Glutathione S-transferase A1 polymorphisms and acute graft-vs.-host disease in HLA-matched sibling allogeneic hematopoietic stem cell transplantation

Treosulfan Exposure Predicts Thalassemia-Free Survival in Patients with Beta Thalassemia Major Undergoing Allogeneic Hematopoietic Cell Transplantation

A toxicity-reduced conditioning regimen with treosulfan, fludarabine, and thiotepa in patients with high-risk β-thalassemia major has significantly improved hematopoietic stem cell transplantation (HCT) outcomes. However, complications resulting from regimen-related toxicities (RRTs), mixed chimerism, and graft rejection remain a challenge. We evaluated the dose-exposure-response relationship of treosulfan and its active metabolite S, S-EBDM, in a uniform cohort of patients with β-thalassemia major to identify whether therapeutic drug monitoring (TDM) and dose adjustment of treosulfan is feasible. Plasma treosulfan/S, S-EBDM levels were measured in 77 patients using a validated liquid chromatography with tandem mass spectrometry method, and the pharmacokinetic parameters were estimated using nlmixr2. The influence of treosulfan and S, S-EBDM exposure, and GSTA1/NQO1 polymorphisms on graft rejection, RRTs, chimerism status, and 1-year overall survival (OS), and thalassemia-free survival (TFS) were assessed. We observed that treosulfan exposure was lower in patients with graft rejection than those without (1,655 vs. 2,037 mg•h/L, P = 0.07). Pharmacodynamic modeling analysis to identify therapeutic cutoff revealed that treosulfan exposure ≥1,660 mg•hour/L was significantly associated with better 1-year TFS (97% vs. 81%, P = 0.02) and a trend to better 1-year OS (90% vs. 69%, P = 0.07). Further, multivariate analysis adjusting for known pre-HCT risk factors also revealed treosulfan exposure <1,660 mg•h/L (hazard ratio (HR) = 3.23; 95% confidence interval (CI) = 1.12-9.34; P = 0.03) and GSTA1*B variant genotype (HR = 3.75; 95% CI = 1.04-13.47; P = 0.04) to be independent predictors for inferior 1-year TFS. We conclude that lower treosulfan exposure increases the risk of graft rejection and early transplant-related mortality affecting TFS. As no RRTs were observed with increasing treosulfan exposure, TDM-based dose adjustment could be feasible and beneficial.

Effect of pharmacokinetics and pharmacogenomics in adults with allogeneic hematopoietic cell transplantation conditioned with Busulfan

Busulfan (Bu) combined with cyclophosphamide (Cy) is commonly used as a myeloablative conditioning regimen for allogeneic hematopoietic cell transplantation (allo-HCT). There is inter-individual variability of Bu pharmacokinetics (PK) and hence in toxicity and efficacy. The introduction of therapeutic drug monitoring (TDM) of Bu has decreased toxicity of the regimen. Hepatic metabolism of Bu is mediated through Glutathione-S-Transferases (GSTs), mainly GSTA1. Patients with GSTA1*A variants are considered normal metabolizers and GSTA1*B corresponds to poor metabolism, defined by nucleotide changes at -52 or -69 locus in GSTA1 promoter region. The aim of the study was to explore the correlation between GSTA1 polymorphisms and Bu-PK in 60 adult patients receiving an allo-HCT in the BuCyBu clinical study (ClinicalTrials.gov I, ID NCT01779882) comparing the sequence BuCy to CyBu. DNA samples prior to conditioning were genotyped for candidate variants at -52 (rs3957356) and -69 (rs3957357) loci in the GSTA1 promoter. Thirty-three % of patients were GSTA1*A*A, 49% GSTA1*A*B and 18% GSTA1*B*B. In GSTA1*A*A patients, median Bu-AUC was 3.6 ± 0.7 mg*h/L, in GSTA1*A*B 4.5 ± 1.6 and in GSTA1*B*B 4.9 ± 1.4 (AUC 35% higher than GSTA1*A*A, p = 0.03), with a similar significant correlation with Bu-clearance (p = 0.04). The correlation between GSTA1 polymorphism and AUC remained significant in multivariate linear regression analysis. There was a trend for lower non-relapse mortality (NRM) in patients with low AUC. We could not demonstrate a correlation between GSTA1 polymorphisms and NRM, acute graft-versus-host disease (aGvHD) in this small cohort, but there is a trend of higher aGvHD incidence in GSTA1*B*B patients.

