Otsuka reported that its subunit Daio has achieved a significant progression-free survival extension in treating advanced non-small cell lung cancer. The phase 3 trial showed hazard ratios of 0.50, highlighting the potential for a new treatment standard.
Daio Pharmaceutical Co., a wholly owned subsidiary of Otsuka, confirmed the primary endpoint of progression-free survival (PFS) in the phase 3 REZILIENT3 trial for patients with advanced or recurrent non-small cell lung cancer bearing EGFR exon 20 insertion mutations. These findings were presented as a presidential symposium at the IASLC 2026 World Conference on Lung Cancer in Seoul, South Korea.
The study randomized 279 previously untreated patients into two groups: those receiving the combination of ziborellitinib (100 mg twice daily) and platinum-based chemotherapy (n=140), and those receiving chemotherapy alone (n=139). Planned interim analysis revealed that the median PFS for the combination group was 14.5 months, significantly surpassing the 8.5 months observed in the monotherapy group by both statistical and clinical standards. The hazard ratio was calculated at 0.50 (95% confidence interval: 0.34-0.73, P=0.00015), indicating a substantial reduction in tumor progression or death risk.
The improvement in PFS remained consistent across all subgroups, including patients with brain metastases who had a hazard ratio of 0.38. Additionally, the objective response rate (ORR) was notably higher at 65.0% for the combination group compared to 40.3% for chemotherapy alone. The median duration of response extended from 9.9 months to 14.2 months. An interim analysis of overall survival (OS) with 30% data maturity showed a death hazard ratio of 0.72. Long-term follow-up is ongoing, making the final OS data the next critical point of interest.
Preliminary safety results indicated no new significant safety signals, aligning generally with the known profiles of existing drugs. The incidence of grade 3 or higher adverse events was 87.1% in the combination group versus 54.4% in the monotherapy group. Although slightly higher in the former, most events were manageable hematological toxicities.
Notably, EGFR-related toxicities such as rash and diarrhea were relatively limited even at grade 3 or higher levels. Rash incidence was kept low at 10.7%, and diarrhea at 1.4% in the combination group, suggesting the potential to maintain patient quality of life while achieving potent antitumor effects. Helena A. Yu, a trial investigator, emphasized that the results demonstrated both statistical significance and clinical meaningfulness in PFS extension, evaluating this combination therapy as a potential new option for first-line treatment of EGFR ex20ins mutation-positive NSCLC.
Fabio Benedetti, Global CMO of Daio Pharmaceutical, stated that the company is advancing consultations with regulatory authorities to achieve rapid availability and address unmet patient needs. Ziborellitinib (development code: CLN-081/TAS6417) is an irreversible EGFR inhibitor co-developed by Daio, its US subsidiary Daio Oncology, and Cullinan Therapeutics. While currently unapproved by any regulatory authority, the company positions this as a crucial milestone for long-term enterprise value growth.
Non-small cell lung cancer with EGFR exon 20 insertion mutations represents a high-need area, accounting for up to 4% of lung cancers (approximately 12% of EGFR-mutation-positive cases in the US). The 6.0 months PFS extension achieved in REZILIENT3 is exceptionally promising compared to existing treatments.
As a multicenter global phase 3 trial, the confirmation of efficacy across a broad patient population, including those with brain metastases, expands its potential applicability in real-world clinical settings. Daio Pharmaceutical and Daio Oncology are expected to accelerate preparations for regulatory approval applications based on these data, engaging with authorities in the United States and Japan.
The company maintains that there is no change to its consolidated financial forecasts for the fiscal year ending December 2026. However, ziborellitinib holds high strategic importance as a growth driver for the Otsuka Group. Future developments regarding OS data maturity and approval trends in various countries will be key determinants for stock prices and business expansion. Investors and medical professionals must closely monitor interactions with regulators and competitive dynamics against rivals such as Amgen's Amivantamab.
Analyst take
Focus on Potential Single IPO or Capital Alliance for Daio Oncology
This disclosure confirms Otsuka Group's decades of oncology drug development capabilities at a global level. The 6.0 months PFS extension is comparable to or superior to existing standards and other candidate drugs, significantly increasing the likelihood that Daio Oncology's enterprise value will be reassessed if licensing out targets emerge. Furthermore, establishing OS data could pave the way for approval, necessitating a focus on long-term business partnerships or capital integration (such as deepening ties with Cullinan or a potential public offering of Daio Oncology) beyond short-term stock fluctuations. Investors must carefully assess approval schedules and competitive clinical data.
