Mertansine, also called DM1 (and in some of its forms emtansine), is a thiol-containing maytansinoid that for therapeutic purposes is attached to a monoclonal antibody through reaction of the thiol group with a linker structure to create an antibody-drug conjugate (ADC).

[citation needed] Mertansine is a tubulin inhibitor, meaning that it inhibits the assembly of microtubules by binding to tubulin (at the rhizoxin binding site).

[citation needed] The following (experimental) drugs are antibody-drug conjugates (ADC) combining monoclonal antibodies with mertansine as the cytotoxic component.

[3] ADCs include: DM1 can also be linked via a more complicated structure – 4-(3-mercapto-2,5-dioxo-1-pyrrolidinylmethyl)-cylohexanecarboxylic acid or SMCC –, in which case the International Nonproprietary Name of the conjugate formed contains the word emtansine.

The abbreviation comes from the chemical designation "succinimidyl-trans-4-(maleimidylmethyl) cyclohexane-1-carboxylate" which is used in the primary literature[6] as well as by the World Health Organization (WHO)[7] despite the fact that the linker contains only one imide group according to the WHO.