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Association between Busulfan Exposure and Outcome in Children Receiving Intravenous Busulfan before Hematopoietic Stem Cell
Transplantation Association Between Pharmacogenomic and
Pharmacokinetic of Busulfan
On behalf of the Pediatric Disease Working Parties of the European Blood and Marrow Transplantion group
M.Ansari, R.Uppugunduri Satyanarayana, C.Peters, Y.Théoret, MA.Rezgui , M.Labuda, M.Champagne, M.Duval, H.Bittencourt, M.Krajinovic
Geneva University Hospital, Geneva, Switzerland
• Busulfan (Bu) is an important alkylating agent for conditioning regimens that presents a narrow therapeutic index and a wide inter- and intra-patient variability of plasma exposures, especially in children
• Therapeutic drug monitoring (TDM) with dose adjustment improves efficacy and safety of Bu-based conditioning regimens
• In adults, an AUC of 900 to 1500µM*min (Css 616-1026 ng/ml) after first dose has been demonstrated to be a suitable target exposure range
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• Optimal target AUC/Css in children undergoing HSCT remains unclear
• Aim of the study: Evaluate the association between Bu iv exposure and
different outcomes after allo-HSCT in pediatrics
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Methods • Patients:
Prospective Single-center (CHU Sainte-Justine in
Montreal) 89 children IV Bu receiving HSCT May 2000 and August 2010 CHU Sainte-Justine Institutional Review Board
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• Bu treatment regimen:
Intravenous Bu (16 doses if MA or 8 doses if NMA):
16mg/m2/dose≤ 3 months old
0.8 mg/kg/dose for infants ≥3 months and <1 year of age
1 mg/kg/dose for children ≥1 year and <4 years old
0.8 mg/kg/dose for children ≥4 years old
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Gender Male 46 52 Race - ethnicity Caucasian 73 82.0
Diagnosis AML / ALL 31/10 35/11
MDS 17 19
Non-malignant 31 35
Conditioning Regimen
Bu + Cy 68 76
Bu + others (MA) 9 10
Bu/Flu (NMA) 12 14
GVHD Prophylaxis CSA + steroids 49 55
CSA + MTX 29 33
ATG 69 78
Stem Cell Source
BM 36 40
Cord Blood 52 58
Unrelated Donor 57 64
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Demographic Characteristics (n=89) Patients
N %
MAC=NMA results
• Definitions of outcomes: VOD: Seattle criteria
GVHD grading: 1994 Consensus Conference on Acute GVHD Grading
Neutrophil recovery: first of 3 days ANC ≥ 0.5x109/L
Platelet recovery: first of 7 days ≥ 50x109/L
Primary graft failure: persistent pancytopenia ≥ 60 days
Secondary graft failure: pancytopenia after neutrophil recovery
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• Pharmacokinetics:
Blood samples collected: Before Bu administration 15, 30, 60, 120, 180 and 240 min
after drug administration
Plasma Bu high-performance liquid chromatography assay
Non-compartmental analysis (WinNonlin, version 3.1)
Bu target Css: 600 - 900 ng/ml
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Parameter Median (Range) Age (years) 8.2 (0.1-20) Weight (kg) 27 (4.3 – 84.8) Height(cm) 126.8 (54-183) BMI 17.4 (13.1-29.5) BSA (m2) 0.97 (0.25-2.02) CMax (ng/mL) 844 (537-1338) CMin (ng/mL) 215 (66.4-522) CMean (ng/mL) 500 (277-870) CSS (ng/mL) 603 (295-1227) AUC (min.ng/mL) 205585 (94859-431260) Clearance (mL/min/kg) 4.10 (1.84-7.68) Bu Cumulative prescribed dose (mg) 297 (52-1530) Bu Cumulative administered dose (mg)
338 (48-1095)
Bu dose increase (%) 15.9 (-36.8 – 98)
Busulfan pharmacokinetic parameters after first dose of iv Bu
1 < 3 months, more than 60 patients > 4 years 9
• Statistical analysis:
Univariate Analysis Kaplan-Meier method and log-rank test or Cumulative incidence with competing risk
and Gray’s test.
