Benzodiazepine dimers having a structure represented bywherein R1 iswherein the variables in formulae (I), (Ia), and (Ib) are as defined in the application. Such dimers are useful as anti-cancer agents, especially when used in an antibody-drug conjugate (ADC).本發明提供苯二氮呯二聚物,其具有由以下表示之結構:其中R1為其中式(I)、(Ia)及(Ib)中之變數如本申請案中所定義。此類二聚物適用作抗癌劑,尤其當用於抗體-藥物結合物(ADC)中時。