Low clinical activity was previously demonstrated when targeting TS in ovarian cancer with the polyglutamatable TS inhibitor raltitrexed (RTX) demonstrating 7 and 11% response rates (Gore et al, 1995; Muggia et al, 1998), and 5-FU a 14% response rate (Look et al, 1995) in relapsed disease. Here, TYMS is linked to ovarian cancer.