Patent Publication Number: US-2023142669-A1

Title: Compositions and methods for treating cystic fibrosis

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority of U.S. Provisional Patent Application No. 63/001,377, titled: “COMPOSITIONS AND METHODS FOR TREATING CYSTIC FIBROSIS”, filed Mar. 29, 2020, and U.S. Provisional Patent Application No. 63/083,942, titled: “COMPOSITIONS AND METHODS FOR TREATING CYSTIC FIBROSIS”, filed Sep. 27, 2020, the contents of which are incorporated herein by reference in their entirety. 
    
    
     FIELD OF INVENTION 
     The present invention is in the field of antisense oligonucleotides and therapeutic use of the antisense oligonucleotides. 
     BACKGROUND 
     Cystic fibrosis (CF) is a common, severe autosomal recessive disease caused by mutations in the CFTR gene. The CFTR gene encodes for a chloride channel responsible for chloride transport in epithelial cells. The major manifestations of CF are in the lungs, with more than 90% mortality related to the respiratory disease. The disease in the respiratory tract is linked to the insufficient CFTR function in the airway epithelium. 
     As of today, approximately 2000 different mutations disrupting the CFTR functions have been identified worldwide. 
     In recent years, fundamental knowledge of molecular and cellular biology has helped to develop therapies for specific CF mutations. The current approved therapies include correcting defects in the CFTR protein processing (corrector: VX-809/Lumacaftor, VX-661/Tezacaftor, and VX-445/elexacaftor), chloride channel function (potentiator: VX-770/Kalydeco) and combination of the two. However, there is no available therapy for patients carrying other mutations that do not respond to the available therapies (such as stop mutations, missense mutations and more). 
     Anti-sense oligonucleotides (AOs or ASOs) administration is one of the most promising therapeutic approaches for the treatment of genetic disorders. AOs are short synthetic molecules which can anneal to motifs predicted to be involved in the pre-mRNA splicing. The method is based on splice-switching. The AOs binding to selected sites is expected to mask the targeted region and promote either normal splicing or enable specific exclusion or inclusion of selected exons. AOs are highly specific for their targets and do not affect any other sequence in the cells. Several types of chemically modified AO molecules are commonly used including: 2′-O-methyl-phosphorothioate (2OMP), phosphorodiamidate morpholino oligomer (PMO), peptide nucleic acids (PNAs), 2-methoxyethyl phosphorothioate (MOE), constrained ethyl (cET), Ligand-Conjugated Antisense (LICA) and alternating locked nucleic acids (LNAs). 
     The AOs modifications maintain their stabilization, improve their target affinity, and provide favorable pharmacokinetic properties and biological stability. The potential of ASOs as therapeutics is demonstrated in several human genetic diseases. Among them is spinal muscular atrophy (SMA), in which the inclusion of exon 7 in the gene survival motor neuron 2 (SMN2) leads to full functional protein. Based on promising results in studies of neonatal mouse pups with severe SMA, the ASO-based drug SPINRZA® (nusinersen) developed by Biogen and Ionis, received FDA approval based on successful completion of a phase-3 clinical trial in patients with infantile-onset SMA, showing a significant improvement in motor function milestones in SMA infants. 
     SUMMARY 
     The present invention is directed to a composition and a method of use thereof comprising oligonucleotides capable of binding to a CFTR pre-mRNA, thereby modulating splicing and restoring or enhancing the function of the CFTR gene product. The present invention thus identifies sequences within the CFTR pre-mRNA which are targeted in order to modulate the splicing cascade of the CFTR pre-mRNA. 
     The present invention is based, in part, on the finding that artificial “anti-sense” oligonucleotide (ASO) molecules are able to target and bind predetermined sequences, and this binding can modulate the splicing of the pre-mRNA molecule into a mature mRNA which is subsequently translated into a functional protein in sufficient levels. 
     According to a first aspect, there is provided a method for inducing skipping of exon 24 of the cystic fibrosis transmembrane conductance regulator (CFTR) pre-mRNA in a cell, comprising contacting the cell with an effective amount of a synthetic antisense oligonucleotide (ASO) comprising 14-24 contiguous nucleobases having at least 75% complementary to an equal-length portion of a nucleic acid sequence derived from a polynucleotide sequence consisting of: GAAAGUAUUUAUUUUUUCUGGAACAUUUAGAAAAAACUUGGAUCCCUAUG AACAGUGGAGUGAUCAAGAAAUAUGGAAAGUUGCAGAUGAGGUAAGGCUG CUAACUGA (SEQ ID NO: 1), thereby inducing skipping of exon 24 of the CFTR pre-mRNA in the cell. 
     According to another aspect, there is provided a method for treating cystic fibrosis (CF) in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a synthetic antisense oligonucleotide (ASO) comprising 14-24 contiguous nucleobases having at least 75% complementary to an equal-length portion of a nucleic acid sequence derived from a polynucleotide sequence consisting of: GAAAGUAUUUAUUUUUUCUGGAACAUUUAGAAAAAACUUGGAUCCCUAUG AACAGUGGAGUGAUCAAGAAAUAUGGAAAGUUGCAGAUGAGGUAAGGCUG CUAACUGA, wherein the ASO induces the skipping of exon 24 of the cystic fibrosis transmembrane conductance regulator (CFTR) pre-mRNA, thereby treating CF in the subject. 
     According to another aspect, there is provided a pharmaceutical composition comprising an ASO comprising 14 to 24 contiguous nucleobases having at least 80% complementary to an equal-length portion of a nucleic acid sequence derived from a polynucleotide sequence consisting of SEQ ID NO: 1, and characterized by inducing skipping of exon 24 of said CFTR pre-mRNA, and a pharmaceutically acceptable carrier. 
     According to another aspect, there is provided a kit comprising: (a) at least one ASO; and at least one of: (b) at least one CFTR modifier; or (c) at least one CF drug, wherein the ASO is selected from the group consisting of SEQ ID Nos. 2-16, and wherein the CFTR modifier is selected from the group consisting of: CFTR potentiator, CFTR corrector, Translational Read-Through agent, and CFTR amplifier. 
     In some embodiments, the method further comprises administering to the subject a therapeutically effective amount of one or more CFTR modifiers. 
     In some embodiments, the CFTR modifier increases the duration of the CFTR gate being open, chloride flow through the CFTR gate, CFTR protein proper folding, the number of CFTR anchored to the cell membrane, or any combination thereof. 
     In some embodiments, the CFTR modifier is selected from the group consisting of: potentiator, corrector, and amplifier. 
     In some embodiments, the CFTR modifier is ivacaftor, lumacaftor, tezacaftor, elexacaftor, VX-659, VX-152, or VX-440, or any combination thereof. 
     In some embodiments, the ASO comprises a backbone selected from the group consisting of: a phosphate-ribose backbone, a phosphate-deoxyribose backbone, a phosphorothioate-deoxyribose backbone, a 2′-O-methyl-phosphorothioate backbone, a phosphorodiamidate morpholino backbone, a peptide nucleic acid backbone, a 2-methoxyethyl phosphorothioate backbone, a constrained ethyl backbone, an alternating locked nucleic acid backbone, a phosphorothioate backbone, N3′-P5′ phosphoroamidates, 2′-deoxy-2′-fluoro-β-d-arabino nucleic acid, cyclohexene nucleic acid backbone nucleic acid, tricyclo-DNA (tcDNA) nucleic acid backbone, ligand-conjugated antisense, and a combination thereof. 
     In some embodiments, the ASO comprises 17 to 22 bases. 
     In some embodiments, the ASO comprises a sequence selected from the group consisting of: SEQ ID Nos. 2-16. 
     In some embodiments, the subject comprises at least one mutation selected from the group consisting of: N1303K, 4006delA, 4010del4, 4015delA, 4016insT, G1298A, T1299I, 4040delA, 4041 4046del6insTGT, 4048insCC, Q1313X, and CFTRdele21. 
     In some embodiments, the at least one mutation is N1303K. 
     In some embodiments, treating comprises improving at least one clinical parameter of CF selected from the group consisting of: lung function, time to the first pulmonary exacerbation, change in weight, change in height, a change in Body Mass Index (BMI), change in the concentration of sweat chloride, number and/or duration of pulmonary exacerbations, total number of days of hospitalization for pulmonary exacerbations, and the need for antibiotic therapy for sinopulmonary signs or symptoms. 
     In some embodiments, the ASO comprises a chemically modified backbone. 
     In some embodiments, the pharmaceutical composition is used in inducing the skipping of exon 24 of the CFTR pre-mRNA. 
     In some embodiments, the pharmaceutical composition is an inhalation composition. 
     In some embodiments, the pharmaceutical is used in the treatment of CF in a subject in need thereof. 
     In some embodiments, the CF drug is an antibiotic drug, a bronchodilator, a corticosteroid, or any combination thereof. 
     Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting. 
     Further embodiments and the full scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIGS.  1 A- 1 B  include micrographs of gel electrophoresis analyses ( 1 A) and graphs ( 1 B) showing fold change of transcript levels with or without exon 24 of the CFTR pre-mRNA. 
     
    
    
     DETAILED DESCRIPTION 
     According to some embodiments, there is provided a method for inducing skipping of exon 24 of the cystic fibrosis transmembrane conductance regulator (CFTR) pre-mRNA in a cell, comprising contacting the cell with an effective amount of a synthetic antisense oligonucleotide (ASO) comprising 14-24 contiguous nucleobases having at least 75% complementary to an equal-length portion of a nucleic acid sequence derived from a polynucleotide sequence consisting of: GAAAGUAUUUAUUUUUUCUGGAACAUUUAGAAAAAACUUGGAUCCCUAUG AACAGUGGAGUGAUCAAGAAAUAUGGAAAGUUGCAGAUGAGGUAAGGCUG CUAACUGA (SEQ ID NO: 1), thereby inducing skipping of exon 24 of the CFTR pre-mRNA in the cell. 
     In some embodiments, contacting comprises contacting in vivo, in vitro, or ex vivo. In some embodiments, the ASO is introduced into a cell mixed with an 
     According to some embodiments, there is provided a method for treating cystic fibrosis (CF) in a subject in need thereof. In some embodiments, the method comprises administering to the subject a therapeutically effective amount of a synthetic ASO comprising 14-24 contiguous nucleobases having at least 75% complementary to an equal-length portion of a nucleic acid sequence derived from a polynucleotide sequence consisting of: SEQ ID NO: 1, wherein the ASO induces the skipping of exon 24 of the cystic fibrosis transmembrane conductance regulator (CFTR) pre-mRNA, thereby treating CF in the subject. 
     In some embodiments, the method further comprises administering to the subject a therapeutically effective amount of one or more CFTR modifiers. 
     In some embodiments, the cell is derived form a subject as described herein. In some embodiments, the cell comprises a cell line or a culture thereof. In some embodiments, the cell is an epithelial cell. In some embodiments, an epithelial cell comprises a respiratory epithelial cell. In some embodiments, a respiratory epithelial cell is derived from the upper respiratory system. In some embodiments, a respiratory epithelial cell is a ciliated columnar epithelial cell. In some embodiments, a respiratory epithelial cell is a ciliated pseudostratified columnar epithelial cell. In some embodiments, a respiratory epithelial cell is selected from: a ciliated cell, a goblet cell, a club cell, an airway basal cell, or any combination thereof. 
     In some embodiments, the CFTR modifier increases the duration of the CFTR gate being open, chloride flow through the CFTR gate, CFTR protein proper folding, the number of CFTR anchored to the cell membrane, or any combination thereof. Each possibility represents a separate embodiment of the invention. 
     In some embodiments, the modifier is selected from: potentiator, corrector, and amplifier. 
     As used herein, the term “potentiator” refers to any agent that increases the probability that a defective CFTR will be open and therefore allows chloride ions to pass through the channel pore. 
     As used herein, the term “corrector” refers to any agent that assists in proper CFTR channel folding so as to enable its trafficking to the cell membrane. 
     As used herein, the term “amplifier” refers to any agent that induces a cell to increase its CFTR protein production rates or yields, therefore resulting in an increased amount of the CFTR protein. 
     In some embodiments, the modifier is selected from ivacaftor, lumacaftor, tezacaftor, elexacaftor, VX-659, VX-152, or VX-440. 
     In some embodiments, the modifier is ivacaftor, lumacaftor, tezacaftor, elexacaftor, VX-659, VX-152, or VX-440, or any combination thereof. 
