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A series of cationic amphiphlic copolymers (Z series) constructed from Tween 85 and low molecular weight (Mw) polyethyleneimine (LPEI) have been evaluated for the delivery of antisense 2′-O-methyl phosphorothioate RNA (2′-OMePS) in both cell culture and dystrophic mdx mice. All Z copolymers improved the 2′-OMePS-induced dystrophin expression both in vitro and in vivo compared with PEI 25k formulated or 2′-OMePS alone. The most effective polymers are in the order of Z9 > Z3 > Z7, Z1, Z2, Z6 > others by formulation at the dose of 20 μg mL−1 in myoblast cell culture. Significantly enhanced exon-skipping of 2′-OMePS with Z polymers in mdx mice was obtained in the order of Z7 > Z9, Z3 > Z8, Z6 > others. The highest efficiency of targeted exon-skipping with Z7 [T85–PEI 2k (1 : 1)] reached over 8 fold compared with 2′-OMePS alone in mdx mice. Further analyses of the structure and function indicate that the more hydrophobicity and lower PEI content of the polymer microstructure are, the greater are the delivery efficiency and exon-skipping. The unique hydrophobic interactions between the Z polymers and 2′-OMePS likely create more stable complexes in primarily hydrophilic environments both in vitro and in vivo. The overall results suggested that Tween 85 modified LPEIs provide a promising delivery approach for applications of 2′-OMePS oligonucleotides as therapeutic reagents.

Mingxing Wang, Bo Wu, Sapana N Shah, Peijuan Lu, Qilong Lu McColl-Lockwood Laboratory for Muscular Dystrophy Research, Department of Neurology, Cannon Research Center, Carolinas Medical Center, Charlotte, NC 28203, USA Background: Antisense oligonucleotide (ASO)-mediated exon skipping has been feasible and promising approach for treating Duchenne muscular dystrophy (DMD) in preclinical and clinical trials, but its therapeutic applications remain challenges due to inefficient delivery. Methods: We investigated a few Saponins for their potential to improve delivery performance of an antisense 2′-Omethyl phosphorothioate RNA (2′-OMePS) in muscle cells and in dystrophic mdx mice. This study was carried out by evaluating these Saponins’ toxicity, cellular uptake, transduction efficiency in vitro, and local delivery in vivo for 2′-OMePS, as well as affinity study between Saponin and 2′-OMePS. Results: The results showed that these Saponins, especially Digitonin and Tomatine, enhance the delivery of 2′-OMePS with comparable efficiency to Lipofectamine 2k (LF-2k)-mediated delivery in vitro. Significant performance was further observed in mdx mice, up to 10-fold with the Digitonin as compared to 2′-OMePS alone. Cytotoxicity of the Digitonin and Glycyrrhizin was much lower than LF-2k in vitro and not clearly detected in vivo under the tested concentrations. Conclusion: This study potentiates Saponins as delivery vehicle for 2′-OMePS in vivo for treating DMD or other diseases. Keywords: antisense delivery, 2′-OMePS, exon skipping, saponin, muscular dystrophy

Background The polymer-based drug/gene delivery is promising for the treatment of inherent or acquire disease, because of the polymer’s structural flexibility, larger capacity for therapeutic agent, low host immunogenicity and less cost. Antisense therapy is an approach to fighting genetic disorders or infections using antisense oligonucleotides (AOs). Unfortunately, the naked AOs showed low therapeutic efficacy in vivo and in clinical trial due to their poor cellular uptake and fast clearance in bloodstream. In this study, a series of triazine-cored amphiphilic polymers (TAPs) were investigated for their potential to enhance delivery of AOs, 2′-O-methyl phosphorothioate RNA (2′-OMePS) and phosphorodiamidate morpholino oligomer (PMO) both in vitro and in vivo. Results TAPs significantly enhanced AO-induced exon-skipping in a GFP reporter-based myoblast and myotube culture system, and observed cytotoxicity of the TAPs were lower than Endoporter, Lipofectamine-2000 or PEI 25K. Application of optimized formulations of TAPs with AO targeted to dystrophin exon 23 demonstrated a significant increase in exon-skipping efficiency in dystrophic mdx mice. The best ones for PMO and 2′-OMePS delivery have reached to 11-, 15-fold compared with the AO only in mdx mice, respectively. Conclusion The study of triazine-cored amphiphilic polymers for AO delivery in vitro and in mdx mice indicated that the carrier’s performances are related to the molecular size, compositions and hydrophilic-lipophilic balance (HLB) of the polymers, as well as the AO’s structure. Improved exon-skipping efficiency of AOs observed in vitro and in mdx mice accompanied with low cytotoxicity demonstrated TAP polymers are potentials as safe and effective delivery carrier for gene/drug delivery.

