AB063. P-34. A multicenter, phase 1b/2 study of varlitinib plus gemcitabine and cisplatin (gem/cis) for treatment naïve advanced or metastatic biliary tract cancer (BTC)

Background: Biliary tract cancer (BTC) is a rapidly progressing cancer with limited response to chemotherapy. First line therapy (gem/cis) was defined in the ABC-02 study (Valle et al.), where a 26% response was seen. HER family receptors are overexpressed and may be involved in tumour proliferation and survival in BTC. Varlitinib, a reversible tyrosine kinase inhibitor of EGFR, HER2, and HER4, shows potent activity as monotherapy in preclinical BTC models and clinical activity in BTC patients (pts) in phase (Ph) 1 trials. We conducted a Ph1b/2 study of varlitinib plus gem/cis in BTC to understand the safety profile and determine the maximum tolerated dose (MTD) of the combination. Methods: A modified 3+3+3 escalation design was used in Ph1b, with 2 varlitinib dose levels (200 and 300 mg BID) plus gem/cis on days 1 and 8 in a 3-week cycle. The primary objectives are to determine the MTD and to characterize the safety profile. Secondary objectives are to assess the preliminary efficacy and to evaluate the pharmacokinetics of varlitinib and any circulating metabolites. Results: As of 10 Sep 2018, 21 pts were enrolled (11 in 200 mg cohort and 10 in 300 mg cohort, with 9 and 4 evaluable for MTD, respectively). Dose limiting toxicities (DLTs) were observed in 3 pts (1 G3 unconjugated hyperbilirubinemia and 1 G3 ALT transaminitis/G4 AST transaminitis in 200 mg cohort; 1 G4 thrombocytopenia/G3 febrile neutropenia/G3 AST elevation in 300 mg cohort). In 19 pts who were on varlitinib ≥1 month, 7 had partial response and 10 achieved stable disease (all >12 weeks), giving the overall response rate of 37% and the disease control rate of 89%. The median PFS for the 200 mg cohort was 248 days and was not reached for the 300 mg cohort. The most common (≥30%) all-grade adverse events (AEs) regardless of causality were thrombocytopenia (62%), neutropenia (52%), anorexia (38%), nausea (38%), diarrhoea (38%), and anaemia (33%); the most common (≥15%) grade ≥3 AEs were neutropenia (48%), thrombocytopenia (33%), and anaemia (19%). Conclusions: Varlitinib plus gem/cis was well tolerated in the 200 mg cohort; the 300 mg cohort is ongoing. Preliminary anti-tumour activity was observed. Data will be updated at the time of presentation.