     Antisense Oligonucleotides 
     In some embodiments, the method comprises administering a splicing modulator which is a synthetic antisense oligonucleotide (ASO). 
     In some embodiments, the ASO is chemically modified. In some embodiments, the chemical modification is a modification of a backbone of the ASO. In some embodiments, the chemical modification is a modification of a sugar of the ASO. In some embodiments, the chemical modification is a modification of a nucleobase of the ASO. In some embodiments, the chemical modification increases stability of the ASO in a cell. In some embodiments, the chemical modification increases stability of the ASO in vivo. In some embodiments, the chemical modification increases the ASO&#39;s ability to modulate splicing. In some embodiments, the chemical modification increases the ASO&#39;s ability to induce skipping of exon 24. In some embodiments, the chemical modification increases the half-life of the ASO. In some embodiments, the chemical modification inhibits polymerase extension from the 3′ end of the ASO. In some embodiments, the chemical modification inhibits recognition of the ASO by a polymerase. In some embodiments, the chemical modification inhibits double-strand trigged degradation. In some embodiments, the chemically modified ASO does not trigger nucleic acid double-stranded degradation upon binding a CFTR pre-mRNA. In some embodiments, the chemical modification inhibits RISC-mediated degradation. In some embodiments, the chemical modification inhibits RISC-mediated degradation or any parallel nucleic acid degradation pathway. 
     In some embodiments, the ASO is devoid of a labeling moiety. In some embodiments, the ASO is not labeled. In some embodiments, the ASO does not emit a detectable signal or does not comprise moieties capable of being recognized so as to enable nucleic acid detection (e.g., digoxigenin and fluorescently labeled anti-DIG antibody). In some embodiments, a detectable signal comprises a dye or an emitting energy which provides detection of a compound, e.g., a polynucleotide, in vivo or in vitro. In some embodiments, a detectable signal comprises: a fluorescent signal, a chromatic signal, or a radioactive signal. 
     In some embodiments, the ASO is devoid of radioactive nucleobase(s); digoxigenin, streptavidin, biotin, a fluorophore, hapten label, CLICK label, amine label, or thiol label. 
     In some embodiments, the chemical modification is selected from: a phosphate-ribose backbone, a phosphate-deoxyribose backbone, a phosphorothioate-deoxyribose backbone, a 2′-O-methyl-phosphorothioate backbone, a phosphorodiamidate morpholino backbone, a peptide nucleic acid backbone, a 2-methoxyethyl phosphorothioate backbone, a constrained ethyl backbone, an alternating locked nucleic acid backbone, a phosphorothioate backbone, N3′-P5′ phosphoroamidates, 2′-deoxy-2′-fluoro-β-d-arabino nucleic acid, cyclohexene nucleic acid backbone nucleic acid, tricyclo-DNA (tcDNA) nucleic acid backbone, ligand-conjugated antisense, and a combination thereof. 
     In some embodiments, the ASO comprises at least 14 bases, at least 15 bases, at least 16 bases, at least 17 bases, at least 18 bases, at least 19 bases, at least 20 bases, at least 21 bases, at least 22 bases, at least 23 bases, at least 24 bases, or at least 25 bases, or any value and range therebetween. Each possibility represents a separate embodiment of the invention. 
     In some embodiments, the ASO comprises 14 to 25 bases, 14 to 23 bases, 14 to 23 bases, 14 to 22 bases, 14 to 21 bases, 14 to 20 bases, 14 to 19 bases, or 14 to 18 bases, or 14 to 17 bases. Each possibility represents a separate embodiment of the invention. in some embodiments, the ASO comprises 17 to 22 bases. 
     In some embodiments, the ASO is complementary to an equal-length portion of a sequence derived from a polynucleotide sequence consisting of: UUACCUUAUAGGUGGGCCUCUUGGGAAGAACUGGAUCAGGGAAGAGUACUU UGUUAUCAGCUUUUUUGAGACUACUGAACACUGAAGGAGAAAUCCAGAUCG AUGGUGU (SEQ ID NO: 1). In some embodiments, an ASO complementary to an equal-length portion of a sequence consisting of SEQ ID NO: 1 comprises 14-24 bases. 
     In some embodiments, the ASO has at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 99%, or 100% complementarity to an equal-length portion of a sequence derived from SEQ ID NO: 1, or any value and range therebetween. Each possibility represents a separate embodiment of the invention. In some embodiments, the ASO has 70-80%, 75-85%, 80-90%, 85-95%, 90-99%, or 95-100% complementarity to an equal-length portion of a sequence derived from SEQ ID NO: 1. Each possibility represents a separate embodiment of the invention. 
     The term “complementary” refers to the ability of polynucleotides to form base pairs with one another. Base pairs are typically formed by hydrogen bonds between nucleotide units in antiparallel polynucleotide strands. Complementary polynucleotide strands can base pair in the Watson-Crick manner (e.g., A to T, A to U, C to G), or in any other manner that allows for the formation of duplexes. As persons skilled in the art are aware, when using RNA as opposed to DNA, uracil rather than thymine is the base that is considered to be complementary to adenosine. However, when a U is denoted in the context of the present invention, the ability to substitute a T is implied, unless otherwise stated. 
     In some embodiments, the ASO comprises or consists of a sequence selected from: CCAGAAAAAAUAAAUACUUUC (SEQ ID NO: 2), AAUGUUCCAGAAAAAAUA (SEQ ID NO: 3), UCUAAAUGUUCCAGAAAA (SEQ ID NO: 4), CCACUGUUCAUAGGGAUC (SEQ ID NO: 5), UCACUCCACUGUUCAUAGG (SEQ ID NO: 6), GAUCACUCCACUGUUCAU (SEQ ID NO: 7), UUCUUGAUCACUCCACUGU (SEQ ID NO: 8), CCAUAUUUCUUGAUCACUCC (SEQ ID NO: 9), ACUUUCCAUAUUUCUUGAUC (SEQ ID NO: 10), GCAACUUUCCAUAUUUCUUG (SEQ ID NO: 11), CAUCUGCAACUUUCCAUAUUU (SEQ ID NO: 12), CUCAUCUGCAACUUUCCAUA (SEQ ID NO: 13), ACCUCAUCUGCAACUUUC (SEQ ID NO: 14), UUAGCAGCCUUACCUCAUC (SEQ ID NO: 15), or UCAGUUAGCAGCCUUACC (SEQ ID NO: 16). 