A set of triazine-cored cationic amphiphilic polymers (TAPs) composed of low molecular weight (Mw) polyethylenimine (LPEI, B) and amphiphilic Jeffamine (A) were prepared with controllable composition and molecular size, and further characterized for plasmid DNA (pDNA) delivery both in vitro and in vivo. These new polymers condensed pDNA efficiently at a polymer/pDNA weight ratio of 5 with particle sizes below 200 nm. The introduction of Jeffamine in the polymers significantly improved the cellular uptake of pDNA, but without increasing its toxicity compared with the parent LPEI. The best formulation resulted in 6- and 29-fold transfection efficiencies of PEI 25k in vitro and in vivo in mdx mice, respectively. Higher transfection efficiency was achieved with more lipophilic A1/A3-based polymers in vitro, with 1A11B3 and 1A12B3 showing the greatest delivery performance. However, the lipophilicity of the TAPs is less critical in vivo as the less lipophilic A2/A4 constructed TAPs also performed similarly well as the more lipophilic A1/A3 constructed ones. In addition, a synergistic effect of LPEI and Jeffamine via chemical conjugation for the delivery of pDNA was revealed in transfection efficiency. These results indicate that the appropriate positive surface and particle size of polymer/pDNA complex and the composition and hydrophilic-lipophilic balance (HLB) of polymers are crucial for effective delivery, although intricate matching exists between A and B in the TAP composition. Triazine-cored cationic amphiphilic polymers are safe and potentially effective carriers for gene/drug delivery.

Antisense oligonucleotide therapy for Duchenne muscular dystrophy has shown great potential in preclinical and clinical trials, but its therapeutic applications are still limited due to inefficient delivery. In this study, we investigated a few polyquaterniums (PQs) with different size and composition for their potential to improve delivery performance of an antisense phosphorodiamidate morpholino oligomer (PMO) both in vitro and in vivo. The results showed that LuviquatTM series, especially PQ-1 and PQ-3, promoted the exon-skipping efficiency comparable to Endoporter-mediated PMO delivery in vitro. Significant enhancement in skipping dystrophin exon 23 has also been achieved with PQ-3 up to seven-fold when compared to PMO alone in mdx mice. Cytotoxicity of the PQs was lower than Endoporter and PEI 25 K in vitro and muscle damage not clearly detected in vivo under the tested concentrations. These results together demonstrate that the optimization of PQ in molecular size, composition and distribution of positive charges is the key factor to achieve enhanced PMO exon-skipping efficiency. The higher efficiency and lower toxicity endow polyquaternium series as AO delivery enhancing agents for treating muscular dystrophy and other diseases.

Mingxing Wang, Bo Wu, Jason D Tucker, Peijuan Lu, Qilong Lu Department of Neurology, McColl-Lockwood Laboratory forMuscular Dystrophy Research, Cannon Research Center, Carolinas Medical Center, Charlotte, NC, USA Abstract: In this study, we investigated a series of cationic polyelectrolytes (PEs) with different size and composition for their potential to improve delivery of an antisense phosphorodiamidate morpholino oligomer (PMO) both in vitro and in vivo. The results showed that the poly(diallyldimethylammonium chloride) (PDDAC) polymer series, especially PE-3 and PE-4, improves the delivery efficiency of PMO, comparable with Endoporter-mediated PMO delivery in vitro. The enhanced PMO delivery and targeting to dystrophin exon 23 was further observed in mdx mice, up to fourfold with the PE-4, compared with PMO alone. The cytotoxicity of the PEs was lower than that of Endoporter and polyethylenimine25,000 Da in vitro, and was not clearly detected in muscle in vivo under the tested concentrations. Together, these results demonstrate that optimization of PE molecular size, composition, and distribution of cationic charge are key factors to achieve enhanced PMO exon-skipping efficiency. The increased efficiency and lower toxicity show this PDDAC series to be capable gene/antisense oligonucleotide delivery-enhancing agents for treating muscular dystrophy and other diseases. Keywords: cationic polyelectrolytes, antisense delivery, exon-skipping, PMO, muscular dystrophy

