Doxorubicin chemotherapy drug, molecular model. This drug, marketed as Doxil, is used in chemotherapy to treat a range of cancers. It binds to DNA, where it inhibits the enzyme that unravels the double helix prior to its transcription, or copying to RNA. This prevents the genetic code from being read and used to manufacture proteins. Doxorubicin also prevents the DNA from recoiling, so it cannot be copied. This halts the replication of cells and the growth of the tumour. In this model, atoms are represented by coloured spheres; carbon is blue, hydrogen is white, oxygen is green, and nitrogen is pink.