Abstract 6180: First-in-human (FIH) phase I studies of SCB-313, a novel TNF-related apoptosis-inducing ligand TRAIL-Trimer™ fusion protein, for treatment of patients (pts) with malignant ascites (MA)

Abstract Background: SCB-313 is a recombinant human TRAIL-Trimer™ fusion protein engineered using a stabilized trimeric form of the TRAIL-protein. Binding of SCB-313 to the death receptors 4 and 5 leads to the activation of the extrinsic apoptosis pathway. Method: We performed a pooled analysis of two phase 1 studies conducted in Australia and China (NCT03443674 and NCT04051112, respectively). SCB-313 was given by intraperitoneal infusion 4 times at day D1, D4, D8, D11 in Australia study and D1, D8, D9, D10 in China study. Five dose cohorts: 10 mg, 20 mg, 40 mg, 80 mg, and 160 mg were evaluated using a sequential dose escalation design (accelerated titration dosing combined with 3+3 design) in pts with MA. The primary objective for both studies was safety and tolerability. Secondary objectives included PK/PD and efficacy. Results: 7 pts were enrolled in Australia (by data cutoff Mar 5th, 2021) and 12 pts in China (by data cutoff May 21st, 2021). 16 pts completed DLT observation period. Median age 57.6y, ECOG 1-2, 36.8% male. Colon cancer, n=5; ovarian cancer, n=4; breast cancer, n=3; gastric cancer, n=2; other cancers, n=5. Treatment-emergent adverse events (TEAE) were reported in 19 pts (100.0%). Most AEs were mild to moderate in severity (Grade 1 or 2). There were 9 (47.4%) pts who experienced Grade 3 AEs and no Grade 4 or 5 AEs were reported. No SCB-313 related SAEs or AEs leading to study discontinuations or death were reported. No DLT occurred. The most common TEAE included abdominal pain, pyrexia, abdominal distension. In Australia study, median (min, max) ascites flow rate of pts with MA (n=7) was 800 (400, 1091) ml/24h at baseline and 163.8 (-767, 412), 137.7 (-796.6, 392.6), -91.5 (-844.8, 517.5) and 120 (-47.92, 1105) ml/24h post first, second, third and the fourth SCB-313 administration respectively. In China study, the median flow rate at baseline (n=11) and post each subsequent SCB-313 dosing were respectively 723.1 (108.2, 1175), 12.1 (-335.1, 965.9), 84.2 (-442.5, 882), -13.9 (-404.4, 431.8) and -57.85 (-446.4, 2028) ml/24h. Estimated half-life of SCB-313 in peritoneal fluid after 1st injection is 3-4 hours (min, max: 1.85, 5.05). Cmax and AUC showed a nonlinear dose-dependent increase and near complete elimination from the peritoneal fluid by 24 hrs. In Australia study, apoptosis specific serum CK-18 concentrations increased following the first dose and remained above baseline for 5/7 pts. Conclusion: Although the MTD was not defined by these studies, SCB-313 therapy presents an acceptable safety profile at all tested dose levels. Measurable ascites flow rate decrease were observed at all dose- levels. These data support further development of SCB-313 for pts with MA. Citation Format: Ye Guo, Aflah Roohullah, Junli Xue, Wei Zhao, Morteza Aghmesheh, David Martin, Yu Zhou, Chao Gao, Yixuan Yang, Derek-Zhen Xu, Jin Li. First-in-human (FIH) phase I studies of SCB-313, a novel TNF-related apoptosis-inducing ligand TRAIL-Trimer™ fusion protein, for treatment of patients (pts) with malignant ascites (MA) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6180.