Antisense oligonucleotide (AON) therapy for Duchenne muscular dystrophy has drawn great attention in preclinical and clinical trials, but its therapeutic applications are still limited due to inefficient delivery. In this study, we investigated a few saponins for their potential to improve delivery performance of an antisense phosphorodiamidate morpholino oligomer (PMO) both in vitro and in vivo. The results showed that these saponins, especially digitonin and tomatine, improve the delivery efficiency of PMO comparable to Endo-Porter-mediated PMO delivery in vitro. The significant enhancement of PMO targeting to dystrophin exon 23 delivery was further observed in mdx mice up to 7-fold with the digitonin as compared to PMO alone. Cytotoxicity of the digitonin and glycyrrhizin was lower than Endo-Porter in vitro and not clearly detected in vivo under the tested concentrations. These results demonstrate that optimization of saponins in molecular size and composition are key factors to achieve enhanced PMO exon-skipping efficiency. The higher efficiency and lower toxicity endow saponins as gene/AON delivery enhancing agents for treating muscular dystrophy or other diseases.

A series of amphiphilic peptides modified PMO (Pt-PMO) were prepared, and their antisense effect and toxicity were evaluated both in vitro and in mdx mice. The results showed that the exon-skipping performance of Pt-PMO are relative to the structure of the conjugated peptide: the Pt3/Pt4 composed of six/seven arginines and one myristoylation modified PMO showed more efficacy and with less toxicity as compared to others, confirming that appropriate hydrophilic-lipophilic balance (HLB) and cationic sequence numbers play a crucial role in improving cell uptake and corresponding exon-skipping efficiency. This was observed particularly in enhanced delivery efficiency of PMO comparable to B-PMO in vitro, while 6-fold improved exon-skipping was achieved against naked PMO in vivo. The multi-PMO modified Pt8-PMO also showed improved exon-skipping both in vitro and in vivo, though there is lower efficiency in systemic delivery as compared to Pt4-PMO. These data suggest that with optimization of peptide in component, charge density has clear potential for exploration towards achieving higher efficiency of antisense oligonucleotide systemic delivery, and thus is more applicable for clinical application.

Hyperbranched poly(ester amine)s (PEAs) based on tris[2-(acryloyloxy)ethyl]isocyanurate (TAEI) cross-linked low-molecular-weight polyethylenimine (Mw: 0.8k/1.2k/2.0k) have been evaluated for delivering antisense phosphorodiamidate morpholino oligomer (PMO) in vitro and in vivo in the dystrophic mdx mouse. The results show that the PEAs constructed with polyethylenimine (PEI) 2.0k (C series) improved PMO delivery more efficiently than those constructed with PEI 0.8k (A series) or 1.2k (B series) in a GFP reporter-based C2C12 mouse myoblast culture system. The highest efficiency of exon-skipping in vitro with the PMO oligonucleotide targeting human dystrophin exon 50 was obtained when the PEA C12 [TAEI-PEI 2.0k (1:2)] was used. Nearly all of the PEAs improved dystrophin expression in mdx mice by local injection with a 2–4-fold increase when compared with PMO alone. Improved transfection efficiency and lower toxicity indicate the potential of the biodegradable PEA polymers as safe and efficient PMO delivery vectors for in vivo applications.

