The study evaluated the investigational carcinoembryonic antigen (CEA)-related cell adhesion molecule 5 (CEACAM5)-targeting antibody-drug conjugate BG-C477 as monotherapy in patients with advanced non-small cell lung cancer (NSCLC) and elevated serum CEA who had exhausted standard treatment options.

This was the phase 1a dose-escalation portion of a global phase 1 study evaluating BG-C477 as monotherapy and in combination with anticancer agents for advanced solid tumors. Patients with advanced NSCLC and serum CEA ≥5 ng/mL received BG-C477 monotherapy in phase 1a dose escalation. Tumor CEA expression was assessed retrospectively by central laboratory immunohistochemistry. Key objectives were safety/tolerability, pharmacokinetics, and antitumor activity.

As of April 9, 2026, 43 patients with NSCLC were treated and had ≥2 post-baseline tumor assessments. Median (range) study follow-up was 4.2 months (0.1-11.6). 81.4% of patients had non-squamous NSCLC and 27.9% had EGFR mutations. Median prior lines of therapies for advanced disease were 3 (range, 1-8).

Grade ≥3 treatment-emergent adverse events occurred in 44.2% of patients and were predominantly hematologic, including anemia (14.0%), neutropenia (14.0%), and thrombocytopenia (2.3%). Two patients (4.7%) experienced treatment-emergent adverse events leading to treatment discontinuation. No treatment-related fatal treatment-emergent adverse events were reported.

Among 43 evaluable patients, confirmed ORR was 34.9% (95% CI, 21.0–50.9). In patients with CEA-high tumor expression (n=25), confirmed ORR was 56.0% (95% CI, 34.9–75.6), including 14 partial responses, compared with 5.6% (95% CI, 0.1–27.3) among patients with CEA-low expression, including 1 partial response. Disease control rates were 81.4% (95% CI, 66.6–91.6) overall , 88.0% (95% CI, 68.8–97.5) in the CEA-high subgroup, and 72.2% (46.5-90.3) in the CEA-low subgroup. Median duration of response was not reached in either the overall population or biomarker-defined subgroups.