Transcript Document

Obatoclax Biodistribution in MLL Leukemia NOG Mouse Model is Predicted by Modeling and Simulation
and Shows High Tissue Penetration at Clinically Important Sites
Alena Y. Zhang1, Jeffrey S. Barrett1,2, Gwenn Danet-Desoyers2, Anthony Secreto2, Vu T. Nguyen, Cathy Keefer2, Xiaochuan Shan, 2 Ralph Bunte2, Manon Lavoie3, Pierre Beauparlant3 , Carolyn A. Felix1,2
II.
Leukemia Xenografts
• Established NOG mouse xenograft model of infant MLL/ENL+ bilineal
leukemia that recapitulates the hyperleukocytosis and involvement of
the CNS and other extramedullary sites in human MLL+ leukemia
III. Experimental Design
OBJECTIVES
•
To construct obatoclax dose-exposure and tissue distribution
relationships in NOG mouse xenograft model of MLL+ leukemia
using an experimental design based on prior PK data from other
strains of mice and adult Phase 1 trial target exposure data
•
To determine the effect of leukemia and mouse strain on drug disposition
Mice injected with 1.3
million leukemia cells
3 weeks post-injection
Diseased Mice
n = 42
1.2 mg/kg
n = 21
4.8 mg/kg
n = 21
Figure 1: Schema of the PK
study. NOG mice with established
xenografts received single IV bolus
dose of 1.2 or 4.8 mg/kg obatoclax.
Concentrations were measured in
plasma, spleen, liver, kidney and
brain at indicated times using a
validated LC-MS method
DESIGN / METHODS
I. Modeling Approach
• Previously had constructed a pop-PK model using TK data from 3
single-dose studies in healthy Balb/C mice (courtesy of GeminX) via
NONMEM with FO method (version 5, level 1.1, Globomax, Hanover,
MD) (Zhang, 2007 ACCP Annual Meeting)
• Simulated obatoclax exposure in the NOG mouse based on adult CLL
phase I target exposure (AUC24hr 180 ng•hr/mL) associated with peak
ODNA release
• Assumptions based on model: 1.2 mg/kg and 4.8 mg/kg would achieve 100%
and 400% of the target exposure
• Optimal sampling schedule to yield model-predicted parameters based on 7
time point design with “big rat” approach (destructive sampling consideration)
• Performed PK study in leukemia-bearing NOG mice and used
NONMEM to develop a pop-PK model from experimental data
PK sampling at 0.08,
0.25, 1, 2, 4, 8, 24 hr
(3 mice per time point
per dose level)
Tissue
sampling
RESULTS
I. Pop-PK Model in MLL+ Leukemia NOG Mice
• A 2-compartment PK model best describes the distribution/elimination
of obatoclax in NOG mice, similar to Balb/C.
• Exponential inter-individual variability model for CL, V1, Q and V2
and proportional error model for residual variability afford unbiased
predictions of drug concentrations.
ACKNOWLEDGEMENTS
• The Leukemia & Lymphoma Society SCOR Grant 7273-07
• NIH R25-CA-101871
0.1
0
1
2
3
4 4
10
16
22
28
Time (hr)
Figure 2. Bi-phasic obatoclax disposition after
IV bolus dosing in diseased NOG mice. Note
good proportionality at both doses. Blue lines
indicate in vitro obatoclax activity.
0.2
CL (L/hr/kg)
V1 (L/kg)
Q (L/hr/kg)
V2 (L/kg)
0
-1
0.1
-2
0.0
0.0
-3
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.1
0.2
0.3
Residual variance
Proportional
(µg/mL)
0.4
Predicted Conc.(g/mL)
Predicted Conc.(g/mL)
Figure 3. Diagnostic plots of pop-PK model fit with observed
concentrations in NOG mice. Left: Observed data versus population
predicted (PRED) plasma concentrations. Right: Weighted residuals
(WRES) versus population predicted (PRED) plasma concentrations.
Simulation NOG vs Balb
II. Simulated pop-PK models show similar
obatoclax exposure between mouse strains but
slower elimination in the NOG
• Similar AUC24hr between strains at both doses.
• Greater than 3-fold longer half-life in NOG mice,
suggesting slower elimination due either to strain
differences, disease burden, or analytical detection
limit at the lower concentration.
1000
1.2 mg/kg1000
1000
100
100
100
10
1
0.1
10
1
0
1
2
3
4 4
% RSE
7
8.9
21
39
0.0746
42
4.8
1.2 mg/kg NOG
1.2 mg/kg Balb/C
Table 2. Comparison of simulated PK parameters
4.8 mg/kg NOG
1.2
mg/kg NOG
between
NOG and Balb/C mice
NOG
4.8 mg/kg Balb/C
1.2
mg/kg Balb/C
Balb/C
Dose
Balb/ Fold
Parameter
NOG
(mg/kg)
C
change
mg/kg
10
1
0.01
10 16 022 128
AUC24hr
(hr*ng/mL)
Terminal t1/2 (hr)
1.2
0.1
0.01
Estimates
4.84
9.50
2.03
15.7
Simulation NOG vs Balb
Simulation NOG vs Balb
0.1
2
03
Time (hr)
14 4 210 316
4 4 2810
22
16
22
28
Figure 4. Simulation of pop-PK models in mouse strains. Simulated
plasma concentration-time profiles (n=100) illustrate median (solid
line), 10th and 90th percentile (dotted lines) of the pop-PK models.