A series of poly (ester amines) (PEAs) constructed from low molecular weight polyethyleneimine (LPEI, Mw: 0.8k, 1.2k Da) and Pluronic (different molecular weight (Mw) and hydrophilic-lipophilic-balance (HLB)) components were synthesized, and evaluated in vitro and in vivo as gene delivery carriers. Most PEA polymers were able to bind and condense plasmid DNA effectively into particles of approximately 150 nm in solution at the polymer/DNA ratio of 5 and above. Transfection efficiency of the PEA polymers depends on particle size of the polymer/DNA complex, molecular weight and HLB of the Pluronics and the size of PEI within PEA composition, as well as the cell type. Significant improvement in gene delivery efficacy was achieved with PEA01/04/05 composed of Pluronic size (Mw: 3000-5000 Da), and HLB (12-18) in CHO, C2C12 and HSkM cell lines; and the effective transfection was reflected with PEA 01/04/07 composed of Pluronics with size (2000-5000 Da) and HLB (12-23) in mdx mice. The best formulation for pDNA delivery was obtained with PEA 01 producing transgene expression efficiency 5, 19-folds of that of PEI 25k in vitro and in vivo, respectively. These results potent some of these PEA polymers as attractive vehicles for gene or oligonucleotide delivery.

A series of poly(esteramine)s (PEAs) constructed from low molecular weight polyethyleneimine (LPEI) and Pluronic were evaluated for the delivery of antisense oligonuclotides (AOs), 2′-O-methyl phosphorothioate RNA (2′-OMePS) and phosphorodiamidate morpholino oligomer (PMO) in cell culture and dystrophic mdx mice. Improved exon-skipping efficiency of both 2′-OMePS and PMO was observed in the C2C12E50 cell line with all PEA polymers compared with PEI 25k or LF-2k. The degree of efficiency was found in the order of PEA 01, PEA 04 > PEA 05 > others. The in vivo study in mdx mice demonstrated enhanced exon-skipping of 2′-OMePS with the order of PEA 06 > PEA 04, PEA 07 > PEA 03 > PEA 01 > others, and much higher than PEI 25k formulated 2′-OMePS. Exon-skipping efficiency of PMO in formulation with the PEAs were significantly enhanced in the order of PEA 02 > PEA 10 > PEA 01, PEA 03 > PEA 05, PEA 07, PEA 08 > others, with PEA 02 reaching fourfold of Endo-porter formulated PMO. PEAs improve PMO delivery more effectively than 2′-OMePS delivery in vivo, and the systemic delivery evaluation further highlight the efficiency of PEA for PMO delivery in all skeletal muscle. The results suggest that the flexibility of PEA polymers could be explored for delivery of different AO chemistries, especially for antisense therapy.

Branched poly(ester amine)s (PEAs) based on tris[2-(acryloyloxy)ethyl]isocyanurate (TAEI) cross-linked low molecular weight polyethylenimine (LPEI, Mw: 0.8k/1.2k/2.0k) polymers have been evaluated for their ability to deliver antisense 2′-O-methyl phosphorothioate RNA (2′-OMePS) through in vitro and in dystrophic mdx mice. Almost all PEAs improved exon-skipping of 2′-OMePS both in vitro and in vivo. Especially the PEAs composed of PEI 2.0k (C series) enhanced 2′-OMePS delivery more effectively than PEI 0.8k or 1.2k-based series using a GFP reporter-based C2C12 myoblast culture system and in mdx mice. The highest efficiency of targeted exon-skipping of 2′-OMePS was obtained by PEA C14 [TAEI-PEI 2.0k (1:4)] with up to 6 fold increase compared with 2′-OMePS only in mdx mice via intramuscular injection without increased muscle damage. Enhanced exon-skipping and lower toxicity highlight the potential of this series biodegradable PEAs as safe and efficient 2′-OMePS delivery vectors for treating diseases such as muscular dystrophy with splicing modulation.

