THE PRESENT INVENTION RELATES TO NOVEL CYTOTOXIC AGENTS AND THEIR THERAPEUTIC USE. MORE SPECIFICALLY, THE INVENTION RELATES TO NOVEL CYTOTOXIC AGENTS COMPRISING TOMAYMYCIN DERIVATIVES AND THEIR THERAPEUTIC USE. THESE NOVEL CYTOTOXIC AGENTS HAVE THERAPEUTIC USE AS A RESULT OF DELIVERING THE TOMAYMYCIN DERIVATIVES TO A SPECIFIC CELL POPULATION IN A TARGETED FASHION BY CHEMICALLY LINKING THE TOMAYMYCIN DERIVATIVE TO A CELL BINDING AGENT. THE TOMAYMYCIN DERIVATIVES USEFUL IN THE PRESENT INVENTION HAVE THE FORMULA (I) SHOWN BELOW: