Last reviewed 2026-04-20 · How we verify

Busulfex (busulfan)

Busulfex works by attaching an alkyl group to the DNA of cancer cells, interfering with their ability to replicate and ultimately leading to cell death.

Busulfex (busulfan) is a small molecule alkylating drug developed by ASPEN GLOBAL and currently owned by Waylis Therap. It targets matrix metalloproteinase-9 and has been FDA-approved since 1954 for various indications, including allogeneic bone marrow transplantation and malignant lymphoma. As an off-patent medication, it is available from multiple generic manufacturers. Key safety considerations include its potential for myelosuppression and hepatotoxicity. Busulfex is a well-established treatment option for patients with certain types of cancer.

At a glance

Mechanism of action

Busulfan is bifunctional alkylating agent in which two labile methanesulfonate groups are attached to opposite ends of four-carbon alkyl chain. In aqueous media, busulfan hydrolyzes to release the methanesulfonate groups. This produces reactive carbonium ions that can alkylate DNA. DNA damage is thought to be responsible for much of the cytotoxicity of busulfan.

Approved indications

• Allogeneic bone marrow transplantation
• Autologous hematopoietic stem-cell transplantation for Ewing's sarcoma family of tumors
• Malignant lymphoma
• Neuroblastoma
• Philadelphia Chromosome Positive Chronic Myelocytic Leukemia

Boxed warnings

• WARNING: MYELOSUPPRESSION Busulfan injection causes severe and prolonged myelosuppression at the recommended dosage. Hematopoietic progenitor cell transplantation is required to prevent potentially fatal complications of the prolonged myelosuppression [see Warnings and Precautions (5.1) ]. WARNING: MYELOSUPPRESSION See full prescribing information for complete boxed warning. Causes severe and prolonged myelosuppression. ( 5.1 ) Hematopoietic progenitor cell transplantation is required to prevent potentially fatal complications of the prolonged myelosuppression. ( 5.1 )

Common side effects

• Hyperuricemia
• Hepatic veno-occlusive disease
• Adrenal insufficiency
• Pneumonia
• Sepsis
• Mucositis
• Infection
• Fatigue
• Nausea
• Vomiting
• Weight loss
• Anorexia

Drug interactions

• metronidazole

Key clinical trials

• Pilot Trial of Allogeneic Blood or Marrow Transplantation for Primary Immunodeficiencies (PHASE2)
• Part B- G1X-CGD (Lentiviral Vector Transduced CD34+ Cells) in Patients With X-Linked Chronic Granulomatous Disease (PHASE1,PHASE2)
• Lentiviral Gene Transfer for Treatment of Children Older Than Two Years of Age With X-Linked Severe Combined Immunodeficiency (XSCID) (PHASE1,PHASE2)
• Venetoclax or Placebo in Combination With Reduced-Intensity Conditioning Hematopoietic Cell (Bone Marrow/Blood Stem Cell) Transplant and as Maintenance Therapy After Transplant in Patients With Acute Myeloid Leukemia (A MyeloMATCH Treatment Trial) (PHASE2)
• MYELOMATCH: A Screening Study to Assign People With Myeloid Cancer to a Treatment Study or Standard of Care Treatment Within myeloMATCH (MyeloMATCH Screening Trial) (PHASE2)
• Pilot Study of Reduced-Intensity Hematopoietic Stem Cell Transplant of DOCK8 Deficiency (PHASE2)
• Base Editing Hematopoietic Stem Cell and T Cell Gene Therapy for CD40L-HyperIgM Syndrome: Single Patient Study (PHASE1,PHASE2)
• Allogeneic Hematopoietic Stem Cell Transplantation for Chronic Granulomatous Disease (CGD) With an Alemtuzumab, Busulfan and TBI-based Conditioning Regimen Combined With Cytokine (IL-6, +/- IFN-gamma) Antagonists (PHASE1,PHASE2)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.