Pretransplant Conditioning in Adults and Children: Dose Assurance With Intravenous Busulfan

PEG 400 Ion Suppression in Busulfan Detection by High-Performance Liquid Chromatography-Tandem Mass Spectrometry

BACKGROUND

Busulfan (Bu), an alkylating agent commonly used in chemotherapy and transplantation, exhibits high intraindividual pharmacokinetic variability and possible time-dependent variations in clearance, which complicate therapeutic drug monitoring. Numerous analytical methods have been developed to reduce analysis time and facilitate timely decision-making regarding treatment changes; however, the validation procedures rarely involve analysis of potentially interfering excipients. Macrogol 400 (PEG 400) should be considered as a possible interfering agent in the detection of plasma Bu levels, especially as an ionization suppressor.

METHODS

Six intravenous formulations of Bu were compared with identify at least 1 common excipient (PEG 400). During the 176 therapeutic drug monitoring analyses of Bu, one of the PEG 400 specific mass-to-charge ratio transitions was determined using an instrumental method. After coelution with Bu and its internal standard (Bu-d8) was confirmed, all analyses were repeated using a different experimental setup free of ion suppression induced by PEG. The concentration-time profile of PEG 400 was also analyzed.

RESULTS

The area under the curve obtained from the 2 data sets was compared and analyzed using Lin concordance correlation coefficient and Bland-Altman plot analysis. The results from the 2 analytical methods were comparable: PEG 400 negatively affected the Bu-d8 coefficient of variation but not the Bu/Bu-d8 ratio.

CONCLUSIONS

The possible interference of PEG 400 should be thoroughly investigated, especially with respect to analytical methods that cannot be supported by correction of the stable isotopically labeled internal standard analog.

Saliva as a noninvasive sampling matrix for therapeutic drug monitoring of intravenous busulfan in Chinese patients undergoing hematopoietic stem cell transplantation: A prospective population pharmacokinetic and simulation study

Therapeutic drug monitoring (TDM) of busulfan (BU) is currently performed by plasma sampling in patients undergoing hematopoietic stem cell transplantation (HSCT). Saliva samples are considered a noninvasive TDM matrix. Currently, no salivary population pharmacokinetics (PopPKs) model for BU available. This study aimed to develop a PopPK model that can describe the relationship between plasma and saliva kinetics in patients receiving intravenous BU. The performance of the model in predicting the area under the concentration-time curve at steady state (AUCss ) based on saliva samples is evaluated. Sixty-six patients with HSCT were recruited and administered 0.8 mg/kg BU intravenously. A PopPK model for saliva and plasma was developed using the nonlinear mixed effects model. Bayesian maximum a posteriori (MAP) optimization was used to estimate the model's predictive performance. Plasma and saliva PKs were adequately described with a one-compartment model and a scaled central compartment. Body surface area correlated positively with both clearance and apparent volume of distribution (Vd), whereas alkaline phosphatase correlated negatively with Vd. Simulations demonstrated that the percentage root mean squared prediction error and lower and upper limits of agreements reduced to 10.02% and -16.96% to 22.86% based on five saliva samples. Saliva can be used as an alternative matrix to plasma in TDM of BU. The AUCss can be predicted from saliva concentration by Bayesian MAP optimization, which can be used to design personalized dosing for BU.

Impact of valproic acid on busulfan pharmacokinetics: In vitro assessment of potential drug-drug interaction

