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2'-O-methoxyethyl splice-switching oligos
multiple patient samples across doses. For our study, the 5 mM and 25 mM dose were used on the same patient and produced no significant differences. However, the 50 mM and 100 mM doses were tested on samples from different patients. As these samples were harvested from different patients, at separate time points, by different collabora- tors, and shipped separately, we cannot make a true side- by-side comparison. Experiments were limited by the availability of donor material and skilled researchers to collect it. Better access to local patient databases or train- ing more collaborators could allow such a large-scale study for more comprehensive comparisons.
A barrier to clinical translation is the ability to target the 2'-MOE-SSO to the bone marrow. 2'-MOE-SSO need physical or chemical manipulation to enter cultured cells. However in vivo and in some primary cell cultures, studies show natural cellular uptake pathways without this manipulation.12 While drug delivery is not in the scope for this paper, modulation of splicing has been demonstrated in preclinical models and in the clinic. As a result, two splicing modulation drugs have been approved, Spinraza® for the treatment of spinal muscular atrophy and Eteplirsen for the treatment of Duchenne muscular dystro- phy, administered by intrathecal and subcutaneous injec- tions, respectively.16,17 Upon systemic delivery, antisense oligonucleotides distribute broadly in the tissues, includ- ing bone marrow. However, in order to improve the deliv- ery to the cell type of interest, a LICA (ligand conjugated antisense) strategy is needed. Triantennary N-acetylgalac- tosamine (GalNAc) conjugated antisense oligonucleotides (ASO) improved potency in hepatocytes by about 30-fold in the clinic;30 GLP-1 conjugated ASO LICA strategy has successfully improved the delivery to pancreatic b cells.31 Finding the LICA to specific bone marrow cell types,
including CD34+ cells, is an area of active investigation. In summary, 2'-MOE-SSO are promising therapeutic tools for certain splicing forms of b-thalassemia. Their ability to correct the underlying splicing defect offers a pharmacological treatment that is both direct and specific. As such, this therapy could help patients reduce their transfusion dependence or even reach transfusion inde- pendence. If combined with the appropriate carrier for optimized delivery and absorption, these molecules repre- sent an attractive therapeutic alternative to increase HbA protein in patients with b-thalassemia, without the need for aggressive conditioning regimens and expensive ex vivo cell manipulation that are mandatory in gene addi-
tion and gene editing therapies.
Disclosures
SR is a consultant for Disc Medicine, Protagonist, LJPC, Meira GTx, SAB for Meira GTx, Ionis Pharmaceuticals, Stocks - Meira Gtx and has received grants (not for this publication) R01DK095112-NIDDK, European Community-FP7, AVLT- Italy, CURE-PA Department of Health, Calliope Foundation, Department of Defense (DOD), Ionis Pharmaceuticals, Merganser Biotech and Medgenics Pharmaceuticals; SG, RP, SMF and AW are employees of Ionis Pharmaceuticals and Ionis intends to file patent; MDC is a member of the advisory board of Vifor, Sanofi/Genzyme, Novartis, Celgene and Bluebird; AD is an employee of Aruvant Sciences and former employee of LEK Consulting; IM is on the advisory board of Sanofi Genzyme.
Contributions
AD, GLB performed research, data analysis, and wrote the manuscript; LB and SR supervised the study; SG, RP, SMF, AW performed research on oligos; IM, YI, DJ, MC, CS, PD, CC, SC, MK, KSW, DM, CC, OA and MDC performed research.
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