A multi-center phase II study of sequential paclitaxel and bryostatin-1 (NSC 339555) in patients with untreated, advanced gastric or gastroesophageal junction adenocarcinoma

Abstract

Protein Kinase C (PKC), involved in transmembrane signaling of cell surface receptors, promotes carcinogenesis and tumor progression. Bryostatin-1 competes with PKC for phorbol esters (tumor promoters), thus inhibiting tumor progression. Bryostatin-1 also increases cytotoxicity of paclitaxel in a sequential fashion. We studied sequential paclitaxel and bryostatin-1 in patients with untreated, advanced gastric adenocarcinoma. Patients with histologic proof of gastric or gastroesophageal junction adenocarcinoma with advanced, measurable cancers were eligible. Patients were required to have near normal organ function and ECOG performance status of 0 or 1. All patients gave an informed consent. Patients received paclitaxel 80 mg/m2 in 2 h intravenously on day 1 and bryostatin-1 40 mcg/m2 in 1 h intravenously on day 2 each week for 3 consecutive weeks out of 4. Primary objective was to assess the objective response rate. In a multi-center setting, 37 patients were enrolled and 35 were assessable for response. A confirmed partial response rate was 29%. The median time-to-progression was 4.25 months and the median survival time was 8 months. Grade 3 cumulative myalgias occurred in 55% of patients. Twelve patients discontinued therapy due to myalgias, including 6 patients who had not progressed after achieving a partial response. Other toxic effects were uncommon. Sequential paclitaxel plus bryostatin-1 resulted in a superior response rate than would be expected of paclitaxel alone in patients with untreated, advanced gastric or gastroesophageal junction adenocarcinoma. Further development of this combination is warranted once an effective method to ameliorate or prevent myalgias can be established.