A series of cationic amphiphlic copolymers constructed from Tween 85 and low molecular weight (Mw) polyethyleneimene (LPEI) were prepared in ambient conditions and characterized. The Mws of these copolymers ranged from around 5,000 to 25,000 Da and PEI content from 8.25% to 20.91%. The new copolymers condensed DNA efficiently with particles size below 200 nm at the weight ratio 5 of polymer/pDNA, and were stable in the presence of Serum or Heparin. The introduction of Tween 85 led to a significant increase in the cellular uptake of complexes with higher transfection efficiency in CHO, C2C12, and HSkM cell lines, but without increase in toxicity compared with the parent LPEI. The best formulation for pDNA delivery produced transgene expression efficiency 5, 20-fold of PEI 25k in vitro and in mdx mice in vivo, respectively. There is no obvious muscle damage with these new copolymers at the injection sites. These results indicated that the presence of more hydrophobic groups within the new polymers is associated with higher transfection efficiency (TE), and the higher PEI content and Mw of polymers show higher TE with relatively higher toxicity. The Tween 85 modified LPEI could be a potentially safe and effective polymeric carriers for gene/drug delivery.

We investigated a series of small-sized polyethylenimine (PEI, 0.8/1.2 k)-conjugated pluronic copolymers (PCMs) for their potential to enhance delivery of an antisense phosphorodiamidate morpholino oligomer (PMO) in vitro and in dystrophic mdx mice. PCM polymers containing pluronics of molecular weight (Mw) ranging 2–6 k, with hydrophilic-lipophilic balance (HLB) 7–23, significantly enhanced PMO-induced exon-skipping in a green fluorescent protein (GFP) reporter-based myoblast culture system. Application of optimized formulations of PCMs with PMO targeted to dystrophin exon 23 demonstrated a significant increase in exon-skipping efficiency in dystrophic mdx mice. Consistent with our observations in vitro, optimization of molecular size and the HLB of pluronics are important factors for PCMs to achieve enhanced PMO delivery in vivo. Observed cytotoxicity of the PCMs was lower than Endo-porter and PEI 25 k. Tissue toxicity of PCMs in muscle was not clearly detected with the concentrations used, indicating the potential of the PCMs as effective and safe PMO carriers for treating diseases such as muscular dystrophy.

Antisense therapy has recently been demonstrated with great potential for targeted exon skipping and restoration of dystrophin production in cultured muscle cells and in muscles of Duchenne Muscular Dystrophy (DMD) patients. Therapeutic values of exon skipping critically depend on efficacy of the drugs, antisense oligomers (AOs). However, no animal model has been established to test AO targeting human dystrophin exon in vivo systemically. In this study, we applied Vivo-Morpholino to the hDMD/mdx mouse, a transgenic model carrying the full-length human dystrophin gene with mdx background, and achieved for the first time more than 70% efficiency of targeted human dystrophin exon skipping in vivo systemically. We also established a GFP-reporter myoblast culture to screen AOs targeting human dystrophin exon 50. Antisense efficiency for most AOs is consistent between the reporter cells, human myoblasts and in the hDMD/mdx mice in vivo. However, variation in efficiency was also clearly observed. A combination of in vitro cell culture and a Vivo-Morpholino based evaluation in vivo systemically in the hDMD/mdx mice therefore may represent a prudent approach for selecting AO drug and to meet the regulatory requirement.

A series of low molecular weight polyethyleneimine (LPEI) conjugated Pluronic copolymers (PCMs) were synthesized and evaluated in C2C12 myoblasts and CHO cells in vitro and in dystrophic mdx mice in vivo as gene delivery carriers. Pluronics with different molecular weights (Mw) and hydrophilic–lipophilic-balance (HLB), and two LPEIs (Mw: 0.8k, 1.2k Da) as composition of PCMs have been synthesized, and the dynamics between the structures and properties were investigated. The conjugation efficiency of PEI ranged from 77.5–95.4% with relatively higher levels of PEI conjugation to the Pluronic size in PCMs, with the Pluronics of smaller size achieving relatively higher levels of PEI conjugation. Almost all of the PCM polymers were able to bind and condense plasmid DNA effectively into particles of approximately 200 nm in solution at the polymer/DNA ratio of 2 and above. The PCMs composed of relatively moderate size (Mw: 2000–5000 Da), intermediate HLB (12–23) of Pluronics, and LPEI produce much higher gene delivery efficacy and less cytotoxicity as compared with PEI 25k in C2C12 myoblasts and CHO cells in vitro. The PCMs were also able to enhance gene delivery in mdx mice in vivo, indicating their potential as biocompatible gene delivery carriers.