     In some embodiments, the ASO is complementary to a nucleic acid sequence starting at nucleobase at position 41 at the 5′ end of SEQ ID NO: 1 and ending at a nucleobase in a position selected from: 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, or 64, from the 5′ end of SEQ ID NO: 1. 
     In some embodiments, the ASO is complementary to a nucleic acid sequence starting at nucleobase at position 42 at the 5′ end of SEQ ID NO: 1 and ending at a nucleobase in a position selected from: 55, 56, 57, 58, 59, 60, 61, 62, 63, 64 or 65, from the 5′ end of SEQ ID NO: 1. 
     In some embodiments, the ASO is complementary to a nucleic acid sequence starting at nucleobase at position 67 at the 5′ end of SEQ ID NO: 1 and ending at a nucleobase in a position selected from: 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, or 90, from the 5′ end of SEQ ID NO: 1. 
     In some embodiments, the ASO is complementary to a nucleic acid sequence starting at nucleobase at position 68 at the 5′ end of SEQ ID NO: 1 and ending at a nucleobase in a position selected from: 81, 82, 83, 84, 85, 86, 87, 88, 89, 90 or 91, from the 5′ end of SEQ ID NO: 1. 
     In some embodiments, the ASO is complementary to a nucleic acid sequence starting at nucleobase at position 87 at the 5′ end of SEQ ID NO: 1 and ending at a nucleobase in a position selected from: 100, 101, 103, 104, 105, 106, or 107 from the 5′ end of SEQ ID NO: 1. 
     In some embodiments, the ASO is complementary to a nucleic acid sequence starting at nucleobase at position 88 at the 5′ end of SEQ ID NO: 1 and ending at a nucleobase in a position selected from: 101, 102, 103, 104, 105, 106, 107, or 108 from the 5′ end of SEQ ID NO: 1. 
     In some embodiments, the ASO does not consist of a sequence selected from: GATCACTCCACTGTTCATAGGGATC (SEQ ID NO: 17), CTCATCTGCAACTTTCCATATTTCT (SEQ ID NO: 18), or ATTTCAGTTAGCAGCCTTACCTCAT (SEQ ID NO: 19). 
     In some embodiments, the ASO is complementary to the CFTR pre-mRNA (Accession number NM_000492). In some embodiments, the pre-mRNA is a wildtype pre-mRNA. In some embodiments, the pre-mRNA is a mutated pre-mRNA. In some embodiments, the CFTR pre-mRNA comprises SEQ ID NO: 1. 
     In some embodiments, the ASO is specific to a CFTR pre-mRNA. As used herein, the term “specific” refers to both base pair specificity and also gene specificity. In some embodiments, the ASO is specific to the CFTR gene. In some embodiments, the ASO is specific to a splice enhancing motif in CFTR. In some embodiments, the ASO is specific to a splice enhancing sequence is CFTR. In some embodiments, the ASO is specific to a splice enhancing region of CFTR. In some embodiments, the splice silencing is splice silencing of exon 24 of CFTR. In some embodiments, the binding of an ASO to a splicing enhancer induces exon skipping, e.g., exon 24 as described herein. In some embodiments, the binding of an ASO to a splicing enhancer results in splice silencing of an exon, e.g., exon 24 as described herein. 
     In some embodiments, the ASO binds the CFTR pre-mRNA with perfect complementarity. 
     In some embodiments, the ASO does not bind any gene product other than CFTR with perfect complementarity. In some embodiments, the ASO does not bind any gene other than CFTR with a complementarity of greater than 70, 75, 80, 85, 90, 95, 97, 99 or 100%. Each possibility represents a separate embodiment of the invention. In some embodiments, the ASO does not bind any gene other than CFTR with a complementarity of greater than 90%. In some embodiments, the ASO binds to SEQ ID NO: 1 with perfect complementarity. In some embodiments, the ASO does not bind to any sequence other than SEQ ID NO: 1 with perfect complementarity. In some embodiments, the ASO does not bind to any sequence other than SEQ ID NO: 1 with complementarity of greater than 70, 75, 80, 85, 90, 95, 97, 99 or 100%. Each possibility represents a separate embodiment of the invention. In some embodiments, the ASO does not bind to any sequence other than SEQ ID NO: 1 with a complementarity of greater than 90%. In some embodiments, the ASO does not bind with perfect complementarity to anywhere in the genome of a cell other than within CFTR. In some embodiments, the ASO does not bind with complementarity of greater than 70, 75, 80, 85, 90, 95, 97, 99 or 100% to anywhere in the genome of a cell other than within CFTR. Each possibility represents a separate embodiment of the invention. In some embodiments, the cell is a mammalian cell. In some embodiments, the mammal is a human. In some embodiments, the ASO may bind to an intronic sequence in the CFTR pre-mRNA. In some embodiments, the binding of an ASO to an intronic sequence in the CFTR pre-mRNA does not induce skipping of exon 24. In some embodiments, the ASO may partially or fully bind (e.g., complement) to an intronic sequence within a gene other than CFTR. In some embodiments, an ASO partially or fully binding to an intronic sequence within a gene other than CFTR does not induce splicing or modifies transcription. In some embodiments, an ASO partially or fully binding to an intronic sequence within a gene other than CFTR binds to an intronic sequence being distant from an exon, an intro-exon junction, or both. 
     In some embodiments, distant comprises at least 50 base pairs (bp), at least 100 bp, at least 200 bp, at least 350 bp, at least 500 bp, at least 750 bp, at least 1,000 bp, at least 2,000 bp, at least 3,500 bp, at least 5,000 bp, at least 7,500 bp, or at least 10,000 bp upstream to an exon, an intro-exon junction, or both, or downstream to an exon, an intro-exon junction, or both, or any value and range therebetween. Each possibility represents a separate embodiment of the invention. 
