Treating CF at the Source
Drugs that work on CFTR
Richard B. Moss MD
Department of Pediatrics
Stanford University
CF Education Day
March 3, 2012
Targeting Primary Defects vs Secondary
Pathophysiologies in CF Lung Disease
CFTR gene
mutation
Defective CFTR
protein
Ivacaftor
Gene
therapy
Defective ion and
fluid transport
Cl-/Na+
channel
modulators
VX-809
VX-661
Ataluren
Hyperosmotic
Therapy
Primary Defects
Infection
Bronchodilators
Obstruction
Anti-infectives
Impaired mucociliary
clearance
Mucolytic Treatment
Anti-inflammatories
Lung Transplant
Inflammation
Based on Amaral, et al. TIBS 2007
Bronchiectasis,
lung function loss
Secondary Pathophysiologies
The steps from CF gene to CFTR protein
• CF gene (chromosome #7)
– Codes for…
• CFTR (cystic fibrosis transmembrane conductance regulator)
– Membrane protein that regulates salt transport
DNA
mRNA
protein
chaperones
Nucleus –
Gene/chromosome
ER/Golgi –
Translation/protein maturation
Plasma membrane –
Pore open/closed
Phenotype Effects of Classes of
CFTR Mutations
Normal
Class I
Class II
Class III
Class IV
Class V
I, II, III (“severe”)
 Pancreatic Insufficiency
 Risk of:
 Meconium ileus,
DIOS
 CFRD
 Severe hepatobiliary
disease
IV, V (“mild”)
No Synthesis
Increased
Degradation
Adapted from Hospital Practice, 1997
Defective
Regulation
Abnormal
Conductance
Reduced
Synthesis/
Trafficking
 Pancreatic Sufficiency
 Risk of:
 Acute, recurrent
pancreatitis
 Chronic pancreatitis
What is a CFTR modulator, and why is it
different from other CF therapies?
• Modulator – targets underlying defects in CFTR
– Restore function (not replace)
• Addresses primary cause of CF
– Not downstream symptoms
• Different defects – different targets – different strategies
– Generally based on CF mutation class
I
II
III
chaperones
Nucleus –
Gene/chromosome
ER/Golgi –
Translation/protein maturation
Plasma membrane –
Pore open/closed
Phenotype Effects of Classes of
CFTR Mutations
Normal
Class I
Class II
Class III
Class IV
Class V
I, II, III (“severe”)
 Pancreatic Insufficiency
 Risk of:
 Meconium ileus,
DIOS
 CFRD
 Severe hepatobiliary
disease
IV, V (“mild”)
No Synthesis
Increased
Degradation
Adapted from Hospital Practice, 1997
Defective
Regulation
Abnormal
Conductance
Reduced
Synthesis/
Trafficking
 Pancreatic Sufficiency
 Risk of:
 Acute, recurrent
pancreatitis
 Chronic pancreatitis
Ribosomal Translation of mRNA to
Protein
Normal Translation
Normal
Termination
Codon
Ribosomes
Amino acid
mRNA
Full-length
Protein
Effect of Stop Mutation
Premature Termination
Nonsense
(Premature Termination)
Codon
mRNA
Normal
Termination
Codon
Truncated
Protein
Read-Through of CFTR Stop
Mutations (Class I) with PTC124
PTC124
Nonsense
(Premature
Termination)
Codon
mRNA
Normal
Termination
Codon
Full-length
Protein
PTC124-Mediated Increases in Epithelial
Cell-Surface CFTR
Pre-treatment
(Day 0)
End of PTC124
10-, 10-, 20-mg/kg Dose Level (Day 45)
Full-length Apical CFTR
Evidence of CFTR Abnormality:
Nasal Potential Difference (NPD)
NORMAL
• Higher basal NPD
NPD (mV)
CF patients have:
• Greater decline in
NPD after amiloride
perfusion