Multivariate analysis Cox or Fine & Gray proportional hazards
regression models. IBM SPSS Statistics 19 and S-plus 6.1
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Neutrophil recovery: 92% - median 19 (9-48) days Platelet recovery: 89% - median 41 (9-173) days Graft failure: 9 (10%) primary graft failure (n=5)
secondary graft failure (n=4)
No impact of Css on hematopoietic recovery in multivariate analysis
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Results – Hematopoietic Recovery
Acute GVHD grade 2-4 cumulative incidence: 10% No impact of Css on aGVHD incidence in uni-/ multivariate analysis
VOD cumulative incidence: 11% Tendency (p=0.15) to a lower VOD incidence with Css < 603ng/ml – not confirmed in multivariate analysis
HC cumulative incidence: 25% Lower incidence of HC wth Css < 603ng/ml (P=0.02) – not confirmed in multivariate analysis.
Lung toxicity cumulative incidence: 8% Lower incidence of lung toxicity with Css < 603ng/ml in multivariate analysis (P=0.03)
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Results – aGVHD and Conditioning Toxicity
TRM cumulative incidence (5 years): 14% – Infection was the lead cause of death (n=4)
Higher TRM incidence with Css > 603ng/ml in uni- and multivariate analysis (HR= 3.13; P <0.001)
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Results – Transplant-related Mortality
0 300 600 900 1200 1500 1800
Days after HSCT
0.0
0.2
0.4
0.6
0.8
1.0
TRM
Css < 603 ng/ml
Css > 603 ng/ml
26%
0%
P<0.001
Cumulative incidence of relapse at 5 years (n=58): 37%
Tendency to a higher relapse incidence with Css > 603 ng/ml in univariate analysis (47% vs. 25% - P=0.06), not confirmed in multivariate analysis
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Results – Relapse
Css < 603 ng/ml
Css > 603 ng/ml
81%
31%
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Results – Event-free Survival (EFS)
Results – Event-free Survival (EFS) Estimated 5 years EFS: 56% Lower EFS with Css > 603ng/ml in univariate analysis and multivariate analysis (HR: 4.76 - P<0.001)
Results – Event-free Survival (EFS)
Ansari et al, Therapeutic Drug Monitoring, 2013
89%
46%
Css < 603 ng/ml
Css > 603 ng/ml
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Results – Overall Survival (OS) Estimated 5 years OS: 67% Lower OS with Css > 603ng/ml in univariate analysis and multivariate analysis (HR: 6.6 - P<0.001)
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Conclusion
Outcome of pediatric patients receiving iv Bu can be predicted according to its pharmacokinetics
Worse outcome if Css > 603 ng/ml is mainly related to TRM
Targeting lower end of the range should be investigated
Do we have to lower the Bu target, change Cy by Flu or reverse Bu Cy order (Cy /Bu)?
What is the impact of pharmacogenetics ?
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Interindividual differences in drug responses are an important cause of resistance to treatment and adverse drug reactions. Identifying pharmacogenomic determinants of a given drug may allow for prospective identification of patients with suboptimal drug responses allowing for complementation of traditional treatment protocols by genotype-based drug dose adjustment.
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Posology : mg per Kg or m2 or according to genotype
Some children with a specific genetic profile are responding without side effects compared to a different group of children with a
different genetic profile who are responding but with toxicity. Give the right medication to the right child.
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Metabolic fate of busulfan. GSTA1 (glutathione-S-transferase), tetrahydrothiophene (THT), cystathionine gamma lyase (CTH), DPEP (dipeptidase/cysteinylglycinase), GGT (gamma glutamyl transferase), NAT (N-acetyl transferase), sulfolane (2,3,4,5-tetrahydrothiophene-1,1-dioxide) Cytochrome P 450 enzymes (CYPs), flavin mono oxidase (FMO).