     In some embodiments, the ASO modulates expression of CFTR. In some embodiments, the ASO modulates splicing of CFTR. In some embodiments, the ASO modulates splicing of exon 24 of CFTR. In some embodiments, the ASO does not cause an off-target effect. In some embodiments, off-target is a target other than CFTR. In some embodiments, off-target is a target other than splicing of exon 24 of CFTR. In some embodiments, the ASO does not substantially or significantly modulate expression of a gene other than CFTR. In some embodiments, the ASO does not substantially or significantly modulate splicing of a gene other than CFTR. In some embodiments, the ASO does not substantially or significantly modulate splicing of an exon other than exon 24 of CFTR. In some embodiments, substantial modulation of expression is a change in expression of at least 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50%. Each possibility represents a separate embodiment of the invention. In some embodiments, substantial modulation of expression is a change in expression of at least 20%. 
     In some embodiments, the ASO comprises an active fragment of any one of SEQ ID Nos: 2-16. 
     As used herein, the term “active fragment” refers to a fragment that is 100% identical to a contiguous portion of the full nucleotide sequence of the ASO, providing that at least: 30%, 40%, 50%, 60%, 70%, 80% or 90% of the activity of the original ASO nucleotide sequence is retained, or any value and range therebetween. Each possibility represents a separate embodiment of the present invention. 
     In some embodiments, the subject comprises a mutation. In some embodiments, the subject comprises a missense mutation. In some embodiments, the subject comprises a nonsense mutation. In some embodiments, the subject comprises a substitution mutation in the CFTR encoding gene, pre-mRNA encoded therefrom, or protein product thereof. In some embodiments, the subject comprises one or more mutations selected from: N1303K, 4006delA, 4010del4, 4015delA, 4016insT, G1298A, T1299I, 4040delA, 4041 4046del6insTGT, 4048insCC, Q1313X, and CFTRdele21. In some embodiments, the subject comprises a wild type (i.e., not mutated) exon 24. In some embodiments, the subject comprises at least one CF-inducing mutation residing in the CFTR gene, or mRNA transcribed therefrom, wherein the mutation does not reside in exon 24, affect exon 24 inclusion or exclusion from the mature mRNA, or both. In some embodiments, the subject comprises both a wildtype exon 24, and at least one CF-inducing mutation residing in the CFTR gene, or mRNA transcribed therefrom, wherein the mutation does not reside in exon 24, affect exon 24 inclusion or exclusion from the mature mRNA, or both. 
     In some embodiments, the subject is homozygous to one or more of the aforementioned mutations. In some embodiments, the subject is heterozygous to one or more of the aforementioned mutations. In some embodiments, a subject treated according to the method of the invention, comprises or is characterized by having a mixture of a wild type full-length and fully functional CFTR protein encoded from the wild type allele and a deleterious CFTR protein encoded from the pre-mRNA from which exon 24 was excluded using the ASO of the invention. In some embodiments, the subject is further heterozygous to additional one or more mutations, wherein the additional one or more mutations is located in the CFTR pre-mRNA in an exon other than exon 24. In some embodiments, the subject is homozygous or heterozygous to the one or more CF-conferring mutations disclosed herein, e.g., N1303K, and is further heterozygous to an additional one or more mutations located in any exon of the CFTR pre-mRNA other than exon 24. 
     In some embodiments, “a mutation” as used herein, refers to any nucleotide substitution or modification which renders a partially or fully non-functional CFTR protein. In some embodiments, “a mutation” as used herein, refers to a nucleotide substitution or modification which induces or results in a “Cystic fibrosis phenotype” in a subject harboring or comprising the mutation. 
     In some embodiments, a modification comprises insertion, deletion, inversion, or a combination thereof, as long as the modification results in a Cystic fibrosis phenotype in a subject harboring or comprising the modification. 
     As used herein, the term “Cystic fibrosis phenotype” encompasses any symptom or manifestation related to Cystic fibrosis. Methods for diagnosing Cystic fibrosis and/or symptoms associated therewith are common and would be apparent to one of ordinary skill in the art. 
     In some embodiments, the subject comprises an Asparagine substituted with a Lysine in the CFTR protein. In some embodiments, the subject comprises a substitution in position 1303 of the CFTR protein. In some embodiments, the subject comprises a N1303K substitution in the CFTR protein. 
     In some embodiments the subject is afflicted with Cystic fibrosis. 
     In some embodiments, the method is directed to improving at least one clinical parameter of CF in the subject, selected from: lung function, time to the first pulmonary exacerbation, change in weight, change in height, a change in Body Mass Index (BMI), change in the concentration of sweat chloride, number and/or duration of pulmonary exacerbations, total number of days of hospitalization for pulmonary exacerbations, or the need for antibiotic therapy for sinopulmonary signs or symptoms. 
     As used herein, the terms “treatment” or “treating” of a disease, disorder, or condition encompasses alleviation of at least one symptom thereof, a reduction in the severity thereof, or inhibition of the progression thereof. Treatment need not mean that the disease, disorder, or condition is totally cured. To be an effective treatment, a useful composition herein needs only to reduce the severity of a disease, disorder, or condition, reduce the severity of symptoms associated therewith, or provide improvement to a patient or subject&#39;s quality of life. 
     As used herein, the term “condition” includes anatomic and physiological deviations from the normal that constitute an impairment of the normal state of the living animal or one of its parts, that interrupts or modifies the performance of the bodily functions. 
     As used herein, the terms “subject” or “individual” or “animal” or “patient” or “mammal,” refers to any subject, particularly a mammalian subject, for whom therapy is desired, for example, a human. 
     Composition 
     According to some embodiments, there is provided a composition comprising the herein disclosed ASO. 
     In some embodiments, the composition further comprises a pharmaceutically acceptable carrier. 
     The term “pharmaceutically acceptable carrier” as used herein refers to any of the standard pharmaceutical carriers known in the field such as sterile solutions, tablets, coated tablets, and capsules. Typically, such carriers contain excipients such as starch, milk, sugar, certain types of clay, gelatin, stearic acids or salts thereof, magnesium or calcium stearate, talc, vegetable fats or oils, gums, glycols, or other known excipients. Such carriers may also include flavor and color additives or other ingredients. Examples of pharmaceutically acceptable carriers include, but are not limited to, the following: water, saline, buffers, inert, nontoxic solids (e.g., mannitol, talc). Compositions comprising such carriers are formulated by well-known conventional methods. Depending on the intended mode of administration and the intended use, the compositions may be in the form of solid, semi-solid, or liquid dosage forms, such, for example, as powders, granules, crystals, liquids, suspensions, liposomes, nano-particles, nano-emulsions, pastes, creams, salves, etc., and may be in unit-dosage forms suitable for administration of relatively precise dosages. 
