Gene replacement therapy for myotubular myopathy

Anna Buj Bello

Myotubular Trust Family Conference, July 12th, 2014

Gene Therapy

Diseased cell

Gene mutation

Treatment of a disease by the administration of nucleic acids (DNA, RNA) in cells

Replacing or supplementing non-functional / mutated genes with

« healthy » genes

Patient

Diseased muscle

In human: ~ 640 muscles

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Gene Therapy

Derived from viruses

Produced in microscopic factories : cells

Carry a normal copy of the gene

Diseased cell Corrected cell

Vectors

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Ex vivo

In vivo

VECTOR

TRANSGENE

VECTORS PATIENT’S CELLS

TRANSDUCED

CELLS

Gene Therapy

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Identify the disease model

Administrate the vector to the

animal model:

- Route of administration

- Dose to be injected

- Determine evaluation tests

- Anticipate secondary effects

Verify the efficacy of the vector:

proof-of-concept

Therapeutic concept Preclinical development Clinical trials

Proof-of-concept

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Myotubular myopathy: animal models

Therapeutic concept Preclinical development Clinical trials

Identify the disease model

Mouse model (KO) - 2002

∆4

Mtm1 exon 4

Absence of myotubularin

Dog model (natural) - 2010

Misense mutation

MTM1 exon 7

Myotubularin (N155K) present but

strongly decreased

#

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Myotubular myopathy : gene

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

100 Kb

>300 different mutations

MTM1 gene - 1996: X chromosome

Protein: MYOTUBULARIN

present in all tissues

lipid phosphatase

MUTATIONS : loss or reduction of protein level

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Therapeutic vector

25 nm

ITR ITR

rep cap

rAAV (adeno-associated vector)

AAV: Non pathogenic virus in humans

Rep–Cap genes replaced by the MTM1 gene

AAV8-Mtm1 (mouse): research grade vector

AAV8-cMTM1 (dog): GMP-like vector

AAV8-hMTM1 (human): GMP vector

MTM1

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Gene therapy: proof of concept

Local delivery (intramuscular) - 2008

Correction of muscle histology (morphology)

Increase in muscle strength

MTM -treated MTM Healthy

Injection in muscle posterior leg (TA)

Analysis + 4 weeks

rAAV1-Mtm1

Mtm1 mKO

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WT+saline KO+saline WT+saline KO Early+AAV

5 weeks 6 months

HE

N

AD

H-T

R

DH

PRα

KO Late+AAV

Muscle histology

Correction of all muscles:

Morphology

Strength

Late stage of disease

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Gene therapy: dose-finding study

rAAV8-Mtm1

systemic administration

Su

rviv

al ra

te (

%)

Days

100

80

60

40

20

0 0 30 60 90 120

Dose 1: 100% survival at 3 months

Dose 2: 50% survival at 3 months

Days B

od

y w

eig

ht

(g)

30

25

20

10

0 0 30 60 90 120

15

5

WT + saline

KO + saline

KO + AAV High 1

KO + AAV Low 2

Dose 1: quasi-normalisation body weight

Dose 2: body weight not fully corrected

Therapeutic dose for long-term phenotype rescue (dose 1)

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Acknowledgements

Laurine Buscara

Karine Poulard

Nathalie Danièle

Romain Joubert

Christelle Moal

Thibaud Jamet

Yohann Garnier

Julie Marchant

Martin K. (Casey) Childers University of Washington, USA

Alan H. Beggs Children’s Hospital Boston, USA

Philippe Moullier

INSERM U649, Nantes

Atlantic Gene Therapies

Carole Masurier

Common Facilities

Genethon Bioprod

Fulvio Mavilio

Michael Lawlor Children’s Hospital and Medical

College of Wisconsin, USA