Silencing DMPK gene by ARO-DM1, an
RNAi therapeutic, for Type 1 Myotonic Dystrophy
Jonathan Van Dyke, Teng Ai, Xiaokai Li, Adijan Kuckovic, Daniel Braas, Holly Hamilton, Maria Afrazi,
Tao Pei, James Hamilton, Zhi-Ming Ding. Arrowhead Pharmaceuticals, Madison, WI
Overview:
- Pathogenesis of type I myotonic dystrophy (DM1) is driven by an expanded CUG trinucleotide repeat in the 3'- untranslated region of DMPK transcripts.
- Pathogenic transcripts of human DMPK sequester RNA splicing factors and thereby cause leading to myotonia, muscular dystrophy, cataracts, and cardiac conduction abnormalities.
- There is no approved drug for treating the root cause of DM1.
- To develop a therapeutic for DM1, we designed siRNA conjugates to silence DMPK mRNA in skeletal muscles
- ARO-DM1and S-ARO-DM1 were identified as the best 2 conjugates, which target different positions of DMPK genes.
- In NHPs, DMPK mRNA expression in quadriceps and triceps was substantially decreased after two IV doses of ARO- DM1 or S-ARO-DM1, respectively.
- In the TREDT960i/HSA-rtTA mouse model of DM1 harboring a pathogenic DMPK transgene (DMPK-CUG),S-ARO-DM1:
- Decreased the DMPK-CUG expression
- Corrected the spliceopathies caused by overexpression of DMPK-CUP transgene
When intravenously injected weekly at 20 and 40 mpk respectively.
Pharmacodynamic study of ARO-DM1 and S-ARO-DM1 in cynomolgus
monkeys
PD
• After a single dose, muscular DMPK expression | ||||||
RNAi, | was reduced in quadriceps and triceps. | |||||
13.3 mpk, IV | Knockdown was maintained through Day 85 after | |||||
Biopsy | a second dose on Day 29. | |||||
• ARO-DM1 and S-ARO-DM1 exhibited similar | ||||||
potency in quadriceps; however, in triceps, S- | ||||||
N =3 | ARO-DM1 was slightly less potent. | |||||
Pharmacological study of S-ARO-DM1 in TREDT960i/HSA-rtTA mouse model of DM1l | Conclusions | |||||||||
TREDT960i/HSA-rtTA mouse model transgene | + Doxycycline | Human DMPK-CUG | • | ARO-DM1 and S-ARO-DM1 are | ||||||
TRE | 960 CTG repeats + HSA promotor rtTA | Mouse Dmpk | ||||||||
Human DMPK | potent RNAi therapeutics that | |||||||||
(e11-15 and 3' flanking genomic) | silence skeletal muscle DMPK | |||||||||
mRNA | ||||||||||
• | S-ARO-DM1 exhibited efficacies | |||||||||
in reducing the expression of | ||||||||||
pathogenic DMPK-CUG | ||||||||||
transgene and correcting | ||||||||||
spliceopathies in the skeletal | ||||||||||
muscles of a mouse model of | ||||||||||
• Using RNAscope, human | • S-ARO-DM1 was selected for | DM1 | ||||||||
• DMPK-CUG expressing mice and noncarrier | DMPK-CUG transcripts were | pharmacological studies due to its sequence | • | ARO-DM1 phase 1/2a studies | ||||||
complementarity to DMPK-CUG in the | ||||||||||
control mice (NCAR) were administered | detected in the myonuclei | are in progress in patients with | ||||||||
transgenic mice. | ||||||||||
doxycycline by diet over 50 days. | while endogenous mouse | DM1 | ||||||||
• In DMPK-CUG expressing mice, DMPK-CUG | Dmpk was detected both in | • Weekly administration of S-ARO-DM1 | ||||||||
expression was induced in skeletal muscles. | the myonuclei as well as in | decreased DMPK-CUG expression induced | ||||||||
• DMPK-CUG expression plateaued by Day 22. | sarcoplasm. | by doxycycline. |
Analysis of Spliceopathies in the TREDT960i/HSA-rTA mice treated with S-ARO-DM1
Relative Mis-splicing by ddPCR-based Competitive Probe Analysis
ddPCR-based Competitive Missplicing Assay | |||||
Inclusion | |||||
Exon A | Exon B | Exon C | |||
Exclusion | |||||
Inclusion Detected | FAM | Exclusion Detected | HEX | ||
HEX | FAM | ||||
Fwd Primer | Fwd Primer | ||||
Exon A | Exon B | Exon C | Exon A | Exon C | |
Rev Primer | Rev Primer |
Mis-splicing Analysis by RNAseq
* | † |
NCAR, 52.9mpk S-ARO-DM1, +Dox
DMPK-CUG, Saline, -Dox
DMPK-CUG, Saline, +Dox
DMPK-CUG, 26.4mpk S-ARO-DM1, +Dox
DMPK-CUG, 52.9mpk S-ARO-DM1, +Dox
Female
Male
Targeted Gene Panel
Abcc9* | Eya4* | Mbnl2 | Rapgef1*† |
Atp2a1*† | Fbxo31* | Mpdz | Ryr1*† |
Best3 | Fn1 | Neb | Slc8a3 |
Bin1*† | Jag2 | Nfix* | Tnik* |
Cacna2d1*† | Kif13a* | Opa1 | Trappc9* |
Clasp1 | Ldb3*† | Phactr4* | Trim55*† |
Clcn1† | Lrrfip2* | Phka1 | Ttn |
Cpeb2 | Map3k4* | Ppp1r12b* | Vps39* |
Dctn4 | Mbnl1* | Ppp3cc* |
- Spliceopathies were analyzed by 2 different assays using the mRNA from the gastrocnemius of DMPK- CUG and NCAR mice: ddPCR-based competitive mis-splicing and RNAseq analysis.
- Mis-splicingof 3 marker genes reported in the literature was detected by the ddPCR based assay.
- S-ARO-DM1treatment corrected the mis-splicing of those 3 marker genes.
- Mis-splicingof a targeted 35 gene panel was examined by RNAseq.
- Composite Percent Splice In Index (PSI)
was analyzed for the entire panel; the 20 most responsive genes to S-ARO-DM1, and 8 genes primarily expressed in skeletal muscles. - S-ARO-DM1treatment corrected the mis-splicing in all 3 panels.
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Arrowhead Pharmaceuticals Inc. published this content on 06 March 2024 and is solely responsible for the information contained therein. Distributed by Public, unedited and unaltered, on 08 March 2024 12:37:05 UTC.