Association between gene polymorphisms in the cyclophosphamide metabolism pathway with complications after haploidentical hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment for patients with hematologic malignances. Haploidentical HSCT (Haplo-HSCT) is an alternative option for patients who do not have an HLA-matched donor. The use of post-transplantation high dose cyclophosphamide (PT-Cy) is commonly employed for graft-versus-host disease (GVHD) prophylaxis in haplo-HSCT. Cyclophosphamide (Cy) is an alkylating agent with antineoplastic and immunosuppressive activity, whose bioactivation requires the activity of polymorphic enzymes in the liver to produce phosphoramide mustard, which is a DNA alkylating agent. To identify polymorphisms in the genes of Cy metabolism and correlate them with post-HSCT complications [GVHD, sinusoidal obstruction syndrome (SOS), hemorrhagic cystitis (HC) and transplant-related mortality (TRM)], we designed a custom next-generation sequencing panel with Cy metabolism enzymes. We analyzed 182 patients treated with haplo-HSCT with PT-Cy from 2007 to 2019, detecting 40 variants in 11 Cy metabolism genes. Polymorphisms in CYP2B6, a major enzyme involved in Cy activation, were associated with decreased activity of this enzyme and a higher risk of Graf-versus-host disease (GVHD). Variants in other activation enzymes (CYP2A6, CYP2C8, CYP2C9, CYP2C19) lead to decreased enzyme activity and were associated with GVHD. Polymorphisms in detoxification genes such as glutathione S-transferases decreased the ability to detoxify cyclophosphamide metabolites due to lower enzyme activity, which leads to increased amounts of toxic metabolites and the development of III-IV acute GVHD. GSMT1*0 a single nucleotide polymorphism previously recognized as a risk factor for SOS was associated with a higher risk of SOS. We conclude that polymorphisms of genes involved in the metabolism of cyclophosphamide in our series are associated with severe grades of GVHD and toxicities (SOS and TRM) after haplo-HSCT and could be used to improve the clinical management of transplanted patients.

Glutathione S-transferase Omega 2 DD genotype is associated with an increased risk of sporadic amyotrophic lateral sclerosis in Chinese men

Objective

To investigate whether GSTA1, GSTO2, and GSTZ1 are relevant to an increased risk of amyotrophic lateral sclerosis (ALS) in a Chinese population.

Methods

In this study, 143 sporadic ALS (sALS) patients (83 men, 60 women) and 210 age- and sex-matched healthy subjects were enrolled. Blood samples were collected by venipuncture. Genomic DNA was isolated by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) according to the manufacturer’s instructions. The potential associations between ALS and GSTA1, GSTO2, and GSTZ1 polymorphisms were estimated using chi-squared analysis and unconditional logistic regression.

Results

The D allele and genotype frequencies of GSTO2 were increased in sALS patients compared with healthy subjects, indicating that the GSTO2 DD genotype was associated with an increased risk of sALS (odds ratio [OR] = 3.294, 95% confidence interval [CI] = 1.039–10.448). However, a significant association between the DD genotype and the risk of sALS was evident in men only (OR = 7.167, 95% CI = 1.381–37.202).

Conclusion

This study revealed that the D allele and genotype frequencies of GSTO2 were increased in sALS patients. The GSTO2 DD genotype was associated with an increased risk of sALS in men in a Chinese population.

