New genetic therapies for inherited neuromuscular diseases

Francesco MuntoniDubowitz Neuromuscular Centre

UCL Institute of Child Health& Great Ormond Street Hospital

London, UK

Francesco Muntoni: disclosuresDuchenne trials• CI of AON clinical trials with AVI / Sarepta. • PI of Prosensa / Biomarin sponsored AON trials• PI of PTC phase II and III sponsored trials. • PI of Pfizer phase II clinical trial (myostatin inhibition)• CI of Summit Phase I and II trials. • CI of Esperare Phase I trial

Spinal Muscular Atrophy trials

• PI of Trophos SMA III trial• PI of Ionis/ Biogen AON Phase III study

• Other• Avexis, Biogen, Sarepta, Pfizer, PTC, Roche, Summit, Wave ad-hoc SAB

Dramatic impact of genetic therapies for Duchenne muscular dystrophy (DMD)and Spinal Muscular Atrophy (SMA)

Dealing with mutant RNA. Splice-switching antisense oligonucleotides for:

- exon skipping for DMD deletions- exon inclusion in SMA

Replacing genes with gene therapy

- AAV gene therapy for DMD- AAV gene therapy for SMA type I

Topics discussed

• Why antisense oligomers for DMD and SMA?

• Emerging data from AAV gene therapy

• Implications for clinical practice

• Most common muscular dystrophy of childhood

• X-linked, 1 in 3,500 male births• 26,000 new cases each year, ~ 100 in UK• De novo mutations hamper genetic

efforts to reduce incidence• Economic cost: at least $ 120,000 per

year

The two most common neuromuscular diseases in children

DMD SMA

• Most common lethal genetic disorder of childhood

• Autosomal recessive, 3 different levels of severity

• Cumulative incidence: 1 in 6,500 -1,10.000 births

• Heterozygous carrier frequency: 1:37 – 1: 60 in Caucasian populations

• Onset in first years of life, however mean age of diagnosis 4.5 years

• Progressive weakness affecting legs> arms• Inability to run, progressive difficulties

raising from the floor, going upstairs• Grossly elevated creatine kinase (CK)• Loss of ambulation 9.513.5 years (steroids)

Main clinical features

DMD SMA 1• Onset by 6 months of age• Diagnostic delay of ~2.5 months• Sitting posture never acquired• Severe respiratory muscle weakness• Feeding difficulties• Mean age of survival 9 months

• Lack of sarcolemmal protein dystrophin• Protects muscle from contraction

induced injury• Absent dystrophin progressive

muscle destruction• Muscle is replaced by connective tissue

and fat

PathogenesisDMD SMA

• Depletion of SMN protein• Ubiquitously expressed protein

necessary for survival of motorneurons

• Expressed in the cytoplasm, in nuclear structures GEMS, and in axons

DMD genetics• 65% out-of-frame DMD deletions• 10% out-of-frame duplications• 10-15%% nonsense mutations• Remaining: small mutations

Becker MD genetics

In framedeletions

Antisense oligonucleotides to

induce exon skipping 52

Antisense oligonucleotides: to modify splicing of the DMD gene

Skipping exon 51: 15% of all DMD boys carrying deletions

Ann Neurol. 2013;74:637-47.

2’Omethyl AON(Prosensa/GSK /Biomarin): drisapersen

Morpholino PMO AON(Sarepta)eteplirsen

AON exon 51 skipping therapy progress2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

Clinical Trials

Muscle biopsy: Baseline vs. Week 180 Patient 01015: Eteplirsen-Treated Week 180Patient 01015: Baseline

Mendell et al, 2015

Morpholino (PMO) AON

Eteplirsen 30 mg/kg is FDA Approved in the US for the Treatment of Patients with Exon 51 Skippable DMD

Treated patients decrease 2.3% annually for FVC% predicted.Natural history data demonstrated a 4.1% decline in FVC% predicted.