Busulfan (Bu) is an alkylating agent commonly used at high doses in the preparative regimens of hematopoietic stem cell transplantation (HSCT). It has been shown that such high doses of Bu are associated with generalized seizures which are usually managed by prophylactic antiepileptic drugs (AEDs) such as valproic acid (VPA). Being a strong enzyme inhibitor, VPA may inhibit Bu metabolism and thus increase its potential toxicity. Despite its clinical relevance, the potential interaction between Bu and VPA has not yet been evaluated. The aim of the present study was to assess and evaluate the potential drug-drug interaction (DDI) between Bu and VPA. This study was carried out by incubating Bu in laboratory-prepared rat liver-subcellular fractions including S9, microsomes, and cytosol, alone or in combination with VPA. The liver fractions were prepared by differential centrifugation of the liver homogenate. Analysis of Bu was employed using a fully validated LC-MS/MS method. The validation parameters were within the proposed limits of the international standards guidelines. Bu metabolic stability was assessed by incubating Bu at a concentration of 8 μg/ml in liver fractions at 37°C. There were significant reductions in Bu levels in S9 and cytosolic fractions, whereas these levels were not significantly (P ˃ 0.05) changed in microsomes. However, in presence of VPA, Bu levels in S9 fraction remained unchanged. These results indicated, for the first time, the potential metabolic interaction of Bu and VPA being in S9 only. This could be explained by inhibiting Bu cytosolic metabolism by the interaction with VPA either by sharing the same metabolic enzyme or the required co-factor. In conclusion, the present findings suggest, for the first time, a potential DDI between Bu and VPA in vitro using rat liver fractions. Further investigations are warranted in human-derived liver fractions to confirm such an interaction.

The Roles of Nurses in Hematopoietic Cell Transplantation for the Treatment of Leukemia in Older Adults

OBJECTIVE

To review and summarize nurses' roles in the care of the older adult undergoing an allogeneic hematopoietic cell transplant (HCT) for the treatment of leukemia.

DATA SOURCES

Published literature indexed in PubMed, CINAHL, textbooks, and clinical expertise.

CONCLUSION

Nurses are a vital component of the highly specialized care delivered before, during, and after an allogeneic HCT.

IMPLICATIONS FOR NURSING PRACTICE

Nurses who are prepared for the complex HCT care trajectory will be able to optimally meet the complex needs of the older adult patient and their caregiver(s).

Intravenous busulfan: a guide to its use as conditioning treatment before transplantation of haematopoietic progenitor cells

With intravenous administration of busulfan (Busilvex®), the therapeutic range of the drug is achieved in more paediatric patients than after oral busulfan administration. In clinical trials in paediatric and adult patients, intravenous busulfan-based preconditioning treatment regimen prior to haematopoietic progenitor cell transplantation (HPCT) provided high rates of engraftment, low transplant-related mortality rates and good overall survival and progression-free survival outcomes. Intravenous busulfan was considered to have an acceptable tolerability profile.

Intravenous busulfan: a guide to its use as conditioning treatment before transplantation of haematopoietic progenitor cells

With intravenous administration of busulfan (Busilvex®), the therapeutic range of the drug is achieved in more paediatric patients than after oral busulfan administration. In clinical trials in paediatric and adult patients, intravenous busulfan-based preconditioning treatment regimen prior to haematopoietic progenitor cell transplantation (HPCT) provided high rates of engraftment, low transplant-related mortality rates and good overall survival and progression-free survival outcomes. Intravenous busulfan was considered to have an acceptable tolerability profile.

Busulfan in hematopoietic stem cell transplant setting

This paper focuses primarily on the data published in the last decade about the pharmacokinetics and pharmacodynamics of oral and intravenous (i.v.) busulfan, therapeutic drug monitoring and clinical outcome in hematopoietic stem cell transplant (HCT) patients. Busulfan is commonly used in HCT as it is toxic to the marrow. Busulfan is available as oral or i.v. formulation. The most common significant toxicity of busulfan is sinusoidal obstruction syndrome. Even with the introduction of i.v. busulfan, variability in the systemic concentrations of busulfan after weight-based dosing and the association between busulfan plasma exposure and outcome in HCT patients have led to the continued use of therapeutic drug monitoring of busulfan. New strategies for personalizing busulfan dosing are being studied to maximize the use of busulfan for optimal disease control with the least toxicity to HCT patients. One such strategy currently being evaluated is if busulfan clearance can be accurately predicted by genetic polymorphism of glutathione S-transferase (GST), with the currently available data suggesting that GST polymorphisms cannot be used to personalize busulfan dosing.

Acute complications of stem cell transplant

OBJECTIVES

To provide a comprehensive review of the acute complications that occur during the first 100 days post stem cell transplant (SCT).

DATA SOURCES

Research studies, book chapters, websites, and articles.

CONCLUSION

Even though the outcomes for SCT continue to improve, the complications seen in the first 100 days post transplant are a significant cause of mortality. Astute nursing assessment with resultant early intervention improves treatment-related mortality.