Amiloride 0 Cl–
Amiloride
–1
0
1
2
3
4
5
6
7
8
9
7
8
9
Time (minutes)
CYSTIC FIBROSIS
NPD (mV)
• Lack of response to
Cl– free perfusion
and isoproterenol
–60
–50
–40
–30
–20
–10
0
Iso
0 Cl–
Amiloride
Amiloride
–70
–60
–50
–40
–30
–20
–10
0
Iso
0 Cl–
Amiloride
Cl–
0
Amiloride
–1
0
1
2
3
4
5
Time (minutes)
6
TEPD ( Cl--free+Isoproterenol)
 SEM (mV)
PTC124 (Ataluren) Improved NPD Chloride Secretion
4
4, 4, 8 mg/kg
(N=10)
10 ,10, 20 mg/kg
(N=7)
Combined
(N=17)
2
0
-2
-4
p<0.02*
p<0.004*
p=0.001*
-6
Treatment Follow-up
-8
0
28 56 84 112 0
28 56 84 112 0
28 56 84 112
Study Day
* Paired t-test versus Day 1
Wilschanski M et al, Eur Respir J 2011;38:59-69
PTC 124 Increased Lung Function and
Decreased Cough Frequency
FEV1
(N=18)
Improved
Mean % Change  SEM (%)
8
FVC
(N=18)
Cough
Frequency
(N=18)
400
6
200
4
2
0
0
-2
-4
-200
-6
p=0.009
Treatment Follow-up
-8
p=0.019
-10
-400
0
28
56
84 112
0
28
56
84 112
0
28
56
84 112
Change in 24-hour Cough Frequency
 SEM (n)
10
Improved
Study Day
* Paired t-test versus Day 1
Wilschanski M et al, Eur Respir J 2011;38:59-69
Phenotype Effects of Classes of
CFTR Mutations
Normal
Class I
Class II
Class III
Class IV
Class V
I, II, III (“severe”)
 Pancreatic Insufficiency
 Risk of:
 Meconium ileus,
DIOS
 CFRD
 Severe hepatobiliary
disease
IV, V (“mild”)
No Synthesis
Increased
Degradation
Adapted from Hospital Practice, 1997
Defective
Regulation
Abnormal
Conductance
Reduced
Synthesis/
Trafficking
 Pancreatic Sufficiency
 Risk of:
 Acute, recurrent
pancreatitis
 Chronic pancreatitis
Potentiators Increase Gating of CFTR
Normal
Levels of
Surface
CFTR
Gating Defect
Low Chloride
Flow
Increased Ion
Flow
• G551D is the most prevalent mutation with gating defect (~5%)
• VX-770 shown active both in vitro and in patients with G551D
VX-770 Restores Gating of G551D CFTR In Vitro
50
Single channel patch clamp studies in Fisher Rat
Thyroid cells expressing G551D CFTR
0.75
EC50 = 240 nM
40
Open Probability
G551D/F508-CFTR Activity
(% wild-type-CFTR)
Ussing chamber studies using
G551D/ΔF508-HBE
30
20
10
0
-11-10 -9 -8 -7 -6 -5 -4
Log M [VX-770]
Average data from 16 replicates
0.50
0.25
0.00
Untreated
10 ųM
VX-770
G551D
Untreated
Wild Type
Van Goor F et al. PNAS 2009;106:18825-30
16
Change in Sweat Chloride after VX-770
Mean Change
from Baseline
Part 1: 14-Day
120
120
4.4
-32.9 *
-40.4 *
60
-42.3 *
40
Sweat Chloride
[SD] (mmol/L)
80
80
0
0
25mg
VX-770
* p ≤ 0.0001 within subject comparison
75mg
VX-770
150mg
VX-770
‡
-32.4
‡
-52.6
40
20
Placebo
‡
-27.6
60
20
4.8
-2.3
100
100
Sweat Chloride
[95% CI] (mmol/L)
Mean Change
from Baseline
Part 2: 28-Day
Placebo
150mg
VX-770
-52.8†
250mg
VX-770
† p < 0.01 within subject comparison
‡ p < 0.05 within subject comparison
Accurso FJ et al. N Engl J Med 2010;363:1991-2003
Change in CFTR-Mediated Chloride Transport after VX-770
NPD: Zero Chloride/Isoproterenol Response
Mean Change
from Baseline
5
5
0
0
-1.6, -1.7
-4.7 *
-5.4 †
-5
Mean Change
from Baseline
Part 2: 28-Day
Mean Change [SD] (mV)
Mean Change [95% CI] (mV)
Part 1: 14-Day
-10
-15
-20
-25
1.9
-3.9
0.3
‡
-5
-8.4
-4.3 ‡
‡
-10
-10.1 ‡
-15
-20