AON for DMD: rapidly evolving field:

1. Targeting additional exons to extend this approach to patients with other deletions

2. Next generation AONs

Targeting other DMD exons: SKIP-NMD Consortium

• Advocacy groups, research, healthcare providers and industry

• Francesco Muntoni project lead (UCL). Individual site leads are as follows:

• Institut de Myologie (Laurent Servais)• University of Newcastle upon Tyne (Volker Straub)• Università Cattolica del Sacro Cuore (Eugenio Mercuri)• Royal Holloway & Bedford New College (George Dickson)- in

vitro sequence selection & steering

Consultants for Research in Imaging & Spectroscopy

16

Increase in Sarcolemma localization of newly expressed dystrophin

BASELINE BIOPSY

ON-TREATMENTBIOPSY: Wk 48

Note: Indirect immunofluorescence staining of tissue cryosections was performed using MANDYS106 and anti-laminin 2 alpha antibodies

Targeting exons other than 51

Mor

phol

ino

AON

Nex

t gen

erat

ion

AO

N

AON: where is the field going

DMD

DMD AAV gene therapy programs

2017 2018 2019

Highly internally deleted dystrophins (AAV capacity

4.7Kb max)

Single IV administration

Full-length

Chromosome 5

SMN1

SMN2

SMN-FL SMND7 SMN-FL

SMN1SMN2

Full-length38kD

Truncated & less stable

~10% ~90% ~100%

Gene

mRNA

Protein

SPINAL MUSCULAR ATROPHY

AONs to induce exon 7 inclusion

SMN2 Gene

1 2 2 3 4 5 6 8 SMN2 mRNA

1 2a 2b 3 4 5 6 7 8

C to T

Functional Protein

7

IONIS-SMNRx

Intratechal administration of the antisense oligonucleotide spinraza

• AONs do not cross the blood brain barrier• Intratechal administration required• After a loading phase (4 IT injection in 2 months),

the long half life of the AON enables infrequent dosing

Motor performance

Infants on nusinersen achieved motor milestones unexpected for individuals with Type I SMA

Respiratory function and survival

AAV9 for SMA gene therapy

Jerry Mendell (Columbus, Ohio) is pursuing AAV gene therapy in infants with SMA I

Single IV injection

Two doses used:A. Cohort 1: 6.7x1013 vg/kgB. Cohort 2: 2.0x1014vg/kg

Inclusion• 9 months/6 months of age¹ or younger at

infusion• Bi-allelic SMN1 gene deletions or point

mutations• 2 copies of SMN2• Onset of disease at birth to 6 months of

age

COHORT 2 (n=12)Baseline Age (months): 3.1 [median], 3.4 [mean]Current Age (months): 20.2 [median], 20.7 [mean]Mean CHOP INTEND Increase: 24.7 points

Dashed lines for individual patients denote missed or partial CHOP-INTEND assessments

Early intervention and dose appear to affect response

0

10

20

30

40

50

60

0 3 6 9 12 15 18 21 24 27 30Age (months) 1 month = 30 days

60

50

40

2/12

10/12

11/12Cohort 2 (proposed therapeutic dose)

Rapid Response in Cohort 2• CHOP INTEND Increase at Month 1: 9.8 [mean]

• CHOP INTEND Increase at Month 3: 15.4 [mean]

Max score is 64

AVXS-101: CHOP-INTEND Motor Function Scores

Cohort 2 Achieved Motor Milestones Not Seen in the Natural History of SMA Type 1

Concluding remarks (1)• Outstanding progress in the therapeutic approaches for DMD and

SMA in the last few years

• Second generation AON therapies now in clinic trials, and AAV gene therapy gaining rapid traction

• The size of therapeutic response in SMA is unprecedented, but also linked to the interval between symptom onset and initiation of treatment

• Reducing the diagnostic delay for these conditions now has very tangible implications

• Consider newborn screening

Concluding remarks (2)• While success and tolerability of these approaches encourages their

continuing development, both their long term safety, and cost/ benefit will require careful analysis

• The cost of some of these intervention is considerable, and this might preclude their access to our patients

• NHSE and NICE do not currently have a swift system to allow the assessment of emerging therapies for these devastating childhood conditions

• While cautious and measured counselling to families is imperative, there are reasons to change from pessimism to optimism for these patients, although there is a lot more work to do

AcknowledgmentClinical and research team atGOSH/ ICH

Matthew Wood, OxfordGeorge Dickson, RHUL