A cytotoxic agent comprising one or more modified doxorubicinsdaunorubicin linked to a cell binding agent. A desired guardband can later be selected for validation. The dimensionless constant is indicative of the potential effectiveness of the material in a particular application, such as a micro-electromechanical system. A method of securing the cable to the connector to provide the required strain relief and not damage the metal cladding is disclosed. The process involves reacting N-3-3–1-oxo-2-propenylphenyl-N-ethylacetamide or a salt thereof with 3-amino-4-cyanopyrazole or a salt thereof under acidic conditions in a reaction medium comprising a mixture of water and a water-miscible organic compound.