Impact of GSTA1 Polymorphisms on Busulfan Oral Clearance in Adult Patients Undergoing Hematopoietic Stem Cell Transplantation

Background: Busulfan pharmacokinetics exhibit large inter-subject variability. Our objective was to evaluate the influence of glutathione S-transferase A1 (GSTA1) gene variants on busulfan oral clearance (CLo) in a population of patients undergoing hematopoietic stem cell transplantation. Methods: This is a quasi-experimental retrospective study in adult patients (n = 87 included in the final analyses) receiving oral busulfan. Pharmacokinetics data (area under the plasma concentration-time curve (AUC) determined from 10 blood samples) were retrieved from patients’ files and GSTA1 *A and *B allele polymorphisms determined from banked DNA samples. Three different limited sampling methods (LSM) using four blood samples were also compared. Results: Carriers of GSTA1*B exhibited lower busulfan CLo than patients with an *A/*A genotype (p < 0.002): Busulfan CLo was 166 ± 31, 187 ± 37 vs. 207 ± 47 mL/min for GSTA1*B/*B,*A/*B and *A/*A genotypes, respectively. Similar results were obtained with the tested LSMs. Using the standard AUC method, distribution of patients above the therapeutic range after the first dose was 29% for GSTA1*A/*A, 50% for *A/*B, and 65% for *B/*B. The LSMs correctly identified ≥91% of patients with an AUC above the therapeutic range. The misclassified patients had a mean difference less than 5% in their AUCs. Conclusion: Patients carrying GSTA1 loss of function *B allele were at increased risk of overdosing on their initial busulfan oral dose. Genetic polymorphisms associated with GSTA1 explain a significant part of busulfan CLo variability which could be captured by LSM strategies.

Effect of glutathione S-transferase genetic polymorphisms on busulfan pharmacokinetics and veno-occlusive disease in hematopoietic stem cell transplantation: A meta-analysis

This meta-analysis was conducted to derive an integrated conclusion about the influence of glutathione S-transferase (GST) genetic polymorphisms on busulfan pharmacokinetic (PK) parameters and veno-occlusive disease (VOD). Studies which analysed the effect of GST genetic polymorphisms on area under the curve (AUC), clearance (CL) or VOD were searched for and selected. A pooled analysis was conducted using Comprehensive Meta-Analysis programme. Nineteen studies were included in this meta-analysis. GSTA1*B and GSTM1 null genotypes significantly decreased CL_IV of busulfan (standardized difference in means (SDM) = -1.103; P = 0.019 and SDM = -0.418; P = 0.002, respectively). GSTA1*B significantly increased AUC_IV of busulfan (SDM = 0.832; P = 0.046), whereas GSTM1 did not (SDM = 0.155; P = 0.478). The PK parameters of oral busulfan did not differ according to GST genotype. GSTA1, GSTM1 and GSTP1 were not significantly associated with VOD occurrence. GSTA1 and GSTM1 genotypes affected CL_IV of busulfan, but only GSTA1 affected AUC_IV . There was no significant difference in the PK parameters of oral busulfan (CL_PO and AUC_PO ) and VOD when only GST genotypes were considered.

Pharmacokinetics-adapted Busulfan-based myeloablative conditioning before unrelated umbilical cord blood transplantation for myeloid malignancies in children

Unrelated umbilical cord blood transplantation (UCBT) is an alternative to provide transplants in children with acute leukemia or myelodysplastic syndrome who lack a related donor. Intravenous Busulfan (Bu) combined with therapeutic drug monitoring-guided dosing has been increasingly used, with more predictable bioavailability and better outcomes comparing to oral Bu. There is still an important variation in Bu pharmacokinetic between patients that is associated with an increased risk of toxicity and graft failure. The objective of the study was to analyze the impact of first-dose pharmacokinetic adapted myeloablative conditioning regimen of intravenous Bu on the different outcomes after transplantation. Data of 36 children who underwent allogeneic HSCT with Bu plus a second alkylating agent at Sainte Justine Hospital in Montreal, Canada, between December 2000 and April 2012 were analyzed. For children with high risk myeloid malignancies receiving an UCBT, first dose Bu pharmacokinetic seems to be a significant prognostic factor, influencing neutrophil (100% vs 67.9%) and platelet recovery (95.5% vs 70.5%), non-relapse mortality (0% vs 18.6%), EFS (64% vs 28.6%) and OS (81.3% vs 37.5%) for a first-dose steady-state concentration (Css) <600ng/mL vs >600ng/mL, respectively. These data reinforce the importance of Busulfan therapeutic drug monitoring-guided dosing in pediatric HSCT patients, particularly in the context of UCBT.

