Wikipedia
Pyrrolobenzodiazepines or PBDs, a class of natural products with antibiotic or anti-tumor properties, are produced by various actinomycetes (a broad group of bacteria that form thread-like filaments in the soil and are responsible for the distinctive scent of freshly exposed, moist soil), are sequence selective DNA alkylating compounds with significant antitumor properties. As a class of DNA-crosslinking agents they are significantly more potent than systemic chemotherapeutic drugs. Some PBDs have the ability to recognize and bond to specific sequences of DNA.
As DNA minor groove binding agents, pyrrolobenzodiazepines bind and cross-link specific sites of DNA of the cancer cell. This blocks the cancer cells’ division without distorting its DNA helix, thus potentially avoiding the common phenomenon of emergent drug resistance.