The present invention relates to a novel class of alkylating agents comprising a thieno-indole moiety linked to a DNA-binding moiety, which have cytotoxic activity and are useful in treating diseases such as cancer, cellular proliferation disorders and viral infections. The present invention also provides methods for preparing these compounds, pharmaceutical compositions comprising them and methods of treating diseases utilizing such compounds or the pharmaceutical composition containing them. The invention also relates to the use of this novel class of alkylating agents in the preparation of conjugates. The present invention also relates to methods of treating ovarian cancer by administration of compounds of formula (II):