GSTA1 diplotypes affect busulfan clearance and toxicity in children undergoing allogeneic hematopoietic stem cell transplantation: a multicenter study

Busulfan (BU) dose adjustment following therapeutic drug monitoring contributes to better outcome of hematopoietic stem cell transplantation (HSCT). Further improvement could be achieved through genotype-guided BU dose adjustments. To investigate this aspect, polymorphism within glutathione S transferase genes were assessed. Particularly, promoter haplotypes of the glutathione S transferase A1 (GSTA1) were evaluated in vitro, with reporter gene assays and clinically, in a pediatric multi-center study (N =138) through association with BU pharmacokinetics (PK) and clinical outcomes. Promoter activity significantly differed between the GSTA1 haplotypes (p<0.001) supporting their importance in capturing PK variability. Four GSTA1 diplotype groups that significantly correlated with clearance (p=0.009) were distinguished. Diplotypes underlying fast and slow metabolizing capacity showed higher and lower BU clearance (ml/min/kg), respectively. GSTA1 diplotypes with slow metabolizing capacity were associated with higher incidence of sinusoidal obstruction syndrome, acute graft versus host disease and combined treatment-related toxicity (p<0.0005). Among other GST genes investigated, GSTP1 313GG correlated with acute graft versus host disease grade 1-4 (p=0.01) and GSTM1 non-null genotype was associated with hemorrhagic cystitis (p=0.003). This study further strengthens the hypothesis that GST diplotypes/genotypes could be incorporated into already existing population pharmacokinetic models for improving first BU dose prediction and HSCT outcomes. (N^o Clinicaltrials.gov identifier: NCT01257854. Registered 8 December 2010, retrospectively registered).

Clarifying busulfan metabolism and drug interactions to support new therapeutic drug monitoring strategies: a comprehensive review

INTRODUCTION

Busulfan (Bu) is an alkylating agent with a limited therapeutic margin and exhibits inter-patient variability in pharmacokinetics (PK). Despite decades of use, mechanisms of Bu PK-based drug-drug interactions (DDIs), as well as the negative downstream effects of these DDIs, have not been fully characterized. Areas covered: This article provides an overview of Bu PK, with a primary focus on how known and potentially unknown drug metabolism pathways influence Bu-associated DDIs. In addition, pharmacogenomics of Bu chemotherapy and Bu-related DDIs observed in the stem cell transplant clinic (SCT) are summarized. Finally the increasing importance of Bu therapeutic drug monitoring is highlighted. Expert opinion: Mechanistic studies of Bu metabolism have shown that in addition to GST isoenzymes, other oxidative enzymes (CYP, FMO) and ABC/MDR drug transporters likely contribute to the overall clearance of Bu. Despite many insights, results from clinical studies, especially in polypharmacy settings and between pediatric and adult patients, remain conflicting. Further basic science and clinical investigative efforts are required to fully understand the key factors determining Bu PK characteristics and its effects on complications after SCT. Improved TDM strategies are promising components to further investigate, for instance DDI mechanisms and patient outcomes, in the highly complex SCT treatment setting.

Glutathione Transferase Gene Variants Influence Busulfan Pharmacokinetics and Outcome After Myeloablative Conditioning

Supplemental Digital Content is Available in the Text.

Background:

Busulfan (Bu) and cyclophosphamide (Cy) are frequently included in conditioning regimens before hematopoietic stem cell transplantation (HSCT). Both drugs are detoxified by glutathione transferases (GST), and GST gene variants may explain some of the interindividual variability in pharmacokinetics and drug toxicity.

Methods:

The study investigated adult patients (n = 114) receiving oral Bu pre-HSCT. Bu doses were adjusted to obtain an average steady-state concentration (C_ss) of 900 mcg/L.

