South San Francisco, California, United States, October 23, 2026
IDEAYA Biosciences has reported updated Phase 1 results for IDE849 (SHR-4849), an investigational DLL3-targeting antibody-drug conjugate (ADC), showing encouraging antitumour activity and preliminary survival outcomes in patients with relapsed small cell lung cancer (SCLC) and other neuroendocrine carcinomas (NECs). The findings, presented by development partner Jiangsu Hengrui Pharmaceuticals at the ESMO Congress 2026, include updated response rates, progression-free survival and preliminary overall survival data.
Phase 1 Results Show Antitumour Activity in Relapsed SCLC
In patients receiving IDE849 at doses of at least 1.8 mg/kg every three weeks, the study reported an overall response rate (ORR) of 72.5% among 51 patients treated in the second-line SCLC setting. The confirmed response rate was 60.8%, and median progression-free survival (PFS) was 6.9 months. Median overall survival (OS) reached 17.4 months in this group, although the survival findings remain preliminary. Across 101 previously treated SCLC patients included in the efficacy analysis, the ORR was 68.3%, the confirmed response rate was 54.5%, and median PFS was 6.8 months. Median OS was 14.7 months. Among 26 patients with brain metastases, the reported ORR was 76.9%, including a confirmed response rate of 65.4%. These figures represent overall tumour responses in that subgroup, not a separately measured intracranial response rate. The updated analysis included 122 patients across the study’s dose levels, with a median follow-up of 12.1 months. Compared with earlier findings presented in 2025, the new update provides longer follow-up and the first reported preliminary overall survival results. However, these are findings from an early-stage, single-arm study and do not establish superiority over existing treatments.
Investigational ADC Targets DLL3-Expressing Tumours
IDE849 is designed to target delta-like ligand 3 (DLL3), a protein expressed in small cell lung cancer and certain other neuroendocrine carcinomas. The antibody-drug conjugate combines a humanised antibody directed against DLL3 with a topoisomerase I (TOP1) inhibitor payload. This design aims to deliver a cancer-killing agent to tumour cells expressing the target. The study also evaluated IDE849 in other neuroendocrine carcinomas. Among 19 patients in this group, the ORR was 52.6%, the confirmed response rate was 36.8%, and median PFS was seven months. The nine-month overall survival rate was 82.4%. These preliminary findings support further research into the treatment’s potential beyond SCLC, but the small patient population limits interpretation.
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Safety Monitoring and Phase 3 Development Plans
At the 2.4 mg/kg expansion dose, Grade 3 or higher treatment-related adverse events occurred in 33.3% of patients. Common treatment-related events included decreases in neutrophil and white blood cell counts and anaemia. Across all 122 patients and dose levels, treatment-related adverse events led to treatment discontinuation in 2.5% of patients, and one treatment-related death due to pneumonia was reported. Continued evaluation will be necessary to better characterise the therapy’s safety profile. IDEAYA is developing IDE849 globally in partnership with Hengrui, which is conducting the Phase 1 study in China. Following discussions with the U.S. Food and Drug Administration, IDEAYA is targeting Phase 3 registrational trials in extensive-stage SCLC and neuroendocrine carcinomas. The company is also evaluating a potential first-line SCLC development strategy. IDE849 remains investigational and is not an approved treatment. Its efficacy and safety must be confirmed in further clinical studies before its potential role in cancer care can be determined. The ESMO 2026 update adds encouraging early evidence, while larger controlled trials will be needed to establish whether these findings translate into meaningful clinical benefits for patients.
Source: Gilead Sciences press release
