A compound of formula I or a pharmaceutically acceptablesalt or ester thereof is provided for the treatment of cancerwherein (i) the cancer is one that has the characteristic of being a typeprone to being or becoming refractory or resistant to platinum drugbased therapy and (ii) the treatment is with a dose of between 1mg/m2and 30mg/m2 of compound per patient body surface area per administration.Method of treatment and novel dosage forms are also provided.Particularly treated are ovarian cancers, particularly those expressinga-folate receptors, including epithelial ovarian, fallopian tube orperitoneal cancer.
