Davis, S. Lindsey

Background and Aims: This study aimed to investigate safety and efficacy of silmitasertib, an oral small molecule casein kinase 2 inhibitor, plus gemcitabine and cisplatin (G+C) versus G+C in locally advanced/metastatic cholangiocarcinoma. Approach and Results: This work is a Phase 1b/2 study (S4‐13‐001). In Phase 2, patients received silmitasertib 1000 mg twice daily for 10 days with G+C on Days 1 and 8 of a 21‐day cycle. Primary efficacy endpoint was progression‐free survival (PFS) in the modified intent‐to‐treat population (defined as patients who completed at least one cycle of silmitasertib without dose interruption/reduction) from both phases (silmitasertib/G+C n = 55, G+C n = 29). The response was assessed by Response Evaluation Criteria in Solid Tumors v1.1. The median PFS was 11.2 months (95% confidence interval [CI], 7.6, 14.7) versus 5.8 months (95% CI, 3.1, not evaluable [NE]) ( p = 0.0496); 10‐month PFS was 56.1% (95% CI, 38.8%, 70.2%) versus 22.2% (95% CI, 1.8%, 56.7%); and median overall survival was 17.4 months (95% CI, 13.4, 25.7) versus 14.9 months (95% CI, 9.9, NE) with silmitasertib/G+C versus G+C. Overall response rate was 34.0% versus 30.8%; the disease control rate was 86.0% versus 88.5% with silmitasertib/G+C versus G+C. Almost all silmitasertib/G+C (99%) and G+C (93%) patients reported at least one treatment emergent adverse event (TEAE). The most common TEAEs (all grades) with silmitasertib/G+C versus G+C were diarrhea (70% versus 13%), nausea (59% vs. 30%), fatigue (47% vs. 47%), vomiting (39% vs. 7%), and anemia (39% vs. 30%). Twelve patients (10%) discontinued treatment because of TEAEs during the study. Conclusions: Silmitasertib/G+C demonstrated promising preliminary evidence of efficacy for the first‐line treatment of patients with locally advanced/metastatic cholangiocarcinoma.

312 Background: Silmitasertib (CX-4945), an oral small molecule inhibitor of casein kinase 2 (CK2), has exhibited preclinical antitumor activity and strong synergism with gemcitabine + cisplatin. We investigated the safety and efficacy of silmitasertib in combination with gemcitabine + cisplatin in patients with unresectable cholangiocarcinoma (CCA). Methods: S4-13-001 is a multicenter, open-label, phase Ib/II study of silmitasertib in combination with gemcitabine + cisplatin in patients with locally advanced or metastatic CCA. The phase Ib portion included dose-escalation, expansion, and exploratory cohorts of silmitasertib with doses ranging from 200 to 1000 mg bid (6 days for the escalation/expansion cohorts and 10 and 21 days’ continuous dosing for the exploratory cohorts). In the phase II portion patients received silmitasertib 1000 mg bid for 10 days in combination with gemcitabine + cisplatin on days 1 & 8 over a 21-day cycle. In this interim analysis, we present findings from the combined population of patients from the phase Ib and II portions of the study. Response to treatment was assessed by RECIST v1.1 every 6 weeks. Primary efficacy outcome measure was progression-free survival (PFS). ClinicalTrials.gov (NCT02128282). Results: A total of 87 patients were enrolled and received silmitasertib in the phase Ib (n=50) and phase II (n=37) portions of the study. Of these, 55 patients were evaluable for efficacy with details as follows: median PFS 11.1 (95% CI 7.6–14.7) months; median overall survival (OS) 17.4 (95% CI 13.4–25.7) months; overall response rate (ORR) 32.1%; and disease control rate (DCR) 79.3%. Almost all patients (79/87; 90.8%) evaluable for safety reported ≥1 treatment-related adverse event (TEAE). The most common TEAEs (all grades) with silmitasertib were diarrhea (65.5%), nausea (50.6%), vomiting (33.3%), fatigue (31.0%), and anemia (21.8%). The most common grade ≥3 TEAEs were diarrhea (13.8%), neutropenia (11.5%), nausea (9.2%), anemia (8.0%), and thrombocytopenia (8.0%). Eleven patients (12.6%) discontinued treatment due to TEAEs. Conclusions: Silmitasertib in combination with gemcitabine + cisplatin yields promising preliminary evidence of efficacy in patients with locally advanced or metastatic CCA. Based on these data a randomized phase III trial is planned. Clinical trial information: NCT02128282.