     In some embodiments, the pharmaceutical composition is formulated for oral, administration. In some embodiments, the pharmaceutical composition is formulated for nasal administration. In some embodiments, the pharmaceutical composition is formulated for administration by inhalation. In some embodiments, the pharmaceutical composition is formulated for abdominal administration. In some embodiments, the pharmaceutical composition is formulated for subcutaneous administration. In some embodiments, the pharmaceutical composition is formulated for intra-peritoneal administration. In some embodiments, the pharmaceutical composition is formulated for intravenous administration. 
     In some embodiments, the pharmaceutical composition is formulated for systemic administration. In some embodiments, the pharmaceutical composition is formulated for administration to a subject. In some embodiments, the subject is a human subject. It will be understood by a skilled artisan that a pharmaceutical composition intended to administration to a subject should not have off-target effects, i.e. effects other than the intended therapeutic ones. In some embodiments, the pharmaceutical composition is devoid of a substantial effect on a gene other than CFTR. In some embodiments, the pharmaceutical composition is devoid of a substantial effect on splicing of an exon other than exon 24 of CFTR. In some embodiments, a substantial effect is one with a phenotypic result. In some embodiments, a substantial effect is a deleterious effect. In some embodiments, deleterious is with respect to the health and/or wellbeing of the subject. 
     In some embodiments, the composition administered by inhalation. In some embodiments, the composition is an inhalation composition. in some embodiments, the composition is a pharmaceutical composition. 
     Being a long-known and well-studied disease, certain drugs and agents are known in the art for the treatment of Cystic Fibrosis patients. Administrating a synthetic polynucleotide molecule according to the present invention with one or more of these drugs may be beneficial in achieving significant therapeutic results. 
     In some embodiments, the composition further comprises at least one additional anti-Cystic-Fibrosis agent (i.e., CF drug). In some embodiments, the additional anti-Cystic-Fibrosis agent is selected from: a CFTR-splicing-modulator (e.g., an ASO as disclosed and as described herein), Translational Read-Through agent, sodium epithelial channel (ENaC) inhibitor, a CFTR amplifier, a CFTR potentiator, or a CFTR corrector. In some embodiments, the CFTR-splicing-modulator has capability to induce or promote exon 24 exclusion from the mature CFTR mRNA; the Translational Read-Through agent is selected from 3-[5-(2-fluorophenyl)-1,2,4-oxadiazol-3-yl]benzoic acid (Ataluren), or ELX-02; the ENaC inhibitor is selected from: VX-371 (P-1037) or IONIS-ENAC-2.5Rx; the CFTR amplifier is PTI-428; the CFTR potentiator is selected from: N-(2,4-Di-tert-butyl-5-hydroxyphenyl)-4-oxo-1,4-dihydroquinoline-3-carboxamide (Ivacaftor), QBW251, PTI-808, or VX-561 (deuterated ivacaftor); the CFTR potentiator is N-(2,4-Di-tert-butyl-5-hydroxyphenyl)-4-oxo-1,4-dihydroquinoline-3-carboxamide (Ivacaftor); or the CFTR corrector is selected from: 3-{6-{[1-(2,2-difluoro-1,3-benzodioxol-5-yl)cyclopropanecarbonyl]amino}-3-methylpyridin-2-yl}benzoic acid (Lumacaftor), 1-(2,2-difluoro-1,3-benzodioxol-5-yl)-˜{N}-[1-[(2˜{R})-2,3-dihydroxypropyl]-6-fluoro-2-(1-hydroxy-2-methylpropan-2-yl)indol-5-yl]cyclopropane-1-carboxamide (Tezacaftor), VX-659, VX-445 (Elexacaftor), VX-152 and VX-440, GLPG2222, FDL169, or PTI-801. 
     In some embodiments, the pharmaceutical composition comprises the synthetic ASO of the invention. In some embodiments, the composition comprises at the ASO in an amount of at least 1 nM, at least 2.5 nM, at least 10 nM, or any value and range therebetween. Each possibility represents a separate embodiment of the invention. In some embodiments, the composition comprises at the ASO in an amount of 2.5 nM to 10 nM, 1 nM to 100 nM, 1 nM to 0.5 μM, or 1 nM to 1 μM. Each possibility represents a separate embodiment of the invention. 
     In some embodiments, an ASO as disclosed and as described hereinabove, or a pharmaceutical composition comprising thereof, is used in the modulation of splicing of a CFTR pre-mRNA transcribed from a CFTR gene. 
     The phrase “modulation of splicing” as used herein refers to affecting a change in the level of any RNA or mRNA variant produced by the CFTR native pre-mRNA. For example, modulation may mean e.g. causing an increase or decrease in the level of abnormal CFTR mRNA, causing an increase or decrease in the level of normal, full-length CFTR mRNA, causing an increase or decrease in the level of abnormal CFTR RNA or mRNA comprising a missense codon, and/or causing an increase or decrease in the level of abnormal CFTR RNA or mRNA comprising a premature termination codon (non-sense codon). It is therefore evident that any change in ratio between certain CFTR splicing variants is also considered to be the result of splicing modulation. Each possibility represents a separate embodiment of the invention. In certain embodiments, modulation means decreasing the level of abnormal CFTR mRNA. In some embodiments, the abnormal CFTR mRNA comprises a mutated exon 24. In some embodiments, modulation means decreasing the level of an abnormal CFTR mRNA comprising a mutated exon 24. In some embodiments, modulation means decreasing the level of an abnormal CFTR mRNA comprising a N1303K mutation. 
     In some embodiments, the use is for reducing the level of an mRNA molecule comprising the nucleotide sequence set forth in SEQ ID NO: 1. In some embodiments, the use is for increasing the level of CFTR mRNA lacking exon 24. In some embodiments, the use is for correcting or improving chloride transport through the CFTR channel. In some embodiments, the use is for increasing the production of functional CFTR protein. In some embodiments, the use is for increasing the duration of the CFTR gate being open. In some embodiments, the use is for increasing the chloride flow through the CFTR gate. In some embodiments, the use is for increasing the CFTR protein proper folding. In some embodiments, the use is for increasing the number of CFTR anchored to the cell membrane. 
