SKB264 (TROP2-ADC) for the treatment of patients with advanced NSCLC: Efficacy and safety data from a phase 2 study.

9114 Background: TROP2 (trophoblast cell surface antigen 2) is commonly overexpressed in non-small cell lung cancer (NSCLC) and associated with poor prognosis. SKB264 is a novel anti-TROP2 ADC developed using sulfonyl pyrimidine-CL2A-carbonate linker to conjugate its payload, a belotecan-derivative topoisomerase I inhibitor, to achieve an average Drug-to-antibody Ratio (DAR) of 7.4. The design was to achieve a more effective balance between stability in circulation and release of the ADC payload in tumor cells. Here we report clinical efficacy and safety results of SKB264 in the treatment of patients (pts) with NSCLC from a Phase 2 expansion cohort. TROP2 expression level by immunohistochemistry was assessed retrospectively. Correlation analyses between response and TROP2 level will be provided. Methods: This is a Phase 1/2, multicenter dose-escalation/expansion study in pts with relapsed or refractory locally advanced/metastatic NSCLC and other tumor types (NCT04152499). All NSCLC pts received SKB264 at 5 mg/kg IV Q2W. Tumor assessments based on RECIST 1.1 were performed every 8 weeks by investigators. Results: As of February 9 th , 2023, 43 pts (63% male, 88% ECOG PS 1, median age 58 yrs [44-74]) were enrolled. Median follow-up was 11.5 months (mo; 95% CI, 10.4-12.2). Median treatment duration was 5.7 mo (range, 0.5-14.1). Among 39 response-evaluable pts, the ORR was 44% (17/39, 15 confirmed and 2 pending confirmation), median DoR was 9.3 mo (range, 1.3+ to 11.2+), 6-month DoR rate was 77%. For EGFR wild type subgroup (previously received median 2 lines of therapy including anti-PD-1/L1), the ORR was 26% (5/19), DCR was 89% (17/19), median PFS was 5.3 mo, and 9-month OS rate was 80.4%. For subgroup with TKI resistant EGFR mutant NSCLC (50% also failed at least one line of chemotherapy), the ORR was 60% (12/20), DCR was 100% (20/20), median PFS was 11.1 mo, and 9-month PFS rate was 66.7%. 67.4% (29/43) of pts had Grade ≥ 3 treatment-related adverse events (TRAEs). The most common Grade ≥3 TRAEs (occurred in ≥5% of pts) were neutrophil count decreased (32.6%), anemia (30.2%), white blood cell count (WBC) decreased (23.3%), stomatitis (9.3%), rash (7.0%), and lymphocyte count decreased (7.0%). Grade 4 TRAEs occurred only for neutropenia and WBC decreased. Most of the hematology toxicity occurred within the first two months of treatment and resolved after treatment with granulocyte colony stimulating factor or erythropoietin without blood transfusions. 23.3% (10/43) of the pts experienced dose reduction due to TRAEs. No neuropathy or drug-related ILD/pneumonitis was reported. No TRAEs led to treatment discontinuation or death. Conclusions: SKB264 at 5 mg/kg Q2W demonstrated encouraging anti-tumor activity and manageable safety profile in pts with relapsed or refractory locally advanced/metastatic NSCLC. TRAEs were mainly hematologic. Phase 3 studies of SKB264 in pts with advanced NSCLC have been planned. Clinical trial information: NCT04152499 .