-25
Baseline
Placebo
Day 14
25mg
VX-770
75mg
VX-770
*† p < 0.005 (75mg) within subject comparison
p < 0.010 (150mg) within subject comparison
Baseline
150mg
VX-770
Placebo
‡
Day 14
150mg
VX-770
Day 28
250mg
VX-770
p < 0.05 within subject comparison
Accurso FJ et al. N Engl J Med 2010;363:1991-2003
Percent Change in FEV1 from Baseline after VX-770
Part 2: 28-Day
Part 1: 14-Day
% Change from Baseline in FEV1
% Change from Baseline in FEV1
30
Mean Change
from Baseline
Mean Change
from Baseline
Mean Percent Change from
Baseline in FEV1 [SD]
Mean Percent Change from
Baseline in FEV1 [95% CI]
30
20
‡
10.5
10.0 *
10
4.9
0.7
0
Baseline
Placebo
20
†
11.6
10
7.4
7.0
‡
0
14 day
25mg
VX-770
75mg
VX-770
150mg
VX-770
Placebo
* p = 0.002 within subject comparison
‡p = 0.008 within subject comparison
150mg
VX-770
250mg
VX-770
† p < 0.01 within subject comparison
‡ p < 0.05 within subject comparison
Accurso FJ et al. N Engl J Med 2010;363:1991-2003
Changes from Baseline in Percent of Predicted FEV1, Respiratory Symptoms, and Weight,
and Time to the First Pulmonary Exacerbation, According to Study Group.
Ramsey BW et al. N Engl J Med 2011;365:1663-1672
Changes from Baseline through Week 48 in Sweat Chloride, According to Study Group.
Ramsey BW et al. N Engl J Med 2011;365:1663-1672
‘Discover’: 24-week randomized, double-blind, placebocontrolled trial; children 6-11 years old with at least one copy of
G551D, (N = 52)
Primary endpoint:
•Ivacaftor was associated with improved lung function; relative
improvement from baseline for FEV1 relative to the placebo
group was 17.4% (p<0.0001)
Secondary endpoints:
•Those in the treated group through week 24 saw a drop of sweat
chloride levels to 60 mmol/L from a base of 104 mmol/L; a
significant drop was not observed in the placebo group
•Those in the treated group gained 3.7kg through 24 weeks
compared to the placebo group that gained 1.8kg
Phenotype Effects of Classes of
CFTR Mutations
Normal
Class I
Class II
Class III
Class IV
Class V
I, II, III (“severe”)
 Pancreatic Insufficiency
 Risk of:
 Meconium ileus,
DIOS
 CFRD
 Severe hepatobiliary
disease
IV, V (“mild”)
No Synthesis
Increased
Degradation
Adapted from Hospital Practice, 1997
Defective
Regulation
Abnormal
Conductance
Reduced
Synthesis/
Trafficking
 Pancreatic Sufficiency
 Risk of:
 Acute, recurrent
pancreatitis
 Chronic pancreatitis
Cystic Fibrosis
Transmembrane Regulator
F508del-CFTR
(CFTR) Protein
• ~90% of CF individuals
have at least one
F508del allele
• F508del-CFTR has a
protein-folding defect that
Extracellular
Intracellular
• Inhibits intracellular
trafficking
Cl-
• Enhances CFTR
protein degradation
508
Ilefunctional
Ile Phe Gly F508del
• Little to no
ATC ATC TTT GGT
F508del-CFTR reaches
Δ
the cell surface
Ile Ile Gly
ATC ATT GGT
Zhang et al. J Struct Biol 2009;167:242
CFF Patient Registry 2008 (US)
O’Sullivan & Freedman. Lancet 2009;373:1891-1904
R domain
R domain
cAMP/PKA
regulation
NBD1
NBD1
NBD2
NBD2
ATP binding /
hydrolysis
ATP binding /
hydrolysis
A model for CFTR maturation and the influence of suppressor mutations in NBD1 and TMD2.