To establish the relationship between GSTM1 and GSTA1 gene variations and drug exposure (Cmax, AUC, Css, Cl) or HSCT outcomes in MAC patients only (RIC excluded). Toxicity (a GVHD and VOD, hemorrhagic cystitis and lung toxicity)
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Cmax (log) AUC (log) Css (log) CL (log)
GSTM1 null genotype and PK
P=0.031 P=0.031P=0.041 P=0.071
+ = null genotype (16) - = without (27) ≥4 years of age
!""""""""""""""""""+" !""""""""""""""""""+" !""""""""""""""""""+" !""""""""""""""""""+"
Ansari et al BMT 2011
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Cmax ng/ml
Haplotype*2A
P=0.02 M-W P=0.02 P=0.02
+ = carrier (29) - = non carrier (40)
GSTA1 - PK Css ng/ml AUC ng/ml
P=0.02 P=0.01 P=0.02
Cmax//mg/kg Css //mg/kg AUC //mg/kg CL ml/min/kg
P=0.01
Ansari et al BMT 2013
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E
FS
P=0.03 62(26)
*2A*2A + 8(0)
*2A*2A - VO
D
GG 7(3)
CC 25(2)
CG 37(4)
CC 22(2) CT 40(4)
TT 7(3)
TT 7(3)
CC&CT 62(6) P=0.008
Time (Days)
GG 7(3)
CC&CG 62(6)
C-69T - *B C-1142G - *B1
P=0.008
GSTA1- clinical outcome EFS 100% vs 54%
VOD seen in 43% homozygous *B or *B1 compared with 9.6% (HR=5.3, 95%CI=1.3-21.5, P=0.009)
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!69 !513 !631 !1142 Haplotype Haplotype1carriers
*A1 C T T C 711(35.5) 451(47.3) *A2 C T G C 421(24.9) 331(34.7) *A3 C T T G 21(1.3)1 11(1) *B1 T T G G 651(32.1) 471(49.4) *B1a T C G G 51(3.1) 51(5.2) *B2 T T G C 51(3.1) 51(5.2)
Minor1allele 751(39.4) 51(2.6) 731(38.4) 721(37.8)
expected
observed
Conclusion
BMT 2013
Conclusion
It seems there is an impact of pharmacogenetics
A prospective multicentric European Blood and Marrow (EBMT)/Swiss Oncology Group (SPOG) study is ongoing to confirm these results in 150 children receiving Busulfan as well as in 50 thalassemia patients and in 400 acute lymphoblastic leukemia children (ALL SCT ped FORUM Study, iBFM 2013)
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In our model, the demographic elements (age, weight) explain 37% of the variability of Busulfan. With the addition of the PG, 54 % of the variability is explained. Hence we must study many more genes and their interaction in order to explain 100% of this variability. Thus there exists today a possible breakthrough on the dose adjustment according to the genotype.
Aknowledgements
The EBMT Paediatric Diseases Working Party and C.Peters as well as the SPOG
Switzerland Canada D.Belli H.Bittencourt Y.Daali M.A.Champagne P.Dayer C.Desjean J.Desmeules C.Drouin M.Fathi S.Dulucq F.Gumy-Pause M.Duval P.Huezo-Diaz M.Krajinovic S.Hughes M.Labuda H.Ozsahin J.F.Lauzon-Joset J.Passweg S.Malouin C.A.Siegrist S.Mezziani S.Suter A.Rezgui A.Tyagi J.Rousseau R.C.Uppugunduri G.St-Onge N.Von-der-Weid Y.Théoret Pierre Fabre Laboratories M.F.Vachon
Thank you to our pharmacogenomic plateforme of pediatric hematology and oncology (CANSEARCH research Laboratory) at
the Geneva University Medical School
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Thank you to the patients and their parents who accepted and signed a consent form for this study
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www.cansearch.ch
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Css Median if rejection, death and relapse , and no event Css low..but IC large
32%
40%
70%
91%
40%
52%
85%
91%
in Group: I Css < 511ng/ml II Css 511-603 III Css 603-714 IV Css >714
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Css Quartiles OS/EFS (5y)
HR (CI) 2.15 (1.41 – 3.28) p< 0.001
HR (CI) 1.80 ( 1.30 – 2.50 ) p< 0.001
I II
III
IV
I
II
III
IV
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