First-Line Treatment for EGFR Exon 20 Lung Cancer Clears Phase 3 Threshold: Zipalertinib Plus Chemotherapy Meets Endpoint

For patients with advanced lung cancer harboring EGFR exon 20 insertion mutations, a new competitor may be emerging in first-line targeted therapy. Taiho Oncology and Cullinan Therapeutics announced that zipalertinib combined with platinum-based chemotherapy met the primary endpoint of progression-free survival in a prespecified interim analysis of the phase 3 REZILIENT3 trial, providing key evidence to support pursuit of a U.S. first-line indication for the oral targeted therapy.

REZILIENT3, registration number NCT05973773, enrolled 285 participants. The randomized phase 3 portion focused on previously untreated patients with non-squamous non-small cell lung cancer harboring EGFR exon 20 insertion mutations. It compared zipalertinib plus pemetrexed and either carboplatin or cisplatin with a control group receiving the same chemotherapy without zipalertinib. The study used an open-label design, while the primary efficacy assessment was conducted by an independent central committee blinded to treatment assignment, according to RECIST 1.1 criteria.

The two companies said the combination treatment produced a statistically significant and clinically meaningful improvement in progression-free survival compared with chemotherapy alone. However, the hazard ratio, median progression-free survival, confidence intervals, and number of events in each group have not yet been disclosed. It is therefore not yet possible to determine the size of the difference or confirm whether the benefit extends evenly across different insertion mutation subtypes or patients with brain metastases.

Zipalertinib is an orally administered tyrosine kinase inhibitor that binds irreversibly to EGFR. The strategy in this study was not to replace chemotherapy entirely with a targeted therapy, but to combine the two from the start of treatment in an effort to harness both chemotherapy’s broad cytotoxic activity and mutation-directed inhibition. This also means that, if approved in the future, its clinical value will depend not only on how long it delays disease progression, but also on additional toxicity, treatment burden, and treatment interruptions.

The trial’s secondary endpoints include objective response rate, disease control rate, duration of response, overall survival, intracranial efficacy, safety, and quality of life. In an update posted on May 28, 2026, ClinicalTrials.gov listed the study as ongoing but no longer recruiting. This means that meeting the primary analysis endpoint does not indicate that all follow-up work has been completed; overall survival and longer-term safety data, in particular, may still affect the final risk-benefit assessment.

Taiho and Cullinan plan to use these results to advance an application for U.S. approval in first-line treatment. For now, the announcement primarily establishes that the trial crossed its prespecified efficacy threshold, but it is not yet sufficient to determine the regimen’s relative advantage or actual place in clinical practice. Once the full data are disclosed, the magnitude of the progression-free survival improvement, serious adverse events, treatment discontinuation rates, and overall survival trends will be central to regulators’ and physicians’ evaluation of the combination regimen.