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Paul Goodyer, McGill University
.
A No Nonsense
Approach to Cystinosis
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1998 (Antignac)
Homozygous mutations of the CTNS gene (17q) encoding a cystine efflux channel in the lysosomal membrane
CYS
Lysosome
Protein
Cystine
6
3
½ Cystine
(umol/g prot)
Leukocytes
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LYSOSOME
CYS
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European CTNS deletion
The 57 kb deletion arose ~ 500 AD in Northern Europe.
It is present in abut 50% of Northern European patients
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French immigration to Quebec: 1608-1763
Irish Immigration to Quebec (Potato Famine) 1846-1851
By 1871, Irish=10-15% of Quebec population
Montreal: Oldest St. Patrick’s Day Parade
W138X
Irish/French Canadian Nonsense Mutation
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T G A
Nonsense Mutations (Premature STOP Codons)
STOP
?
T G G
W138X
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CTNS Nonsense Mutations
2
2 16
16 11
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Type of CTNS Mutation Matters!
It may be possible to overcome Nonsense Mutations
Using compounds related to Aminoglycoside antibiotics
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Translational
Readthrough !!
Aminoglycoside antibiotics
trick the ribosome
into “reading through”
a nonsense mutation
STOP
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1st generation 2nd generation 3rd generation 4th generation 5th generation
Bioorg. Med. Chem. Lett. 2006 J. Med. Chem. 2009 Bioorg. Med. Chem. 2010 Med. Chem. Comm. 2011 J. Med. Chem. 2012
Designer aminoglycosides - nontoxic Eloxx
Pharmaceuticals
ELX-02
--TGA--
Tryptophan
Does ELX-02 work?
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A nonsense mutation in the Tyrosinase
gene halts production of melanin, the
black pigment in mouse hair cells
PROOF OF PRINCIPLE
Wildtype C57Black mouse
Albino mouse with Tyr489X
nonsense mutation
Fatima
Tokhmafshan
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Tyrosinase
AAG TAG (STOP)
489
533
(LYSINE)
ELX02
Tyrosinase
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Treated Albino Mouse
Untreated Albino Mouse Black Mouse
ELX02 restores melanin production
(black pigment) to hair cells
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Fibroblast Line CTNS Allele1 CTNS Allele2
WG1012 W138X W138X
WG1896 W138X W138X
WG0881 del57Kb del57Kb
WG2379 del57Kb W138X
MCH070 Wildtype Wildtype
Cystinosis Fibroblast Lines
Emma
Brasell
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No evidence of ELX-02 toxicity in human fibroblasts
or human proximal tubular cell line (HK2)
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E L X -0 2 (u g /m L )
nm
ol
Ha
lf C
ys
tin
e/m
g p
ro
tein
0100
200
400
0
1 0
2 0
3 0
4 0
**
*
Does ELX-02 permit sufficient CTNSW138X/W138X
readthrough to reduce cystine accumulation ?
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CTNS
MUTATION
Autophagy
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Live Cell Imaging of LC3B-stained
autophagosomes in proximal tubular
cells from a CTNSW138X/del patient
Normal
CTNSW138X/del CTNSW138X/del
+ELX-02 24 hrs
ELX-02 reverses
accumulation of abnormal
autophagosomes
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Does ELX-02 reduce WBC cystine in
patients with a CTNSW138X Mutation?
Eloxx Pharmaceuticals Inc
Genome Quebec/Genome
Canada and CRF
Montreal
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ELX02 Dose-Finding Clinical Trial (2019)
0.3mg/kg
0.75mg/kg
1.5mg/kg
3mg/kg
CTNS Nonsense Mutations
Discontinue Cysteamine X 6 weeks
Stay in Montreal for 4-5 weeks
Not Yet approved/recruiting
N=3 >18 yrs
N=3 > 12 yrs
Goal: Find appropriate dose for long-term trial
Safety
Safety
Safety
1 Week
ELX02 < gentamycin (7.5mg/kg)
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Emma Brasell
LeeLee Chu
Murielle Akpa
Diana Iglesias
Fatima Tokhmafshan
Yojiro Yamanaka
Elena Torban
Elena Levchenko
Franciso Emma
Corinne Antignac CRF, CRN, CFI
KFOC
GENOME CANADA
ELOXX PHARMA