A novel drug interaction between busulfan and blinatumomab

Area of Science:

• Pharmacology
• Oncology
• Immunology

Background:

• Busulfan is a key alkylating agent for pre-transplant conditioning in hematopoietic stem cell transplantation (HSCT).
• Busulfan pharmacokinetics are influenced by factors like age, liver function, genetics, and drug interactions.
• Cytochrome P450 3A4 (CYP3A4) and glutathione conjugation are primary busulfan metabolic pathways.

Observation:

• A case study identified a significant drug interaction between intravenous busulfan and blinatumomab, a T-cell engager.
• Busulfan clearance decreased when administered 48 hours after blinatumomab, leading to higher drug exposure (AUC).

Findings:

• Therapeutic drug monitoring revealed reduced busulfan clearance and increased area under the concentration-time curve (AUC) post-blinatumomab administration.
• Subsequent pharmacokinetic testing showed increased busulfan clearance and a 31% higher dose recommendation.
• The interaction is hypothesized to stem from blinatumomab-induced cytokine elevations causing CYP3A4 suppression.

Implications:

• This interaction necessitates careful busulfan therapeutic drug monitoring and dose adjustments in HSCT patients receiving blinatumomab.
• The observed CYP3A4 suppression mechanism may impact other CYP3A4-metabolized drugs used in HSCT (e.g., calcineurin inhibitors, cyclophosphamide).
• This pharmacokinetic consideration is relevant in conditions with elevated cytokines, including haploidentical HSCT, graft-versus-host disease, and CAR T-cell therapy.