Tricyclo-dna antisense oligonucleotides, compositions, and methods for the treatment of disease

Abstract

Provided are tricyclo-DNA (tc-DNA) AON and methods employing tc-DNA AON for modifying splicing events that occur during pre-mRNA processing. Tricyclo-DNA (tc-DNA) AON are described that may be used to facilitate exon skipping or to mask intronic silencer sequences and / or terminal stem-loop sequences during pre-mRNA processing and to target RNase-mediated destruction of processed mRNA. Tc-DNA AON described herein may be used in methods for the treatment of Duchenne Muscular Dystrophy by skipping a mutated exon 23 or exon 51 within a dystrophin gene to restore functionality of a dystrophin protein; in methods for the treatment of Spinal Muscular Atrophy by masking an intronic silencing sequence and / or a terminal stem-loop sequence within an SMN2 gene to yield modified functional SMN2 protein, including an amino acid sequence encoded by exon 7, which is capable of at least partially complementing a non-functional SMN1 protein; and in methods for the treatment of Steinert's Myotonic Dystrophy by targeting the destruction of a mutated DM1 mRNA comprising 3′-terminal CUG repeats.

Description

BACKGROUND OF THE DISCLOSURE [0001]1. Technical Field[0002]The present disclosure relates, generally, to synthetic antisense oligonucleotides (AON) and methods employing antisense oligonucleotides for modifying splicing events that occur during pre-mRNA processing or for down-regulating the expression of mutated mRNA that contain repeated sequences such as, for example, 3′ or 5′ CUG, CAG, and / or CCUG. More specifically, disclosed herein are tricyclo-DNA (tc-DNA) AON that are effective in facilitating exon skipping during pre-mRNA processing, in masking intronic silencer sequences and / or stem-loop sequences in pre-mRNA, and in targeting the RNase-mediated destruction of mRNA. Described herein are tc-DNA AON that may be used in methods for the treatment of Duchenne Muscular Dystrophy by skipping mutated exons, such as a mutated exon 23 or exon 51, within a dystrophin gene to restore functionality of a dystrophin protein. Also described are tc-DNA AON that may be used in methods for th...

AI Technical Summary

Benefits of technology

[0045]a deleterious mutation that can be compensated by the inclusion of an atypical exon in the mRNA coded by said gene, and the tc-DNA is complementary to an ISS or TSL present in a pre-mRNA coded by said gene and facilitates inclusion of an atypical exon, or

[0047]In a particular embodiment, when the alteration is an in-frame mutation of an exon, said tc-DNA can facilitate skipping of said exon. In another embodiment, when the alteration is a mutation disrupting the translational reading frame of the gene, said tc-DNA can facilitate skipping of an exon so as to restore the reading frame of the gene. In another embodiment, when the alteration is a mutation resulting in the presence of deleterious 3′ CUG amplification(s) in a mRNA coded by said gene and, said tc-DNA AON can destroy the mRNA containing said amplification.

[0049]As described in greater detail, below, exon skipping is achieved in the nucleus during the maturation process of pre-mRNAs. It includes the masking of key sequences involved in the splicing of targeted exons by using antisense oligonucleotides (AON) that are complementary to exon definition sequences within a pre-mRNA. Provided herein are tc-DNA AONs that may be suitably employed for exon skipping through the masking of splice sites at intron / exon junctions, or more generally sites used for exon definition, within a dystrophin pre-mRNA thereby facilitating the deletion of a deleterious exon during the processing of the pre-mRNA to a mature mRNA. Such tc-DNA AON will find utility in the treatment of Duchenne Muscular Dystrophy by restoring an open reading frame in a mutated dystrophin gene comprising an exon that contains a non-sense, a stop, a frameshift mutation, or an intronic sequence that contains a deleterious cryptic exon.

[0050]For example, a non-sense or frameshift mutation within exon 23 or exon 51 of a dystrophin gene yields a carboxy-terminally truncated, non-functional dystrophin protein. By hybridizing to nucleotides comprising a dystrophin pre-mRNA splice donor site in intron 23 or intron 51, respectively, and adjacent 5′ nucleotides of exon 23 or exon 51, tc-DNA AON disclosed herein are capable of preventing the inclusion of the mutated exon 23 or exon 51 into the mature mRNA transcript. The expression of that mature mRNA transcript yields a functional dystrophin protein that is deleted in the amino acids encoded by exon 23 or exon 51 but that includes dystrophin amino acids both N-terminal and C-terminal to those deleted amino acids and, therefore, constitutes a semi-functional ‘quasi-dystrophin’.

Problems solved by technology

The foremost consequence of DMD is that muscle fibers become particularly fragile and natural muscle activity provokes general damage in muscle tissue.

Mutations in the dystrophin gene result in a failure to produce dystrophin in striated muscles.

Others have point mutations or very small deletions or duplications that are difficult to identify.

Out-of-frame deletions or non-sense mutations that yield premature stop codons and subsequent abortion of translation result in dystrophin deficiencies characterized by severe phenotypes.

Several studies over the past 10 years support the benefit of steroid treatment (prednisone and deflazacort) in Duchenne boys, although a broad statistical evaluation has not yet been fully completed.

Recent developments have also provided evidence that stem cells from either bone marrow or vascular origins can target skeletal muscle through the systemic pathway, even though the extent of the genetic correction is still insufficient.

Although AAV vectors lack all viral genes, their cargo shipment is limited to 4.5 kb.

Although the proportion of revertant fibers increases with time, their number is unfortunately too low to confer a significant clinical benefit.

Nevertheless, the weakness of this approach is that it requires regular administration of the synthetic AOs, and systemic delivery has not been fully achieved.

Even so, producing “therapeutic” antisense RNA molecules in vivo poses many problems such as stability and subcellular localization.

Mental retardation is a symptom frequently associated with DMD and can result from the lack of dystrophin in neuronal cells.

SMA is the most common cause of genetically determined neonatal death.

Once symptoms appear, the motor neuron cells quickly deteriorate.

Infants with the severe form of SMA frequently succumb to respiratory disease due to weakness of the muscles that support breathing.

Pneumonia is considered the ultimate cause of death due to deterioration of survival motor neurons; motor neuron death causes insufficient functioning of the major bodily organ systems, particularly respiratory (e.g., breathing and ridding of pooled secretions inside lungs).

The SMN2 gene also contains a mutation that makes it less efficient at making protein, though it does so in a low level.

There is currently no drug known to alter the course of SMA and it is likely that gene replacement for SMA will require many more years of investigation before it can be applied to humans.

DM1 patients often present with myotonia, disabling distal weakness and severe cognitive problems.

Once there are more than 37 triplet repeats in the DMPK gene the sequence becomes unstable and slippage becomes more common.

There is currently no cure for or treatment specific to myotonic dystrophy.

Heart problems, cataracts, and other abnormalities associated with the condition can be treated but not cured.

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