Sanofi Aventis and Taiho Pharmaceutical reported positive results from a phase III trial of S-1 for the treatment of gastric cancer, at the 43rd Annual Meeting of the American Society of Clinical Oncology. This randomized trial, dubbed SPIRTS, enrolled 305 subjects in Japan. Subjects were randomized to receive either oral S-1 (40 mg/m2) twice daily for 28 days followed by a 14-day rest period, or oral S-1(40 mg/m2) twice daily for 21 days plus IV cisplatin on the eighth day of treatment, followed by the 14-day rest period.

The primary endpoint was overall survival (OS). Secondary endpoints included Response Rate, Time to Treatment Failure (TTF) and toxicity. Results revealed overall survival with a two-year follow-up was significantly higher in the S-1/cisplatin combination arm compared to the S-1 alone arm, with a median rate of 13 months versus 11 months, respectively (p=0.036).

The overall response rate was also significantly higher in the combination arm, with 54% of subjects in the S-1/cisplatin arm showing response to treatment compared with 31.1% with S-1 alone, p=0.001). In addition, S-1 with cisplatin significantly reduced the risk of death by 22.6% (HR: 0.774; 95% CI [0.608-0.985]) over S-1 alone.

Several phase III trials of S-1 are underway in the United States.