Results:

Median first dose Bu C_ss was 1000 mcg/L (600–1780 mcg/L). Patients carrying 1 and 2 GSTA1*B (rs3957357) alleles demonstrated median 12% and 16% higher Bu C_ss (P ≤ 0.05). Bu exposure (average C_ss; odds ratio = 1.009, 95% confidence interval = 1.002–1.017, P = 0.013) and GSTM1 gene copy number (odds ratio = 17.1, 95% confidence interval = 1.46–201, P = 0.024) were significant predictors of mortality ≤30 days. The mortality was 25% versus 2% among carriers of 2 versus no GSTM1 copies (P = 0.021). Mortality ≤3 months was associated with higher first dose Bu exposure (1090 versus 980 mcg/L, P = 0.021). GSTM1 expression and high Bu exposure may increase Cy toxicity by reducing intracellular glutathione.

Conclusions:

GST genotyping before HSCT may allow better prediction of Bu pharmacokinetics and drug toxicity, and thereby improve outcome after BuCy conditioning.

Population pharmacokinetics and pharmacodynamics of busulfan with GSTA1 polymorphisms in patients undergoing allogeneic hematopoietic stem cell transplantation

AIM

A population pharmacokinetic (PPK) analysis was conducted to describe the influence of GSTA1 polymorphisms on intravenous busulfan in adults undergoing allogeneic hematopoietic stem cell transplantation.

PATIENTS & METHODS

A PPK model was developed from 36 patients by a one-compartment model with first-order elimination.

RESULTS

The typical value of clearance and volume of distribution were 11.0 l/h and 42.4 l, respectively. Clearance decreased by 15% and area under the concentration-time curves (AUCs) increased with GSTA1 variants compared with wild-type (both p < 0.05). Subtherapeutic AUCs were seen only in wild-type patients.

CONCLUSION

To our knowledge, this is the first PPK study to suggest that GSTA1 polymorphisms in adults are associated with busulfan PK.

Association of GSTO2 (N142D), GSTT1, and GSTM1 Polymorphisms With Graft-Versus-Host Disease in Allogeneic Hematopoietic Stem Cell Transplant Recipients

OBJECTIVES

Graft-versus-host disease is a major problem after bone marrow transplant. GSTM1, GSTT1, and GSTO2 are important genes that interfere with xenobiotic and drug metabolism. Polymorphisms of these genes may influence the metabolism of immunosuppressive drugs given for inhibition of graft-versus-host disease and may influence their susceptibility to diseases, which bone marrow transplant could alleviate.

MATERIALS AND METHODS

We examined the polymorphisms of 2 groups: The first group was composed of 88 patients who had undergone a bone marrow transplant and 100 otherwise healthy persons; the second group was composed of 54 patients without graft-versus-host disease and 34 patients with graft-versus-host disease. We used polymerase chain reaction-restriction fragment length polymorphism method for genotyping GSTO2 and also for multiplexing polymerase chain reactions for GSTT1 and GSTM1 genotypes.

RESULTS

No significant association existed between the genotypes GSTO2 (DD: P = .458, OR 0.422), GSTM1 (P = .349, OR 1.52), or GSTT1 (P = .887, OR 1.086), and the incidence of GVHD. Moreover, we saw no association between these polymorphisms and the problems that lead to bone marrow transplant (GSTO2: DD, P = .181, OR 0.465; GSTM1: P = .699, OR 0.892; GSTT1: P = .656, OR 0.845). We showed that men have more bone marrow transplants than do women (P = .019, OR 2.034).

CONCLUSIONS

Our results show that these poly-morphisms may have no effect on the metabolism of drugs used to treat graft-versus-host disease and also, may play no significant role in creating the problems that lead to bone marrow transplant.

