Key Clinical Summary:

• Design/Population: In this non-randomized, phase 2 study 77 treatment-naïve patients with extensive-stage small cell lung cancer received izalontamab brengitecan plus serplulimab with or without anlotinib. 
• Key Outcomes: Izalontamab brengitecan plus serplulimab demonstrates high response rates and encouraging survival signals in first-line ES-SCLC with manageable toxicity. 
• Clinical Relevance: These results support further evaluation as a novel chemo-free immunotherapy–ADC combination in this high-need setting.

According to results from the phase 2 BL-B01D1-204-01 study, izalontamab brengitecan, a first-in-class EGFR×HER3 bispecific antibody-drug conjugate, plus serplulimab, an anti–PD-1 antibody, demonstrated encouraging efficacy with manageable safety among treatment-naïve patients with extensive-stage small cell lung cancer (ES-SCLC). 

These results were presented at the 2026 European Lung Cancer Congress in Copenhagen, Denmark, by Fei Zhou, MD, PhD, Tongji University School of Medicine, Shanghai, China.

In this non-randomized study, 77 patients received either 2.5 mg/kg (n = 40) or 2.75 mg/kg (n = 37) of izalontamab brengitecan (administered on days 1 and 8 of each 3-week cycle) plus serplulimab, with or without anlotinib. Primary end points included objective response rate (ORR), disease control rate, duration of response, progression-free survival (PFS), and overall survival (OS) in intention-to-treat population and in both treatment arms. A key secondary end point was safety. 

At a median follow up was 10.5 months, the ORR was 88.3% with a confirmed ORR of 77.9% in the intenton-to-treat population. Disease control rate was 94.8% and median duration of response was 7.3 months. Median PFS was 8.2 months, and the 12-month OS rate was 80.8%. In the 2.5 mg/kg arm, the ORR was 85% with a confirmed ORR of 77.5%. Disease control rate was 92.5% and median duration of response was 7.3 months. Median PFS was 8.2 months, and 12-month OS rate was 85.7%. In the 2.75 mg/kg arm, the ORR was 91.9% with a confirmed ORR of 78.4%. Disease control rate was 97.3% and median duration of response was 8 months. Median PFS was 8.3 months, and the 12-month OS rate was 76.5%. 

The most frequently reported all-grade hematologic treatment-related adverse events included anemia (93.9%), thrombocytopenia (72%), leukopenia (67.1%), and neutropenia (62.2%). The most frequently reported non-hematologic adverse event was decreased appetite (54.9%). Grade ≥3 treatment-related adverse events were primarily hematologic and manageable, with a discontinuation rate of 7.3%. There were 2 deaths possibly related to treatment. No new safety signals were identified.

“[Izalontamab brengitecan] in combination with serplulimab demonstrated encouraging efficacy with a manageable safety profile in treatment-naïve ES-SCLC,” concluded Dr Zhou et al. The “2.5 mg/kg D1D8 Q3W was selected for combination with a PD-1 inhibitor in China.” 

Source:

Zhou F, Gao Y, Zhou J, et al. Phase II study of iza-bren (BL-B01D1) in combination with serplulimab in patients with small cell lung cancer (SCLC). Presented at European Lung Cancer Congress. March 25 - 28, 2026. Copenhagen, Denmark. 4080.