 82% of responders had a duration of response of at least six months and 69% had a duration of response of at least 12 months. 1

The approval followed FDA Breakthrough Therapy and Orphan Drug designations, according to GSK. 20

The WCLC dataset concerns a different potential use: treatment before a prior ROS1 TKI. GSK said it plans to submit a supplemental FDA application in 2026 seeking a first-line indication. Until a regulator authorizes that use, Jideytro is not FDA-approved as frontline therapy. 17

Bottom line

The ARROS-1 data give Jideytro a strong early first-line evidence package: a 94% response rate, 90% PFS at 12 months, and responses in all 10 evaluable patients with measurable baseline brain metastases. 7

The critical limitation is evidence maturity. These findings come from a selected 94-patient, single-arm analysis, not a randomized comparison with established ROS1 therapies. Longer follow-up and regulatory review will determine whether the promising response and CNS-activity signals translate into a new first-line treatment option.