Randomized, Double-Blind, Placebo-Controlled Phase III Study of Paclitaxel ± Napabucasin in Pretreated Advanced Gastric or Gastroesophageal Junction Adenocarcinoma

PURPOSE: To compare napabucasin (generator of reactive oxygen species) plus paclitaxel with paclitaxel only in patients with second-line advanced gastric or gastroesophageal junction (GEJ) adenocarcinoma. PATIENTS AND METHODS: In the double-blind, phase III BRIGHTER study (NCT02178956), patients were randomized (1:1) to napabucasin (480 mg orally twice daily) plus paclitaxel (80 mg/m(2) i.v. weekly for 3 of 4 weeks) or placebo plus paclitaxel. The primary endpoint was overall survival (OS). Secondary endpoints included progression-free survival (PFS), objective response rate (ORR), disease control rate (DCR), and safety. RESULTS: Overall, 714 patients were randomized (napabucasin plus paclitaxel, n = 357; placebo plus paclitaxel, n = 357). 72.1% were male, 74.6% had gastric adenocarcinoma, and 46.2% had peritoneal metastases. The study was unblinded following an interim analysis at 380 deaths. The final efficacy analysis was performed on 565 deaths (median follow-up, 6.8 months). No significant differences were observed between napabucasin plus paclitaxel and placebo plus paclitaxel for OS (6.93 vs. 7.36 months), PFS (3.55 vs. 3.68 months), ORR (16% vs. 18%), or DCR (55% vs. 58%). Grade ≥3 adverse events occurred in 69.5% and 59.7% of patients administered napabucasin plus paclitaxel and placebo plus paclitaxel, respectively, with grade ≥3 diarrhea reported in 16.2% and 1.4%, respectively. CONCLUSIONS: Adding napabucasin to paclitaxel did not improve survival in patients with pretreated advanced gastric or GEJ adenocarcinoma. Consistent with previous reports, the safety profile of napabucasin was driven by manageable gastrointestinal events; grade ≥3 diarrhea occurred at a higher frequency with napabucasin plus paclitaxel versus placebo plus paclitaxel.