Observed GX15-070 Plasma Concentration
400
• Brain:plasma ratios  2-10, indicate substantial CNS penetration.1
• Higher ratios in the kidney for 1.2 mg/kg dose group suggest the
0.1 potential for
0
4
8
12
16
saturable elimination.
Time (hr)
• Increasing tissue to plasma ratios with time in liver relative to other target organs
with more consistent accumulation.
• Equilibrium of splenic uptake at 8 hours forms rationale for pre-treating
with obatoclax 4 hours prior to chemotherapy to achieve
chemosensitization in the upcoming preclinical diseased NOG mouse
efficacy study.
4.8
700
Spleen
1000
III. Obatoclax biodistribution is extensive and sustained in murine
equivalent sites of MLL+ leukemia
100
• Sustained drug retention in spleen, liver and brain, which are
desired target
10
sites of anti-leukemia activity.
AUC24hr
(hr*ng/mL)
Terminal t1/2 (hr)
Time (hr)
Time (hr)
1.2 mg/kg
4.8 mg/kg
300
200
100
213
189
+ 1.13
6.05
1.80
+ 3.36
796
736
+ 1.08
6.00
1.58
+ 3.80
Liver
1.2 mg/kg
600
4.8 mg/kg
Liver/plasma
MLL+
1
0.3
1
1.2 mg
4.8 mg
500
400
300
200
100
0
0
0
4
8
16
20
0
24
Time (hr)
400
20
12
Kidney
24
4
8
200
100
0
16
20
24
Brain
1.2 mg/kg
4.8 mg/kg
300
12
Time (hr)
15
Brain/plasma
Single-dose IV
bolus PK study
10
0.4
Parameter
Model
Spleen/plasma
Simulations of
doses to achieve
target threshold
(NONMEM)
IC50
2
Kidney/plasma
•
2compartment
pop-PK model
(NONMEM)
PBPK model
(PK Sim®)
100
0.5
Table 1. Structural model in NOG mice
Cp (ng/mL)
•
Pop-PK model
(NONMEM)
CLL trial target
exposure
AUC24hr  180
ng•hr/mL
IC90
1.2 mg/kg
4.8 mg/kg
3
Cp (ng/mL)
•
3 single dose
IV bolus PK
studies
1000
0.6
Weighted Residuals
•
• Compared simulated secondary PK parameters using WinNonLin (Pharsight,
Mountain View, CA)
MLL Leukemia
Healthy
Human
Human Adult
Xenograft
NOG
Balb/C Mouse
Pediatric?
Mouse
Observed GX15-070 Plasma Concentration
Cp (ng/mL)
MLL translocations
, which are chemotherapy resistant, occur
in ~80% of infant ALL and AML and are a poor prognostic factor in
infant ALL. MLL translocations also occur in secondary leukemias
after exposure to chemotherapeutic topoisomerase II poisons.
Cell death pathways are desired targets of small molecule inhibitors
since their deregulation plays an important role in chemotherapy
resistance; e.g. imbalanced expression of BCL-2 family proteins leads
to deregulated homeostatic binding between pro- and anti-apoptotic
BCL-2 family members and impairs cell death.
Obatoclax inhibits pro- and anti- apoptotic BCL-2 family protein
interactions by binding to the BH3 pocket of the anti-apoptotic
proteins.
Obatoclax has potent single agent in vitro activity in MLL+ leukemias
and cell lines. Adult phase I CLL trials indicate single agent activity
with minimal toxicity.
NOD-scid-IL-2Rnull (NOG) mice lack natural killer cell activity,
resulting in superior engraftment of human leukemia xenografts
compared to other immuno-deficient mouse strains.
RESULTS (continued)
Cp (ng/mL)
•
(MLL+)
DESIGN / METHODS (continued)
• Performed simulations based on obatoclax pop-PK models in diseased
NOG and healthy Balb/C mice
Cp (ng/mL)
BACKGROUND
Children’s Hospital of Philadelphia, 2University of Pennsylvania, Philadelphia, PA. 3Gemin X Pharmaceuticals, Inc., Montreal, Canada
Observed Conc. ( g/mL)
1The
1.2 mg
4.8 mg
10
5
0
0
4
8
12
Time (hr)
16
20
24
0
4
8
12
16
20
24
Time (hr)
Figure 5. Obatoclax tissue biodistribution in diseased NOG mice.
CONCLUSIONS
• M&S provides novel information on the impact of mouse strain and leukemia burden on PK.
• Obatoclax has desirable tissue penetration at murine equivalent sites of MLL+ leukemia.
• PBPK model will be developed from biodistribution data to predict obatoclax exposure and target organ toxicities in the pediatric population.