Phase I study of oral S-1 in combination with oxaliplatin (oxali) and bevacizumab (bev) in patients with advanced solid tumors

Abstract

4091 Background: S-1 is a novel oral fluoropyrimidine (tegafur, CDHP and potassium oxonate) designed for enhanced DPD inhibition and reduced GI toxicity. Bev and oxali have demonstrated safety and synergistic anti-tumor activity with oral and IV fluoropyrimidines. The primary objective is to investigate the safety and maximum tolerated dose (MTD) of S-1 combined with bevacizumab and oxaliplatin in patients with advanced solid tumors. Secondary objective is to investigate the clinical pharmacokinetics (PK) of the components of S-1 (FT, CDHP, Oxo), 5-FU, a-fluoro-β-alanine, cyanuric acid, uracil, and oxali and to document any antitumor activity. Methods: ECOG 0/1 patients with advanced or metastatic solid tumors received oral S-1 starting at 20 mg/m2/dose BID x 14 days (classic 3+3 cohort dose escalation by 5mg/m2/dose until MTD), plus fixed doses of bev 7.5 mg/kg IV day 1, and Oxali 130 mg/m2 IV day 1 of every 3 week cycle, with discontinuation of oxali after 4 cycles. Reintroduction of oxali was allowed upon progression of disease. Toxicity, antitumor activity and PKs were assessed. The MTD was defined as the highest dose level at which < 33% of the patients experience a dose- limiting toxicity (DLT) during the first 2 cycles. Results: Of 22 evaluable patients, 3 patients were treated at 20mg/m2 S1 and 13 patients were treated at 25mg/m2 S1 without a DLT. At 30mg/m2, two patients experienced a DLT(Grade 3 diarrhea, Grade 4 mucositis). The MTD and recommended phase II dose of S-1 is 25mg/m2 in combination with oxali and bev. A median of 8 cycles of S-1 were initiated at the 25 mg/m2 dose level. Common MTD level toxicities included fatigue (62%), nausea (62%) and diarrhea (46%), with no grade 4 toxicities observed. Best responses (RECIST): stable disease(16 patients), partial response (2 patients), non-measurable disease (3 patients). The Day 8 AUC(0–8) of 5-FU at 20/25/30 mg/m2 dose level were 230±115 hr*ng/ml, 470±172 hr*ng/ml and 502±169 hr*ng/ml, respectively. Conclusions: The MTD combination of 25mg/m2 S-1, oxali and bev can be given safely. The study will be expanded to test S-1 one week on, one week off schedule in combination with oxali/bev every two weeks. No significant financial relationships to disclose.