     In some embodiments, an ASO as disclosed and as described hereinabove, or a pharmaceutical composition comprising thereof, is used in method for improving at least one clinical parameter of Cystic Fibrosis. In some embodiments, an ASO as disclosed and as described hereinabove, or a pharmaceutical composition comprising thereof, is used in treating of CF. 
     Kit 
     In one embodiment, the present invention provides combined preparations. In one embodiment, “a combined preparation” defines especially a “kit of parts” in the sense that the combination partners as defined above can be dosed independently or by use of different fixed combinations with distinguished amounts of the combination partners i.e., simultaneously, concurrently, separately or sequentially. In some embodiments, the parts of the kit of parts can then, e.g., be administered simultaneously or chronologically staggered, that is at different time points and with equal or different time intervals for any part of the kit of parts. The ratio of the total amounts of the combination partners, in some embodiments, can be administered in the combined preparation. 
     In some embodiments, the kit of the invention comprises: at least one ASO; and at least one of: at least one CFTR modifier; or at least one CF drug, wherein the ASO is selected from SEQ ID Nos. 2-16, and wherein the CFTR modifier is selected from: CFTR potentiator, CFTR corrector, and CFTR amplifier. 
     In some embodiments, the CF drug is an antibiotic drug, a bronchodilator, a corticosteroid, or any combination thereof. 
     Types and doses of CF drugs, such as an antibiotic, a bronchodilator, and a corticosteroid, would be apparent to one of ordinary skill in the art. Non-limiting examples of CF drugs, such as antibiotics include, but are not limited to, cloxacillin, dicloxacillin, cephalosporin, trimethoprim, sulfamethoxazole, erythromycin, amoxicillin, clavulanate, ampicillin, tetracycline, linezolid, tobramycin or aztreonam lysine, fluoroquinolone, gentamicin, and monobactam with antipseudomonal activity. 
     In some embodiments, the components of the kit disclosed above are sterile. As used herein, the term “sterile” refers to a state of being free from biological contaminants. Any method of sterilization is applicable and would be apparent to one of ordinary skill in the art. 
     In some embodiments, the components of the kit are packaged within a container. 
     In some embodiments, the container is made of a material selected from the group consisting of thin-walled film or plastic (transparent or opaque), paperboard-based, foil, rigid plastic, metal (e.g., aluminum), glass, etc. 
     In some embodiments, the content of the kit is packaged, as described below, to allow for storage of the components until they are needed. 
     In some embodiments, some or all components of the kit may be packaged in suitable packaging to maintain sterility. 
     In some embodiments, the components of the kit are stored in separate containers within the main kit containment element e.g., box or analogous structure, may or may not be an airtight container, e.g., to further preserve the sterility of some or all of the components of the kit. 
     In some embodiments, the instructions may be recorded on a suitable recording medium or substrate. For example, the instructions may be printed on a substrate, such as paper or plastic, etc. 
     In some embodiments, the instructions may be present in the kit as a package insert, in the labeling of the container of the kit or components thereof (i.e., associated with the packaging or sub-packaging) etc. In other embodiments, the instructions are present as an electronic storage data file present on a suitable computer readable storage medium, e.g. CD-ROM, diskette, etc. In other embodiments, the actual instructions are not present in the kit, but means for obtaining the instructions from a remote source, e.g. via the internet, are provided. An example of this embodiment is a kit that includes a web address where the instructions can be viewed and/or from which the instructions can be downloaded. As with the instructions, this means for obtaining the instructions is recorded on a suitable substrate. 
     Method of Production 
     According to some embodiments, there is provided a method for producing a compound suitable for treating CF. 
     In some embodiments, the method comprises obtaining a compound that binds to exon 24 of the CFTR pre-mRNA. In some embodiments, the method comprises assaying the skipping of exon 24 of the CFTR pre-mRNA in the presence of the obtained compound. In some embodiments, the method comprises selecting at least one compound that induces the exclusion of exon 24 from the CFTR pre-mRNA. 
     In some embodiments, the method comprises obtaining a compound that binds to exon 24 of the CFTR pre-mRNA, and assaying the skipping of exon 24 of the CFTR pre-mRNA in the presence of the obtained compound, and selecting at least one compound that induces the exclusion of exon 24 from the CFTR pre-mRNA, thereby producing a compound suitable for treating CF. 
     In some embodiments, the method comprises obtaining a compound that binds to SEQ ID NO: 1. 
     In some embodiments, the compound is an ASO. In some embodiments, the ASO is an ASO as disclosed and as described herein. 
     Methods of assaying exon skipping are common. Non-limiting examples of such methods include, but are not limited to, PCR, qPCR, gene sequencing, northern-blot, dot-blot, in situ hybridization, or others all of which would be apparent to one of ordinary skill in the art. 
     In the discussion unless otherwise stated, adjectives such as “substantially” and “about” modifying a condition or relationship characteristic of a feature or features of an embodiment of the invention, are understood to mean that the condition or characteristic is defined to within tolerances that are acceptable for operation of the embodiment for an application for which it is intended. Unless otherwise indicated, the word “or” in the specification and claims is considered to be the inclusive “or” rather than the exclusive or, and indicates at least one of, or any combination of items it conjoins. 
     It should be understood that the terms “a” and “an” as used above and elsewhere herein refer to “one or more” of the enumerated components. It will be clear to one of ordinary skill in the art that the use of the singular includes the plural unless specifically stated otherwise. Therefore, the terms “a,” “an” and “at least one” are used interchangeably in this application. 
     For purposes of better understanding the present teachings and in no way limiting the scope of the teachings, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. 
     In the description and claims of the present application, each of the verbs, “comprise”, “include” and “have” and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of components, elements or parts of the subject or subjects of the verb. 
     Other terms as used herein are meant to be defined by their well-known meanings in the art. 
     Unless specifically stated or obvious from context, as used herein, the term “or” is understood to be inclusive. 
     Throughout this specification and claims, the word “comprise”, or variations such as “comprises” or “comprising”, indicate the inclusion of any recited integer or group of integers but not the exclusion of any other integer or group of integers. 
