Distinguishing DMD from BMD

1
Phenylbutyrate increases SMN gene expression in
vitro and in vivo
Christina Brahe
Università Cattolica del S.Cuore, Roma
2
SMA is caused by homozygous absence of the SMN1
gene
SMN1
SMN2
tel
cen
3
(No Transcript)
4
Hypothesis
Particular drugs may activate the SMN2 genes
to produce more SMN protein
SMN
SMN
improvement of muscle strength
5
There are drugs that open up the DNA to allow the
expression of genes at a higher level
inactive gene
HDAC
active gene
HAT
condensed chromatin
accessible chromatin
6
Phenylbutyrate belongs to this class of drugs

• FDA approved
• for the treatment of another pediatric disease
• is generally well tolerated
• crosses the blood-brain barrier

7
Study of the effect of phenylbutyrate on SMN2
expression in cell cultures from SMA patients

Results

• Increase in SMN transcripts (precursor of
  protein)
• in most but not all cultures
• the increase in transcripts ranged from 50-400
  
• increase in SMN protein

8
Maximum increase in SMN2-fl transcript levels
500
450
400
350
300
increase in SMN2-fl transcripts
250
200
150
100
50
patient
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
SMA I
SMA II
SMA III
9
Increase in SMN protein
120
16 h
100
24 h
80
increase in SMN protein
60
40
20
SMA I
SMA II
SMA III
10
Study of the effect of phenylbutyrate on SMN2
expression in leukocytes of SMA patients

• Phenylbutyrate was administered to 6 patients
• (4 type II and 2 type III) and 3 parents for 7
  days
• blood samples were taken before, during and
  after the trial
• leukocyte SMN2 transcripts were measured

11
PB increases SMN expression in leukocytes
900
800
500
400
SMN-fl transcripts () relative to T0
300
200
100
0
-100
1
2
3
4
5
6
M2
M3
F6
1
2
3
4
5
healthy untreated controls
patients
parents
Brahe et al., EJHG 2005
12
Open pilot trial

• 10 patients with SMA II (age 30 months-12
  years)
• Treatment with phenylbutyrate for 13 weeks
• (1 week on, 1 week off)
• Efficacy was evaluated by using a functional
  motor scale

13
Functional motor scale
Three point scoring
system 2 scores for unaided, 1 for assistance
and 0 for inability

20 items
Score 2 points
Score 1 point Score 0
Score Touch one hand to head
flexes head to hand unable
( )
14
Results on the functional scale
before
35
3 weeks
30
25
9 weeks
20
score
15
10
5
0
2.6
3.5
3.6
3.8
4.1
6.1
6.3
7.7
9.7
12.7
Age (years)
Mercuri et al., 2004
15
Mean scores in treated patients and control group
22
20
18
16
14
score
12
10
8
6
4
2
T1
T2
T0
T3 (6 months)
T0
treated patients
untreated controls
Mercuri et al., 2004
16
Conclusions of the open trial

• improvement of functional ability
• children lt5 years had a more obvious improvement
• great variability of response (as previously
  observed
• in vitro)

17
Large randomised, double-blind, placebo
controlled trial

• Enrolled 106 patients SMA II or non-ambulant
  type III
• Age 30 months -12 years
• Drop out 14 (13)
• Schedule intermittent (1 week on, 1 week off)
  for 13 weeks
• Assessments
• Hammersmith functional motor scale
• myometry (gt5 years)
• FVC (gt5 years)

18
Problems to be solved

• More reliable outcome measures
• (more sensitive functional motor scale and
  quantitative muscle
• testing, etc)
• protocol design to achieve the maximum response
• (dosage, continuous or pulsed administration,
  duration)
• gain information on the mechanisms underlying
  the
• difference in response

19
Istituto di Genetica Medica Università
Cattolica, Roma Danilo Tiziano Carla
Angelozzi Federica Borgo Anna Maria
Pinto Daria Darelli Tiziana Vitali Giovanni
Neri
Istituto di Neurologia Università Cattolica,
Roma Eugenio Mercuri
Ospedale Bambino Gesù Rome Enrico Bertini
Acknowledgements Patients and parents FSMA
USA FSMA Italy A.S.A.M.S.I. Telethon - Italy