Modification formats having modified nucleotides are provided for siRNA. Short interfering RNA having modification formats and modified nucleotides provided herein reduce off-target effects in RNA interference of endogenous genes. Further modification formatted siRNAs are demonstrated to be stabilized to nuclease-rich environments. Unexpectedly, increasing or maintaining strand bias, while necessary to maintain potency for endogenous RNA interference, is not sufficient for reducing off-target effects in cell biology assays.

Aspects of the present invention include the production and use of chemically modified RNAi agents (e.g., shRNAs) in gene silencing applications. The chemically modified RNAi agents disclosed herein have reduced immunostimulatory activity, increased serum stability, or both, as compared to a corresponding RNAi agent not having the chemical modification. Compositions containing chemically modified RNAi agents according to aspects of the present invention (including pharmaceutical compositions) and kits containing the same are also provided.

Neutral lipid formulations for nucleic acid delivery are provided according to the invention. The neutral lipid formulations include hydrophobically modified polynucleotides and fat mixtures. Methods of using the neutral lipid formulations are also provided.

Methods, kits and devices for dosing a subject to reduce a hypersensitivy response to a lipid-formulated nucleic acid (e.g., RNA) molecule are disclosed.

The invention provides compositions and methods for reducing expression of a target gene in a cell, involving contacting a cell with an isolated double stranded nucleic acid (dsNA) in an amount effective to reduce expression of a target gene in a cell. The dsNAs of the invention possess a single stranded extension (in most embodiments, the single stranded extension comprises at least one modified nucleotide and/or phosphate back bone modification). Such single stranded extended Dicer-substrate siRNAs (DsiRNAs) were demonstrated to be effective RNA inhibitory agents compared to corresponding double stranded DsiRNAs.

Provided herein are methods and compositions for editing the genome of a cell. In some embodiments, a nucleotide sequence of at least 200 nucleotides in length is inserted into a target region in the genome of a cell.

The present invention relates to methods of administering to a subject multimeric oligonucleotides having monomeric subunits joined by linkers. The multimeric oligonucleotides have a molecular weight of at least about 45 kD and other characteristics, such that their clearance due to glomerular filtration is reduced. The present invention also relates to such multimeric oligonucleotides and methods of synthesizing such multimeric oligonucleotides.

Provided herein are compositions and methods for increasing editing efficiency of a target nucleic acid. A composition may comprise a guide nucleic acid, a Cas9 nickase, or a reverse transcriptase. The reverse transcriptase may be fused to the Cas9 nickase. The reverse transcriptase may heterodimerize with the Cas9 nickase. The reverse transcriptase may bind to a guide nucleic acid. The reverse transcriptase may be engineered to increase processivity. The guide nucleic acid may be engineered to facilitate synthesis or editing of a sequence. The guide nucleic acid, Cas9 nickase, and reverse transcriptase may be engineered to fit within AAV vectors. The guide nucleic acid may comprise a region that binds to another region on the guide nucleic acid to improve gene editing.

The present disclosure provides DNA-guided CRISPR systems; polynucleotides comprising DNA, RNA and mixtures thereof for use with CRISPR systems; and methods of use involving such polynucleotides and DNA-guided CRISPR systems.

Generally, the present disclosure is directed to methods for gRNA design and products thereof that can be used as antivirals in which the produced gRNAs can be tolerant to polymorphisms across clinical strains and/or adapted for activity at multiple viral sites. Aspects of example gRNAs can also include reduced interactions with the human genome or transcriptome.