     As used herein, the term “consists essentially of”, or variations such as “consist essentially of” or “consisting essentially of”, as used throughout the specification and claims, indicate the inclusion of any recited integer or group of integers, and the optional inclusion of any recited integer or group of integers that do not materially change the basic or novel properties of the specified method, structure or composition. 
     As used herein, the terms “comprises”, “comprising”, “containing”, “having” and the like can mean “includes”, “including”, and the like; “consisting essentially of or “consists essentially” likewise has the meaning ascribed in U.S. patent law and the term is open-ended, allowing for the presence of more than that which is recited so long as basic or novel characteristics of that which is recited is not changed by the presence of more than that which is recited, but excludes prior art embodiments. In one embodiment, the terms “comprises,” “comprising, “having” are/is interchangeable with “consisting of”. 
     Additional objects, advantages, and novel features of the present invention will become apparent to one ordinarily skilled in the art upon examination of the following examples, which are not intended to be limiting. Additionally, each of the various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below finds experimental support in the following examples. 
     It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements. 
     EXAMPLES 
     Generally, the nomenclature used herein, and the laboratory procedures utilized in the present invention include molecular, biochemical, microbiological and recombinant DNA techniques. Such techniques are thoroughly explained in the literature. See, for example, “Molecular Cloning: A laboratory Manual” Sambrook et al., (1989); “Current Protocols in Molecular Biology” Volumes I-III Ausubel, R. M., ed. (1994); Ausubel et al., “Current Protocols in Molecular Biology”, John Wiley and Sons, Baltimore, Md. (1989); Perbal, “A Practical Guide to Molecular Cloning”, John Wiley &amp; Sons, New York (1988); Watson et al., “Recombinant DNA”, Scientific American Books, New York; Birren et al. (eds) “Genome Analysis: A Laboratory Manual Series”, Vols. 1-4, Cold Spring Harbor Laboratory Press, New York (1998); methodologies as set forth in U.S. Pat. Nos. 4,666,828; 4,683,202; 4,801,531; 5,192,659 and 5,272,057; “Cell Biology: A Laboratory Handbook”, Volumes I-III Cellis, J. E., ed. (1994); “Culture of Animal Cells—A Manual of Basic Technique” by Freshney, Wiley-Liss, N.Y. (1994), Third Edition; “Current Protocols in Immunology” Volumes I-III Coligan J. E., ed. (1994); Stites et al. (eds), “Basic and Clinical Immunology” (8th Edition), Appleton &amp; Lange, Norwalk, Conn. (1994); Mishell and Shiigi (eds), “Strategies for Protein Purification and Characterization—A Laboratory Course Manual” CSHL Press (1996); “Monoclonal Antibodies: Methods and Protocols”. Vincent Ossipow, Nicolas Fischer. Humana Press (2014); “Monoclonal Antibodies: Methods and Protocols”. Maher Albitar. Springer Science &amp; Business Media (2007), all of which are incorporated by reference. Other general references are provided throughout this document. 
     Materials and Methods 
     Cell Transfection 
     HEK cells are transiently transfected with a construct bearing a CFTR transcript having exon 24 completely deleted from it (CFTR del Ex24). Transfection is carried out using Lipofectamine 2000 transfection reagent (Invitrogen) according to the lipofectamine 2000 reagent protocol using the following lipofectamine amounts: 96 well—0.15 μl, 6 well—3 μl, 10 mm plate—15 μl. 
     Studies of CFTR Function Using a Membrane Potential Assay 
     16HBEge N1303K System Studies 
     In order to analyze the ability of the ASOs to induce skipping over exon 24 in the presence of the mutation N1303K, the inventors use a cellular system that is developed in the CFFT lab, 16HBEge N1303K. The cellular system is based on an immortalized bronchial epithelial cell line which has endogenous WT CFTR containing all exonic and intronic sequences (16HBE14o-) (Cozens et al.,). 16HBE14o- are genetically engineered using CRISPR-based gene editing to establish an isogenic cell line homozygous for the CFTR N1303K mutation (16HBEge N1303K) (Valley et al.,). 
     Transfection 
     Each ASO is transfected into 16HBEge N1303K cells using Lipofecatmine 2000 transfection reagent (Invitrogen) according to the lipofectamine 2000 reagent protocol. In each experiment the effect of different ASOs is analyzed in comparison to cells treated with a control ASO. 
     RNA Extraction 
     Twenty four (24) hr following transfection, total RNA is extracted using RNeasy Mini Kit (QIAGEN). RNA concentration is determined using a nanodrop. Complementary DNA (cDNA) synthesis is performed using the High Capacity cDNA Reverse Transcription kit (Applied Biosystems). The cDNA is analyzed by PCR. 
     Determine the Ratio Between These Two Transcripts (PCR) 
     PCR is performed using the Platinum™ SuperFi™ Green PCR Master Mix 12359-10 (Invitrogen). PCR products are then separated on an agarose gel for detection of the correctly and aberrantly spliced transcripts. The gels are exposed to UV light for visualization and the PCR products are recorded. 
     Quantitative Detection of Correctly and Aberrantly Spliced CFTR Transcripts (qPCR) 
     Real-time RT-PCR is performed in QuantStudi 3 Real-Time PCR System using TaqMan® Fast Advanced Master Mix (Applied Biosystems) with TaqMan probes specific for transcripts including exon 24 or transcripts without exon 24. The expression level is normalized to the transcript levels of GUSb. Technical duplicates are analyzed for each sample. Analysis is performed using the ΔΔCt analysis. SPL24-2 (UCCAACUUUUUUCUAAAUGU, SEQ ID NO: 17), and SPL24-3 (GGAUCCAACUUUUUUCUAAAUG, SEQ ID NO: 18) ASOs were used as positive controls. 
     Example 1 
     ASOs Induce Exon 24 Skipping 
     ASOs complementary to SEQ ID NO: 1 were found to be more effective in inducing exon 24 skipping ( FIG.  1   ), compared to neighboring sequences flanking SEQ ID NO: 1 on the CFTR pre-mRNA. 
     While the present invention has been particularly described, persons skilled in the art will appreciate that many variations and modifications can be made. Therefore, the invention is not to be construed as restricted to the particularly described embodiments, and the scope and concept of the invention will be more readily understood by reference to the claims, which follow.