On September 7, 2025 IDEAYA Biosciences, Inc. (Nasdaq: IDYA), a leading precision medicine oncology company, and Hengrui Pharma, a global pharmaceutical company focused on scientific and technological innovation, reported initial data from Hengrui’s Phase 1 clinical trial of IDE849 (SHR-4849), a potential first-in-class delta-like ligand 3 (DLL3)-targeting Topoisomerase-1 (TOP1) antibody drug conjugate (ADC), in an oral presentation today at the IASLC 2025 World Conference on Lung Cancer (WCLC) in Barcelona, Spain (Press release, Ideaya Biosciences, SEP 7, 2025, View Source [SID1234655803]). The presentation included data from a total of 100 patients who received IDE849 at doses between 0.8 mg/kg to 4.2 mg/kg with a once every 3-week dosing interval.

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"We believe the ORR, median PFS, and overall safety data presented at WCLC 2025 in over 70 efficacy evaluable SCLC patients provides a potential best-in-class DLL3 TOP1 ADC profile," said Yujiro S. Hata, President and Chief Executive Officer, IDEAYA Biosciences. "We look forward to advancing the global clinical development of IDE849 in SCLC, NETs, and additional DLL3 upregulated solid tumors, as both a potential first-in-class and best-in-class DLL3 TOP1 ADC to address areas of high unmet medical need in cancer."

Data in the presentation were as of a cut-off date of June 20, 2025, and included 87 patients with small-cell lung cancer (SCLC) and 13 patients with other neuroendocrine carcinomas (NEC). All patients had progressed after front-line therapy, with 33% having progressed after two prior lines and 15% after three or more prior lines of therapy. Of the 87 SCLC patients enrolled, 72.4% (63/87) had received prior immunotherapy. A total of 71 patients with refractory SCLC (2L+) were evaluated for initial efficacy at doses of 2.4 mg/kg (n=19), 3.0 mg/kg (n=18) and 3.5 mg/kg (n=31) in the expansion phase of the trial. Patients in the 4.2 mg/kg cohort (n=3) of the dose escalation phase were also included in the analysis. All efficacy-evaluable patients had received at least one post-baseline tumor assessment per RECIST v1.1.

Key data highlights from the presentation

Efficacy (n=71 evaluable SCLC patients treated with IDE849)

IDE849 Dose Level

2.4 mg/kg

Total (≥2.4 mg/kg)

Treatment setting
(# patients)

2L
(n=10)

All-lines
(n=19)

2L
(n=35)

All-lines
(n=71)

ORR (%, n)

80.0% (8/10)

73.7% (14/19)

77.1% (27/35)

73.2% (52/71)

Confirmed ORR (%, n)

70.0% (7/10)

57.9% (11/19)

60.0% (21/35)

47.9% (34/71)

Pending confirmation

—

5.3% (1/19)

11.4% (4/35)

14.1% (10/71)

DCR

100% (10/10)

94.7% (18/19)

97.1% (34/35)

93.0% (66/71)

Robust overall response rate (ORR) and disease control rate (DCR) were consistently observed across all expansion doses evaluated and in patients across all lines of therapy, with a modest reduction in ORR/DCR observed in later-line patients, consistent with their more advanced stage of disease.

14.1% (10/71) of patients across all doses >2.4 mg/kg are still pending confirmation, as well as multiple patients who have had limited follow-up (e.g. one post-baseline scan) highlighting the study has not yet achieved a fully mature confirmed ORR%.

In patients with baseline brain metastasis, a confirmed ORR of 83.3% (5/6) and a DCR of 100% (6/6) was observed at the 2.4 mg/kg dose. Across all doses ≥2.4 mg/kg (n=18) with baseline brain metastasis, the confirmed ORR was 66.7% (12/18) with a DCR of 100% (18/18). A confirmation scan for one unconfirmed partial response is pending, which if confirmed, would increase the confirmed ORR to 72.2% (13/18).

Median PFS was 6.7 months across all lines of treatment at doses of IDE849 ≥2.4 mg/kg (n=86); median PFS was not yet reached (NR) in 2L patients (n=42).

As of the cut-off date of June 20, 2025 the median length of follow-up was 3.5 months.
Safety (n=100 SCLC and NEC patients treated with IDE849)

Across all patients and all dose levels (n=100), Grade 3 or higher (Gr>3) treatment-related adverse events (TRAEs) occurred in 48% (48/100) and serious TRAEs in 16% (16/100) of patients. The most common TRAEs were white blood cell reduction (27% Gr>3), neutropenia (33% Gr>3), anemia (6% Gr>3) and nausea (0% Gr>3).

TRAEs leading to dose reduction in 15% (15/100) of patients; treatment-related discontinuation rate of 2% (2/100) with no treatment-related deaths reported.
IDEAYA will review the data that was presented by Hengrui at their 10-Year Anniversary R&D Day on September 8th in New York. A link to the oral presentation from WCLC will be available on the Investor Relations page of the IDEAYA corporate website: View Source

In December 2024, Hengrui Pharma granted IDEAYA an exclusive worldwide license to develop and commercialize SHR-4849 (IDE849) outside of Greater China. The partners will collaborate to accelerate global development of this innovative therapy for patients worldwide.