Carmustine is a mustard gas-related β-chloro-nitrosourea compound used as an alkylating agent in chemotherapy. As a dialkylating agent, BCNU is able to form interstrand crosslinks in DNA, which prevents DNA replication and DNA transcription. It is used in the treatment of several types of brain cancer (including glioma, glioblastoma multiforme, medulloblastoma and astrocytoma), multiple myeloma and lymphoma. BCNU is sometimes used in conjunction with alkyl guanine transferase (AGT) inhibitors, such as O6-benzylguanine. The AGT-inhibitors increase the efficacy of BCNU by inhibiting the Direct Reversal pathway of DNA repair, which will prevent formation of the interstrand crosslink between the N1 of guanine and the N3 of cytosine. It is also used as part of chemotherapeutic protocol to prepare for hematological stem cell transplantation, to reduce the white blood cells in the recipient (patient).