Thibodeau P H et al. J. Biol. Chem. 2010;285:35825-35835
©2010 by American Society for Biochemistry and Molecular Biology
Effect of F508 CFTR on ‘Destiny’
• F508 CFTR – most common cause of CF
– 80-90% of CF patients, 65-70% of CF chromosomes
– Protein misfolding in the endoplasmic reticulum
• Protein marked for degradation
• Failure to ‘mature’ and reach plasma membrane
Riordan, J. Ann Rev. Biochem. 2008
CFTR Correctors
CFTR correctors aim to increase the delivery and amount
of functional CFTR protein to the cell surface, resulting in
improved ion transport
ER
ER
VX-809 resulted from a high-throughput screening and
medicinal chemistry optimization program to generate
F508del-CFTR corrector compounds
VX-809 Improved F508del-CFTR Maturation
and Cl– Secretion In Vitro
Cl– Secretion
Western blot showing B- to C-band conversion with
cultured human bronchial epithelia (HBE) from
F508del homozygous CF donors
Ussing chamber studies with HBE from
F508del homozygous CF donors (n=7)
VX-809 (Log M)
VX-809 conc.
Plasma Membrane
0 -7.5
-7 -6.5
-6 -5.5
-5 -4.5
CBGolgi
0.8
C/C+B Ratio
ER
0.7
0.6
% Non-CF-HBE Cl- transport
CFTR Maturation
18
15
12
9
6
3
0
-9
-8
-7
-6
-5
-4
VX-809 (Log M)
0.5
0.4
-9
-8
-7
-6
-5
VX-809 (Log M)
-4
Van Goor F el al, PNAS 2011; 2011;108:18843-8
CFTR-mediated Cl– Transport:
Sweat Cl– biomarker
Change from baseline in average sweat Cl–
25
Change in sweat chloride (mmol/L)
(mean [range])
15
5
4
Placebo
VX-809 25 mg
VX-809 50 mg
VX-809 100 mg
VX-809 200 mg
2
0
-2
-4
-6
-8
-15
-25
-35
Baseline
Day 7
Day 14
Day 21
Day 28
Washout
Clancy JP et al, Thorax 2012;67:12-8
CFTR-mediated Cl– Transport:
Sweat Cl– biomarker
Change from baseline at Day 28 – difference vs placeboa
Change in sweat chloride (mmol/L)
(mean [95% CI])
8
+0.10
(n=16)
- 4.61
(n=16)
- 8.21†
(n=16)
- 6.13*
(n=15)
6
4
2
0
-2
-4
-6
-8
-10
-12
-14
-16
VX-809 25 mg
VX-809 50 mg VX-809 100 mg VX-809 200 mg
* P<0.05 vs placebo and within-subject
† P<0.01 vs placebo and within-subject
Linear trend test for dose-response: P=0.0013
a treatment
effect analysis based on an
Analysis of Covariance (ANCOVA) model
Sweat Cl– responders change from baseline to Day 28
Responder 20,* n (%)
Responder 10,† n (%)
Placebo
(n=17)
0
0
100 mg
(n=15)
0
6 (40%)‡
VX-809
200 mg
(n=16)
1 (6%)
6 (38%)‡
*20 mmol/L reduction vs baseline; †10 mmol/L reduction vs baseline; ‡P=0.02 vs placebo
Clancy JP et al, Thorax 2012;67:12-8
Combination Corrector-Potentiator
Therapy: VX809-770 Program
F508-CFTR
VX-770 (M):
0
0.1
0.03
1
VX-809
Cl-
Cl-
Cl-
Cl-
POTENTIATOR: Increases
channel opening of cell
surface F508del-CFTR
VX-770
ClCl-
ClCl-
ClClCl-
Cl-
ClCl- ClClCl-Cl-
25
ISC (A/cm2)
CORRECTOR: Increases
cell surface density and
function of F508del-CFTR
VX-770
VX-809
+
VX-770
20
15
10
VX-809
5
0
-9
Basal Activity
-8
-7
-6
-5
-4
Log M [VX-809]
Cells from one homozygous F508del
donor tissue
VX809-Ivacaftor Combination Trial
Part 1 Sweat Chloride Results
8/17 Arm 2 patients had sweat Cl- reduction >15 (4 of these >20)
Vertex Press Release, 11/3/11