An analysis of the therapeutic benefits of genotyping in pediatric hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation is a high-risk procedure that is offered, with curative intent, to patients with malignant and nonmalignant disease. The clinical benefits of personalization of therapy by genotyping have been demonstrated by the reduction in transplant related mortality from donor-recipient HLA matching. However, defining the relationship between genotype and transplant conditioning agents is yet to be translated into clinical practice. A number of the therapeutic agents used in stem cell transplant preparative regimens have pharmacokinetic parameters that predict benefit of incorporating pharmacogenomic data into dosing strategies. Busulfan, cyclophosphamide, thio-TEPA and etoposide have well-described drug metabolism pathways, however candidate gene studies have identified there is a gap in the identification of pharmacogenomic data that can be used to improve transplant outcomes. Incorporating pharmacogenomics into pharmacokinetic modeling may demonstrate the therapeutic benefits of genotyping in transplant preparative regimen agents.

Role of pharmacogenetics in busulfan/cyclophosphamide conditioning therapy prior to hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) is a curative treatment for several malignant and nonmalignant disorders. Busulfan (Bu) and cyclophosphamide (Cy) are the most commonly used alkylators in high-dose pretransplant conditioning for HSCT; a treatment that is correlated with drug-related toxicity and relapse. Pharmacogenetic investigations have shown that CYP450, as well as aldehyde dehydrogenase, are clearly involved with Cy metabolism and are associated with altered treatment response, Cy metabolism and the unique stem-cell sparing capacity. Moreover, glutathione-S-transferase isoenzymes have been associated with cellular outward transport of various alkylating agents, including Cy metabolites, melphalan, Bu and chlorambucil. A shift from genetic-based studies to whole-genome-based investigations of Cy- and Bu-associated markers may contribute to personalizing the conditioning therapy and enhancing the clinical outcome of HSCT.

Influence of GST gene polymorphisms on the clearance of intravenous busulfan in adult patients undergoing hematopoietic cell transplantation

Intravenous (i.v.) busulfan can produce a more consistent pharmacokinetic profile than oral formulations can, but nonetheless, significant interpatient variability is evident. We investigated the influence of polymorphisms of 3 GST isozyme genes (GSTA1, GSTM1, and GSTT1) on i.v. busulfan clearance. Fifty-eight adult patients who received 3.2 mg/kg/day of busulfan as conditioning for hematopoietic cell transplantation were included in this study. Stepwise multiple linear regression demonstrated that GSTA1 variant GSTA1∗B (P = .004), GSTM1/GSTT1 double-null genotype (P = .039), and actual body weight (P = .001) were significantly associated with lower clearance of i.v. busulfan. A trend test analyzing the overall effect of GST genotype on busulfan pharmacokinetics, combining GSTA1 gene polymorphism and the number of GSTM1- and GSTT-null genotypes, showed a significant correlation between GST genotype and busulfan clearance (P = .001). The clearance of i.v. busulfan was similar between patients with GSTA1∗A/∗A and GSTM1/GSTT1 double-null genotypes and those with GSTA1∗A/∗B and GSTM1/GSTT1 double-positive genotypes. In conclusion, a pharmacogenetic approach using GST gene polymorphisms may be valuable in optimizing the i.v. busulfan dosage scheme. Our results also highlight the importance of including polygenic analyses and addressing interactions among isozyme genes in pharmacogenetic studies.

Pharmacogenetics of intravenous and oral busulfan in hematopoietic cell transplant recipients

Kinetics-based dose targeting is often conducted in hematopoietic cell transplant (HCT) patients conditioned with intravenous (IV) or oral busulfan to lower rates of rejection, nonrelapse mortality, and relapse. Using the candidate gene approach, the authors evaluated whether busulfan clearance was associated with polymorphisms in the genes regulating the predominant metabolizing enzymes involved in busulfan conjugation, specifically glutathione S-transferase (GST) isoenzymes A1 (GSTA1) and M1 (GSTM1). Busulfan clearance was estimated after the morning dose on days 1, 2, and 3; each patient's average clearance was used for analyses. The average (± standard deviation) busulfan clearance was 3.2 ± 0.56 mL/min/kg in the separate population of 95 patients who received oral busulfan and 103 ± 24 ml/min/m(2) in the 57 patients who received IV busulfan. Oral busulfan clearance was associated with GSTA1 (P = .008) but not GSTM1 (P = .57) genotypes. However, among the GSTA1 haplotypes (ie, *A*A, *A*B, *B*B), there was significant overlap in the observed oral busulfan clearance and similar rates of achieving the target busulfan exposure. Clearance of IV busulfan was not associated with GSTA1 (P = .21) or GSTM1 (P = .99). These data suggest that personalizing either IV or oral busulfan dosing cannot be simplified on the basis of GSTA1 or GSTM1 genotype.

