Key Findings
IDE849 demonstrated a median OS of 17.4 months in second-line (2L) SCLC (n=51) and 14.7 months in a combined cohort of 2L and ≥3L SCLC (n=101). In the 2L SCLC group, the overall response rate (ORR) was 72.5% (37/51) and the confirmed ORR (cORR) was 60.8% (31/51), with a median progression-free survival (PFS) of 6.9 months. For the combined 2L + ≥3L SCLC cohort (n=101), the ORR was 68.3% (69/101) and cORR was 54.5% (55/101), with a median PFS of 6.8 months.
Technical Details
IDE849 is an antibody-drug conjugate (ADC) targeting delta-like ligand 3 (DLL3) with a topoisomerase I (TOP1) inhibitor payload. In a subgroup of SCLC patients with brain metastases, the cORR was 65.4% (17/26), and disease control was observed in all 26 patients. For other NECs (n=19), the ORR was 52.6% (10/19), cORR was 36.8% (7/19), and median PFS was 7.0 months, with a nine-month OS rate of 82.4%.
Safety data indicated a Grade ≥3 treatment-related adverse event (TRAE) rate of 33.3% at the 2.4 mg/kg expansion dose. Across the total study population (n=122), the treatment-related discontinuation rate was 2.5% and the Grade ≥3 interstitial lung disease (ILD) rate was 0.8%.
Background and Context
The data, presented at the ESMO 2026 Congress by partner Jiangsu Hengrui Pharmaceuticals, expands on 2025 WCLC findings with longer follow-up (median 12.1 months) and a larger patient population. The study included 103 SCLC patients and 19 NEC patients receiving doses ≥1.8 mg/kg IV every 3 weeks. Notably, 78.6% of SCLC patients had received prior immunotherapy.
Significance and Outlook
Following Type C meetings with the U.S. FDA, IDEAYA is targeting the initiation of two Phase 3 registrational trials for IDE849 in extensive-stage SCLC (ES-SCLC) and NEC. The company is also evaluating a potential Phase 3 study design for first-line ES-SCLC. IDE849 targets high unmet needs in DLL3-expressing tumors, including gastroenteropancreatic (GEP-NEC) and large cell neuroendocrine carcinomas (LC-NEC).
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