Merestinib Monotherapy or in Combination for Japanese Patients with Advanced And/or Metastatic Cancer: A Phase 1 Study

This phase 1, multi-center, nonrandomized, open-label, dose-escalation study consisted of Part A wherein merestinib 80 or 120 mg (40-mg tablets) was administered orally QD during a 28-day cycle to patients diagnosed with solid tumors and Part B wherein merestinib 80 mg (40-mg tablets) was administered orally QD, and cisplatin 25 mg/m  + gemcitabine 1000 mg/m administered IV on Day 1 and Day 8 of a 21-day cycle (for a maximum of eight cycles) to patients diagnosed with biliary tract carcinoma (BTC). Nineteen patients were screened and 18 patients were (Part A, n = 10; Part B, n = 8) enrolled in the trial and received treatment. All patients in Parts A and B were from Japan and were within an age range of 43-73 years, with an ECOG PS of 0.1. No dose-limiting toxicity or deaths were experienced in the study. Dose-limiting toxicity equivalent toxicity of Grade 4 platelet count decreased (n = 1) and was observed in Part B. In Part A, treatment-related Grade ≥3 TEAEs were reported in one patient (PT: ALT increased and AST increased), while in Part B, five patients reported treatment-related Grade ≥3 TEAEs with four of the five patients reporting an event of neutrophil count decreased. No complete response was reported in either Part. One patient in Part B reported partial response while four patients in each part reported stable disease. Merestinib monotherapy was concluded to be tolerable in Japanese patients, and its combination with cisplatin and gemcitabine is a tolerable regimen for Japanese patients with BTC. Trial registration: NCT03027284 (ClinicalTrials.gov) registered on 23 January 2017.