Attaching a biotin tail to a cancer drug makes it possible to see very specifically which proteins the drug targets in lysed cancer cells, as a Dutch team shows in ChemBioChem.

Olaparib is a commonly used drug for breast and ovarian cancer. It is known to inhibit the PARP1 and PARP2 enzymes, but any off-target activity could cause unwanted side effects. To get a complete picture of what else the drug binds to in the cell, researchers from Leiden University, the NKI and Radboud University decided to give the drug a ‘biotin tail’ that can be pulled out later when the drug has bound to other proteins or enzymes.