Two Abstracts of SKB264/sac-TMT (TROP2 ADC) published at 2024 ASCO Annual Meeting

ASCO 2024| Two Abstracts of the Study Results of Kelun-Biotech’s TROP2-ADC SKB264/sac-TMT Published Today: Phase 3 OptiTROP-Breast01 study & Phase 2 OptiTROP-Lung01 study

(May 24th, Chengdu and New Jersey) - At the 2024 American Society of Clinical Oncology (ASCO) Annual Meeting to be held in Chicago, Illinois from May 31 to June 4, 2024, Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. (the “Company”) will present the latest results from two clinical studies.

1. The Phase 3 OptiTROP-Breast01 study of its anti-TROP2 ADC sacituzumab tirumotecan (sac-TMT) (formerly SKB264/MK-2870) in patients with previously treated locally recurrent or metastatic triple-negative breast cancer (TNBC).
-Session: Special clinical science symposium (Abstract #104; Next-Generation Antibody–Drug
Conjugates: The Revolution Continues),
-Time: June 2, 2024, 9:45 AM to 11:15 AM local time

2. The Phase 2 OptiTROP-Lung01 study of sac-TMT in combination with KL-A167 (an anti-PD-L1 mAb) as 1L treatment for patients with advanced non-small cell lung cancer (NSCLC)
-Session: oral (Abstract #8502; Lung Cancer—Non-Small Cell Metastatic Oral)
-Time: May 31, 2024, 2:45 PM to 5:45 PM local time

Sac-TMT is being jointly developed by Kelun-Biotech and MSD (the tradename of Merck & Co., Inc., Rahway, NJ, USA) in multiple ongoing clinical trials.

The abstracts for the above studies were published on ASCO’s official website on May 23, 2024, local time. The study results are summarized as follows:

TNBC

Patients were randomly assigned (1:1) to receive sac-TMT (n = 130) or chemotherapy (n = 133). The median age was 51 years; 87% had visceral metastases; 26% received prior PD-1/PD-L1 inhibitors; 48% received three or more prior lines of chemotherapy for advanced disease. The primary endpoint of progression free survival (PFS) was met based on interim analysis (data cut-off: Jun 21, 2023) with a 69% reduction in risk of progression or death (HR 0.31; 95% CI, 0.22 to 0.45; P <0.00001).

The median PFS, as assessed by BICR, was 5.7 months (95% CI, 4.3 to 7.2) with sac-TMT and 2.3 months (95% CI, 1.6 to 2.7) with chemotherapy; PFS rate at 6 months was 43.4% vs 11.1%. In the subset of patients with trophoblast cell-surface antigen 2 (TROP2) H-score > 200, the median PFS was 5.8 months with sac-TMT and 1.9 months with chemotherapy (HR 0.28; 95% CI, 0.17 to 0.48). At the first planned interim analysis for overall survival (OS) (data cut-off: Nov 30, 2023) with median follow-up of 10.4 months, OS was statistically significant in favor of sac-TMT (HR 0.53; 95% CI, 0.36 to 0.78; P =0.0005); the median OS was not reached (95% CI, 11.2 to NE) with sac-TMT and 9.4 months (95% CI, 8.5 to 11.7) with chemotherapy. The objective response rate (ORR) assessed by BICR was 43.8% with sac-TMT and 12.8% with chemotherapy.

Most common grade ≥ 3 treatment-related adverse events (TRAEs) (sac-TMT vs. chemotherapy) were neutrophil count decreased (32.3% vs. 47.0%), anemia (27.7% vs. 6.1%) and white blood cell count (WBC) decreased (25.4% vs. 36.4%).

A Phase 3 global study led by MSD of sac-TMT plus pembrolizumab versus treatment of physician's choice (TPC) in TNBC who received neoadjuvant therapy and did not achieve a pathological complete response (pCR) at surgery (NCT06393374) and a Phase 3 study led by the Company of sac-TMT in China for 1L treatment of unresectable locally advanced, recurrent or metastatic PD-L1 negative TNBC (NCT06279364) are also ongoing.


NSCLC

Patients with treatment-naïve advanced NSCLC without actionable genomic alterations were enrolled to receive sac-TMT 5 mg/kg Q3W plus KL-A167 1200 mg Q3W (cohort 1A) or sac-TMT 5 mg/kg Q2W plus KL-A167 900 mg Q2W (cohort 1B) in a non-randomized manner until disease progression or unacceptable toxicity. As of January 02, 2024, 40 and 63 patients have been enrolled in cohort 1A and 1B, respectively. Median ages were 63/63 years (cohort 1A/1B); 97.5%/85.7% had Eastern Cooperative Oncology Group (ECOG) Performance status (PS) of 1; 30.0%/33.3%, 32.5%/30.2% and 37.5%/36.5% of patients had programmed death ligand 1 (PD-L1) expression < 1%, 1%-49% and ≥ 50% of tumor cells by IHC 22C3 pharmDx assay, respectively.

After median follow-up of 14.0 months for cohort 1A, the ORR was 48.6% (18/37, 2 pending confirmation), disease control rate (DCR) was 94.6% and median PFS was 15.4 months (95% CI: 6.7, NE) with a 6-month PFS rate of 69.2%. After median follow-up of 6.9 months for cohort 1B, the ORR was 77.6% (45/58, 5 pending confirmation), DCR was 100% and median PFS was not reached with a 6-month PFS rate of 84.6%. Additional subgroup analysis of cohort 1B was also performed.

In cohorts 1A and 1B, the most common Grade ≥ 3 TRAEs were neutrophil count decreased (30.0%/30.2%), WBC decreased (5.0%/17.5%), anemia (5.0%/15.9%), rash (5.0%/6.3%) and drug eruption (7.5%/0%). Treatment-related adverse events leading to discontinuation of sac-TMT occurred in 1 patient of cohort 1B due to drug hypersensitivity, and there were no treatment-related deaths.

Two Phase 3 global studies led by MSD of sac-TMT in patients with 3L+ EGFR mutant NSCLC (NCT06074588), and 2L EGFR mutant NSCLC (NCT06305754) and a Phase 3 study led by the Company of sac-TMT in China in patients with 2L EGFR mutant NSCLC (NCT05870319) are ongoing. Additionally, three Phase 3 global studies led by MSD of sac-TMT plus pembrolizumab are ongoing: the first in patients with 1L Metastatic Squamous NSCLC (NCT06422143), the second in patients with metastatic NSCLC expressing PD-L1 ≥ 50% (NCT06170788), and the third in patients with resectable NSCLC not achieving a pathological complete response (NCT06312137).