BBI608-503-103HCC: A phase Ib/II clinical study of napabucasin (BBI608) in combination with sorafenib or amcasertib (BBI503) in combination with sorafenib (Sor) in adult patients with hepatocellular carcinoma (HCC).

4077 Background: Napabucasin, a first-in-class cancer stemness inhibitor in clinical development, suppresses cancer stemness by targeting STAT3-driven gene transcription. Amcasertib targets multiple serine threonine stemness kinases and inhibits Nanog and other cancer stemness pathways. Preclinically, potent and broad-spectrum anti-cancer activity was observed in vitro and in vivo, alone and in combination with sorafenib. Methods: A phase Ib/II open-label, multi-center study in adult patients with advanced HCC who have not received prior systemic chemotherapy was performed to determine the safety, tolerability, and recommended Phase II dose (RP2D) ,according to the criteria for DLT and for dose-escalation of Napabucasin (Arm 1), administered at 160 mg BID (dose level I) and at 240 mg BID (dose level II) in combination with sorafenib and of Amcasertib (Arm 2), administered at 100 mg QD (dose level I) and at 200 mg QD (dose level II) in combination with sorafenib. Results: 20 pts were enrolled, 10 in Arm 1 and 10 in Arm 2. 12 patients were evaluable for DLT determination; 2 pts d/c prior to starting protocol treatment; 11 pts received evaluation by RECIST, 6 pts in Arm 1 and 5 pts in Arm 2. The safety profile was consistent with that of each agent as monotherapy and most common AEs were attributed to (Sor) and included rash, PPE, grade 1/2 diarrhea, nausea, abdominal cramps, and vomiting. No signs of drug-drug interactions were observed in pharmacokinetics. Among all patients who received RECIST evaluation, Disease Control Rate (DCR=CR+PR+SD) for Arm 1 was 100% (6/6pts) and 100% (5/5pts) for Arm 2. DCR in ITT Arm 1 population was 67% and 50% in Arm 2. Median OS is not yet reached. Conclusions: In this phase Ib study, RP2D were determined for napabucasin and amcasertib to be safely combined with sorafenib at full dose, showing encouraging anti-tumor activity in patients with HCC who have not received prior systemic chemotherapy. A randomized phase II is schedule to start. Clinical trial information: NCD02279719. [Table: see text]