Abstract CT247: Updated Efficacy and Safety of Anti-Trop2 ADC SKB264 (MK-2870) for Previously Treated Advanced NSCLC in Phase 2 Study

Abstract Background: TROP2 (trophoblast cell surface antigen 2) is commonly over-expressed in non-small cell lung cancer (NSCLC) and associated with poor prognosis. SKB264 (MK-2870) is a TROP2 ADC developed with a novel linker to conjugate the payload, a belotecan-derivative topoisomerase I inhibitor. The linker is affected by both extracellular pH-sensitive cleavage and intracellular enzymatic cleavage within tumor cells, which leads to efficiently release payload inside tumor cells as well as within tumor microenvironment to exert its anti-tumor effects. Here, we present the updated data from a Phase 2 expansion cohort for patients (pts) with advanced NSCLC. Methods: Pts with previously treated advanced NSCLC were enrolled to receive SKB264 at 5 mg/kg Q2W until disease progression or unacceptable toxicity (KL264-01, NCT04152499). Tumor assessment was performed every 8 weeks per RECIST v1.1 assessed by investigator. Results: As of Nov 22, 2023, 43 NSCLC pts had been enrolled. Median follow-up was 17.2 months (mo). 21 pts with EGFR wild type had received median prior 3 regimens of therapy including anti-PD-1/L1 inhibitors. 22 pts with EGFR mutant had progressed on or after TKI therapy, 50% of whom also failed at least one line of chemotherapy. Updated efficacy results are shown in the Table. Overall, 30 pts (69.8%) experienced Grade ≥3 treatment-related adverse events (TRAEs). The most common Grade ≥3 TRAEs were neutrophil count decreased (34.9%), anemia (30.2%), WBC count decreased (25.6%), stomatitis (9.3%), and rash (7.0%). No TRAEs leading to treatment discontinuation or deaths occurred. No drug-related ILD/pneumonitis was reported. Conclusions: The updated data continues to demonstrate that SKB264 monotherapy delivers promising clinical efficacy with manageable toxicity in pretreated advanced NSCLC pts. A Phase 3 global study of SKB264 in pts with 3L+ EGFR mutant NSCLC (NCT06074588) and a Phase 3 study of SKB264 in China in pts with 2L EGFR mutant NSCLC (NCT05870319) are ongoing. TABLE 1: NAND Table Clinical outcomes by EGFR mutation status Overall (N=43) EGFR mutant (N=22) EGFR wild type Total (N=21) Non-squamous (N=9) Squamous (N=12) ORR*, % 43.6% 60.0% 26.3% 22.2% 30.0% Median DoR, mo (95%CI) 9.3 (3.7, 10.3) 8.7 (3.7, 10.3) 9.6 (3.5, NE) / / Median PFS, mo (95% CI) 7.2 (5.4, 11.3) 11.5 (5.7, 12.9) 5.3 (3.5, 6.2) 5.8 (1.5, 12.1) 5.1 (1.9, 9.3) Median OS, mo (95% CI) 22.6 (13.1, NE) 22.7 (19.7, NE) 14.1 (10.7, NE) 16.2 (5.8, NE) 12.8 (3.5, NE) 12-mo OS rate, % (95% CI) 69.0% (52.7, 80.7) 81.0% (56.9, 92.4) 57.1% (33.8, 74.9) 66.7% (28.2, 87.8) 50.0% (20.8, 73.6) 18-mo OS rate, % (95% CI) 56.5% (40.1, 70.0) 76.2% (51.9, 89.3) 35.9% (16.0, 56.4) 44.4% (13.6, 71.9) 30.0% (7.7, 56.9) *Including confirmed or unconfirmed response. Based on response evaluable pts (≥1 on-study scans) with 4 pts (2 EGFR mutant pts with non-squamous histology and 2 EGFR wild type pts with squamous histology) excluded. Citation Format: Wenfeng Fang, Ying Cheng, Zhendong Chen, Wei Wang, Yongsheng Li, Yongmei Yin, Xingya Li, Huiting Xu, Guohua Yu, Yanjun Mi, Zev A. Wainberg, Jordi Rodon, Xiang Wang, Xian Wang, Xiaoqing Zhang, Xiaoping Jin, Lian Lu, Junyou Ge, Jin Li, Li Zhang. Updated efficacy and safety of anti-TROP2 ADC SKB264 (MK-2870) for previously treated advanced NSCLC in Phase 2 study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT247.