Influence of glutathione S-transferase A1, P1, M1, T1 polymorphisms on oral busulfan pharmacokinetics in children with congenital hemoglobinopathies undergoing hematopoietic stem cell transplantation

BACKGROUND

Busulfan (BU), often used in high dose for myeloablation before hematopoietic stem cell transplantation (HSCT), has been implicated in certain HSCT toxicities, including the occurrence of hepatic veno-occlusive disease (HVOD). In addition to weight and age, gene polymorphisms in specific members of the glutathione-transferase (GST) gene family (A1, P1, M1, and T1), involved in BU metabolism, may play a role in the wide inter-patient variability in systemic BU concentrations.

PROCEDURE

The present study integrated clinical data regarding the occurrence of HVOD, graft versus host disease (GVHD), BU pharmacokinetics and GSTA1, GSTP1, GSTM1, and GSTT1 genotypes of 18 children who received BU in their pre-HSCT conditioning regimen. The children were all treated for congenital hemoglobinopathies and were all of Arab Moslem descent.

RESULTS

The data demonstrate an association between GSTA1 and GSTP1 genotypes and BU-maximal concentration (C(max)) (P = 0.01, P = 0.02, respectively), area under the concentration-time curve (AUC) (P = 0.02, P = 0.01, respectively) and oral BU clearance/kg body weight (P < 0.02, P = 0.08, respectively). GSTM1-null individuals demonstrated lower BU-AUC/Kg compared to GSTM1-positive individuals. In addition, an association between GVHD and GSTM1-null genotype was found.

CONCLUSIONS

GSTA1, GSTP1, and GSTM1 genotyping prior to HSCT in children with congenital hemoglobinopathies may allow better prediction of oral BU kinetics and the need for BU dose adjustment, as well as prediction of transplant related toxicity such as GVHD, thereby improving clinical outcome.

Analysis of the host pharmacogenetic background for prediction of outcome and toxicity in diffuse large B-cell lymphoma treated with R-CHOP21

Knowledge on the impact of pharmacogenetics in predicting outcome and toxicity in diffuse large B-cell lymphoma (DLBCL) is scant. We tested 106 consecutive DLBCL treated with R-CHOP21 for 19 single nucleotide polymorphisms (SNPs) from 15 genes potentially relevant to rituximab-CHOP (R-CHOP) pharmacogenetics. Associations of SNPs with event-free survival (EFS) and toxicity were controlled for multiple testing. Genotypic variants of nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase p22phox (CYBA rs4673) and alpha1 class glutathione S-transferase (GSTA1 rs3957357) were independent predictors of EFS (CYBA rs4673 TT genotype: HR 2.06, P=0.038; GSTA1 rs3957357 CT/TT genotypes: HR 0.38, P=0.003), after adjusting for International Prognostic Index (IPI). CYBA rs4673 and GSTA1 rs3957357 also predicted outcome in DLBCL subgroups by IPI. Impact of SNPs on toxicity was evaluated in 658 R-CHOP21 courses utilizing generalized estimating equations. NCF4 rs1883112 was an independent predictor against hematologic (odds ratios (OR): 0.45; P=0.018), infectious (OR: 0.46; P=0.003) and cardiac toxicity (OR: 0.37; P=0.023). Overall, host SNPs affecting doxorubicin pharmacodynamics (CYBA rs4673) and alkylator detoxification (GSTA1 rs3957357) may predict outcome in R-CHOP21-treated DLBCL. Also, NCF4 rs1883112, a SNP of NAD(P)H oxidase p40phox, may have a function in protecting against hematologic and nonhematologic toxicity. These results highlight the need to improve characterization of the host genetic background for a better prognostication of DLBCL.