IMPLICATIONS FOR NURSING PRACTICE

Because SCT patients are seen in every oncology care setting, knowledge of these acute complications is essential to helping the nurse care for and educate SCT recipients.

Successful unmanipulated peripheral blood progenitor cell transplantation from an HLA haploidentical 2-locus-mismatched mother in a thalassemic patient with primary graft failure after transplantation of bone marrow and cord blood from unrelated donors

We report on a boy with beta-thalassemia major who developed early graft failure after double-unit unrelated cord blood transplantation, who subsequently received a myeloablative preconditioning regimen using non-T-cell-depleted PBSCT from his HLA-haploidentical 2-loci-mismatched mother. Neutrophil recovery with full donor chimerism was observed at post-transplantation day +11. Furthermore, GVHD was easy to control. The patient was transfusion-independent with complete donor chimerism eight months post-transplant. The result indicated that fetomaternal microchimerism may be an important attribute of a successful transplant. We suggested that a third allo-HSCT may be taken into consideration for patients with transfusion-dependent thalassemia who experience graft failure, even after two previous transplants.

Intravenous busulfan: in the conditioning treatment of pediatric patients prior to hematopoietic stem cell transplantation

An intravenous formulation of busulfan, a cytotoxic bifunctional alkylating agent, has been developed to replace oral busulfan as a conditioning treatment prior to hematopoietic stem cell transplantation (HSCT) in pediatric patients. Doses of intravenous busulfan based on actual bodyweight, but not age, reduce inter- and intraindividual variability in exposure. In a study of intravenous busulfan as a conditioning treatment prior to allogeneic or autologous HSCT, the majority of pediatric patients, who received one of five bodyweight-based doses, achieved busulfan area under the plasma concentration-time curve (AUC) values within the targeted therapeutic range. Although mean busulfan clearance values were highly variable between bodyweight strata, exposure was not affected, with no significant differences between bodyweight groups in mean AUC values. The achievement of therapeutic AUC values with intravenous busulfan resulted in a high rate of sustained engraftment, low transplant-related mortality, and promising survival outcomes post-transplant. Intravenous busulfan was considered to be well tolerated, in the particular context of HSCT, and no failure of HSCT due to organ toxicity was reported. Nonhematologic adverse events commonly associated with busulfan conditioning regimens were frequent, but generally of mild to moderate severity. The intravenous busulfan regimen was frequently associated with elevated liver enzymes, but hepatic veno-occlusive disease (HVOD) was infrequent, of mild to moderate severity, and resolved within 10 days of diagnosis. Unlike oral busulfan, intravenous busulfan does not appear to be associated with severe HVOD or death due to organ toxicity.

Reduced expression of Rho guanine nucleotide dissociation inhibitor-α modulates the cytotoxic effect of busulfan in HEK293 cells

High-dose busulfan is an important component in many conditioning protocols for hematopoietic stem cell or bone marrow transplantation. Treatment with busulfan results in the inhibition of cell cycle progression and apoptosis of tumor cells. As Rho GTPases are involved in cell cycle regulation, we investigated the influence of modified Rho guanine nucleotide dissociation inhibitor-alpha (GDI), a physiological inhibitor of Rho GTPases, on busulfan activity in cancer cells. RhoGDIalpha has been shown to be overexpressed in multiple types of tumors such as ovarian and breast cancer. To investigate the role of RhoGDIalpha, we established a RhoGDIalpha knockdown by the transient transfection of HEK293 cells with specific small interfering RNA resulting in strongly reduced RhoGDIalpha mRNA and protein expression. Other members of the RhoGDI family such as RhoGDIbeta and RhoGDIgamma were not affected. In RhoGDIalpha knockdown cells, cell cycle regulation was not altered by the downregulation of RhoGDIalpha; however, the rate of apoptotic cells increased when compared with the control small interfering RNA-transfected cells. In addition, treatment of cells with busulfan resulted in a further increased apoptotic rate, as determined by fluorescence-activated cell sorter analysis and caspase-3 activation. Such a sensitization of RhoGDIalpha small interfering RNA transfected cells was also found upon treatment with doxorubicin and taxol. In summary, we could demonstrate that the expression of RhoGDIalpha influences the sensitivity of cells toward busulfan-induced cytotoxicity.