Salbutamol increases survival motor neuron (SMN) transcript levels in leucocytes of spinal muscular atrophy (SMA) patients: relevance for clinical trial design.
BACKGROUND
Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by mutations of the SMN1 gene. Based on severity, three forms of SMA are recognised (types I-III). All patients usually have 2-4 copies of a highly homologous gene (SMN2) which produces insufficient levels of functional survival motor neuron (SMN) protein. Recently, evidence has been provided that SMN2 expression can be enhanced in vitro by salbutamol, a β2-adrenergic agonist. This compound has also been shown to improve motor function of SMA patients in two different pilot trials.


OBJECTIVE
To evaluate the in vivo molecular efficacy of salbutamol in SMA patients.


METHODS
Twelve type II-III patients took salbutamol orally for 6 months. SMN2 full length transcript levels were determined in peripheral blood leucocytes by absolute real-time PCR, at baseline and after 3 and 6 months of treatment.


RESULTS
A significant and constant increase in SMN2 full length transcript levels was detected; the response was directly proportional to SMN2 gene copy number.


CONCLUSIONS
The data strongly support salbutamol as a candidate for treating SMA, and suggest that SMN2 copy number may predict the molecular response to treatment and may be a useful randomisation parameter in a double blind placebo controlled clinical trial design.
Tiziano
Francesco Danilo
FD
Istituto di Genetica Medica, Università Cattolica del Sacro Cuore, Largo Francesco Vito, 1 00168 Roma, Italy. fdtiziano@rm.unicatt.it
Lomastro
Rosa
R
Pinto
Anna Maria
AM
Messina
Sonia
S
D'Amico
Adele
A
Fiori
Stefania
S
Angelozzi
Carla
C
Pane
Marika
M
Mercuri
Eugenio
E
Bertini
Enrico
E
Neri
Giovanni
G
Brahe
Christina
C
D058666:Adrenergic beta-2 Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology; D000328:Adult; D000420:Albuterol / Q000008:administration & dosage / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007962:Leukocytes / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009134:Muscular Atrophy, Spinal / Q000235:genetics* / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D055540:Survival of Motor Neuron 2 Protein / Q000235:genetics* / Q000378:metabolism
D058666:Adrenergic beta-2 Receptor Agonists; D012333:RNA, Messenger; D055540:Survival of Motor Neuron 2 Protein; D000420:Albuterol